Thermodynamic analysis of endoreversible six-stroke Otto cycle with respect to equivalence ratio, residual gas fraction and mean piston speed

Abstract

The analysis of the six-stroke Otto cycle was performed using the finite-time thermodynamics dependence on mean piston speed, equivalence ratio and residual gas fraction. In the analysis, friction loss, internal irreversibilities, heat transfer losses were taken into account by empirical correlations. Relations between power output, thermal efficiency, and compression ratio were obtained by detailed numerical examples. The results were presented as comparative for four- and six-stroke Otto cycle. It was assumed that the cycles operate with the same mixture flow per second so that both performances of cycles can be compared. The study showed that more fuel flow can be supplied to the six-stroke Otto cycle for the same mixture flow. However, there was a slight increase in the maximum cycle temperature. For this reason, the results are crucial in providing a good guideline for evaluating and improving the performance of real six-stroke Otto engines.