Performance of Universal Reciprocating Heat-Engine Cycle with Variable Specific Heats Ratio of Working Fluid.

Lingen Chen,Chang Liu,Huijun Feng,Giulio Lorenzini,Yanlin Ge

doi:10.3390/e22040397

Abstract

Considering the finite time characteristic, heat transfer loss, friction loss and internal irreversibility loss, an air standard reciprocating heat-engine cycle model is founded by using finite time thermodynamics. The cycle model, which consists of two endothermic processes, two exothermic processes and two adiabatic processes, is well generalized. The performance parameters, including the power output and efficiency (PAE), are obtained. The PAE versus compression ratio relations are obtained by numerical computation. The impacts of variable specific heats ratio (SHR) of working fluid (WF) on universal cycle performances are analyzed and various special cycles are also discussed. The results include the PAE performance characteristics of various special cycles (including Miller, Dual, Atkinson, Brayton, Diesel and Otto cycles) when the SHR of WF is constant and variable (including the SHR varied with linear function (LF) and nonlinear function (NLF) of WF temperature). The maximum power outputs and the corresponding optimal compression ratios, as well as the maximum efficiencies and the corresponding optimal compression ratios for various special cycles with three SHR models are compared.

Highlights

The specific heats (SH) of working fluid (WF) will change with the occurrence of the combustion reaction, and this change has a great influence on cycle performance
The air standard (AS) reciprocating heat-engine cycle (RHEC) model considering heat transfer loss (HTL), friction loss (FL) and irreversibility loss (IIL) is established in this paper
The cycle performances with various specific heats ratio (SHR) are analyzed

Summary

Introduction

Using finite time thermodynamics (FTT) [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16] to optimize the performances of practical cycles and processes, a series of achievements were made, including Novikov heat engines [17,18,19,20,21], Curzon–Ahlborn heat engines [22,23,24], solar-driven engines [25,26], Maisotaenko cycle [27,28,29], OTEC systems [30,31,32], Kalina cycle [33], thermoelectric devices [34,35,36,37,38,39], dissipative heat engine [40], refrigeration cycle [41], earth [42], quantum systems [43,44,45,46,47,48,49,50], economic systems [51,52], chemical systems [53,54,55,56,57,58,59,60,61], reciprocating internal combustion engines [62,63,64,65,66], etc. Reference [73] founded a more universal RHEC (including Miller, Dual, Atkinson, Brayton, Diesel and Otto cycles) which consisted of two endothermic processes, two exothermic processes and two adiabatic processes, derived the PAE and PC, and gave out the maximum power output and the maximum efficiency orders of each special cycle. In the third class, considering the variable SHR of WF with the LF of temperature, Ebrahimi established endoreversible [90] and irreversible [91] Dual cycle, endoreversible Atkinson cycle [92], endoreversible Diesel cycle [93] and irreversible Otto cycle [94] models, and analyzed the impacts of variable SHR and loss items on cycle PC. The maximum power outputs (MPOs) and the corresponding optimal compression ratios, as well as the maximum efficiencies and the corresponding optimal compression ratios for various special cycles with three SHR models will be compared

Cycle Model

Power Output and Thermal Efficiency

Discussions

Numerical Examples

Findings

Conclusions