EXHAUST ANALYSIS OF A RAPESEED OIL/DIESEL

FUELLED MICRO TURBINE

Tomasz Stanislaw Gaca

B. Eng. Mechanical Engineering Project Report

Department of Mechanical Engineering

Curtin University of Technology

Completed in association with

Fachhochschule Aachen

Nowum-Energy

2004

iii

I would like to thank all the people at Nowum-Energy in Jülich, Germany, who

have been involved with the Micro Turbine Project and to those that have helped

me with the research for this project. They have supported and encouraged me

throughout my stay in Germany and made my time here enjoyable. I would

especially like to extend my appreciation to Dipl-Ing Yvonne Schmellekamp for

her guidance, aid, support and knowledge.

Furthermore, I would like to thank the staff members of the Curtin University

Department of Mechanical Engineering who have made the completion of this

project possible.

Many Thanks.

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CONTENTS Submission Letter...................................................................................................ii Acknowledgements ...............................................................................................iii Contents.................................................................................................................iv 1.0 Introduction..................................................................................................... 1

1.1 The Objectives .............................................................................................. 1 1.2 Overview of Results...................................................................................... 2 1.3 Report Synopsis ............................................................................................ 2 1.4 Applications of the Technology.................................................................... 2

2.0 The Micro Turbine ......................................................................................... 4 2.1 Turbine History............................................................................................. 4 2.2 Delocalised Electricity Generation ............................................................... 5 2.3 Capstone C30 Micro Turbine Theory........................................................... 6

3.0 Rapeseed Oil .................................................................................................... 9 3.1 Production of Rapeseed Oil .......................................................................... 9 3.2 Chemical & Physical Properties ................................................................. 10 3.3 Comparison to Diesel.................................................................................. 11

4.0 Combustion and Emissions .......................................................................... 13 4.1 Introduction to Combustion ........................................................................ 13 4.2 Hydrocarbon Combustion........................................................................... 13 4.3 Introduction to Emissions ........................................................................... 15 4.4 Emission Calculation .................................................................................. 19

5.0 The Exhaust Gas Analysis Unit: VISIT 02S............................................... 22 5.1 VISIT 02S Capabilities ............................................................................... 22 5.2 Theory of Operation.................................................................................... 24 5.2.1 Electrochemical Sensor............................................................................ 24 5.2.2 Non-Dispersive Infrared Sensor .............................................................. 27 5.3 Rationale for the VISIT-02S? ..................................................................... 28

6.0 Setup............................................................................................................... 29 7.0 Procedure....................................................................................................... 32

7.1 Testing ........................................................................................................ 32 7.2 Data Analysis .............................................................................................. 35

8.0 Results and Discussion.................................................................................. 36 8.1 Carbon Dioxide Emissions ....................................................................... 37 8.1.1 Analysis ................................................................................................... 38 8.1.2 Discussion................................................................................................ 38

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8.2 Carbon Monoxide ..................................................................................... 40 8.2.1 Analysis ................................................................................................... 41 8.2.2 Discussion................................................................................................ 41 8.3 Nitrogen Oxides......................................................................................... 44 8.3.1 Analysis ................................................................................................... 45 8.3.2 Discussion................................................................................................ 45 8.4 Lambda ...................................................................................................... 48 8.4.1 Analysis ................................................................................................... 49 8.4.2 Discussion................................................................................................ 49 8.5 Fuel Usage.................................................................................................. 50 8.5.1 Analysis ................................................................................................... 51 8.5.2 Discussion................................................................................................ 51 8.6 Engine Speed ............................................................................................. 52 8.6.1 Analysis ................................................................................................... 53 8.6.2 Discussion................................................................................................ 53 8.7 Exhaust Temperature............................................................................... 54 8.7.1 Analysis ................................................................................................... 55 8.7.2 Discussion................................................................................................ 55 8.8 Efficiency ................................................................................................... 56 8.8.1 Analysis ................................................................................................... 57 8.8.2 Discussion................................................................................................ 57

9.0 Conclusion ..................................................................................................... 59 10.0 References.................................................................................................... 63 Appendix A.......................................................................................................... 66

Carbon Dioxide Calculations using the Combustion Chemical Equation........ 66 Appendix B .......................................................................................................... 70

B.1 Efficiency ................................................................................................... 70 B.2 Lambda....................................................................................................... 70 B.3 Losses ......................................................................................................... 71

Appendix C.......................................................................................................... 72 Appendix D.......................................................................................................... 74 Appendix E .......................................................................................................... 75

1

1.0 Introduction

In the developed world, the lack of space for growth and advancement has led

civilisation to advance upon the environment. The ecosystem has been and is

being disrupted by ongoing expansion and construction. Over time this has

resulted in pockets of natural reserves and conservation areas scattered around the

globe. In the German state of Nordrhein Westfalen, 18 million inhabitants occupy

the 34,000 square kilometres of land space and 180 million people live within

500km of its capital, Düsseldorf. This has placed immense pressure on the

environment. The 700km of waterways within the state provide a large source of

water, income and leisure. The need to provide low risk, clean and low profile

energy within these areas has led to a coolant and lubricant free, vegetable oil

fuelled turbine.

1.1 The Objectives

This paper reports one part, the emission analysis, of an ongoing, long term

project to determine the viability of rapeseed oil as a fuel in micro turbines. The

project is funded by the German government and directed by Nowum-Energy, a

research group operating within the guidance of Fachhochschule Aachen.

To successfully complete the project, it was divided into stages. The first stage

objective was to determine whether the turbine would start and operate on

rapeseed oil. After this was established, the following stages concerned with

efficiency, emissions and applications were to be studied.

It was during the first stage that these emission tests were done. The emission

tests serve to highlight any areas that may need more in-depth research or

investigation. The carbon dioxide, carbon monoxide and nitrous oxide emissions

were explored as well as the fuel to air ratio, exhaust temperature, engine speed,

2

fuel usage and overall efficiency. The results of these tests will be used to direct

the project with the intention of limiting costs and reducing the project duration.

1.2 Overview of Results

The Capstone C30 micro turbine was successfully tested with fuel containing

100% rapeseed oil. Apart from the addition of fuel line heating, no changes were

made to the turbine that was originally designed to run on diesel fuel. The

emission analysis, accomplished with a VISIT 02-S from Messtechnik, showed

that emissions of CO2, CO and NO increased markedly, albeit insufficiently to

rise above recommended limits. Other observed changes include a higher fuel

usage, lower exhaust temperature and higher overall efficiency.

1.3 Report Synopsis

The majority of previous work concerning rapeseed oil has concentrated on the

adaptation of fuel systems in automotive diesel engines to run on rapeseed oil, or

rapeseed oil based bio-diesel. Therefore, to provide a background for this report,

the fundamentals of turbines and rapeseed oil were investigated and are discussed

in the next chapter. The chapter following that is the theory of combustion,

emissions and exhaust gas analysis. After the project setup and testing procedures

are explained, the results and discussion chapter analyse and discuss each

parameter tested before moving on to the next parameter. Conclusions and

suggestions follow to complete the report.

1.4 Applications of the Technology

A power source that is compact, independent, low in emissions, environmentally

safe and efficient has a range of applications. Apart from use in protected, water-

based ecosystems, the technology could be applied to other regions. Isolated or

independent regions, like Antarctica, are regions where protection from toxic

3

liquid-spills and exhausts could see this technology applied. Hospitals, military

installations and isolated towns are other regions that may benefit from this

technology.

Another application is decentralised electricity production. By producing

electricity where it is needed, the inefficiency of electricity transmission and

distribution can be eliminated.

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2.0 The Micro Turbine

2.1 Turbine History

The operating principle of a turbine was first described in 1500AD by Leonardo

Da Vinci who envisaged turbines propelled by hot rising gases in a chimney

stack. It was after many years that the first turbine was created on modern

principles, by Franz Stolze, in 1872. The turbines that followed were evolutions

of that first turbine by Stolze, slowly increasing power output and efficiency

while reducing bulk and fuel usage.

In the modern era, the most common applications of turbines are in aircraft

propulsion and electricity generation. Aircraft type turbines are fundamentally the

same as electricity generating turbines, known as gas turbines. The main

differences arise from the fact that the two types of turbines have been developed

separately for completely different operating environments resulting in different

adaptations and designs. As a result, aircraft type turbine will not be further

discussed in this report. For further reading regarding jet turbines the reader

should pursue Aircraft Gas Turbine Engine Technology (1970) by Irwin Treager

or, if detailed theory is required, Gas Turbine Aero-Thermodynamics with Special

Reference to Aircraft Propulsion (1981), written by Sir Frank Whittle.

Since the main land-based application of turbines is in electricity production, the

size and power of gas turbines has grown to keep up with the ever increasing

demand for electricity, with modern units being able to develop in excess of

200MW. The continual demand for larger turbines has meant that research into

low-output, compact gas turbines was largely overlooked for a long period of

time. The existence of niche markets and experimentation however, has allowed

for development to persist. Currently there are numerous low power turbines

available for procurement.

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2.2 Delocalised Electricity Generation

Micro turbines are becoming more popular, especially in Germany, due to the

trend to produce power in a decentralised fashion. The trend towards localised

power production has been caused by many reasons including the realisation that

the congestion of modern transmission and distribution (T&D) electricity grids

has seen energy losses rise to 15% during peak usage times [4]. Other reasons for

the trend are that centralised power production is unable to match the efficiency

of combined heat and power plants (CHP) which can achieve up to 95%

efficiency, three times higher than conventional central generation [4]. CHP

achieves this efficiency by recycling waste heat; however the CHP must be

located near the thermal users. Thus, decentralised generation (DG) can operate

with high efficiency and avoids the losses of the T&D grid. The other advantage

of DG is that excess electricity can be transferred to neighbouring units when they

are under high load. This eliminates the waste associated with T&D grids and,

furthermore, the dynamic nature of smaller electricity generation plants allows

them to respond faster to peaks and troughs in the electricity demand. These

benefits and the inherent nature of renewable energy to be small scale; e.g. wind

power, solar panels; has meant that DG has become a common feature of

Germany and other developed European countries.

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2.3 Capstone C30 Micro Turbine Theory

One producer of micro turbines, Capstone, is an American company that currently

produces two models; a 30kW multi-fuel turbine and a 60kW high-pressure

natural gas turbine. The turbines offered by Capstone are similar to many other

turbines regarding their operation and thermodynamic cycle. A comparison of

available turbines is shown in Figure 2.1.

