FACULTY OF ENGINEERING & TECHNOLOGY

LAB SHEETInternal Combustion EngineEME 4096TRIMESTER 3 (2013/2014)Experiment 1:Otto Cycle Model

Name Mohammed Islam

ID 1112702923

Table of Contents

Abstract...3Objective....4Introduction..4Procedures.6Result.7Discussion and Data Analysis.8Conclusion...15References...15

AbstractIn this experiment we have solely concentrated on Otto engine on which 3 main aspects have been tested so as to study its effect on the engine performance. The 3 main aspects were carried on by changing the compression ratio, bore/stroke ratio and fuel type. The default readings created in the lab were was basically compared by changing the compression ratio, bore/stroke ratio and fuel type each time and again compared with the default readings to get a clearer perspective as to how it effects the engine performance. The default fuel type used in the lab was gasoline which was compared with ethanol in this lab report by changing the value of LHV. Based on the reading a complete summation was concluded as to how an engine performance can be improved by changing certain parameters of the engine.

Objectivei. To study the effect of the compression ratio on the engine performance and other parameters ii. To study the effect of the fuel type on the engine performance and other parametersiii. To study the effect of bore to stroke ratio on engines parameters

IntroductionAnengineis a device that is specifically designed to convertenergyinto usefulmechanical motion.Heat engines, includinginternal combustion enginesandexternal combustion engines(such assteam engines) burn afuelto createheat, which then creates motion.The principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. Almost all cars currently use what is called afour-stroke combustion cycleto convert gasoline into motion. The four-stroke approach is also known as theOtto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated inFigure 1. They are: Intake stroke Compression stroke Combustion stroke Exhaust stroke

Fig.1Improving internal combustion (IC) engine efficiency is a prime concern today. A lot of engineering research has gone into the improvement of the thermal efficiency of the (IC) engines, so as to get more work from the same amount of fuel burnt. Of the energy present in the combustion chamber only a portion gets converted to useful output power. Most of the energy produced by these engines is wasted as heat. In addition to friction losses and losses to the exhaust, there are other operating performance parameters that affect the thermal efficiency.

According to our objective of this experiment, we are to study the change in the engine performance related to the OTTO cycle based on the 3 changes of aspects explained below:1) Compression RatioThecompression ratioof aninternal-combustion engineorexternal combustion engineis a value that represents the ratio of the volume of itscombustion chamber from its largest capacity to its smallest capacity. In a piston engine it is theratiobetween the volume of thecylinderand combustion chamber when thepistonis at the bottom of itsstroke, and the volume of the combustion chamber when the piston is at the top of its stroke A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higherthermal efficiency.

2) Different Types of FuelThere are different types of fuels introduces to be used in the Otto Engines such as Gasoline, Methanol, Ethanol, Natural Gas (NG), Gaseous Fuels, Hydrogen and Synthetic Fuels.There are different Impacts of each fuel on the performance of engine.The effect of Using Ethanol will be shown below using the graphs.

3) Bore to stroke ratio

It describes the ratio betweencylinder borediameter andpistonstroke. This can be used for either aninternal combustion engine, where the fuel is burned within the cylinders of the engine, orexternal combustion engine, such as asteam engine, where the combustion of the fuel takes placeoutsidethe working cylinders of the engine.The engines are classified as 1. Square, if Bore/Stroke =12. Undersquare, if Bore/Stroke < 13. Oversquare, if Bore/Stroke > 1

Procedure1. Engine parameters and specification of each engine component was provided as shown in the table below:engine performance parmameters

engine displace8000CC

bore/stroke ratio12

number of cylinders8

angle between banks90DEGREES

compression ratio8.5:1

RPM2000

engine component weights and dimensions

piston mass1kg

piston pin mass0.3kg

piston ring mass0.18kg

connecting rod mass1.5kg

connecting rod length c-c25cm

connecting rod piston pin CG distance10cm

2. Being familiar with the excel program was necessary to build the simulation model because we had to generate the equation of the piston position which were derived in the lab.3. After that a chart was plotted based on the readings of the piston position.4. Procedure 2 and 3 were repeated by deriving different sets of equation to build the simulation and plot the chart based on the readings of inertia effects with gas pressure = 0.5. The thermodynamics equations of Otto cycle derived in the lab were used to build the simulation and plot the chart based on the readings of engine pressure and temperature development6. Instantaneous torque with pressure development and heat released were also plotted using the thermo equations.7. After plotting the graphs stated in the above procedures, 5 different graphs were generated which are as follows:Graph 1: piston positionGraph 2: Reciprocating Forces w/gas pressure = 0Graph 3: Engine Pressure and Temperature DevelopmentGraph 4: Instantaneous Torque with Pressure Development with Controlled Heat additionGraph 5: Heat Release8. To further study the different effects of parameters on the engine performance, the same procedure as stated above were repeated using different values of the combustion ratio, bore/stroke ratio and different type of fuel. The changes created are as follows:i) The combustion Ratio was changed to 10.5ii) The bore to stroke ratio was changed to 1.5iii) Fuel type used comparison was Ethanol

ResultCp1.0052KJ/(kg-K)

Cv0.718KJ/(kg-K)

