Performance analysis and optimization of a supercharged Miller cycle Otto engine

One of the major alternatives of the Otto cycle has been examined to determine its potential for increased efficiency and net work power in the spark ignited internal combustion engine is to shorten the compression process relative to the expansion process by early close or late of intake valve. The modified Otto cycle is called Miller cycle. This paper deals with the analysis of a supercharged Otto engine adopted for Miller cycle operation. The Miller cycle shows no efficiency advantage and suffers a penalty in power output in the normally aspirated version. In the supercharged Otto engine adopted for Miller cycle version, it has no efficiency advantage but does provide increased net work output with reduced propensity to engine knock problem. Sensitivity analysis of cycle efficiency versus early close of intake valve and that of cycle net work versus early close of intake valve are performed. Optimization on the cycle efficiency is obtained.