Manufacturer Capstone Cummins Ingersoll-Rand Elliott TurbecModel C30 GTAA 70L TA-100 T100Country USA USA USA Japan Sweden

Power Electrical kW 29 30 70 100 105Power Heat kW 85 - - 172 167Electrical Efficiency % 25% 26% 28% 29% 30%Heat Rate kJ/kWh 14,400 - 14,300 - -Exhaust Temp C 275 260 232 279 85*Exhaust Energy kJ/hr 327,000 305,000 - 619,000 601,000Weight kg 405 636 2,200 1,814 2,000

*Temperature after heat exchanger. Figure 2.1 - Currently available micro turbines and their specifications. [3, 6, 9,

11, 27]

The Capstone C30 turbine, the model chosen for this research, is unique due to its

lack of lubricant. The turbine is completely cooled by air and makes use of

Capstone patented air bearings to support the shaft, thus resulting in a lubricant

free turbine. Consequently, the turbine was chosen for its environmental safety in

regard to lubricant spills. Since the turbine operates in the absence of lubricants, it

has a few operation and the hardware differences from the other turbines

mentioned above. These include the lack of lubricant pumps, radiators and

lubricant filters.

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The cross section of the C30 micro turbine in Figure 2.2 shows the simple, all-in-

one design and single rotating shaft. Attached to the shaft is the compressor,

turbine and permanent magnet generator.

Figure 2.2 - Cross section of the Capstone C30 micro turbine. [3]

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The combustion process can be followed using Figure 2.3 below. Cold air, which

flows past the generator, is drawn in by the compressor. The air cools the

generator and is then compressed by the centrifugal compressor. The compressed

air, now at a pressure of 4 bar and temperature of 205°C, enters the recuperator

where it is heated by the exhaust gas. The air is heated to a temperature of 510°C

and enters the combustion chamber where it is mixed with fuel and ignited. The

turbine is used to expand the gas, which is now at 816°C, and this provides drive

for the generator and compressor. The burnt air is then passed through the

recuperator where its temperature is lowered from 590°C to 275°C as it

exchanges heat with the incoming unburnt air. The exhaust gas is then allowed to

escape to the atmosphere directly or used in a heat exchanger to further extract

energy for heating purposes. [3]

Figure 2.3 - The air flow within the C30 micro turbine. [3]

A power turbine employs the same basic cycle as the one mentioned above. The

major difference is that the process occurs at many different locations. The

pressures are also much higher and the power output can be factors of 1000 or

more higher than the micro turbine versions.

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3.0 Rapeseed Oil

3.1 Production of Rapeseed Oil

Rapeseed oil (RSO) is produced from the seed of rapeseed plants. Rapeseed

crops, part of the Brassica family, are grown all over the world in temperate

climates. Rapeseed is primarily grown for its oil and as meal for livestock. The

small, black, round seeds found in rapeseed plants are pressed to extract the oil.

World-wide production of rapeseed, in 2002/03, was 32 million metric tons with

the European Union and China producing about 10 million tons each. Germany,

achieving a yield of more than twice that of China, was the largest producer

within the EU. According to A. Czernichowski, M. Czernichowski and K.

Wesolowska [7], a seed yield of 3.3 tons per hectare is possible in Europe, which

would produce 1.35 tons of RSO. The global RSO production for 2002/03 was

12.8 million metric tons. RSO accounts for one third of vegetable oil produced in

Europe and represents are large and growing market.

Rapeseed oil is divided into two main categories; canola oil and industrial

rapeseed. The industrial variation has a different chemical composition (See

Section 3.2) and is used mainly in high-heat stability applications like greases and

lubricants and is not suitable for human consumption. Canola oil (canola and

rapeseed are interchangeable terms) is used in cooking and food processing and

can be used as a fuel in diesel engines with minimal modifications. The

esterification1 of RSO produces rape-methyl-ester, which is a direct substitute for

diesel. Canola oil is the most widely produced RSO and almost all rapeseed crops

grown in Europe are of this kind. Rapeseed production can be expected to grow as

more and more RSO is consumed.

1 Esterification is the process where methanol or ethanol is reacted, in the presence of a catalyst, with oil. The products are methyl ester or ethyl ester and the by-product is glycol.

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3.2 Chemical & Physical Properties

RSO is a mixture of many different fatty acids that occur naturally in rapeseed

seeds. The fatty acids include palmitic, linoleic, linolenic, oleic and erucic acid.

The percentage composition of these acids in RSO determines whether it is canola

oil or industrial rapeseed oil, also known as HEAR (High Erucic Acid Rapeseed).

Table 3.1 below shows the composition of canola oil and HEAR.

Fatty Acid Name Annotation Canola Oil HEAR

Arachidic Acid C20:0 1% 1%

Erucic Acid C22:1 Trace >45%

Linoleic Acid C18:2 21-23% 14%

Linolenic Acid C18:3 10% 9%

Oleic Acid C18:1 59-61% 15%

Palmitic Acid C16:0 4-5% 5-6%

Chemical Composition of Two RSO Varieties - Canola & HEAR

Table 3.1 - Chemical Composition of Canola oil and HEAR.2 [19]

The long fatty acid chain, erucic acid, according to Davies (1996) [8], gives

HEAR its characteristics that make it suitable for industrial lubricants.

The variability in the amount of these acids in canola oil makes it difficult to

accurately state its chemical formula. However, for the purpose of fundamental

calculations and equation writing, the average formula of C18.1H34.1O2 [7] was

used. The same dilemma is unearthed when trying to pinpoint the physical and

2 The notation C20:0 refers to a hydrocarbon chain of 20 carbon elements with zero double bonds, otherwise known as the saturated fatty acid, eicosanoic acid. Like wise C18:2 is a polyunsaturated fatty acid hydrocarbon with 18 carbon atoms with 2 double bonds.

11

chemical properties of canola oil. Some basic values are given below in Table 3.2

for canola oil with an erucic acid composition of less than 2%.

Density @ 20°C kg/m3 914 - 917Cetane Number 40 - 50Viscosity (Kinemtic @ 20°C) mm2/s 37Flash Point, Open Cup °C 275 - 290

Canola Oil Properties

Table 3.2 – Properties of canola oil. [13, 19]

The values in the above table need to be taken into consideration when attempting

to substitute Diesel for RSO. The next section will compare RSO and diesel.

3.3 Comparison to Diesel

Diesel is a hydrocarbon-based fuel that is extracted from crude oil. In the

distillation process, diesel fuel forms from hydrocarbons that have melting points

ranging between 250°C and 380°C [25]. These distillation temperatures are in the

range of the boiling points of C9 to C12 hydrocarbons. Therefore, like RSO,

diesel is a mixture of many different compounds. However, diesel fuel is refined

to ensure that a standardized quality product is produced. Table 3.3 shows some

properties of diesel fuel.

Density @ 20°C kg/m3 820 - 860Cetane Number 51Viscosity (Kinemtic @ 20°C) mm2/s 2.0 - 4.5Flash Point, Open Cup °C 55

Diesel Properties

Table 3.3 – Properties of diesel fuel. [25]

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Diesel can be directly substituted by bio-diesel, as mentioned earlier, however,

using the esterification method requires the further addition of energy to refine

natural oil into a bio-fuel. This additional energy can be avoided if the oil can be

used directly. This leads to further pollution control and increased efficiency by

decreasing the fuel’s cost of production.

One difference between RSO and diesel is particularly important in today’s aim

towards renewable energy. The known crude oil reserves of the world have been

estimated to be insufficient to fuel our industries for more than the next few

centuries at best. For this reason it has become important to find sources of fuel

that do not depend on the oil reserve. Renewable oil, such as rapeseed oil, is an oil

that may be a fuel for the future.

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4.0 Combustion and Emissions

4.1 Introduction to Combustion

Combustion is a phenomenon that can be easily accepted and understood in its

simple form. It is defined by Lissianski, Zamansky and Gardiner Jr. (2000) as a

fast chemical reaction in which a fuel combines with an oxidizer to form

combustion products. In most cases the oxidizer is oxygen from the air and the

fuel is most commonly a form of hydrocarbon. For combustion to occur, the

presence of heat or a source of ignition is vital to allow the reaction to take place.

The fuel must be heated beyond its flame point or ignition temperature to initiate

combustion. If these conditions prevail, combustion will continue. However the

study of the science of combustion is extensive and ongoing. It can be analysed

using chemistry, physics, heat transfer and fluid flow. In this section, combustion

will be looked at chemically, as a reaction, to depict the fundamental compounds

involved and their ratios in the burning of diesel and rapeseed oil in air. For

further information on combustion, there are a great number of books written in

the last 50 years available that deal with combustion exclusively and

comprehensibly.

4.2 Hydrocarbon Combustion

A chemical equation represents the transformation of reactants to products. In this

case, the reactants are air and fuel (diesel or rapeseed oil) and the products are the

exhaust gases, water (and heat).

( )HeatWater Emission Air Fuel ++→+

The micro turbine receives oxygen from the air. Air is a mixture of gases that

includes 78.07% nitrogen, 20.95% oxygen and 0.93% argon [12]. The remainder

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0.05% is comprised of carbon dioxide, hydrogen and other rare gases. To simplify

the task of writing equations, the content of air is assumed to be 79% nitrogen

(N2) and 21% oxygen (O2) and will be referred to as perfect air. In terms of moles,

this translates to 1 mol of O2 for every 3.76 mol of N2.

The combustion of a hydrocarbon like methane, CH4, in oxygen results in the

following equation.

O2H CO O2CH 2224 +→+

Diesel and rapeseed oil are also hydrocarbons composed of hydrogen and carbon

(rapeseed oil contains oxygen as well). Therefore a similar equation for each can

be written. The difficulty arises when one tries to define the exact chemical

formula. The chemical formula of rapeseed oil was shown earlier to be

C18.1H34.1O2. The chemical formula for diesel is more difficult to define due to the

variability in its composition. Current estimates stand at a mixture of C9 to C20

hydrocarbon chains that are 65% aliphatic and 35% aromatic. This was

interpreted as a chemical formula of C14.5H29.

Therefore the combustion of ‘clean’3 diesel in the presence of perfect air can be

represented as…

( ) 222222914.5 N78.81O14.5H 14.5CO N76.3O75.21HC ++→++ Eq.1

And the combustion of rapeseed oil in perfect air as…

( ) 222222.034.118.1 N35.96O17.05H 18.1CO N76.3O625.25OHC ++→++ Eq.2

3 In this case, clean diesel refers to diesel with no additives or impurities.

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In reality, such perfect reactions are not realised. There is, almost always, a

presence of excess air, the fuel is contaminated with sulphur based compounds

and other additives and the gases in the air may also react in the reaction, for

example nitrogen to form nitrous oxides (NOX). Further more, small amounts of

carbon leave the reaction in the form of carbon monoxide, an under-oxidised

carbon dioxide molecule. The excess air situation is necessary because the ideal

oxygen volume is not sufficient for complete combustion due to inadequate fuel

and oxygen mixing. By allowing extra oxygen to be present during combustion,

the fuel molecules have a greater chance of being completely oxidised and thus

burning entirely.

