A Heat Transfer Model for Low Temperature Combustion Engines

Low Temperature Combustion is a technology that enables achieving both a higher efficiency and simultaneously lower emissions of NO_x and particulate matter. It is a noun for combustion regimes that operate with a lean air-fuel mixture and where the combustion occurs at a low temperature, such as Homogeneous Charge Compression Ignition and Partially Premixed Combustion. In this work a new model is proposed to predict the instantaneous heat flux in engines with Low Temperature Combustion. In-cylinder heat flux measurements were used to construct this model. The new model addresses two shortcomings of the existing heat transfer models already present during motored operation: the phasing of the instantaneous heat flux and the overprediction of the heat flux during the expansion phase. This was achieved by implementing the in-cylinder turbulence in the heat transfer model. The heat transfer during the combustion was taken into account by using the turbulence generated in the burned zone. This allowed the model to accurately predict the instantaneous heat flux and the effect of varying the engine settings and the fuel on the heat transfer. Contrary to the existing heat transfer models, the new model does not require a recalibration of its model coefficients. Moreover, the model implements the mixture’s gas properties to make it fuel independent.