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[EN] Reactivity controlled compression ignition (RCCI) engines as one of low temperature auto ignition combustion strategies have shown a good performance to reduce NO (x) and soot emission while increasing engine thermal efficiency. Combustion control of these types of engines is relatively complex because of their ignition type which makes it difficult to have a direct control on the start of the combustion. In this research, combustion phase of an RCCI engine was modeled with using a control-oriented method. The combustion properties such as start of the combustion, crank angle degree where 50 percent of the fuel is burnt(CA50) and the burn duration were modeled in this research. A modified knock integral model was used for start of combustion estimation. Using the effect of spontaneous front speed, burn duration was modeled where a mathematical model is developed; and Wiebe function is used to model CA50. Indicated mean effective pressure(IMEP) also estimated in this modeling. To validate the developed models, five experimental data sets from a heavy-duty RCCI engine were used. The results show the maximum mean errors of 1.7, 1.9 and 2.3 crank angle degree (CAD) for start of combustion, burn duration(BD) and the CA50, respectively and this quantity is 0.5 bar for IMEP in steady state condition. The transient condition of the engine operation was also investigated. The results and trends are promising in all characteristics of the combustion process especially in the modeling of the indicated mean effective pressure where the majority of the data have errors less than 1.5 bar., The authors acknowledge the support of Spanish Ministerio de Economia, Industria y Competitivad through project TRA2016-78717-R (AEI/FEDER, EU). Alvin Barbier participation was funded through grant ACIF/2018/141, Programa Operativo del Fondo Social Europeo (FSE) de la Comunitat Valenciana 2014-2020. Alireza Kakoee participation was funded through grants 43/3/298624 from Iran ministry of science, research and technology.

A new criterion for the determination of the start of combustion (SOC) from the diesel engine in-cylinder pressure diagram was developed. It is defined as the maximum of the third-order derivative of the cylinder pressure with respect to the crank angle. This criterion declares SOC more precisely than other previously published criteria based on pressure diagnostics. This fact was proven analytically and was discernable from the analysis of the experimental data. Besides its accuracy it is also robust enough to allow automatic evaluation of the SOC during processing of the pressure data for a large number of cycles. By applying the first law of thermodynamics analysis to the engine cylinder it was discovered that the third-order derivative of the in-cylinder pressure with respect to the crank angle is the most suitable criterion for determination of the SOC from the in-cylinder pressure diagram. Subsequently, the criterion was validated through experimental data analysis of the in-cylinder pressure diagrams for various engine speeds and loads. In order to evaluate the rate of heat release (ROHR), which formed the base for the experimental validation, in-cylinder pressure diagrams were processed with a computer code based on the first law of thermodynamics. The cylinder pressure was measured with an advanced piezoelectric sensor at the resolution 0.1 deg CA. Top dead center was determined with the capacitive top dead center sensor. Due to the analytic foundation of the developed method and its validation through highly accurate experimental data it can be concluded that new criterion is credible for the determination of the SOC.