These considerations must be taken into account when attempting to predict

combustion emissions. Therefore the most reliable method to determine emission

composition is to measure it. These equations may serve to confirm the magnitude

of the results, to ensure that the figures are within the expected range and that all

elements are or can be accounted for.

4.3 Introduction to Emissions

The reactants of a combustion reaction are termed the emissions or exhaust gases.

Many exhaust gases are air pollutants, poisons or both. For this reason the

quantity and type of emissions must be minimised and must conform to

government regulations. Typical emissions include [12]:

• Nitrogen (N2)

Odourless, colourless, tasteless and harmless gas that acts as a medium for

heat transfer. Largely uninvolved in the combustion process.

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• Carbon Dioxide (CO2)

Odourless and colourless gas with a slightly sour taste. Produced in all

combustion processes and exist as 0.03% of the atmosphere. At concentrations

of 15% it causes immediate unconsciousness.

• Water Vapour

The hydrogen of the fuel is reacted with the oxygen to form water. Present as

humidity in high temperature exhaust gases.

• Oxygen (O2)

A portion of oxygen that is not consumed during combustion can be used to

assess efficiency, as a reference value or as a method to determine combustion

parameters.

• Carbon monoxide (CO)

Odourless, colourless, tasteless and toxic gas that is formed by incomplete

combustion of carbon-containing matter. CO is lethal and at concentrations

above 700ppm (0.07%) death occurs within hours. A widely recommended

safe workplace exposure concentration is between 30ppm and 50ppm [10, 18].

• Nitrous Oxides (NOX)

Existing as NO and NO2, these are both dangerous and toxic pollutants. NO2

contributes to ozone formation and is a lung poison. NO is formed when

nitrogen from the fuel reacts with oxygen (fuel NOX) or when the nitrogen

(nitrogen from the air) reacts with oxygen in the presence of high

temperatures (thermal NOX). The NO compound is later oxidised and forms

NO2. NOX can be removed from the exhaust by using catalytic converters.

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The source responsible for NO in exhaust gases is difficult to determine, since

there are four sources from which NO can develop [14]. These are:

1. Thermal NO

2. Nitrous Oxide Mechanism

3. Prompt NO

4. Fuel NO

Each one of these sources may be responsible for some of the several

molecules of NO that are produced per million particles of exhaust gas.

Therefore it is difficult to show conclusively that one mechanism is more

responsible than another. However, by understanding each mechanism, we

can draw conclusions on the relative influence of each.

Thermal NO is the term given to NO that is formed as a result of high

temperature reactions between Nitrogen and Oxygen in the air. At

temperatures in excess of 1850K, nitrogen gas molecules combine with

oxygen atoms to form NO. In fuel rich combustion, oxygen reacts

preferentially with fuel over NO. In fuel lean combustion, sufficient oxygen is

present to react with nitrogen and form NO. According to Snyder, Rosfjord,

McVey and Chiappetta [24], a 650K to 700K combustion temperature using

No 2 Fuel Oil will produce approximately 6 to 20 ppm of NO

Nitrous Oxide Mechanism is, according to Nicol, Malte, Lai, Marinov and

Pratt [16], initiated by the reaction

ON O N 22 =+

The N2O is then oxidized to NO.

NO NO O ON 2 +=+

Prompt NO is the result of a premature reaction of N2 with CH. This occurs

early in the flame region and is gradually transformed to NO through

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reactions involving HCN, CN and NCO. Prompt NO is independent of

pressure and usually occurs in lean premix combustion [5].

Fuel NO is produced when nitrogen-containing distillate fuels undergo

combustion. The nitrogen in fuel (as much as 1.8%) is oxidized to NO and the

reaction is more prominent at higher temperatures.

According to Nicol et al. [16], the proportion of each form of NO present is

dependant on the fuel/air ratio and the temperature of combustion. Little

information on liquid fuel turbine NO emissions exists and therefore these

proportions are widely unknown.

• Other gases (SO2, H2S, HC’s and Soot)

The sulphur compounds are both toxic and have pungent odours. H2S is

converted to SO2 in exhaust gases due to its high toxicity. SO2 contributes to

acid rain. Sulphur is added in low concentrations to diesel fuel.

• Unburnt hydrocarbons (HC’s) can pose heath hazards since some are a

known carcinogenic. Soot is the term given to the solid carbon particles of

unburnt liquid or solid fuel. These are also called particulate matter and pose

health risks due to there small size (around 10µm).

The German basis for pollution control and prevention is based on the law

amended in 1990 and 1994, Bundesimmisionsschutzgesetz (BimschG) (Federal

Emission Control Act). The BimschG is implemented according to the regulations

outlined in the BimschV (Federal Emission Control Regulation Order). The

Technische Anleitung Luft (TA Luft), (Technical Instruction Air), is the

regulation that supports authorities with the enforcement of the 4th ordinance of

the BimschV. The recommended emission values for turbines, according to these

laws, are shown in Table 4.1.

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CO2 %CO ppmNO2 ppmNO ppmNOX ppm

* Recommended NL No Limit

Maximum Allowable Gas Concentrations in Exhaust

from TurbinesGas

73NLNL40

7-8%*

Germany

Table 4.1 - The allowable concentrations of certain gases in the exhaust of a

turbine, according to German regulations. [28]

4.4 Emission Calculation

Each of the gases mentioned in 4.3 are formed during the combustion process.

Due to the difficulty associated with accurate combustion analysis, only carbon

dioxide will be analysed using chemical equations. The analysis below will omit

the calculations, however they can be found in Appendix A.

For diesel:

From equation 1, 14.5 moles of carbon dioxide are released for every mole of

diesel combusted. The number of moles of products produced during the reaction

is 110.78 moles when a lambda of 1 is observed (i.e. an ideal air/fuel ratio). This

corresponds to a total mass of 3190.9 grams. The percentage by mass of this

weight that is made up by CO2 is 20.0%, and by volume4, CO2 accounts for

13.1%.

4 The moles of a gas are related to the volume through Avogadro’s Law (equal volumes of gas contain equal numbers of particles) and the Ideal Gas Law (PV = nRT, the relationship between moles, temperature, pressure and volume).

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For combustion at lambda values other than 1, the following equation can be used

to determine the quantity of products.

( )( )

2222

222914.5

O 2

35.14275.21 N 78.81 OH 14.5 CO 14.5

N76.3O 75.21 HC×−×

+++

→++λλ

λ Eq1.1

For the purpose of demonstration, let us assume λ=8. At this air/fuel ratio, 835.49

moles, or when calculated in terms of mass, 24 103.10 grams of products are

formed. The percentage by mass of this weight that is made up by CO2 is 2.65%,

and by volume, CO2 accounts for 1.74%. These series of calculations can help

confirm the validity of the results obtained by the VISIT 02S. The equations lead

to the information in Table 4.2 that shows the theoretical CO2 emissions as a

percentage by volume for various values of lambda.

Rapeseed Oil Diesel

CO2 Vol % CO2 Vol %

8 1.84 1.749 1.63 1.5410 1.47 1.3911 1.34 1.2712 1.23 1.16

Lambda

Theoretical Carbon Dioxide Concentration of Exhaust Gas

Table 4.2 - The theoretical CO2 concentrations of exhaust gas from either diesel

or rapeseed oil fuelled micro-turbines at common values of lambda are shown

above.

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For rapeseed oil:

From equation 2 it is seen that 18.1 moles of carbon dioxide are released for every

mole of rapeseed oil reacted. Following the same reasoning as before the

following values result:

Number of moles of products produced: 131.5 moles

Mass of products: 3803.34 grams

Percentage CO2 by mass: 20.9%

Percentage CO2 by volume: 13.8%

For combustion at lambda values other than 1, the following equation can be used

to determine the quantity of products.

( )( ) ( )

2222

222.034.118.1

O2

05.1721.182225.625 N 6.359 OH 17.05 CO 18.1

N76.3O 625.25 OHC+×−+×

+++

→++λλ

λ

Eq.2.1

For the purpose of demonstration, let us once again assume λ=8. At this air/fuel

ratio, 985.33 moles, or when calculated in terms of mass, 28 441.59 grams, of

products are formed. The percentage by mass of this weight that is made up by

CO2 is 2.80%, and by volume, CO2 accounts for 1.84%. Table 3.1.4 above shows

the theoretical CO2 emissions as a percentage by volume for various values of

lambda.

22

5.0 The Exhaust Gas Analysis Unit: VISIT 02S

5.1 VISIT 02S Capabilities

The VISIT 02S System, produced by Messtechnik EHEIM GmbH, is a portable,

multi-function exhaust gas measuring unit that is suitable for continuous

measurement and calculation of exhaust gas constituents. The unit is designed to

be compatible with liquid, gas, solid or biomass fuels and is appropriate for

industrial applications. The VISIT 02S meets the highest quality and

environmental standards of Germany and Europe; these include the:

1. German Federal Pollution Protection Act5 (1. BimSchV), [28]

2. the Voluntary Control Council for Interference by Data Processing

Equipment and Electronic Office Machines (Council Directive

89/336/EEC),

3. the standards EN 50 081 Part 1, EN 50 082 Part 1 and

4. the TÜV (Technischer Überwachungsverein – Technical Control Board)

Bayern-RgG200.

This device is able to measure the gas concentrations in the exhaust gas, ambient

air temperature, exhaust gas temperature and absolute pressure. The VISIT is also

capable of calculating many values internally from the measured parameters.

These include Efficiency (η), Lambda (λ) and Exhaust Gas Losses (qA). Refer to

Table 5.1 below for the range and units of measurements and possible

calculations using the VISIT 02S.

The Eta (η)6 value refers to the efficiency of combustion, expressed as a

percentage. It is calculated as 100 percent minus ASME heat losses. To maintain

brevity, calculations have been omitted and can be found in Appendix B.1.

5 This standard states the limits of emissions allowable from a ‘Small Power Plant’. 6 Eta is the Greek symbol (η). It is usually used to represent efficiency in thermodynamics.

23

The Lambda (λ) value indicates the amount of excess air present during

combustion, using the ratio of total air to stoichiometric air. Otherwise known as

excess air, a λ-value greater than 1 refers to an excess of air in the combustion

mixture. Further information can be found in Appendix B.2.

The Losses refer to the exhaust gas heat losses, calculated using the Siegert

Formula (according to ASME) and expressed as a percentage. Once again refer to

Appendix B.3 for equations and calculation methods.

Table 5.1 - The functioning principle, range and accuracy of the VISIT’s sensors.

