Abstract: 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 (QR) and the performance outputs, such as the power (P) and the efficiency (QR). We explore the fluctuant behavior for QR, 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 QR 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 QR 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.
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Curto-Risso, P.L.; Medina, A.; Calvo-Hernández, A.; Guzmán-Vargas, L.; Angulo-Brown, F. Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability. Entropy 2013, 15, 3277-3296.
Curto-Risso PL, Medina A, Calvo-Hernández A, Guzmán-Vargas L, Angulo-Brown F. Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability. Entropy. 2013; 15(8):3277-3296.
Curto-Risso, Pedro L.; Medina, Alejandro; Calvo-Hernández, Antonio; Guzmán-Vargas, Lev; Angulo-Brown, Fernando. 2013. "Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability." Entropy 15, no. 8: 3277-3296.