MINI PROJECT ON

MAINTENANCE OF VARIABLE COMPRESSION RATIO ENGINE

ARUN BABUARUN THANKACHANASHIK SAHADEVAN

GUIDED BY Dr. SUDHIR KUMAR . R

PROJECT TEAM

Variable Compression EngineTheoryOur WorkExperiment & ResultConclusion

CONTENTS

What is 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

Compression Ratio (CR)

CR – How is it determined?

volcylinder

volcylinderCR

min

max

-or-

Where b=cylinder bore (diameter) s = piston stroke lengthVc = Clearance volume

For an ideal Otto cycle the theoretical efficiency is given by,

Where r is the compression ratio and γ is the ratio of specific heats. For an SI-engine operating at stoichiometric mixture γ=1:3.

Theoretically, increasing the compression ratio of an engine can improve the thermal efficiency of the engine by producing more power output.

If the compression ratio is too high, the air/fuel mixture are exposed to higher temperatures, the fuel will auto ignite, giving rise to knocking, which could damage the engine.

Increased Efficiency and Pollution Reduction with VCR:

VCR - advantages

CR modified to meet power demand (CR’s range from 7:1 to 21:1)

Increased fuel efficiency Claims of up to 30% reduction in fuel

consumption Adding variable valve actuation and turbo-

charging further improves fuel efficiency (7-10% additional reduction in fuel consumption)

Reduced combustion emissions

VCR - Disadvantages

New technology results in high research and development and manufacturing costs.

Reliability is not proven. Consumer reactions are unknown

and unpredictable. Repairs and maintenance initially

may be difficult and costly.

Ways to Modify CR

Moving the cylinder head. Variation of combustion chamber volume. Variation of piston deck height. Modification of connecting rod geometry. Moving the crankpin within the

crankshaft (effectively varying the stroke).

Moving the crankshaft axis.

Ways to Modify CR:

A: articulated cylinder head

B: hydraulic pistons

C: eccentrics on bearings

D: multilink rod-crank mechanisms

E: additional piston in cylinder head

F: gear-based mechanisms

OUR WORK

VARIABLE COMPRESSION RATIO ENGINE TEST RIG

SPECIFICATIONS FOUR STROKE,SINGLE

CYLINDER,VERTICALLY MOUNTED PETROL ENGINE

BRAKE POWER : 2.20 kW SPEED : 2000rpm STROKE : 66.7 mm BORE : 70 mm ORIFICE DIA : 20 mm

FAULT DETECTION

We find out the following components were not in working condition1. Spark Plug2. Condenser3. Contact Switch4. Scale showing Compression Ratio5. Cooling Water Pipe6. Fuel pipe

CHANGING COMPRESSION RATIO

EXPERIMENT

Note down the time taken for 10cc fuel consumption by varying CR(at 2000 rpm)

At load we conduct the same experiment ,ie note down the time taken for 10cc fuel consumption by varying CR( at 2000 rpm, 110 v and 3 Ampere)

CHARACTERISTICS

Conclusions

Variable Compression Ratio engines have great potential to increase engine power and fuel economy.

When coupled with technologies such as turbocharging, variable valve actuation, and direct fuel injection, the effectiveness of the system is further increased.

Once established, this technology will likely become commonplace due to increasing energy and environmental concerns and the ease of integration.

THANK YOU