Preformance of Two Stroke Engine

8/11/2019 Preformance of Two Stroke Engine

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THE PERFORMANCE OF TWO STROKE

ENGINE WITH PRE HEATING AIR USING

PELTIER MODULE

For partial fulfillment of the requirements for the degree of

ME/M.Sc/PhD

In---------------- Engineering

Submitted by

NAME

ROLL NUMBER

Under the guidance of:PROFESSOR


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[Type the document title]

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ACKNOWLEDGEMENT

The project bears the imprints of the efforts extended by many people to whom we are deeply

indebted. We would like to thank our mentor Mr. xxxxxxx under whose able guidance we

gained the insights and ideas without which the project could not have seen the light of the day.

His suggestions have been valuable and his teachings during the course of our discussions would

continue to be a guiding principle in our works in the future as well. We would also like to thank

Mr. xxxxx for his valuable guidance, advice and constant support throughout the project.

Finally, we would like to thank the whole Mechanical Department for providing us an

opportunity to apply our technical knowledge and see it materialize in the form of this project.


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ABSTRACT

The two stroke engine was developed to obtain a greater output from the same size of engine.

The engine mechanism eliminates the valve arrangement making it mechanically simpler.

Theoretically a two stroke engine develops twice the power of a comparable four stroke engine,thus making it more compact.

Getting air into an engine is the key to making power and there are many ways to increase the air

flow into the engine. There are such forced induction, nitrous system, better port and valve

shapes to improve flow. But for this study the technique that has been selected were the better

port size. The claims that this where the harnessing the inertia of the airs velocity to better fill the

cylinders.

Modification in intake port is made. Also use of different fuel metering jets is used for different

A/F mixtures. At various throttle positions and with torque and speed as input, and with porting

done performance parameters of engine are calculated.

Based on the results various curves are plotted. The objective of the project is to determine how

much improvement in fuel economy with the modification in intake system in compared to the

original intake system. Modification to the engine without additional system attach to the engine

operation were the best solution to have an optimum engine operation in term of torque and

horsepower. To optimize the power and intake port flow produce by the engine modification

were through a very limited value. The value is limited due to the restricted area of the engine

production by the manufacturer. Hence modification must be planned carefully as over

modification of the inlet port can end up with a device slower than its stock counterpart. It was

found out experimentally that mechanical thermal efficiency was improved after modification. In

other words Fuel economy was improved after modification in intake port.


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INTRODUCTION


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INTRODUCTION

A two stroke engine is one which completes its cycle of operation in one revolution of crankshaft

or in two stroke of the piston. In this engine the function of intake and exhaust processes of the

4-stroke engine are taken care of by the incoming fresh charge which is compressed either in thecrankcase or by a separate blower while the piston is near the BDC. The combustible A/F

mixture is obtained from simple carburetor.

The conventional, carbureted, two-stroke SI engine has a number of potential advantages over

the equivalent four stroke engine; these include higher specific power output, compactness,

simple construction, lower production and maintenance costs, lower brake-specific NO,

emissions, lower engine friction, and reduced part-load pumping losses. As a result of theseadvantages, the two stroke

SI engine is widely used in mopeds, motorcycles, three wheeled auto rickshaws, chainsaws,

snowmobiles, lawn mowers, and outboard marine applications. In India, the two wheeled

vehicles powered by two-stroke SI engines are numbered around 17 million, compared to only

2.8 million

Modification to the engine without additional system attach to the engine operation was the best

solution to have an optimum engine operation in term of torque and horsepower. To optimize the

power and intake port flow produce by the engine modification were through a very limited

value. The value is limited due to the restricted area of the engine production by the

manufacturer.

Hence modification must be planned carefully as over modification of the inlet port can end up

with a device slower than its stock counterpart. In our project modification in intake port is done,

also with the use of two jets (0.85mm & 0.70mm) and readings are taken at a particular

rpm(580).It was found that mechanical thermal efficiency was and Fuel economy was improved

after modification in intake port.


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LITERATURE REVIEW


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LITERATURE REVIEW

The two-stroke internal combustion engine has now been developed to a degree that was not

thought possible just a few years ago. Getting air into an engine is the key to making power and

there are many ways to increase the air flow into the engine. There are such forced induction,nitrous system, better port and valve shapes to improve flow. But for this study the technique that

has been selected were the better port size. The claims that this where the harnessing the inertia

of the airs velocity to better fill the cylinders.

