Vol-3 Issue 4 2017 IJARIIE-ISSN(O)-2395-4396 5975 www.ijariie.com 520 Comparison of Air-Standard Atkinson, Diesel and Otto Cycles with Constant Specific Heats Sethi Upasna Vijay 1 , Mansha Kumari 2 1 Assistant Professor, Mechanical Engineering Department, Vadodara Institute of Engineering College, Kotambi, Gujarat, India 2 Assistant Professor, Mechanical Engineering Department, Vadodara Institute of Engineering College, Kotambi, Gujarat, India ABSTRACT The current paper examines the application of finite-time thermodynamics in order to compare the performance between air-standard cycles, i.e. Atkinson, Diesel and Otto cycles with constant specific heats of working fluid. The effects of input temperature and compression ratio on the net output work and efficiency of the Atkinson cycle, Diesel cycle and Otto cycle are analyzed. It is assumed that the compression and power processes are isentropic and any convective, conductive and radiative heat transfer to cylinder wall during the heat rejection process may be ignored. The efficiency of these cycles is compared for equal maximum temperature as well. The findings may present guidance concerning performance evaluation and improvement of practical internal combustion engines. Keyword: Atkinson Cycle, Diesel Cycle, Efficiency, Otto Cycle 1 INTRODUCTION Atkinson, Diesel and Otto cycles are three types of four-stroke engines. The Atkinson cycle was designed and built by James Atkinson in 1882. The Diesel cycle was invented by Rudolph Diesel in 1893, and the Otto cycle was developed by Nikolas August Otto in 1876 [1]. In recent years, many attentions have been paid to analyse the performance of internal combustion engines. The Comparison of performances of air- standard Atkinson and Otto cycles with heat transfer considerations has been made by Hou [2]. Performance analysis and parametric optimization of an irreversible Atkinson heat-engine are studied by Zhao [3] and Chen [4]. Optimization of Dual cycle considering the effect of combustion process on the power is studied by Chen [5]. The effect of heat transfer on the performance of an air-standard Diesel cycle is studied by Akash [6]. Effect of mean piston speed, equivalence ratio and cylinder wall temperature on performance of an Atkinson engine and Performance of an end a reversibe Atkinson cycle with variable specific heat ratio of working fluid have been examined by Ebrahimi [7], [8],[12]. Influence of heat loss on the performance of an air-standard Atkinson cycle examined by Hou [9] and the effects of friction and temperature-dependent specific-heat of the working fluid on the performance of a Diesel- engine is investigated by Al-Sarkhi [10]. In this paper, a comparative study for the performance of the Atkinson, Diesel and Otto cycles are investigated. The related analysis has been done as a case study regarding the constant maximum temperature per cycle and input temperature. 1.1 Nomenclature C p : Constant pressure specific heat (kJ/kg.K) r: Cut-off ratio Cv: Constant volume specific heat (kJ/kg.K) r c : Compression ratio k: Specific heat ratio (C p /C v ) r p : Pressure ratio q in : Heat added to working fluid (kJ/kg) s: Entropy (kJ/kg.K) T i : Temperature at state i (K) w: Network output (kJ/kg) V i : Volume at state i (m 3 ) η: Efficiency