[2]

Lower Higher

Air Temp. NiCr-Ni (Type K) -30°C 300°C 0.1°C ± 1°C

Exhaust Temp. NiCr-Ni (Type K) -30°C 800°C 0.1°C ± 4°C @ 400°C

O2 Electrochemical 0% 21% 0.1% ± 0.2 %

CO Electrochemical 0 10,000 1 ppm ± 5 ppm

NO Electrochemical 0 4,000 1 ppm ± 5 ppm

SO2 Electrochemical 0 4,000 1 ppm ± 5 ppm

CO2 NDIR 0 250,000 100 ppm ± 5 %

HC (C3H8) NDIR 0 20,000 5 ppm ± 5 %

Pressure Silicon ?? -350hPa 350hPa 0.1hPa <± 2%

Efficiency (η) Calculated 0 100% - -

Lambda (λ) Calculated 0 9.99 (-) - -

Flue Losses (qA) Calculated 0 100% - -

NOX Calculated - - - -

NO2 Calculated - - - -

CO2 (%) Calculated - - - -

Messtechnik VISIT 02S Measurement & Calculation Details

AccuracyParameter Operating Principle

Range (ppm unless stated) Resolution

24

The calculated parameters are determined using fuel-specific constants stored

within the VISIT memory. The VISIT has internal settings for 14 different fuel

types, which need to be appropriately selected to ensure the VISIT accurately

calculates the efficiency, lambda, losses and CO2 values.

The measurement recording process involves an internal real-time clock and a

512kb RAM. The data measurements (up to 5000) can be stored within this

inbuilt memory. The highest frequency of measurements allowed by the processor

is 14 values performed once per second. The unit may be connected to a PC using

one of the two RS323 ports. Using this connection and the supplied WIN-Data

software, the measurements can be sent in real-time to the PC for continuos

measurement recording. Using this approach it is possible to record data for 24

hours or more.

5.2 Theory of Operation

The VISIT employs electrochemical, non-dispersive infrared, thermoelectric and

silicon semi-conductor measuring bridge sensors to measure the variables of

concentration, temperature and pressure. The theory behind the operation of the

two most important sensors, electrochemical and non-dispersive infrared sensors,

will be explained to better understand the limitations of these sensors and the

requirements for an accurate measurement.

5.2.1 Electrochemical Sensor

Electrochemical sensors measure gas concentrations by converting chemical

reactions rates to electrical signals [26]. All electrochemical sensors function on

the same basic principle and only the materials involved change. Therefore only

the carbon monoxide sensor will be explained in detail.

25

The sensor is composed of three electrodes which are immersed in an electrolyte,

usually a non-metallic liquid such as dissolved salts or acid. The three electrodes

are the working electrode (WE), the reference electrode (RE) and the counter

electrode (CE). The WE is made of platinum, which is a catalyst for the CO, O2

reaction, and is the most important electrode. It is backed by a gas-porous but

waterproof barrier that allows the CO gas to diffuse through to the electrode and

be oxidized according to Equation 1 below.

Eqn. 1 [26]

The electrons freed in the reaction flow from the work electrode to the signal

output node via the external circuit. Figure 5.2 shows a diagrammatic

representation of an electrochemical sensor. The RE provides a stable and

constant electrochemical potential difference in the electrolyte that is ensured by

shielding the electrode from gas, thus maintaining its thermodynamic potential.

This stable electrochemical potential difference assures that the WE maintains a

suitable thermodynamic potential, vital to ensure the oxidation reaction takes

place. To maintain the thermodynamic potential in the RE, no current is allowed

to flow through it. The CE fulfils the role of the second half cell and allows

electrons to flow in or out of the electrolyte. The sensor also employs a

chemically selective filter that removes interfering gases.

2e 2H CO OH CO 2

Platinum

2 ++⇒+ +

26

Figure 5.2 - The diagrammatic representation of an electrochemical

gas sensor and its circuit. [26]

The control circuit is called a potentiostat and it converts the current signal to a

voltage and maintains the potential of the WE. The operational amplifier (op-

amp) U2 is responsible for converting the current signal from the WE to a voltage

signal. The op-amp U1 ensures that the voltage between the RE and the WE is

constant by supplying a voltage to the CE that creates a current at the CE that is

equal and opposite to the WE.

This operational theory applies to all other electrochemical gas sensors installed

in the VISIT. Figure 5.3 shows the WE material that is used for each type of gas

to catalyse the reaction.

27

Gas CatalystNO2 Au

CO PtH2 Au

NO2 AuO2 Au, Ag, Pt

SO2 AuH2S Au

Figure 5.3 - The electrode material used in sensors

to catalyse the required reaction. [26]

5.2.2 Non-Dispersive Infrared Sensor

The non-dispersive infrared (NDIR) sensor uses light reflection and absorption to

measure gas molecule concentration. The amount of IR light absorbed is

proportional to the concentration. Each gas absorbs specific wavelengths of IR

light. These are representative of the type of bonds present. For CO2 gas, the

wavelength 4.26µm has the strongest absorption. The CO2 absorbance spectrum is

unique for hydrocarbons and thus is easy to identify in an exhaust plume. [20]

A NDIR sensor is designed as shown in Figure 5.4. The gas floats in from the top

and passes through the IR radiation from the lamp. The IR detectors have filters

that allow only light with a wavelength of 4.26µm to pass. By changing the filters,

it is possible to measure other hydrocarbons, like propane for example.

28

Figure 5.4 - The design of a NDIR sensor. [20]

5.3 Rationale for the VISIT-02S?

There are many other portable and fixed-location gas analysis instruments that are

available on the market. Many share features and capabilities with the VISIT

model. All have temperature and gas sensors; however the range and accuracy of

measurements may vary. This particular gas analyser was chosen because it is

capable of measuring the data that is of interest, to the accuracy that is required.

Since it was procured by Nowum-Energy for earlier work it was made available

for this project. The accuracy of the analyser is sufficient to ensure the success of

the testing since the variable composition of rapeseed oil means that the exact

Siegert values cannot be input to the VISIT to give accurate calculations of CO2,

NOX and NO2. Furthermore, the diesel/rapeseed oil ratio will be limited in

accuracy due to the current pumping arrangement. Therefore the exact

composition of the fuel and therefore the CO2max value will be difficult to

determine. To ensure, however, that the VISIT was working accurately, it was

calibrated and serviced before testing commenced.

29

6.0 Setup

The two main pieces of equipment that are required for the testing have been

already mentioned and analysed. These are the Capstone micro turbine and VISIT

02-S emission measuring device. However there is a vast array of other tools and

apparatus required to complete the tests. They can be divided into the three

groups: Turbine, Fuel System and Emission Recording.

1. Turbine: The Capstone C30 Micro turbine is the only piece of equipment

in this group. It includes the entire turbine package, the exhaust pipe and

control software as one unit.

2. Fuel System: This group contains all additions and modifications to the

fuel system to monitor and feed fuel into the turbine.

• 2 Storage tanks – One 1000L tank each for diesel and rapeseed oil

stored in the cool dry basement, directly beneath the turbine.

• 2 Feed Pumps – One pump for each fuel tank. The pumps feed fuel

to a premix heating chamber. The 0.55kW positive displacement

230V AC electric pumps sourced from Stimel GmbH have an inline

filter between the pump output and premix heating chamber.

• Premix heating chamber – A spherical, 60 litre, glass flask with

multiple outlets. Used to mix diesel and rapeseed to ensure a

homogeneous mixture and also the vessel where the fuel is preheated.

• Fuel Agitator – An electric agitator mounted on the premix heating

flask to agitate the fuel to produce a homogeneous mixture. The

agitator employs a pair of 2 vane propellers to stir the mixture.

• Flask Heater – A 3 phase heating element that surrounds the

bottom half of the premix chamber. Used to heat the fuel mixture to

ensure the viscosity is below the turbine fuel inlet maximum value.

30

• Fuel line heaters – The heaters are mounted on the fuel line

between the turbine injectors and premix chamber. This is to ensure

that the turbine fuel pump and injectors are supplied with liquid with a

suitable viscosity.

• Inline flow property measuring system – The Promass 83 from

Endress & Hauser GmbH is capable of reporting, in real time, the

viscosity, mass flow, volume flow temperature and density of the

incoming fuel. It is situated between the turbine fuel pump and premix

heating chamber.

3. Emission Recording: This group contains all the tools used in the

measuring and recording of the emission data.

• VISIT 02-S – The emission sensing and measuring device sourced

from Messtechnik GmbH. For further information refer to section 5.1.

• Win-Data Software – For real time emission data collection.

• 1GHz Pentium Computer – Storing and recording data.

Figure 6.1 shows the majority of the equipment described above. Figure 6.2 on

the following page gives a real world view of the test apparatus.

Figure 6.1 – An indication of the setup used to run the turbine tests.

31

Figure 6.2 - (clockwise from top left). The fuel heating, agitation and storage

setup. The filters, pumps and heaters are all visible. The exhaust pipe and exhaust

gas heated probe. The turbine and fuel tank, with the Promass 83 visible.

32

7.0 Procedure

7.1 Testing

The testing procedure begins with the mixing and heating of the fuel and

concludes with the final data interpretation. The procedure is explained as

follows.

• Fuel Preparation

1. The required amount of diesel and rapeseed oil was pumped from

each storage tank to the premix heating chamber to produce the

necessary fuel composition.

2. For mixtures containing more than 30% rapeseed oil, the premix

heating chamber must be heated and the fuel line heaters must be

activated until such time that the viscosity of the fuel, as shown on

the Promass 83, falls below 6cSt.

3. The fuel agitator was set to 200rpm for the last ten minutes before

the test commenced when the speed was reduced to 100rpm for the

duration of the test.

4. The fuel inlet valve on the fuel line leading into the turbine was

opened.

• Turbine Settings

1. A preliminary visual check was completed on the turbine prior to

commencement. This included ensuring fuel line integrity and

checking communication connections.

2. The turbine control software was loaded onto the computer and

settings were set to enable control and data recording of the

turbine.

3. The turbine clock was synchronized with the computer clock.

33

4. The data recording interval was set to 2 seconds and a new file was

created on the hour during the test. See Appendix C for an example

of parameters measured and data recorded.

• Preparing the VISIT 02S

1. The unheated probe, calibration line and temperature sensor were

all attached to their respective orifices on the VISIT.

2. The VISIT was taken outside to a source of fresh air and allowed

to self-calibrate.

3. On completion of calibration, it was brought back to the testing

location and the unheated probe was exchanged for the heated

probe and the calibration line was removed.

4. The communications and main-power connection were re-

established. The probe heater was turned on.

5. The recording software was loaded into the computer and setup

with a data recording interval of 2 seconds. The VISIT clock was

synchronized with the computer clock.

6. Sufficient time, approximately 10mins, was allowed for the probe

to become fully heated

• Initiating the Test

1. Before the test was commenced, atmospheric conditions were

recorded.

2. The turbine was set to 8kW and the data recording systems of both

the turbine and VISIT software were activated.

