Thermodynamic Analysis and Comparison of Performances of Air Standard Atkinson, Otto, and Diesel Cycles with Heat Transfer Considerations

Abstract

This paper focuses on the overall performances of Otto, Atkinson, and Diesel air standard cycles. This study compares performance of these cycles with regard to parameters such as variable specific heat ratio, heat transfer loss, frictional loss, and internal irreversibility based on finite-time thermodynamics. The relationship between thermal efficiency and compression ratio, and between power output and compression ratio of these cycles are obtained by numerical examples. In this study, it is assumed that during the combustion process, the heat transfer occurs only through the cylinder wall. The heat transfer is affected by the average temperature of both the cylinder wall and the working fluid. The results show that for each cycle, with the increase of the compression ratio in the specific mean piston speed, power output and thermal efficiency first increase and after reaching their maximum value, start to decrease. The results also indicate that maximum power output and maximum thermal efficiency of an Atkinson cycle could be higher than the values of these parameters in Diesel cycle and Otto cycle in the same operating conditions. The maximum power output and the maximum thermal efficiency of the Otto cycle have the lowest value among studied cycles. By increasing the mean piston speed, power output and thermal efficiency of Atkinson, Diesel, and Otto cycles start to decrease. The results of this study provide guidance for the performance analysis and show the improvement areas of practical Otto, Atkinson, and Diesel engines. C⃝ 2017 Wiley Periodicals, Inc. Heat Trans Asian Res, 46 (7): 996-1028, 2017; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj).

Demystifying the lifecycle environmental benefits and harms of LNG as marine fuel

“…The LS-HPDF engines work on a Diesel cycle in gas mode. Diesel cycle is operated at high temperature and pressure, compared to Otto cycle [30]. Since the formation of NOx emissions, which comprise mainly NO and NO2, are highly sensitive to the temperature and gas injection pressure (300 bar) in combustion chambers, NOx emission levels with Diesel cycle are normally greater than that with Otto cycle engines [31].…”