In two stroke engines the cycle is completed in one revolution of the crankshaft. The main

difference between the two stroke and four stroke engines is the method of filling fresh charge

and removing the burnt gases from the cylinder.

The two stroke engine is of simple design which also facilitates servicing and maintenance;

secondly it has a very good performance/weight ratio, and thirdly it will operate in any working

position.

OPERATION:


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Although a two-stroke engine has less moving parts than a four-stroke engine, a two-stroke is a

complex engine because it relies on gas dynamics. There are different phases taking place in the

crankcase and in the cylinder bore at the same time. That is how a two-stroke engine completes a

power cycle in only 360 degrees of crankshaft rotation compared to a four-stroke engine which

requires 720 degrees of crankshaft rotation to complete one power cycle.

1) Starting with the piston at top dead center (TDC 0 degrees) ignition has occurred and the

gasses in the combustion chamber are expanding and pushing down the piston. This pressurizes

the crankcase causing the reed valve to close. At about 90 degrees after TDC the exhaust port

opens ending the power stroke. A pressure wave of hot expanding gasses flows down the exhaust

pipe. The blow-down phase has started and will end when the transfer ports open. The pressure

in the cylinder must blow-down to below the pressure in the crankcase in order for the unburned

mixture gasses to flow out the transfer ports during the scavenging phase.

2) Now the transfer ports are uncovered at about 120 degrees after TDC. The scavenging phase

has begun. Meaning that the unburned air fuel mixture are flowing out of the transfer ports and

merging together to form a loop. The gasses travel up the back side of the cylinder and loops

around in the cylinder head to scavenge out the burnt mixture gasses from the previous power

stroke. It is critical that the burnt gasses are scavenged from the combustion chamber, in order to

make room for as much unburned gasses as possible. That is the key to making more power in a

two-stroke engine. The more unburned gasses you can squeeze into the combustion chamber, the

more the engine will produce. Now the loop of unburned mixture gasses has traveled into the

exhaust pipe's header section. The gasses aren't lost because a compression pressure wave has

reflected from the end of the exhaust pipe, to pack the unburned gasses back into the cylinder

before the piston closes off the port. This is the unique super-charging effect of two-stroke

engines. The main advantage of two-stroke engines is that they can combust more volume of

fuel/air mixture than the swept volume of the engine. Example: A 125cc four-stroke engine

combusts about 110cc of F/A gasses but a 125cc two-stroke engine combusts about 180cc of F/A

gasses.


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3) Now the crankshaft has rotated past bottom dead center (BDC 180 degrees) and the piston is

on the upstroke. The compression wave reflected from the exhaust pipe is packing the unburned

gasses back in through the exhaust port as the piston closes off the port the start the compression

phase. In the crankcase the pressure is below atmospheric producing a vacuum and a fresh

charge of unburned mixture gasses is flowing through the reed valve into the crankcase.

4) The unburned mixture gasses are compresses and just before the piston reaches TDC, the

ignition system discharges a spark causing the gasses to ignite and start the process all over

again.

TYPES OF ENGINE

Various types of engine used depending on the number of cylinders:

Flat: The cylinder lies flat. Half of the cylinders are located on one side of the crankshaft and the

other half on other side. This makes a car more stable due to lower centre of gravity.

Inline: Inline have cylinders on top of the crankshaft. They stand in line at a vertical 90 degrees.

Inline engines can run smooth and provide a lot of power.

V Type: The cylinders are located on opposite side of the crankshaft and are elevated up a

varying amount of degrees depending on the manufacturer.

W Type: W type work well for a large number of cylinders because everything become more

compact and shorter. These are found in few cars.

The engines are classified based on combustion (ignition), fuel used, cooling, application and

construction.

Based on the combustion type: 1. External combustion engine.

2. Internal combustion engines.

Based on fuel used: 1. Diesel engines


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2. Petrol engines

3. CNG engines and LPG engines.

Based on cooling system: 1. Air cooled engines

2. Liquid cooled engines

Based on applications: 1. Stationary engine2. Rocket engine

3. Automobile engine

Based on construction: 1. Inline engines

2. Opposed engines

3. Rotary engine

4. V-engines5. W engines

INTAKE SYSTEM OF TWO STROKE ENGINE

CARBEURETOR:

It is a device which is used in SI engine for the purpose to provide a combustible homogeneous

mixture of fuel and air in the required quantity and quality for efficient operation of the engine

under all condition.

