This document summarizes a technical seminar presented by Ravikumar Devappa Baraker on variable compression ratio engines. It defines compression ratio and discusses how a variable compression ratio can be achieved by altering the clearance volume and swept volume. The optimal compression ratio depends on factors like inlet air temperature. Variable compression ratio technology allows the compression ratio to be adjusted based on engine load, improving efficiency and reducing emissions and fuel consumption. However, the technology also has drawbacks like high costs and mechanical complexity. In conclusion, variable compression ratio has great potential but commercialization faces challenges.

1. DEPARTMENTOF MECHANICAL ENGINEERING
BAPUJI INSTITUTE OF ENGINEERING &
TECHNOLOGY
TECHNICAL SEMINAR ON
APRIL 20,2018
PRESENTED BY
RAVIKUMAR DEVAPPA BARAKER
PROJECT GUIDE Dr.S KUMARAPPA Ph.d,M.I.S.T.E
ANAND K J M.Tech Professor and Head
Assistant professor Dept. of Mechanical engineering
Dept. of Mechanical engineering
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2. contents
 Introduction
 Compression ratio
 Variable compression ratio
 CR Characterstics
 Ways to modify CR
 VCR Advantages
 VCR Disadvantages
 Conclusion
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3. WHAT IS IT ?
 It is the ratio by which the fuel/air mixture is
compressed
before it is ignited.
 limited in conventional engines due to auto ignition.
 Determines how efficiently the engine can utilize the
energy in the fuel.
 Variable compression ratio can be obtained by
alternating
The clearance volume.
both the clearance volume & the swept
volume.
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5. optimum compression ratio is determined by
 Inlet air temperature
 Engine coolant temperature
 Exhaust gas temperature
 Engine knock
 Fuel type
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6. INTRODUCTION TO VCR
• Variable compression ratio ia a technology to adjust the
compression ratio of an internal combination engine while
the engine is in operation.
• This is done to increase efficiency of the fuel while under varying
loads .Higher loads require lower ratios to be more efficient & vice
versa.
• Variable compression engines allow for the volume above the
piston at the top dead centre to be changed. For automotive use
needs to be done dynamically in response to the load and
driving demands. 6

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8. VARIABLE COMPRESSION RATIO
TECHNOLOGY
From,
Ravikumar Baraker
Department of Mechanical Engineering,
BIET ,Davangere 8

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10. WAYS TO MODIFY COMPRESSION
RATIO
• Crowning of cylinder head with the spring.
• Crowning the piston.
• Moving the crankshaft axis.
• Eccentric crankshaft bearing
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11. CROWNING OF CYLINDER HEAD & PISTON WITH THE SPRING
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12. 0
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MOVING THE CRANKSHAFT AXIS

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ECCENTRIC CRANKSHAFT BEARING

14. For an ideal otto cycle the theoroetical efficiciency is given by
𝜂 = 1 − (1/𝑟
𝛾_1
)
 Where r is the compression ratio and 𝛾 is the ratio of
specific heats .
 Theoretically,increasing the compression ratio of an engine
can improve the thermal efficiency of the engine by produ
cing more power output.
 If the compression ratio is too high,the air/fuel mixture are
exposed to higher temperature , the fuel will auto ignite
giving rise to knocking,which will damage the engine.
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18.  CR modified to meet the power demand ( CR’s range
from 7:1 to 21:1)
 Increased fuel efficiency
• Claims of upto 30% reduction in fuel consumption.
• Adding variable valve actuation & turbo charging
further
improves fuel efficiency, 7-10% additional reduction
in the
fuel consumption.
 Reduced combustion emissions. 18

19. • New technology results in high research and
development and manufacturing costs
• Not adopted in some industries due to mechanical
complexities.
• Consumer reactions are unknown and unpredictable.
• Reparirs & maintanance are initially may be difficult
&costly.
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20. Conclusion
 Variable compression ratio engines have great potential
to increase engine power and fuel economy.
 When coupled with technologies such as turbocharging
and direct fuel injection.The effectiveness of the
system is further increased.
 Once established ,this technology will likely become
commanplace due to increasing energy and
environmental concerns and the ease of integration
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