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Study of the performance parameter of the variable compression
ratio engine with variable loading conditions
Submitted To:
Dr. S.K.MohapatraSr. Professor MEDThapar University
Submitted by:
Shubham Jain
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Objective of the Project
Our main aim ,in this project is to find out, how compression ratio affects the performance parameters of an engine .These parameters include brake thermal efficiency, specific fuel consumption, power output ,pressure inside the cylinder, exhaust gas temperature etc. This is done to identify the parameters ,which would help us control the performance of an engine ,according to our needs.
After analyzing an attempt has been made to suggest the best optimal compression ratio at which engine could work with higher thermal efficiency and lower fuel consumption.
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Experimental Setup
VARIABLE COMPRESSION RATIO ENGINE TEST RIG
SPECIFICATIONS FOUR STROKE,SINGLE
CYLINDER,VERTICALLY MOUNTED KIRLOSKAR DIESEL ENGINE
BRAKE POWER : 3.50 kW SPEED : 1500rpm STROKE : 110 mm BORE : 87.50 mm COMPRESSION : 12 to 18 RATIO VARY
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Power Vs. Load
0 1 2 3 4 5 6 7 8 90
1
2
3
4
5
6
Brake Power CR-14Brake Power CR-16Brake Power CR-17Brake Power CR-18Indicated Power CR-14Indicated Power CR-16Indicated Power CR-17Indicated Power CR-18
Load (kg)
Pow
er (k
W)
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Variation of Brake Thermal Efficiency
Brake thermal efficiency increases with load ,because brake power is also increased with increased load. Also better efficiency is obtained at higher compression ratio , due to better combustion of fuel.
0.22 2 4 6 80
5
10
15
20
25
30
CR-14CR-16CR-17CR-18
Load (kg)
Brak
e th
erm
al e
ffici
ency
(%)
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Variation of BSFC
From the graph we can see that Bsfc decreases as the load increases .This happens because Bsfc is inversely propotional to Brake Power , and Brake Power is increasing with load . Another variation that can be seen , with respect to compression ratio is that , better fuel consumption is observed at high compression ratio ,because the thermal efficiency of the engine also increases, causing better and complete combustion.
0.22 2 4 6 80
1
2
3
4
5
6Specific fuel consumption vs Load
CR-14CR-16CR-17CR-18
Load (kg)
Spec
ific
Fuel
Con
sum
ptio
n (k
g/kW
h)
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Brake Specific Energy Consumption
0.22 2 4 6 80
50000
100000
150000
200000
250000
CR-14CR-16CR-17CR-18
Load (Kg)
Brak
e Sp
ecifi
c Ene
rgy
Cons
umpti
on
Specific energy consumption is directly proportional to specific fuel consumption ,thus showing the same trend.
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Variation of Fuel Consumption
Here from the graphs we can see that , the fuel consumption is increasing with load , because more fuel is needed to produce more power ,to counteract high load. Also the fuel consumption is lowest for compression ratio 18 , because the engine is running at higher efficiency and thus requires comparatively less fuel.
0.22 2 4 6 80
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9Fuel consumption vs Load
CR-14CR-16CR-17CR-18
Load (kg)
Fuel
Con
sum
ption
(kg/
h)
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Variation of Indicated Mean Effective Pressure
As the load increases , more fuel is injected into the cylinder ,which causes more pressure rise in the cylinder ,as can be seen from the graph. Also , at higher compression ratio , more compression occurs, giving rise to higher temperatures ,rapid and proper combustion ,causing pressure to rise more , comparatively.
0.22 2 4 6 80
1
2
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Indicated mean effective pressure vs Load
CR-14CR-16CR-17Cr-18
Load (kg)
Indi
cate
d m
ean
effec
tive
pres
sure
(bar
)
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Torque
0.22 2 4 6 80
2
4
6
8
10
12
14
16
CR-14CR-16CR-17CR-18
Load (Kg)
Torq
ue (N
m)
Torque is directly proportional to the brake power ,so we get the same trend.
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Exhaust Gas Temperature
We get the least temperature of the exhaust gases at CR 18 ,due to better conversion of heat to work.
0 1 2 3 4 5 6 7 8 90
50
100
150
200
250
300
CR-14CR-16CR-17CR-18
Load (Kg)
Tem
pera
ture
(°C)
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Literature Review
Research Paper
Author Year Key findings
Remarks
Studying the effect of compression ratio on an engine fueledwith waste oil produced biodiesel/diesel fuel
Mohammed EL, Medhat A. NemitAlexandria Engineering Journal (2013) 52, 1–11
28 November 2013
o The brake thermal efficiency increased by more than 18.5% when the compression ratio was raised from 14 to 18 for the blend B30.
o Increasing the compression ratio had more benefits with biodiesel than with high pure diesel
o Bsfc for all blends decreases as the compression ratio increases.
o This may be attributed to reduced ignition delay.
o Blended fuel performed better at high compression ratio due to high temperature and pressure
o Due to better engine efficiency.
