Energy Reports (Nov 2022)
Thermodynamic optimization criterion for practical Meletis–Georgiou cycle
Abstract
A new engine patent was awarded to Meletis and Georgiou in 1998. The engine is with vane rotor and the rotor is fully balanced and symmetric. It also has an exhaust gas recirculation (EGR) process. Symmetric rotor mechanism leads much smother running, and EGR process makes working fluid (WF) preheated before entering to compression stage which provides very high temperature after compression so that the compression ignition can be implemented. An irreversible (practical) Meletis–Georgiou heat engine cycle (IMGC) model with irreversible heat transfer loss (IHTL) as well as internal irreversibility loss (IIL) is built by applying finite-time thermodynamic theory. A non-linear relation between specific heat (NLRSH) of WF and WF’s temperature is considered. Analytical expressions of output work and thermal efficiency versus compression ratio (CPR) of the IMGC are derived. Performance analyses and optimizations of the IMGC are done using numerical calculations. Both of output work and thermal efficiency of the IMGC with NLRSH of WF and its temperature are larger than those with constant specific heat of WF at the same CPR. There are an optimal CPR make output work approaches maximum and another optimal CPR make thermal efficiency approaches maximum. The range of maximum output and maximum thermal efficiency gives the design optimization criterion for the IMGC, which means the thermodynamic trade-off optimization with the two performance indicators for the IMGC. Effect features of IHTL, IIL, NLRSH and other parameters on the optimal performances and optimization criterion are analyzed.
