Combustion Simulations for a Self Controlling Variable Compression Ratio Connecting Rod 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
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 NOx and CO emissions
were reduced by up to 35%.