Prediction of State of Gas Inside an I.C. Engine During Exhaust Blow Down Process

Prediction of state of gas inside an I.C.Engine cylinder during exhaust blow down process, is needed for optimizing exhaust port size and lead height relative to transfer port in case of a two stroke engine. The exhaust Blow Down Process (EBDP), here refers to a process which occurs as soon as the exhaust port opens, venting burnt charge accompanied by reduction in pressure, temperature, density & mass inside the barrel until atmospheric pressure or manifold pressure is attained.

The analysis predicts variations of pressure, density, temperature and mass flow rate with crank angle and time. The results are also interpreted in terms of lead height requirements. A lead height reduction of about 3 mm can cause about 35% decrease in mass flow rate during the initial part of induction process i.e. transfer process.