Thermodynamic Analysis and Comparison of the Air-Standard Atkinson and Dual-Atkinson Cycles with Heat Loss, Friction and Variable Specific Heats of Working Fluid

Employing finite-time thermodynamics, the effects of irreversibility factors, i.e., friction, heat transfer of cylinder wall, compression and expansion efficiencies and variable specific heats (temperature-dependent specific heats of the working fluid) on the air-standard Atkinson and Dual-Atkinson cycles are analyzed. In addition, a numerical comparison between the Atkinson and Dual-Atkinson cycles is made. Moreover, numerical examples show the relations between the thermal efficiency and compression ratio and between power and compression ratio. As mentioned, compression ratio, rc, initial temperature, T1, specific heat defined by ap, bv and k1, friction defined by b and heat transfer defined by α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\alpha}$$\end{document} and β\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\beta}$$\end{document} are some of the key parameters of the internal combustion engines. The effects of these on the performances of the Atkinson and Dual-Atkinson cycles are presented in this article. According to the findings, the thermal efficiency and the output power of the Dual-Atkinson are higher than those of the Atkinson cycle at the same condition. Also, these irreversibility factors must be considered to design and analyze the Atkinson and Dual-Atkinson cycles. The obtained results also will provide guidance for the design of internal combustion engines.