Effects of Friction Loss Models and Cycle Parameters on the Performance of the Irreversible Dual-Miller Cycle

Since the effects of various irreversible losses and cycle conditions on the internal combustion engine performance are significant, it is important to compare the effects of the parameters on the performance in a cycle study. Thermodynamic cycle studies should take into account the irreversible losses such as internal irreversibility, friction losses, heat transfer losses, and the variation of the specific heat of the working fluid. This study aims at deriving the analytic equation with respect to ecological function of the irreversible Dual-Miller cycle (DMC) by using the specific heat model of polynomial, and comparing results of performance calculation of different friction losses, and analyzing the effect of the cycle parameters for optimum performance. The calculation results show that the friction loss has a considerable influence on the engine performance, but there is no significant difference in the choice of the cycle parameters for optimum performance. It is also found that optimizing the ecological function is an effective way to simultaneously increase the power and efficiency, and the friction loss is not affected. The cut-off ratio, which gives the ecological function maximum, is between the cut-off ratio, which gives the power and efficiency maximum, and the Miller cycle ratio, respectively, which is closer to the efficiency maximum. The Miller cycle ratio that maximizes performance is slightly larger than the cut-off ratio. The presented models and results are expected to provide guidelines for the design and optimization of DMC engines, and for the performance improvement and to perform the cycle modeling close to the cycle of the actual engine.