WORKING PRINCIPLE:


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The carburetor works on Bernoulli's principle: the faster air moves, the lower its static pressure

and the higher its dynamic pressure. The throttle (accelerator) linkage does not directly control

the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air

being pulled into the engine. The speed of this flow, and therefore its pressure, determines the

amount of fuel drawn into the airstream. When carburetors are used in aircraft with piston

engines, special designs and features are needed to prevent fuel starvation during inverted flight.

Later engines used an early form of fuel injection known as a pressure carburetor.

The main disadvantage of basing a carburetor's operation on Bernoulli's principle is that, being a

fluid dynamic device, the pressure reduction in a venturi tends to be proportional to the square of

the intake air speed. The fuel jets are much smaller and limited mainly by viscosity, so that the

fuel flow tends to be proportional to the pressure difference. So jets sized for full power tend to

starve the engine at lower speed and part throttle. Most commonly this has been corrected by

using multiple jets. In SU and other movable jet carburetors, it was corrected by varying the jet

size. For cold starting, a different principle was used in multi-jet carburetors. A flow resisting

valve called a choke, similar to the throttle valve, was placed upstream of the main jet to reduce

the intake pressure and suck additional fuel out of the jets.

OPERATION:


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A carburetor basically consists of an open pipe through which the air passes into the inlet

manifold of the engine. The pipe is in the form of a venturi: it narrows in section and then widens

again, causing the airflow to increase in speed in the narrowest part. Below the venturi is a

butterfly valve called the throttle valvea rotating disc that can be turned end-on to the airflow,

so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the

flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity

of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The

throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely

by pneumatic link, to the accelerator pedal on a car or the equivalent control on other vehicles or

equipment.

Fuel is introduced into the air stream through small holes at the narrowest part of the venturi and

at other places where pressure will be lowered when not running on full throttle. Fuel flow is

adjusted by means of precisely calibrated orifices, referred to as jets, in the fuel path

ADVANTAGES OF TWO STROKE ENGINE

The power developed is nearly twice as compared to four stroke engine of the same

dimensions and operating at same speed.

Two stroke engines are lighter than four stroke engine for the same output and speed.

It eliminates the valve arrangement which making it simpler.

Work required to overcome the friction of the exhaust and suction strokes is saved.

DISADVANTAGES OF TWO STROKE ENGINE


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The application of the two stroke petrol engine is that it is suitable only for the small

engine. Such as motor cycles, scooters, lawn mowers etc.

It has more fuel consumption and low thermal efficiency.

It required more cooling and lubrication because of one power stroke in each revolution

of crankshaft.

Two stroke engines are liable to cause a heavier consumption of lubricating oil.

MODIFICATION IN TWO STROKE ENGINE:

Technical modifications are basically made in order to increase the overall efficiency. Similarly

modifications in a two stroke petrol engine are made to increase the power output of the engine.

Getting air into an engine is the key to making power and there are many ways to increase

performance of the engine. There are such forced induction, nitrous system, better port and valve

shapes to improve flow. But for this project the technique that has been used was preheating of

the air before the intake.

PERCENTAGE INCREASE IN A/F RATIO OF 0.70MM IN THE INLET

ma/ mf) = (cda/cdf) * (At/Af)* (Pa/Pf)

Wherema= mass of air flow

mf =mas of fuel

cda =coefficient of discharge for venturicdf =coefficient of discharge of fuel nozzle

At =area of throat

Af =area of jetPa =pressure inside the cylinder

Pf)=pressure depression at throat

For 0.70 mm

(ma/ mf) = 1/(*0.72*10^-6/4)* (cda/cdf) * (At)* (Pa/Pf)(ma/ mf) = 2598448.05*[(cda/cdf) * (At)* (Pa/Pf)]


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At a design and development stage an engineer would design an engine with certain aims in his

mind. The aims may include the variables like indicated power, brake power, brake specific fuel

consumption, exhaust emissions, cooling of engine, maintenance free operation etc. The other

task of the development engineer is to reduce the cost and improve power output and reliability

of an engine. In trying to achieve these goals he has to try various design concepts. After the

design the parts of the engine are manufactured for the dimensions and surface finish and may be

with certain tolerances. In order verify the designed and developed engine one has to go for

testing and performance evaluation of the engines.

