Thermodynamic Optimization for an Endoreversible Dual-Miller Cycle (DMC) with Finite Speed of Piston

Power output (P), thermal efficiency (eta) and ecological function (E) characteristics of an endoreversible Dual-Miller cycle (DMC) with finite speed of the piston and finite rate of heat transfer are investigated by applying finite time thermodynamic (FTT) theory. The parameter expressions of the non-dimensional power output ((P) over bar), eta and non-dimensional ecological function ((E) over bar) are derived. The relationships between (P) over bar and cut-off ratio (rho), between (P) over bar and eta, as well as between (E) over bar and rho are demonstrated. The influences of rho and piston speeds in different processes on (P) over bar, eta and (E) over bar are investigated. The results show that (P) over bar and (E) over bar first increase and then start to decrease with increasing rho. The optimal cut-off ratio rho(opt) will increase if piston speeds increase in heat addition processes and heat rejection processes. As piston speeds in different processes increase, the maximum values of (P) over bar and (E) over bar increase. The results include the performance characteristics of various simplified cycles of DMC, such as Otto cycle, Diesel cycle, Dual cycle, Otto-Atkinson cycle, Diesel-Atkinson cycle, Dual-Atkinson cycle, Otto-Miller cycle and Diesel-Miller cycle. Comparing performance characteristics of the DMC with different optimization objectives, when choosing (E) over bar as optimization objective, eta improves 26.4% compared to choosing (P) over bar as optimization objective, while (P) over bar improves 74.3% compared to choosing eta as optimization objective. Thus, optimizing E is the best compromise between optimizing P and optimizing eta. The results obtained can provide theoretical guidance to design practical DMC engines.