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Literature Review
Research Paper
Author Year Key findings Remarks
Performance, emission and combustion characteristics of a variablecompression ratio engine using methyl esters of waste cooking oil and diesel blends
K. Muralidharan , D. Vasudevan PSNA College of Engineering & Technology Applied Energy 88 (2011) 3959–3968
2 April 2011 o Engine torque increase with increasing compression ratio .
o Bsfc decreases for increase in compression ratio.
oThis is due to the high pressure rise in the cylinder, increasing the indicated power and thus torque . oThis may be due to improved combustion at higher compression ratios.
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Literature Review
Research Paper
Author Year Key findings
Remarks
Experimental evaluation of the effect ofcompression ratio on performance andemission of SI engine fuelled with gasolineand n-butanol blend at different loads
Rinu Thomas, M. Sreesankaran, Jeevan Jaidi,Dileep M. Paul, P. Manjunath Perspectives in Science (2016) 8, 743—746
8 June 2016 o Brake thermal efficiency improves at higher compression ratios, particularly at part-loads.
o At higher compression ratios, reduced exhaust gas temperatures were observed,.
o This can be attributed to the larger volume expansion ratio associated with the higher compression ratios thus improving expansion work output.
o Due to better heat to work conversion, which in turn is due to effective combustion.
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Literature Review
Research Paper
Author Year Key findings Remarks
Effect of compression ratio on the performance of diesel engine at diiferent loads
Abhishek Reddy G, Nirmal Pratap SinghIJERA-ISSN:2248-9622
2015 o Study is carried out from CR 14 to 18 and as the CR increases, bsfc decreases.
o As the CR increases , brake thermal efficiency increases.
o Better engine efficiency at higher compression ratio.
o Better heat conversion to work.
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Continued…..
Research Paper
Author Year
Key findings Remarks
Variable compression ratio diesel engine performance analysis
K. SatyanarayanVinod kumar padala, T.V. Hanumantha Rao,IJETT-ISSN:2231-5381
2015 o 5% Diethyl ether is used as a oxygenated agent for improving the performance.
o Optimal value of CR is 19, at which bsfc is minimum.
o Mechanical efficiency increases with the increment in CR & load.
o More oxygen will lead to better combustion.
o At lower side of CR fuel consumption is high due to incomplete combustion.
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Continued….
Research Paper
Author Year
Key findings Remarks
Exhaust emission features of variable compression ratio (VCR) diesel engine
Pawel Wos, Hubert Kuszewski,Journal of KONES powertrain and transport, vol 17, no. 3 2010
2010 o Carbon dioxide emission decreases with CR but it increases after CR 16. so the optimum value of CR is 16
o NOX emission increases as CR increases continuosly.
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Continued…….
Research Paper Author Year Key findings
Study of characteristics performance of variable compression ratio engine for different fuels
Vishwanath Shavi, Adiveppe Ramapuri, chetan IJECS-ISSN: 2319-7242
2015 o Here Honge oil is used as a biodiesel for blending.
o At 100% diesel condition , bsfc increases with CR but at higher CR it decreases due to charge dilution, optimal CR is 17
o At 20% blending condition optimal value of CR is 20.6
o Brake thermal efficiency is higher at 20% blending condition as compare to the 100% diesel condition.
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Conclusion
Various parameters of the Variable Compression ratio were studied and we can conclude from the graphs that :• Total fuel consumption increased with brake power ,at all compression ratios.• Brake specific fuel consumption decreased with brake power at all compression ratios. The • Brake thermal efficiency increases with compression ratio from 5%→7.5%→6.56% when the compression
ratio is increased from 14 to 18.It is due to the increase in working gas temperature affected by an increase in compression ratio.
• Mechanical efficiency increases with brake power at all compression ratios.• Low exhaust gas temperatures were observed at higher compression ratio. This can be attributed to better
heat to work conversion, which is in turn due to effective combustion.
In general we can say that higher compression ratio is better for the engine to run , as it gives better fuel economy and less fuel consumption . Thus compression provides a good degree of control over the engine parameters. The current rise in global mileage standards is forcing every maker to search for additional means of curbing fuel consumption , and variable compression ratio engine could help in this. However , previous experiments show that , increasing the Compression ratio beyond a certain point ,could cause an increase in early detonation , and lead to knocking. Thus we could use high compression ratio at low load condition. Low compression ratio could be used for full load condition , to prevent knocking.
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THANK YOU
