Evaluation of the vaporization energy of a diesel and a biodiesel spray via infrared imaging and 1D model

This paper deepens the study on fuel evaporation in a modern internal combustion engine fed with commercial diesel fuel and the biofuel rapeseed methyl ester (RME) by modeling and infrared diagnostics. A one-dimensional (1D) model has been coupled to experimental results of infrared imaging measurements carried out in a research compression ignition engine equipped with the head of a commercial diesel engine. Images of the in-cylinder processes have been recorded at different crank angles through the optical access in the piston. An infrared band-pass filter has been used to isolate the fuel vapor phase (3.4 µm) and to analyze the spatial evolution and concentration of fuel in the combustion chamber. On the other hand, a 1D model of fuel injection has been implemented to calculate the instantaneous fuel vapor mass and the evaporation rate. The energy required for the vaporization of the fuel and its contribution to the calculated rate of heat release in the cylinder has been evaluated. Model results of fuel concentration inside the jet structure are in line with qualitative infrared data. A slower evaporation rate has been estimated for RME and a correspondence between the peak of evaporation rate and the IR signal has been noted.