3. The turbine was started.

34

• Testing Procedure

1. All Promass sourced data was recorded in a spreadsheet as shown

in Appendix C.

2. The fluid properties were measured after the turbine reached a

steady state of operation, judged by when the exhaust temperature

was constant.

3. The power demand was then raised by 2kW and allowed to reach

steady state. The data was again recorded. This was continued until

maximum power output was reached.7

4. The density, viscosity, temperature, volume flow rate and mass

flow rate of the fuel was recorded, along with the time that power

demand was changed and the time that the demanded power was

attained.

5. On completion of testing the turbine was allowed to undertake

standard, automatic shutdown procedures. The data recording

systems were allowed to record data at least until the turbine

reached standby conditions.

6. All associated systems were shut down and the fuel line valve was

closed.

7 The Capstone C30 Micro turbine is capable of producing 30kW maximum power, however due to atmospheric conditions, was able to only produce 26kW for the first 4 tests, therefore this was used as the maximum output.

35

7.2 Data Analysis

The 3 sets of data (turbine, VISIT and Promass 83) were complied together into

one spreadsheet. This was completed by slowly reducing the amount of

information. The start-up and shutdown data was removed first, followed by the

unwanted parameter data recordings (e.g. date and customer ID). Finally,

everything except the last minute of data that was recorded before a power

demand change was removed. In essence, this isolated 60 second ‘packages’ of

data for power outputs from 8kW, in steps of 2kW, to the maximum power output

of 26kW. For each parameter recorded in the package, the average was

determined and used to produce the spreadsheet shown in Appendix C.

This spreadsheet was labelled the ‘One Minute Averages’ spreadsheet and these

values were used to provide comparisons between fuel types. The data is depicted

in the results graphically.

36

8.0 Results and Discussion

The results and discussion, usually presented as individual sections, have been

combined into one chapter. Due to the large quantity of data that will be presented

and discussed, it was concluded that the combination of these two chapters will

aid readability and assist in comprehension. Each section of results will be

followed by the relevant discussion and conclusion.

The testing method and setup allowed for a large number of parameters to be

monitored and recorded. This resulted in vast quantities of examinable data and

trends. The complete set of parameters was used to plot graphs. All graphs

showed the parameter in question plotted against the power demand, which ranges

from 8kW to 26kW, for a few different fuel types, usually D100, R30, R60 and

R1008.

Many parameters were excluded from this final report due to results that showed

no trends or little change and were considered to be of minor interest. These

include the inlet air temperature data (no change), oxygen concentration in

exhaust gas (no change), flue gas losses (opposite to flue gas efficiency), exhaust

static pressure (no change), turbine exit temperature (no change) and turbine

compressor inlet temperature (only related to ambient conditions).

Therefore the eight parameters that will be analysed and discussed further is the

carbon monoxide, carbon dioxide and nitrous oxides emissions, exhaust gas

temperature, lambda values, fuel usage, engine speed and overall efficiency.

8 The letter R refers to rapeseed oil and the number following refers to the percentage presence in the fuel. Therefore, R30 is a 30% rapeseed oil mixture and is equivalent to D70, a 70% diesel mixture.

37

Car

bon

Dio

xide

Em

issi

ons

1600

0

1700

0

1800

0

1900

0

2000

0

2100

0

2200

0

810

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W)

CO2 ppm

D10

0

R30

R60

R10

0

8.1 Carbon Dioxide Emissions

38

8.1.1 Analysis

The previous graph, showing carbon dioxide emissions, reveals many trends. The

quantity of carbon dioxide released during combustion increases as the power

demand of the turbine increased. The increase of emissions seems to abide by

linear growth; a linear line of best fit matches the measured points suitably. This

held true for all fuel types, however the rate of change increased as larger

percentages of rapeseed oil were present in the fuel. As power demand increased,

it was observed that proportionally more CO2 was measured. At 8kW, the

difference in emissions between D100 and R100 was 2.9%, however, at 26kW the

difference had increased to 9.1%.

8.1.2 Discussion

Carbon dioxide is the primary waste-product9 of combustion since hydrocarbons

contain large amounts of carbon. Rapeseed oil has a heating value10 that is more

than 11% lower than that of diesel [21]. Since the turbine must achieve a pre-set

power output, it draws larger quantities of fuel into the combustion chamber to

satisfy its energy requirements. As this occurs the increased numbers of carbon

atoms produce greater numbers of CO2 molecules. This may be one factor that

leads to higher CO2 emissions.

Another factor that may contribute to higher carbon dioxide emissions are the fuel

settings of the turbine and/or the fuel injectors. According to Capstone algorithms,

the fuel used can be represented by two variables. These variables differ for each

fuel type. Since the difference between the fuel variables for R100 and D100 was

of the order of 1%, the injectors seem to have played a larger role. Injectors are

designed with the fuel type in mind. If injectors are required to operate with fuel

9 Excluding water vapor as this is generally considered harmless and rarely of interest in exhaust gas. 10 The heat (energy) gained from combusting a specified amount of fuel.

39

that is other than the design fuel, it may cause problems in fuel atomisation, fuel

distribution and fuel-air mixing [17]. This may lead to inefficient combustion,

hot-spots inside the combustion chamber or incomplete combustion and therefore

result in increased CO2 emissions.

The increase of CO2 emissions can also be interpreted as a sign that the

combustion process is becoming less efficient. If greater quantities of carbon

dioxide are present in the exhaust gas, it suggests that more fuel is used to achieve

the required power output.

Carbon dioxide emissions increased to 21500 ppm, up approximately 10%, when

diesel fuel was substituted by rapeseed oil. It is however, still below

recommended emission figures (7%-8%) and accounts for approximately 2% of

the total exhaust contents.

40

Car

bon

Mon

oxid

e Em

issi

ons

051015202530354045

810

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er (k

W)

CO ppm

D10

0

R30

R60

R10

0

8.2 Carbon Monoxide

41

8.2.1 Analysis

The graph showing carbon monoxide emissions, on the previous page, shows that

CO emissions follow an exponential decay pattern. For an 8kW power demand,

CO emissions were approximately 40 ppm; however at 14kW they had decreased

5 fold to an average value of 8 ppm. At 18kW and above the CO concentration

had fallen to below 5 ppm (0.0005%). Rapeseed oil-fuelled emissions consistently

had a higher CO concentration than diesel emissions. At low power outputs, the

difference is approximately 10ppm, however, at high power outputs, the

difference falls to 3 ppm. Inspecting the figure in Appendix D, which is the

complete version of the graph on the previous page, it is clear that as power

increases, CO concentrations become more consistent between fuel types. At 8

kW, the range in CO concentration is more than 18 ppm11. At 26 kW, the range is

5 ppm with 5 fuel mixtures registering concentrations below 1 ppm.

8.2.2 Discussion

Considering the allowable safe occupational level of CO in Australia is 30 ppm

[18], these values are low. The area surrounding the turbine would be safe for

human presence and even if the turbine would be required to run at low power,

the exhaust system would ensure that dangerous gases do not collect in an

enclosed area.

CO is usually formed during fuel-rich combustion [14]. If the amount of fuel is

greater than what is required for complete combustion, the shortage of oxygen

will result in large quantities of CO. Since oxygen content in the exhaust gas was

high, a lack of oxygen cannot be the cause of CO forming.

11 The results for the R40 test were ignored. The results were irregular and probably caused by to the 3 week break in testing.

42

However, even in fuel-lean combustion, CO is present. This may occur due to

dissociation. At high temperatures, around 1800K, combustion products like CO2

may dissociate into less complex molecules and radicals like CO [14]. Within the

combustion chamber temperatures of 1100K are readily achieved but higher

temperatures may be present at hot-spots or other isolated regions. Even if 1800K

is not reached, there may be dissociation present, though at low levels. Therefore,

CO2 may dissociate into CO. This does not however explain the lower CO levels

at higher power outputs and higher temperatures.

The majority of CO is formed, according to the equilibrium theory, due to

incomplete combustion caused by [14]:

1. Inadequate burning rates due to low fuel/air ratios or insufficient residence

time.

2. Inadequate mixing of fuel and air, resulting in over-rich combustion that

yields high local CO concentrations.

3. Quenching of the flame through contact with the air-cooled combustion

wall.

These factors may explain the trends that appear in the CO emissions. Insufficient

residence time (the duration of fuel presence in the combustion chamber before

combustion) may lead to insufficient combustion and cause CO emissions. The

next two factors, inadequate mixing and quenching, are suspected to be the main

factors.

The injectors are directly responsible for mixing the fuel and air mixture before it

enters the combustion chamber. Due to a design that does not have rapeseed oil in

mind, fuel atomisation may not occur as planned and result in a larger mean drop

size. This reduces the volume available for combustion since more volume is used

for fuel evaporation. This may lead to a CO rise.

Quenching of the flame can result when combustion reactions in the primary

combustion zone migrate towards the combustion walls. The temperature there

43

was low and the CO may have became entrained in the wall cooling air. This

effectively froze the reactions and prevented CO to further oxidise to CO2. Unless

the CO is reintroduced to the central core, the CO will appear in the exhaust gas.

CO emissions become more regular as turbine power increases and hence it can

be concluded that, as the turbine temperature and fuel flow increases, the

conditions in the combustion chamber are less favourable for CO creation. This

may be due to better fuel mixing as a result of higher injection and fuel flow

pressures and/or more turbulence due to higher turbine speeds that better agitates

the combustion chamber and reduces the effect of wall quenching.

CO emissions are difficult to predict and are almost always higher than what is

predicted in equilibrium theory. However the trend of lower emissions as power

and temperature rises is predicted by equilibrium calculations.

The use of rapeseed oil led to larger quantities of CO present in the exhaust gas

than diesel. Apart from the greater number of fuel molecules, and thus carbon

atoms, present to make the same amount of power as diesel fuel, the increased CO

emissions may be attributed to the fuels lower flame and smoke points. This

results in a fuel that is more difficult to combust and thus can cause inefficient

combustion. These conditions would lead directly to greater CO concentrations.

Rapeseed oil, however, does not increase the CO emissions to a level that would

make it unsuitable for widespread use. Apart from low power outputs, below

8kW, the exhaust would be safe enough to release to the environment. If further

cleaning is required, OH or H2O, in low temperature situations, can be added

downstream to oxidise the CO to CO2 [14].