Thus, in general, a development engineer will have to conduct a wide variety of engine tests

starting from simple fuel and air-flow measurements to taking of complicated injector needle lift

diagrams, swirl patterns and photographs of the burning process in the combustion chamber. The

nature and the type of the tests to be conducted depend upon various factors, some of which are:

the degree of development of the particular design, the accuracy required, the funds available,

the nature of the manufacturing company, and its design strategy. In this chapter, only certain basic tests

and measurements will be considered.

INTRODUCTIONConventional 2-stroke engines are commonly used for two-wheeled and marine vehicles that have small

engine displacement. However problems such as unstable combustion, high fuel consumption rate, high HC

emission, need to be resolved. 2-stroke engines have advantages over 4-stroke engines such as higher torqueand power, being more compact and lighter. In order to solve these problems without compromising these

advantages, a new 2-stroke engine was designed with pre heating unit to improve the performance of the

engine and reduce the fuel consumption.

In this study, performance of the 2 stoke engine was researched, and considerations concerning fuel

consumption, performance and exhaust gas emissions were made. These findings were then compared via

simulations done using the ANSYS software.

Objectives Understand the performance parameters in evaluation of IC engine performance,

Calculate the speed of IC engine, fuel consumption, air consumption, etc.,

Evaluate the exhaust smoke and exhaust emission, and

Differentiate between the performance of SI engine and CI engines.

PERFORMANCE PARAMETERSEngine performance is an indication of the degree of success of the engine performs its assigned task, i.e. theconversion of the chemical energy contained in the fuel into the useful mechanical work. The performance of

an engine is evaluated on the basis of the following:

Specific Fuel Consumption.

Brake Mean Effective Pressure.


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Specific Power Output.

Specific Weight.

Exhaust Smoke and Other Emissions

The particular application of the engine decides the relative importance of these performance parameters.

For Example: For an aircraft engine specific weight is more important whereas for an industrial engine specific

fuel consumption is more important.For the evaluation of an engine performance few more parameters are chosen and the effect of various

operating condition, design concepts and modifications on these parameter are studied. The basic performanceparameters are the following:

Power and Mechanical Efficiency.

Mean Effective Pressure and Torque.

Specific Output.

Volumetric Efficiency.

Fuel-air Ratio.

Specific Fuel Consumption.

Thermal Efficiency and Heat Balance.

Exhaust Smoke and Other Emissions. Specific Weight.

.


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POWER AND MECHANICAL EFFICIENCYThe main purpose of running an engine is to obtain mechanical power.

(a) Power is defined as the rate of doing work and is equal to the product of force and linear velocity or

the product of torque and angular velocity.

(b) Thus, the measurement of power involves the measurement of force (or torque) as well as speed. The

force or torque is measured with the help of a dynamometer and the speed by a tachometer.

The power developed by an engine and measured at the output shaft is called the brake power (bp) and is given

by,

Where, T is torque in N-m andN is the rotational speed in revolutions per minute.

The total power developed by combustion of fuel in the combustion chamber is, however, more than the bp

and is called indicated power (ip). Of the power developed by the engine, i.e. ip, some power is consumed inovercoming the friction between moving parts, some in the process of inducting the air and removing the

products of combustion from the engine combustion chamber.


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It is the power developed in the cylinder and thus, forms the basis of evaluation of combustion efficiency or

the heat release in the cylinder.

Where, pm = Mean effective pressure, N/m2,

L = Length of the stroke, m,A = Area of the piston, m2,

N = Rotational speed of the engine, rpm (It is N/2 for four stroke engine), and

k = Number of cylinders.

Thus, we see that for a given engine the power output can be measured in terms of mean effective pressure.The difference between the ip and bp is the indication of the power lost in the mechanical components of the

engine (due to friction) and forms the basis of mechanical efficiency; which is defined as follows:

The difference between ip and bp is called friction power (fp).

fp ip bp

MEAN EFFECTIVE PRESSURE AND TORQUEMean effective pressure is defined as a hypothetical/average pressure which is assumed to be acting on the

piston throughout the power stroke. Therefore,

Where,Pm = Mean effective pressure, N/m2,

Ip = Indicated power, Watt,

L = Length of the stroke, m,

A = Area of the piston, m2,

N = Rotational speed of the engine, rpm (It isN/2 for four stroke engine), and

k = Number of cylinders.

