Abstract:
Energy, economy and pollution factor of internal combustion engine profoundly influence the development of the society. It is well known that efficiency of an internal
combustion engine increases by compression ratio, and is limited due to knocking
and high thermal stress development in the combustion chamber of an engine. On
another side, an efficiency of internal combustion engine decreases toward the
more top engine speed. Considering this, a concept is proposed which can change
its compression ratio with speed. Variation in compression ratio is achieved by a
change in stroke length through moving crank pin within the crank. In this paper the
mechanism of operation and prediction of performance characteristics of variable
compression ratio spark ignition engine with varying speed using quasi-dimensional
combustion simulation mode is presented. It was observed that proposed mechanism
provides better fuel efficiency at higher engine speed. Further, it is inferred that 3 mm
increase in crank length results in 7% increment in thermal efficiency and 8% decrement in brake specific fuel consumption for 13 compression ratio at 6000 rpm.