44

Nitr

ous

Oxi

de E

mis

sion

s

024681012

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D10

0R

30R

60R

100

8.3 Nitrogen Oxides

45

8.3.1 Analysis

The graph shows the NOx concentrations and since the concentration of NO2 was

0 ppm for all tests, the NOx values are equal to the NO concentrations and shall be

referred to NO from here on. At power outputs less than or equal to 14kW, there

were only slight differences in the NO concentrations. At high power outputs, the

range of NO increased greatly. The emissions rose further as greater quantities of

rapeseed oil were used in the fuel. At 26kW, diesel fuel resulted in a NO

concentration of more than 50% lower than that of rapeseed oil fuel. The largest

concentration of NO recorded was 13ppm, using R100 fuel, at 26kW. After

inspecting the graph in Appendix E, the NO emissions of fuels R70 to R100 were

much greater than the emissions of fuel R60 and below. This was especially

evident in the 8kW to 24kW power range, where operating on D100 to R60 fuel,

resulted in a range of only 1 ppm of NO between the fuel types. Fuels R80, R90

and R100 resulted in NO levels that were much higher than R60 fuels at 16kW

and above.

8.3.2 Discussion

NO can be formed by 4 different methods, as explained previously. For

simplicity, assuming that one type of NO dominates over the others, through

elimination, it could be possible to determine the dominant form. The combustion

conditions in the combustion chamber are composed of 1100K gas temperature,

high gas pressure and an extremely lean mixture. The lambda values show that the

equivalence ratio was around 0.1. This means that there was 10 times more air

than required. The temperature was too low to suggest that thermal NO was the

dominate form, since it occurs most commonly at temperatures of 1850K and

higher. Apart from hotspots and isolated regions, the chamber temperature was

800K lower. Fuel NO was a possible type of NO since organic materials and

diesel both contain small amounts of nitrogen. However, the exact level is

difficult to show without chemical analysis. Fuel NO can represent a large

46

proportion of total NO, especially in liquid fuels [15]. Prompt NO and Nitrous

Oxide Mechanism NO is complex to judge and since no data was available

regarding liquid fuel turbines, it was assumed that they had no effect on the NO

emissions. Considering the conditions and fuel, the fuel NO seemed to represent

the largest proportion of NO in the exhaust. This was further supported by the

mean drop size observations by Rink and Lefebvre [10, 17].

The gradual increase of NO levels as rapeseed oil concentrations rose can be

accredited to the injector design and therefore the mean drop size. According to

Rink et al., the NO emissions in a continuos flow combustor increased when the

mean drop size was increased, especially at low equivalence ratios. This effect is

due to the envelope flame phenomenon. Large droplets of fuel tend to burn in

diffusion mode and form a surrounding layer of flames around the drop. These

regions produce stoichiometric conditions and result in high temperature, high

NO yield zones. This may be the defining cause for NO emissions when running

on rapeseed oil. The fuel drop size would increase as the fuel becomes more

viscous and would thus lead to increased NO emissions.

The similar results for D100 through to R60 fuels was an unexpected result,

especially since the next 4 fuel mixtures (R70-R100) increased so dramatically. A

possible explanation may be that the mean drop size was altered suddenly. The

addition of 10% more rapeseed oil does not necessarily lead to a 10% increase in

viscosity. Another explanation is that, after the R60 test, the fuel line heaters and

the fuel tank heater were used to increase the fuel temperature. This may have

upset the chemical nature of the fuel mixture.

In terms of safety, NO regulations and legislation tends to be complex due to

varying laws between countries and supplements imposed by site-specific boards,

local councils or state governments. The lowest enforceable NO limit is 80 ppm

for turbines developing between 700kW and 7000kW. For turbines below this

47

power output, no legislation exists [14]. At a maximum of 13 ppm, using R100,

the NO concentration is still 6 times lower than the recommended level for much

larger turbines. Generally, the NO emissions are low and safe.

48

Lam

bda

8.00

8.50

9.00

9.50

10.0

0

10.5

0

11.0

0

11.5

0

12.0

0

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Lambda

D10

0

R30

R60

R10

0

8.4 Lambda

49

8.4.1 Analysis

An inverse relationship between Lambda and power was observed and as the

rapeseed oil concentration rose, lambda decreased. The difference between

lambda values over the range of fuels remained approximately constant. Lambda

values from 11.6 to 8.2 were recorded which represents an equivalence ratio of

0.086 to 0.122 respectively.

8.4.2 Discussion

As power increased, the amount of excess air available was reduced. This

observation agrees with expectations, where more power will lead to more fuel

and thus produce a richer combustion mixture. It is suspected that the air volume

would increase, the engine speed rise would lead to higher intake pressures and

flow rates; however, since the lambda value was reduced, it is concluded that

proportionally more fuel was added to the combustion chamber.

For accuracy, and validity, the VISIT-calculated lambda values can be checked by

referring to the calculations in Chapter 4. The predicted CO2 concentrations for

certain lambda values are shown and correspond closely to the measured values.

These can only be taken as a guide since the chemical compositions of each fuel

is based on averages and is variable from batch to batch.

Further analysis of the lambda values would require intensive combustion

chemistry and the measurement of many more parameters. The results analysed

show no unexplained or unpredicted behaviour and agree with Capstone supplied

specifications.

50

Turb

ine

Fuel

Usa

ge

3456789101112

810

1214

1618

2022

2426

Pow

er (k

W)

Fuel Flow (kg/hr)

D10

0

R30

R60

R10

0

8.5 Fuel Usage

51

8.5.1 Analysis

The fuel mass flow increased in a linear fashion as power was increased. The

addition of rapeseed oil to the fuel led to a left shift of the fuel flow curve,

meaning that fuel usage increased as more rapeseed oil was used. Additionally,

the fuel usage at high power demands showed a larger range over the different

fuel types than low-power-demand fuel usage. This is represented by the

increasing gradient difference. At its lowest, fuel usage was 4kg/hr for D100 at

8kW, 33% lower than RSO at the same power. The highest fuel usage was

11.5kg/hr for R100 at 26kW, representing a 25% increase over diesel fuel.

8.5.2 Discussion

As larger power outputs were demanded, the fuel flow rate increased, as expected.

The higher flow rate of rapeseed oil fuel is due to its lower heating value. The

11% lower heating value relates to an approximate 25% increase in fuel usage.

This may be reduced with the addition of ethanol to the mixture or other

chemicals that may improve the heating value and viscosity. Furthermore, fuel

efficiency may be improved by modifying the fuel system. This may include

changes to the fuel pump, filter, injectors and lines.

The increased fuel usage when running on rapeseed is something that would need

to be weighed up against the environmental benefits in terms of site protection,

not just fuel costs per hour of operation per se. Additionally, the life cycle

emissions would need to be considered.

52

Turb

ine

Spee

d

65707580859095100

810

1214

1618

2022

2426

Pow

er (k

W)

Speed ( '000 rpm)

D10

0

R30

R60

R10

0

8.6 Engine Speed

53

8.6.1 Analysis

The engine speed decreased by 2% when rapeseed oil was used. The speed curve

for all fuel mixtures followed the form of the D100 curve extremely closely and

did not deviate.

8.6.2 Discussion

The relative stability of the engine speed is based on the fact that the micro

turbine uses a preset engine speed and turbine exit temperature to achieve the

desired power output. The turbine exit temperature was unchanged and thus the

engine speed changes were necessary to achieve the desired power output.

The engine speed can be assumed to be independent of the fuel type and turbine

operating conditions. The measurements were taken to see what change to the

service life could be achieved through using rapeseed oil. A 2% reduction in

engine speed would represent negligible increases in service life, and in this case,

the effect of the rapeseed oil on the turbine blades and injectors would be of much

higher relevance for making comments regarding the life of the turbine.

For further comments regarding turbine life, the turbine impeller and stator would

need to be removed and analysed for wear on the blades. This would provide a

better estimate for turbine wear.

54

Exha

ust G

as T

empe

ratu

re

200

210

220

230

240

250

260

270

280

810

1214

1618

2022

2426

Pow

er (k

W)

Temperature °C

D10

0

R30

R60

R10

0

8.7 Exhaust Temperature

55

8.7.1 Analysis

A reduction in exhaust temperature was seen as larger proportions of rapeseed oil

were used in the fuel. The reduction was as high as 7K for 26kW power outputs.

8.7.2 Discussion

The exhaust temperature is a function of many variables. This would include the

volume and pressure of the exhaust gas, the exhaust gas flow rate and the ambient

air conditions. As the turbine speed decreased, the volume of air flowing through

the exhaust would have been lower. This may have resulted in a lower exhaust

mass to transport the temperature and thus the gases would cool faster.

The lower engine speeds also result in a reduced gas flow rate. The reduced flow

rate of gas through the exhaust pipe would increase the potential for heat

exchange with the surroundings and this may have led to the observed reduction

of exhaust temperature.

The ambient air temperature around the exhaust surface could also change the

exhaust temperature; however the large diameter of the exhaust pipe and similar

ambient conditions suggests that this was not a factor in the reduction of exhaust

gas temperature.

The reason for the decrease in exhaust gas temperature between fuel types could

be accredited to the lower heating value of RSO. This would have resulted in less

energy available to heat the exhaust gas. This theory could be supported by the

efficiency increase. A larger proportion of the fuel’s energy is used to produce

mechanical energy, thus the exhaust temperature was lower.

56

Turb

ine

Effic

ienc

y

2526272829303132333435

810

1214

1618

2022

2426

Pow

er (k

W)

Efficiency %

D10

0R

30R

60R

100

8.8 Efficiency

57

8.8.1 Analysis

On average, the usage of rapeseed oil in the fuel increased the efficiency of the

turbine. It must be remembered that the efficiency in this case is a representation

of proportion of the total energy value of the fuel that is converted to power, by

measuring the amount of energy, present as heat, in the exhaust gas. The

efficiency increased from 29% using D100 to 32% using R100.

The other interesting observation that can be made is that the efficiency tends to

peak and pit at similar power outputs for all fuel types. The efficiency increased

from 8kW to 14kW where there was a peak. Another peak in efficiency was

present at the 20kW mark. At 26kW, the efficiency was climbing for all fuel

mixtures. The power outputs that shared pits include the 16-18kW range and the

22-24kW range.

8.8.2 Discussion

The higher efficiency achieved by using rapeseed oil was not expected. The lower

heating value, the fuel flow rate increases and the emission increases all point to a

lower efficiency. The efficiency was calculated using Siegert constants that

represent the burning characteristics of a fuel and are derived from laboratory

tests. The Siegert values for rapeseed were was unavailable, however the

constants that correspond to light fuel oil were used for all tests. This may have

led to errors in the efficiency calculations that are performed by the VISIT and

these errors may have become increasingly large as more rapeseed oil was used.

The efficiency was relatively good and corresponds to the expected electrical

efficiency of a micro turbine as shown in Chapter 2.3. The claimed efficiency by

most micro turbine manufactures was between 25% and 30%. This was matched

and exceed in these tests. The accuracy of these figures, however, would need to

58

be ascertained by at least determining the correct Siegert values and implementing

them into the VISIT calculation algorithms.

