Combustion Simulations for a Self Controlling Variable Compression Ratio Connecting Rod

Frank Stefan Will; Dylan Mayson

doi:10.4271/2012-01-1154

Variable compression ratio enables an engine to achieve increased efficiency at part loads, where the majority of driving occurs, without sacrificing full load power requirements or increasing the risk of engine knock. Although over 100 patents and patent applications exist none of these systems has been commercialized yet due to issues related to feasibility, cost and frictional loss.

A new approach of a self-controlling variable compression ratio connecting rod is presented that does not need a friction intensive external activation and that could even be retrofitted.

The potential in fuel consumption and exhaust emission reduction as well as increased power and torque output for this concept has been verified in combustion simulations utilizing the latest research results related to the dynamic heat transfer in the combustion chamber from Professor Kleinschmidt from the University of Siegen, Germany.

The self-controlling variable compression ratio connecting rod allows the con rod to compress at high load conditions thereby increasing cylinder volume to alleviate combustion pressures and temperatures and therefore limit knock onset. The biggest efficiency gains can be achieved at medium load where the reduction of heat loss during the compression of the connecting rod plays a major role additional to the well known efficiency gains of an increased compression ratio.

The combustion simulation results shows fuel consumption can be reduced by between 3% and 5% during part load and wide open throttle operation at various engine speeds. Emissions are also reduced significantly; particularly NO_x and CO emissions were reduced by up to 35%.

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Combustion Simulations for a Self Controlling Variable Compression Ratio Connecting Rod 2012-01-1154

SAE MOBILUS