CP/Cv1.4

air density1.2kg/m^3

fuel LHV44MJ/kg

The results of the data created in the lab and other data created for comparison purposes are to cast to be visually represented in this lab report and hence the results have its own excel file. But the important aspects as to how the data has been acquired are explained in this section.The default data created in the lab were meant to be for gasoline. The important data of the default file are as follows:engine performance parmameters

engine displace8000CC

bore/stroke ratio12

number of cylinders8

angle between banks90DEGREES

compression ratio8.5:1

RPM2000

To show the change in engine performance due to compression ratio, the value of compression ratio was changed from 8.5 to 10.5.To show the change in engine performance due to bore/stroke ratio, the value of bore/stroke ratio was changed from 1 to 1.5.To show the change in engine performance due to change in fuel type, the fuel type chosen was ethanol by changing the value of fuel LHV from 44 MJ/kg to 26.95 MJ/kg

Discussion an Data AnalysisCompression ratio:Changing the compression ratio does not bring any changes to Reciprocating Engine Parameters and Reciprocating Forces w/gas pressure=0 of the engine. In the development stage, the temperature is independent to the change in compression ratio. In this section the compression ratio has been changes from 8.5 to 10.5 and the changes are shown in the graphs below:

As shown in the Engine Pressure and Temperature Development graph, the only significant changes in the engine are related to pressure which have a significant increase when the compression ratio is increased. The same applies for Instantaneous Torque with Pressure Development with Controlled Heat addition graphs in addition that the instant torque increases since the compression ratio was increased as shown below:

This shows us the compression ratio of an engine is directly proportional to the instant torque and pressure with and without heat addition. No changes in the temperature parameter may be because the change in compression ratio was not too significant.

Bore/stroke ratio:Changing the bore/stroke ratio gives change to the engine parameters and reciprocating forces. Pressure, temperature and instantaneous torque development parameters are independent to the changes in bore/stroke ratio.In this section the bore/stroke ratio has been increased from 1 to 1.5.As shown in Reciprocating Engine Parameters graphs below, increasing the bore stroke engine decreases the piston position, velocity and acceleration but increases the cylinder volume.

In the Reciprocating Forces w/gas pressure=0 graphs below, increasing the bore/stroke ratio decreases all the force parameters of the engine as shown in the graphs below.

From the data shown on the graph above we can conclude that bore/stroke ratio is indirectly proportional to all the physical parameters and forces of the engine related to the motion of the piston but directly proportional to the cylindrical volume of the engine.

Fuel Type:The fuel type in default is gasoline. The fuel type has been changed to ethanol which has a significantly lower fuel LHV compared to gasoline. Gasoline has a fuel LHV of 43MJ/kg where as ethanol has a fuel LHV of 26.95MJ/kg.Changing the fuel type makes no changes in the Reciprocating Engine Parameters and Reciprocating Forces w/gas pressure=0 graphs.The only changes that occur when fuel type is changed are pressure with heat added, temperature with heat added and instant torque during development. Pressure without heat added and temperature without heat added is independent to change in fuel type. The following are shown in the graphs below:

The parameters show a significant decrease when choosing ethanol instead of gasoline. Hence we can conclude that a fuels LHV is directly proportional to pressure with heat added, temperature with heat added and instant torque during development.

Heat Release

The graph above shows amount fraction burned with respect to its piston position. The data in the graph above shows no changes in it when the 3 paramets (compression ratio, bore/stroke ratio and fuel type) were changed

ConclusionThis experiment gives a better insight on computing engine displacement and the output power and also the analysis of dimension by using Microsoft excel. Thus complex repetitive equations are solved in easeIn addition to the already default data produced in the lab, several comparison of parameter was studied to achieve the objective of this experiment like the comparison in terms of difference in type of compression ratio, bore/stroke ratio and fuel typeBased on the 3 aspects to study engine performance change, the conclusion are as follows:If the Compression ratio is increased then there is a significant increase in pressure and the instantaneous torque. It will also show change in temperatures development but for that the increase in compression ratio has to be significantly high. No other parameters show change with change in compression ratio. If the bore stoke is increased, all forces and parameters related to the motion of the piston decreases which describes that if the bore stoke ratio is increased the combustion efficiency tends to decrease and mechanical efficiency tend to increase. Due to increase in bore/stroke ratio, there is an increase in the cylindrical volume

If the fuel type is changed from a higher fuel LHV to a lower one then a large decrease in Pressure with heat and Temperature with heat occurs. Since in this experiment we have changed fuel type to Ethanol, it describes that using Ethanol instead of Gasoline causes no change to other parameters or performance of engine except the Pressure and Temperature. This also explains that a fuel with lower fuel LHV will have lower combustion efficiency.

Referenceshttp://auto.howstuffworks.com/engine.htmhttp://www.sciencedirect.com/science/article/pii/S1364032108001020http://www.benthamscience.com/open/toefj/articles/V002/1TOEFJ.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol3-iss4/AASR-2012-3-4-1915-1922.pdfhttps://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/20_2_PHILADELPHIA_04-75_0059.pdfhttp://www.energyresourcefulness.org/Fuels/methanol_fuels/methanol_fuels_general.html