Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability

Entropy

Pedro L. Curto-Risso¹  Alejandro Medina¹  Antonio Calvo-Hernández¹  Lev Guzmán-Vargas¹ 

[1] ¹Instituto de Ingeniería Mecánica y Producción Industrial, Universidad de la República, Montevideo 11300, Uruguay

关键词: spark ignition engine;    quasi-dimensional simulations;    cycle-to-cycle variability;    energetics;   

DOI  :  10.3390/e15083367

来源: mdpi

【 摘 要 】

We study the energetic functions obtained in a simulated spark-ignited engine that incorporates cyclic variability through a quasi-dimensional combustion model. Our analyses are focused on the effects of the fuel-air equivalence ratio of the mixture simultaneously over the cycle-to-cycle fluctuations of heat release (Q_R) and the performance outputs, such as the power (P) and the efficiency (Q_R). We explore the fluctuant behavior for Q_R, P and n related to random variations of the basic physical parameters in an entrainment or eddy-burning combustion model. P and n show triangle shaped first return maps, while Q_R exhibits a structured map, especially at intermediated fuel-air ratios. Structure disappears to a considerable extent in the case of heat release and close-to-stoichiometry fuel-air ratios. By analyzing the fractal dimension to explore the presence of correlations at different scales, we find that whereas Q_R displays short-range correlations for intermediate values of the fuel ratio, both P and n are characterized by a single scaling exponent, denoting irregular fluctuations. A novel noisy loop-shaped P vs. n plot for a large number of engine cycles is obtained. This plot, which evidences different levels of irreversibilities as the fuel ratio changes, becomes the observed loop P vs. n curve when fluctuations are disregarded, and thus, only the mean values for efficiency and power are considered.

【 授权许可】

CC BY   
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.