The peaks and pits of the efficiency curves may show the ‘sweet-spots’ for

operation. All machines have running characteristics which allow optimum

operation. These may be dependent on temperature, engine speed, fuel

temperature, ambient temperature and load, along with many other factors. It may

be concluded that at conditions where peaks are evident, the turbine is operating

in one of its so called ‘sweet-spots’. Since a large range of variables could be

accountable for this ‘sweet-spot’, it would be difficult to confidently proclaim

which parameter, or group of parameters, is responsible. Judging by the results,

the fuel type is independent of the efficiency peaks and pits.

59

9.0 Conclusion

The analysis of emissions from a Capstone micro turbine operating on rapeseed

oil has shown that, compared to diesel fuel:

• CO2 emissions increased by approximately 10%

• CO emissions increased by approximately 5 to 18 ppm

• NO emissions increased by as much as 50%

• Fuel to air ratio remained largely unchanged

• Fuel usage increased by up to 33%

• Engine speed showed negligible decreases

• Gas exhaust temperature also showed negligible decreases

• Efficiency increased from 29% to 33%

Although all 3 major emissions increased when running on rapeseed oil, the

absolute value of each is within the recommended limits for turbines of much

greater size and should pose no excessive danger to the environment, ecosystem

and human population.

The purpose of the tests was to gain an understanding of the behaviour of the

turbine when operating on fuel it was not specifically designed to operate on. The

results should not be interpreted as anything other than a baseline from which to

start improvements.

The complex nature of combustion makes it difficult to pinpoint reasons or

explanations for the results attained, however, the following points offer possible

causes.

60

• Increasing fuel drop size as a result of injectors not designed specifically

for rapeseed oil and/or increasing fuel viscosity, leading to increased CO2,

CO and NO emissions

• Inadequate turbulence in the combustion chamber leading to wall-

quenching and increased CO production.

• Worse fuel characteristics, including lower heating values, flame points

and viscosity.

• Incorrect calculation of Siegert values and fuel variables for use in VISIT

and Capstone software.

The results may be improved by addressing these possible causes and

incorporating solutions that may improve them. However, it might prove more

efficient to further investigate each result in isolation to determine specific

reasons and thus make changes which may be more appropriate. Some

suggestions include:

1. Independent tests of the injector to establish fuel drop size for different

fuel mixtures at various pressures and temperatures. This would help in

establishing the influence of injector design on mean drop size and

whether controlling the viscosity of the fuel is sufficient to control the

drop-size.

Alternatively, injectors designed for higher viscosity fuels may be tested

to see the effect on drop size. The results would influence a majority of the

tested parameters.

2. Measuring the combustion chamber temperature to determine temperature

distribution within the chamber would help in concluding the causes for

CO and NO emissions.

3. Alternatively, CO sensors could be mounted along the length of the

exhaust pipe to monitor the change of CO levels, thus indicating whether

diffusion of CO2 to CO is a cause of CO emissions.

61

4. To further establish the cause of NO emissions, NO sensors along the

length of the pipe would indicate whether Prompt NO or Nitrous

Mechanism NO is formed after combustion.

5. Chemical analysis of the fuel is one simple method of determining the

possibility of Fuel NO and confirming the efficiency. The nitrogen content

and Siegert values of rapeseed oil and diesel could be established.

6. Repeating the tests multiple times would confirm that results were

accurate. The R40 test, for example, was highly irregular with NO and CO

levels several times higher than expected.

7. Turbine inspections to determine the effects of rapeseed oil on the life of

the turbine.

Several other factors may be improved to provide better results in future tests.

One factor which is fundamental in these tests is the fuel composition. The fuel

tank was filled by hand using a 1 litre measuring beaker. The addition of 25 litres

of fuel in 1 litre increments proved to be a source of human error. The fuel tank

should be drained after each test and a larger (5L) beaker would have reduced the

errors in measurement. For this reason, the percentage of rapeseed oil in the fuel

is estimated and not to be assume 100% accurate.

Many of the above solutions and improvements are feasible. The deciding factor

for the testing accuracy was in all cases a lack of sufficient funding. The long

term project is being completed in steps and currently the project is in its

beginning days.

The results provide a strong belief that the emissions and fuel efficiency may be

improved to levels that will be lower than diesel fuel. If these improvements can

be realised, the large scale utilization of rapeseed oil in micro turbines has a

strong and successful future. However, even if improvements can not be achieved,

the application of these machines to environmentally protected areas, especially

62

waterways, has a future. The zero possibility of non-biodegradable fluid spill and

low emissions ensure that damage to the ecosystem, even under fault conditions,

is extremely limited.

Rapeseed oil and micro turbines provide a strong combination for low pollution

and high environmentally friendly energy and heat production.

63

10.0 References

1. Analytical Specialties, Electrochemical (Trace Oxygen) - Trace O2

Theory,

http://www.analyzer.com/theory/documents/Oxygen%20Analysis/Electroc

hemical%20(Trace%20Oxygen).aspx, Accessed 14 June 2004.

2. Booklet, 2003, The Guide to the VISIT 02-S, Messtechnik GmbH,

Germany.

3. Capstone Turbines, www.capstoneturbine.com/technology/techdownload,

Accessed 22 May 2004.

4. Casten, Thomas R., Collins, Martin J., 2002, Optimizing Future Heat and

Power Generation, www.primaryenergy.com/articles/reports, Accessed 18

May 2004.

5. Correa, S. M., 1991, Lean Premixed Combustion for Gas Turbines:

Review and Required Research, Fossil Fuel Combustion ASME, Vol. 33.

6. Cummins Northwest, www.cumminsnorthwest.com/powergen, Accessed

22 May 2004.

7. Czernichowski, A., Czernichowski, M., Wesolowska, K., 2003, Glidarc-

Assisted Production of Synthesis Gas from Rapeseed Oil,

www.waterstof.org/20030805EHECP1-66.pdf, Accessed 11 May 2004.

8. Davies, H. M., 1996, Engineering new Oil Seed Crops from Rapeseed,

www.hort.purdue.edu/newcorp/proceedings1996, 31 August 2004.

9. Elliot Micro Turbines, www.elliottmicroturbines.com/files/ta_100_r2.pdf,

Accessed 22 May 2004.

10. Gislason, S., 2004, The Book of Breathing,

www.nutramed.com/environment/monoxide.htm, Accessed 13 September

2004.

11. Ingersoll-Rand Energy Systems,

www.irpowerworks.com/product_mt_70l.htm, Accessed 22 May 2004.

64

12. Jecht, U., Bürssner, R., Flue Gas Analysis in Industry-Practical Guide for

Emission and Process Measurements, Testo AG, Germany.

13. Journey to Forever, Oil Yields and Characteristics,

http://journeytoforever.org/biodiesel_yield2.html, Accessed 5 May 2004.

14. Lefebvre, Arthur H., 1999, Gas Turbine Combustion, Second Edition,

Taylor and Francis, London.

15. Merryman, E. L., Levy, A., 1975, Nitric Oxide Formation in Flames: Role

of NO2 and Fuel Nitrogen, pp. 1073-1083, Fifteenth Symposium on

Combustion, The Combustion Institute, Pittsburgh.

16. Nicol, D., Malte, P. C., Lai, J., Marinov, N. N., Pratt, D. T., 1992, NOx

Sensitivities for Gas Turbine Engines Operated on Lean Premixed

Combustion and Conventional Diffusion Flames, ASME Paper 92-GT-

115.

17. Personal Conversation with Prof. Dielmann, Lecturer at Fachhochschule

Aachen, 22 September 2004.

18. Prevention of CO Poisoning from Petrol and Gas Powered Equipment,

www.safetyline.wa.gov.au/pagebin/guidwswa0069.pdf, Accessed 13

September 2004.

19. Przybylski, R., 2000, Canola Oil Physical and Chemical Properties,

www.canola-council.org/pubs.Chemical1-6.pdf, Accessed 5 May 2004.

20. RAE Systems, Theory and Operation of NDIR Sensors,

www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-

169_NDIR_CO2 _Theory. PDF, Accessed 14 June 2004.

21. Rauber, M., 2004, Practical course of the lesson Energy Technology,

Technische Universität München.

22. Rink, K. K., Lefebvre, A. H., 1989, Influence on Fuel Drop Size and

Combustor Operating Conditions on Pollutant Emissions, International

Journal of Turbo and Jet Engines, Vol. 6 pp. 113-122.

65

23. Rink, K. K., Lefebvre, A. H., 1989, The Influence of Fuel Composition

and Spray Characteristics on Nitric Oxide Formation, Combustion

Science and Technology, Vol. 68. pp. 1-14.

24. Snyder, T. S., Rosfjord, T. J., McVey, J. B., Chiappetta, L. M., 1994,

Comparison of Liquid Fuel/Air Mixing and NOx Emissions for a

Tangential Entry Nozzle, ASME 94-GT-283.

25. TDI Club, Recommended Guideline on Diesel Fuel,

www.tdiclub.com/articles/Diesel_Fuel_Guidelines, Accessed 7 June 2004.

26. TSI Incorporated, The Theory behind Electrochemical Sensors,

http://www.tsi.com/combustion/app_note/ti-132.htm, Accessed 14 June

2004.

27. Turbec, www.turbec.com/products/t100chp.htm, Accessed 22 May 2004.

28. Umwelt-Online, Regelungen im Immissionsschutz, www.umwelt-

online.de/recht/luft/ueber_lu.htm, Accessed 7 July 2004.

66

Appendix A

Carbon Dioxide Calculations using the Combustion Chemical Equation

The basic chemical equation that predicts the combustion of hydrocarbons in air is

shown below.

( ) 22222yx N76.34yxOH

2y xCO N76.3O

4yxHC

×

+++→+

++

Applying this to Diesel fuel (C14.5H29) gives,

( ) 222222914.5 N78.81O14.5H 14.5CO N76.3O75.21HC ++→++

CO2 = 14.5 mol

H2O = 14.5 mol

N2 = 81.78 mol

Total Products = 110.78 mol

Molar Mass of CO2 = 44.01 g/mol

Molar Mass of H2O = 18.02 g/mol

Molar Mass of N2 = 28.02 g/mol

Total Mass of Products = 14.5x44.01 + 14.5x18.02 + 81.78 x 28.02 = 3190.2 g

Percentage of CO2:

By Mass = %0.20%1002.3190

01.445.14=×

×

By Volume = %1.13%10078.1105.14

=×

67

This is true for all combustion where all the available oxygen is consumed in

combustion. In reality this is rarely the case and introducing lambda (λ) into the

equation compensates for the presence of this excess air.