If the mean effective pressure is based on bp it is called the brake mean effective pressure (bmep Pmb replace ip

by bp in Eq. 5.5), and if based on ihp it is called indicated mean effective pressure (imep). Similarly, the

friction mean effective pressure (fmep) can be defined as,

fmap imep bmep

The torque is related to mean effective pressure by the relation

Substituting the previous equation in the following equation


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Thus, the torque and the mean effective pressure are related by the engine size. A large engine produces moretorque for the same mean effective pressure. For this reason, torque is not the measure of the ability of an

engine to utilize its displacement for producing power from fuel. It is the mean effective pressure which gives

an indication of engine displacement utilization for this conversion. Higher the mean effective pressure, higherwill be the power developed by the engine for a given displacement.

Again we see that the power of an engine is dependent on its size and speed. Therefore, it is not possible tocompare engines on the basis of either power or torque. Mean effective pressure is the true indication of the

relative performance of different engines.

SPECIFIC OUTPUT

Specific output of an engine is defined as the brake power (output) per unit of piston displacement and is givenby,

The specific output consists of two elementsthe bmep (force) available to work and the speed withwhich it is working.

Therefore, for the same piston displacement and bmep an engine operating at higher speed will give

more output.

It is clear that the output of an engine can be increased by increasing either speed or bmep. Increasing

speed involves increase in the mechanical stress of various engine parts whereas increasing bmep

requires better heat release and more load on engine cylinder.

VOLUMETRIC EFFICIENCY

Volumetric efficiency of an engine is an indication of the measure of the degree to which the engine fills its

swept volume. It is defined as the ratio of the mass of air inducted into the engine cylinder during the suction

stroke to the mass of the air corresponding to the swept volume of the engine at atmospheric pressure and

temperature. Alternatively, it can be defined as the ratio of the actual volume inhaled during suction stroke

measured at intake conditions to the swept volume of the piston.

Volumetric efficiency =

The amount of air taken inside the cylinder is dependent on the volumetric efficiency of an engine and henceputs a limit on the amount of fuel which can be efficiently burned and the power output.

For supercharged engine the volumetric efficiency has no meaning as it comes out to be more than unity.

FUEL-AIR RATIO (F/A)Fuel-air ratio (F/A) is the ratio of the mass of fuel to the mass of air in the fuel-air mixture. Air-fuel ratio (A/F)

is reciprocal of fuel-air ratio. Fuel-air ratio of the mixture affects the combustion phenomenon in that it


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determines the flame propagation velocity, the heat release in the combustion chamber, the maximum

temperature and the completeness of combustion.

Relative fuel-air ratio is defined as the ratio of the actual fuel-air ratio to that of the stoichiometric fuel-air ratio

required to burn the fuel supplied. Stoichiometric fuel-air ratio is the ratio of fuel to air is one in which case

fuel is completely burned due to minimum quantity of air supplied.

Relative fuel-air ratio, Fr=

BRAKE SPECIFIC FUEL CONSUMPTIONSpecific fuel consumption is defined as the amount of fuel consumed for each unit of brake power developed

per hour. It is a clear indication of the efficiency with which the engine develops power from fuel.

Brake specific fuel consumption (bsfc)=

THERMAL EFFICIENCY AND HEAT BALANCEThermal efficiency of an engine is defined as the ratio of the output to that of the chemical energy input in the

form of fuel supply. It may be based on brake or indicated output. It is the true indication of the efficiency with

which the chemical energy of fuel (input) is converted into mechanical work. Thermal efficiency also accounts

for combustion efficiency, i.e., for the fact that whole of the chemical energy of the fuel is not converted intoheat energy during combustion.

Where, Cv = Calorific value of fuel, kJ/kg, and

mf = Mass of fuel supplied, kg/sec.

The energy input to the engine goes out in various formsa part is in the form of brake output, a partinto exhaust, and the rest is taken by cooling water and the lubricating oil.

The break-up of the total energy input into these different parts is called the heat balance.

The main components in a heat balance are brake output, coolant losses, heat going to exhaust,

radiation and other losses.

Preparation of heat balance sheet gives us an idea about the amount of energy wasted in various parts andallows us to think of methods to reduce the losses so incurred.

EXHAUST SMOKE AND OTHER EMISSIONSSmoke and other exhaust emissions such as oxides of nitrogen, unburned hydrocarbons, etc. is nuisance for the

public environment. With increasing emphasis on air pollution control all efforts are being made to keep them

as minimum as it could be.

