Otto and Diesel engine models with cyclic variability

Abstract

Typically, in an internal combustion engine, thousands of cycles are performed in a minute. In this sequence of cycles many physical and chemical quantities change from cycle to cycle. For example, the combustion heat changes due to residual gases, imperfect combustion and other reasons. In this work, we present two finite-time thermodynamics models for both an Otto and a Diesel cycle, in which the cyclic variability is studied as occurring in the heat capacities of the working fluid. The fluctuations considered are of the uncorrelated type (uniform and gaussian) and one correlated case (logistic map distribution). We find that in the correlated fluctuations case, the power output and the efficiency of both cycles reach bigger fluctuations than in the uncorrelated cases. This result can provide insights over the performance of internal combustion engines.