{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:33:04Z","timestamp":1760243584996,"version":"build-2065373602"},"reference-count":43,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2013,8,19]],"date-time":"2013-08-19T00:00:00Z","timestamp":1376870400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>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.<\/jats:p>","DOI":"10.3390\/e15083367","type":"journal-article","created":{"date-parts":[[2013,8,19]],"date-time":"2013-08-19T12:27:44Z","timestamp":1376915264000},"page":"3277-3296","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability"],"prefix":"10.3390","volume":"15","author":[{"given":"Pedro","family":"Curto-Risso","sequence":"first","affiliation":[{"name":"Instituto de Ingenier\u00eda Mec\u00e1nica y Producci\u00f3n Industrial, Universidad de la Rep\u00fablica, Montevideo 11300, Uruguay"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alejandro","family":"Medina","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica Aplicada, Universidad de Salamanca, Salamanca 37008, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5058-0395","authenticated-orcid":false,"given":"Antonio","family":"Calvo-Hern\u00e1ndez","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica Aplicada and IUFFYM, Universidad de Salamanca, Salamanca 37008, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lev","family":"Guzm\u00e1n-Vargas","sequence":"additional","affiliation":[{"name":"Unidad Profesional Interdisciplinaria en Ingenier\u00eda y Tecnolog\u00edas Avanzadas, Instituto Polit\u00e9cnico Nacional, Av. IPN 2580, L. Ticom\u00e1n, Mexico D.F. 07340, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fernando","family":"Angulo-Brown","sequence":"additional","affiliation":[{"name":"Departamento de F\u00edsica, Escuela Superior de F\u00edsica y Matem\u00e1ticas, Instituto Polit\u00e9cnico Nacional, Edif. No. 9 U.P. Zacatenco, Mexico D. F. 07738, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2013,8,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2811","DOI":"10.1103\/PhysRevE.57.2811","article-title":"Observing and modeling nonlinear dynamics in an internal combustion engine","volume":"57","author":"Daw","year":"1998","journal-title":"Phys. Rev. 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