Smoke is an indication of incomplete combustion. It limits the output of an engine if air pollution control is the

consideration. Exhaust emissions have of late become a matter of grave concern and with the enforcement of

legislation on air pollution in many countries; it has become necessary to view them as performance

parameters.

SPECIFIC WEIGHT

Specific weight is defined as the weight of the engine in kilogram for each brake power developed and is anindication of the engine bulk. Specific weight plays an important role in applications such as power plants foraircrafts


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The following figure shows a cross section of the test engine. The main characteristic of the test engine ishaving intake valves which are on the cylinder head rather than the cylinder wall, on the opposite side to the

exhaust port.


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Two Stroke Design AdvantagesThe two stroke diesel engine has some advantages not found in the four stroke types which are of huge

advantage to its application as an aero engine.

Weight and PowerWith twice as many power strokes per engine revolution, a diesel two stroke engine produces more power than

a four stroke diesel of the same displacement. A two stroke engine of the same power as a four stroke will not

have the same weight and is usually heavier.

Response and AccelerationSince every cylinder of a two stroke engine produces a power stroke for every revolution, there is a quick

response to load changes. This becomes an advantage if the engine is equipped with a constant speed propeller

where its RPM control will be quicker to react.

DurabilityThe two stroke "spreads the load", each piston is producing two lighter power impulses per two revolutions

instead of the single heavy impulse of a four stroke. At normal loads and speeds, there is no load reversal onpistons, rods, and bearings; this continuous downward loading reduces impact load effects. Lighter loading

permits two stroke diesels to use more compact structural and load bearing parts without over stressing. The

lighter power impulses are produced by smaller displacement cylinders, which mean smaller pistons and

shorter connecting rods for comparable performance. Shorter stroke lowers piston speed, a major factor in

cylinder kit life. All of these weight and size advantages are achieved without sacrificing engine life.

SmoothnessTwo stroke engines run smoother than four stroke engines. This is because two stroke engines have twice as

many power impulses at the same RPM. The lighter, more frequent power impulses mean less damping isrequired from the flywheel; hence smaller, lighter flywheels can be used. This permits more rapid acceleration

and unsurpassed transient load response.

Lower Exhaust TemperaturesMore air goes through a two stroke engine than a four stroke for the same amount of fuel consumed. This

results in lower exhaust temperatures for two stroke diesels and in longer valve and turbo life.Higher piston loadsThe piston loads in a two stroke diesel are higher than in a four stroke, mainly because there is always a

downward pressure on the piston either by the combustion or by pushing out the exhaust gasses. There is noload reversal to build up the oil film on the piston pin. An innovative manufacturer uses a sort of ball bearing

in the piston with pressure lubrication, this design also solves the problem with piston cooling and lubrication.

Time will tell if this will work and be durable over thousands of engine hours.

Indirect vs direct fuel injection


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A DI (direct injection) engine has the diesel fuel injected straight into cylinder almost at the top of the

compression stroke. In the old days this meant that it burned and expanded very quickly, making it a noisy,

rattly engine. This is why most diesel cars were IDI (indirect injection); the rough behaviour was fixed by

injecting the fuel into a small precombustion chamber which is connected to the cylinder by a narrow passage.

This slows down the combustion as the gasses have to escape through the narrow passage into the cylinder.

This gives a softer bang and a smoother engine, but the gasses have to work harder, which spoils the efficiency

a little. However, the newer breed of DI engines use other techniques to tame the behaviour: such as two stageinjection, electronic control (FADEC), and acoustic shrouds and fancy engine mounts to mask the rattle.

For an aircraft to have a DI engine this means extra hardware (2 stage injectors, common rail etc), dual

electronics for redundancy, weight and all of this complexity for about 10% more efficiency. The IDI does not

have all of these but in return is simpler and more reliable, which definitely is what we are looking for in an

aircraft engine.

Performance at altitude

A two stroke diesel is able to run without a turbocharger just by using a roots blower to scavenge the engine

from exhaust gasses. This roots blower is not a supercharger but supplies the engine with enough air to clean

the cylinders for the next fuel injection and power stroke. This is seen as a naturally aspirated engine.

Adding a turbocharger would give the advantage of more air thus more fuel which can be injected and theengine would able to sustain its rated power to a much higher altitude. More air means also better scavenging

and cooler exhaust valves translating to a longer life and more reliable engine.

Preformance of Two Stroke Engine

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