( )( )

2222

222914.5

O 2

35.14275.21 N 78.81 OH 14.5 CO 14.5

N76.3O 75.21 HC×−×

+++

→++λλ

λ

Using λ = 8;

CO2 = 14.5 mol

H2O = 14.5 mol

N2 = 654.24 mol

O2 = 152.25 mol

Total Products = 835.49 mol

Molar Mass of CO2 = 44.01 g/mol

Molar Mass of H2O = 18.02 g/mol

Molar Mass of N2 = 28.02 g/mol

Molar Mass of O2 = 32.00 g/mol

Total Mass of Products =

g24.2410325.15200.3224.65402.285.1402.185.1401.44 =×+×+×+×

Percentage of CO2:

By Mass = %65.2%10024.2410301.445.14

=××

By Volume = %74.1%10049.8355.14

=×

68

For Rapeseed oil (C18.1H34.1O2);

( ) 222222.034.118.1 N35.96O17.05H 18.1CO N76.3O625.25OHC ++→++

CO2 = 18.1 mol

H2O = 17.05 mol

N2 = 96.35 mol

Total Products = 131.5 mol

Molar Mass of CO2 = 44.01 g/mol

Molar Mass of H2O = 18.02 g/mol

Molar Mass of N2 = 28.02 g/mol

Total Mass of Products = 18.1x44.01 + 17.05x18.02 + 96.35 x 28.02 =

3803.34 g

Percentage of CO2:

By Mass = %9.20%10034.3803

01.441.18=×

×

By Volume = %8.13%1005.1311.18

=×

69

Introducing lambda (λ) into the equation to compensate for the presence of excess

air.

( )( ) ( )

2222

222.034.118.1

O2

05.1721.182225.625 N 6.359 OH 17.05 CO 18.1

N76.3O 625.25 OHC+×−+×

+++

→++λλ

λ

Using λ = 8;

CO2 = 18.1 mol

H2O = 17.05 mol

N2 = 770.8 mol

O2 = 179.38 mol

Total Products = 985.33 mol

Molar Mass of CO2 = 44.01 g/mol

Molar Mass of H2O = 18.02 g/mol

Molar Mass of N2 = 28.02 g/mol

Molar Mass of O2 = 32.00 g/mol

Total Mass of Products =

g59.2844138.17900.3280.77002.2805.1702.181.1801.44 =×+×+×+×

Percentage of CO2

By Mass = %80.2%10059.2844101.441.18

=××

By Volume = %84.1%10033.9851.18

=×

70

Appendix B

B.1 Efficiency

The following is the equation that is used to arrive at the efficiency. See B.3 for

further details.

( )

( )

+

−×−−=

−=

BO

AATFTEta

qALossesEta

2212100

100

B.2 Lambda

Lambda represents the ratio of fuel to air in a form that makes it understandable.

Simply claiming that the air to fuel ratio is, for example, 10 does not clarify

whether the combustion is lean, rich or stoichiometric. Lambda compares the

actual ratio to the stoichiometric ratio and expresses it as a number.

λφ 1

===AFAF

FAFA S

S

Where FA is the Fuel to Air ratio, FAS is the stoichiometric fuel air ratio, AF is

the air to fuel ratio, AFS is the stoichiometric air to fuel ratio and φ is the

equivalence ratio. The equivalence ratio is the inverse of lambda and is favoured

among the American culture.

71

B.3 Losses

The energy loss is based on the difference in heat capacity between the inlet air

and exhaust air which is compared to the heat value of the fuel using the Siegert

values and the oxygen volumetric concentration. This is used to express the

percentage of energy that is used to drive the turbine, based on the notion that all

the energy of a fuel is converted into exhaust heat and mechanical movement

(including friction etc).The equation is as follows.

( ) ( )

+

−×−= B

OAATFTqALosses

2212

Where FT is exhaust gas temperature, AT is ambient temperature, O2 is the

concentration of Oxygen in the exhaust gas and A2 and B are the Siegert Values.

72

Appendix C

Figure C.1 below shows the parameters recorded by the Capstone software and

VISIT data software.

Figure C.1 – The raw data from the VISIT and Capstone software.

The spreadsheet as shown in Figure C.2 was used to record data that was not

saved using software programs. This included all the data from the Promass Fluid

meter. The fuel flow rates, viscosity, density and temperature were recorded.

Power Mass Flow Volume Flow Dynamic Viscosity Kinematic Viscosity Density Temperature

8101214etc

Figure C.2 – Data collection spreadsheet.

T (s

ec)

T-Ai

r °C

T-Ga

s °C

O2 %

CO2

%

Loss

%

Eta

%

Lam

bda

NOxc

al m

g/m

3

P2 h

Pa

CO p

pm

CO m

g/m

3

NO p

pm

NO m

g/m

3

NO2

ppm

NO2

mg/

m3

NOx

ppm

NOx

mg/

m3

SO2

ppm

SO2

mg/

m3

CO2

ppm

Engin

e Sp

eed

(rpm

)

Turb

ine E

xit T

emp

(°C)

Com

pres

sor I

n Te

mp

(°C)

Powe

r Dem

and

(W)

Outp

ut P

ower

(W)

32 22.9 25.6 20.9 0 0 100 0 0 0 0 0 0 0 0 0 0 0 0 0 400 25086 36 23.9 8000 -168134 22.9 26.3 20.9 0 0 100 0 0 0 0 0 0 0 0 0 0 0 0 0 400 25116 41 23.8 8000 -153836 22.9 26.9 19.9 0.7 2.7 97.3 21.77 0 0 6 8 0 0 0 0 0 0 8 23 500 25830 96 23.8 8000 -132438 22.9 27.5 16.1 3.6 0.7 99.3 4.32 0 0 101 126 0 0 0 0 0 0 30 86 600 29962 288 23.8 8000 -110440 22.9 28.2 13.8 5.2 0.5 99.5 2.95 2 0 318 397 0 0 1 2 1 1 97 277 1700 33844 454 23.8 8000 -62142 22.9 29.2 12.2 6.4 0.5 99.5 2.39 6 0 876 1094 0 0 3 6 3 4 185 529 5200 37872 546 23.7 8000 -13744 22.9 30.7 11.2 7 0.6 99.4 2.15 10 0 1717 2145 0 0 5 10 5 7 274 783 11200 41816 639 23.7 8000 47246 22.9 33 10.9 7.2 0.8 99.2 2.1 19 0 2785 3479 2 3 7 14 9 12 318 909 18600 45244 692 23.5 8000 129148 22.9 35.4 12.3 6.1 1.1 98.9 2.43 21 0 3706 4629 2 3 8 16 10 14 318 909 25200 45244 692 23.5 8000 245550 22.9 37.2 12.8 5.8 1.3 98.7 2.59 25 0 4412 5511 3 4 9 19 12 17 295 843 32200 47284 670 23.5 8000 197252 22.9 38.1 13.4 5.2 1.5 98.5 2.8 25 0 4795 5989 3 4 9 19 12 17 259 741 38800 49502 653 23.5 8000 276354 22.9 38.6 13.6 5 1.6 98.4 2.88 27 0 4910 6133 4 5 9 19 13 18 220 629 44800 51446 647 23.4 8000 346156 22.9 39.1 13.7 5 1.6 98.4 2.91 29 0 4718 5893 4 5 10 21 14 19 179 512 48400 53018 647 23.3 8000 409858 22.9 39.6 13.8 5 1.7 98.3 2.96 29 0 4300 5371 4 5 10 21 14 19 144 412 50200 54300 647 23.3 8000 465360 22.9 40.1 14 4.9 1.8 98.2 3.02 33 0 3840 4796 5 7 11 23 16 22 118 337 51100 55604 650 23.2 8000 5164

73

Table C.3 shows the averages of 60 seconds of operation for a variety of

parameters. The values below correspond to the R60 test.

Tim

e (s

ec)

T-Ai

r °C

T-G

as °C

O2

%

CO

2 %

Loss

%

Eta

%

Lam

bda

NO

xcal

mg/

m3

P2 h

Pa

CO

ppm

CO

mg/

m3

NO

ppm

NO

mg/

m3

NO

2 pp

m

NO

x m

g/m

3

CO

2 pp

m

Engi

ne S

peed

(rpm

)

Turb

ine

Exit

Tem

p (°

C)

Com

pres

sor I

n Te

mp

(°C

)

Pow

er D

eman

d (k

W)

Out

put P

ower

(kW

)

2427 20.9 209.0 19.0 1.4 68.6 31.4 11.19 4.0 0.8 38.8 48.8 2.0 3.0 0.0 3.0 16980 66600 638.0 30.9 8 8.03265 21.1 216.3 19.0 1.4 67.7 32.3 10.75 4.0 1.0 24.5 30.6 2.0 3.0 0.0 3.0 17327 70816 631.6 31.2 10 10.04047 21.2 223.0 18.9 1.5 66.8 33.2 10.31 4.0 1.2 15.8 19.8 2.0 3.0 0.0 3.0 17707 74415 626.1 31.5 12 12.04797 21.3 230.4 18.8 1.6 66.6 33.4 9.89 4.1 1.3 10.0 13.0 2.0 3.0 0.0 3.0 18100 77687 621.1 31.8 14 14.05495 21.2 237.0 18.7 1.6 67.9 32.1 9.52 6.0 1.6 7.8 9.8 3.0 4.0 0.0 4.0 18600 80754 616.2 31.8 16 16.06117 21.3 243.8 18.6 1.7 67.3 32.7 9.23 6.3 1.9 5.2 6.3 3.1 4.1 0.0 4.3 19100 83785 611.6 32.1 18 18.06677 21.4 250.2 18.6 1.7 66.4 33.6 8.98 8.0 2.1 4.0 5.0 4.0 5.0 0.0 6.0 19553 86722 607.3 32.5 20 20.07279 21.3 256.5 18.5 1.8 68.0 32.0 8.73 10.0 2.5 4.0 5.0 5.0 7.0 0.0 7.0 20100 89515 603.0 32.4 22 22.07915 21.0 262.9 18.5 1.8 67.5 32.5 8.55 12.0 2.8 3.9 4.9 6.0 8.0 0.0 8.0 20450 92498 598.5 32.7 24 24.08551 21.1 269.6 18.4 1.9 66.7 33.3 8.28 19.0 3.1 2.2 3.2 9.0 12.0 0.0 12.0 20917 95384 594.0 32.4 26 26.0

Figure C.3 – Each data entry is an average of 60 seconds of collected data. Each

row corresponds to a single power output.

74

Car

bon

Mon

oxid

e Em

issi

ons

05101520253035404550

810

1214

1618

2022

2426

Pow

er (k

W)

CO ppm

D10

0R

10

R20

R30

R40

R50

R60

R70

R80

R90

R10

0

Appendix D

75

Nitr

ous

Oxi

de E

mis

sion

s

02468101214161820

810

1214

1618

2022

2426

Pow

er (k

W)

NO (ppm)

D10

0R

10R

20R

30R

40R

50R

60R

70R

80R

90R

100

Appendix E