Abstract
Power output (), thermal efficiency () and ecological function () 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 (), and non-dimensional ecological function () are derived. The relationships between and cut-off ratio (), between and , as well as between and are demonstrated. The influences of and piston speeds in different processes on , and are investigated. The results show that and first increase and then start to decrease with increasing . The optimal cut-off ratio 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 and 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 as optimization objective, improves 26.4% compared to choosing as optimization objective, while improves 74.3% compared to choosing as optimization objective. Thus, optimizing is the best compromise between optimizing and optimizing . The results obtained can provide theoretical guidance to design practical DMC engines.
Highlights
Petrescu et al [76,77,78,79] performed analysis and optimization for irreversible Otto cycle (OC) [76], Diesel cycle (DC) [77] and Carnot cycle [78,79] based on P and η characteristics by applying finite speed thermodynamics (FST) and the direct method [80,81,82]
Performance characteristics are discussed and analyzed when Dual-Miller cycle (DMC) are simplified to other cycles
The results show that, the faster the piston speeds are, the larger the maximum values of P and E are
Summary
Finite time thermodynamics (FTT) theory [1,2,3,4,5,6,7,8,9,10,11] plays an increasingly important role in analyzing and optimizing performance characteristics of the thermodynamic processes [12,13,14] and cycles [15,16,17,18,19]. Petrescu et al [76,77,78,79] performed analysis and optimization for irreversible OC [76], Diesel cycle (DC) [77] and Carnot cycle [78,79] based on P and η characteristics by applying finite speed thermodynamics (FST) and the direct method [80,81,82]. Gonca [92] considered internal irreversibilities to perform an optimization study on Diesel-Miller cycle (DiMC), Otto-Miller cycle (OMC) and DMC using the maximum power output and power density criteria, as well as the maximum thermal efficiency. Gonca and Sahin [93] considered finite rate of HT, HL and internal irreversibilities to analyze and optimize ECOP of irreversible ICE cycles, such as Dual-Diesel cycle (DDC), OMC and DMC. To σ [kε H2 (1 − ε H1 ) + ε H1 ](1 − T2 /TH )(1 + T0 /TH ) − [kε L1 (1 − ε L2 ) + ε L2 ][( T5 /TH − TL /TH )
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