Research Article First and Second-Law Efficiency Analysis and ANN Prediction of a Diesel Cycle with Internal Irreversibility, Variable Specific Heats, Heat Loss, and Friction Considerations M. M. Rashidi, 1,2 A. Hajipour, 3 A. Mousapour, 4 M. Ali, 5 Gongnan Xie, 6 and N. Freidoonimehr 7 1 Mechanical Engineering Department, Engineering Faculty of Bu-Ali Sina University, Hamedan 651754161, Iran 2 Mechanical Engineering Department, University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 201101, China 3 Young Researchers and Elite Club, Ayatollah Amoli Branch, Islamic Azad University, Amol 4615143358, Iran 4 Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran 1477893855, Iran 5 Mechanical Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia 6 School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, China 7 Young Researchers and Elite Club, Hamedan Branch, Islamic Azad University, Hamedan 6518115743, Iran Correspondence should be addressed to M. Ali; mali@ksu.edu.sa Received 27 January 2014; Revised 13 March 2014; Accepted 18 March 2014; Published 24 April 2014 Academic Editor: Jiin Y. Jang Copyright © 2014 M. M. Rashidi et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e variability of speciﬁc heats, internal irreversibility, heat and frictional losses are neglected in air-standard analysis for diﬀerent internal combustion engine cycles. In this paper, the performance of an air-standard Diesel cycle with considerations of internal irreversibility described by using the compression and expansion eﬃciencies, variable speciﬁc heats, and losses due to heat transfer and friction is investigated by using ﬁnite-time thermodynamics. Artiﬁcial neural network (ANN) is proposed for predicting the thermal eﬃciency and power output values versus the minimum and the maximum temperatures of the cycle and also the compression ratio. Results show that the ﬁrst-law eﬃciency and the output power reach their maximum at a critical compression ratio for speciﬁc ﬁxed parameters. e ﬁrst-law eﬃciency increases as the heat leakage decreases; however the heat leakage has no direct eﬀect on the output power. e results also show that irreversibilities have depressing eﬀects on the performance of the cycle. Finally, a comparison between the results of the thermodynamic analysis and the ANN prediction shows a maximum diﬀerence of 0.181% and 0.194% in estimating the thermal eﬃciency and the output power. e obtained results in this paper can be useful for evaluating and improving the performance of practical Diesel engines. 1. Introduction e cycle experienced in the cylinder of an internal combus- tion engine is very complex; to make the analysis of an engine cycle much more manageable, the real cycle is approximated with an ideal air-standard cycle, which diﬀers from the actual one by some aspects. Variable speciﬁc heat of the working ﬂuid, internal irreversibility, heat transfer through the cylinder wall, and friction are factors that aﬀect the engine performance, whereas they are neglected in dealing with thermodynamic analysis of ideal air-standard cycles. e Diesel cycle is the ideal air-standard cycle for CI reciprocating engines. e CI engine, ﬁrst proposed by Rudolph Diesel in the 1890s, is very similar to the SI engine, diﬀering mainly in the method of initiating combustion [1–3]. In recent years, several attentions have been paid to the performance of internal combustion engines for diﬀerent cycles. Eﬀects of friction and temperature-dependent speciﬁc heat of the working ﬂuid on the performance of a Diesel engine have been performed by Al-Sarkhi et al. [4]. Performance analysis of air-standard Diesel cycle using an alternative irreversible heat transfer approach has been investigated by Al-Hinti et Hindawi Publishing Corporation Advances in Mechanical Engineering Volume 2014, Article ID 359872, 16 pages http://dx.doi.org/10.1155/2014/359872