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Analysis of spray-wall interaction is a major issue in the study of the combustion process in DI diesel engines. Along with spray characteristics, the investigation of impinging sprays and of liquid wall film development is fundamental for predicting the mixture formation. Simulations of these phenomena for diesel sprays need to be validated and improved; nevertheless they can extend and complement experimental measurements. In this paper the wall film thickness for impinging sprays was investigated by evaluating the heat transfer across a temperature controlled wall. In fact, heat transfer is significantly affected by the wall film thickness, and both experiments and simulations were carried out to correlate the wall temperature variations and film height. The numerical simulations were carried out using the STAR-CD and the KIVA-3V, rel. 2, codes.

Wall wetting can occur irrespective of combustion concept in diesel engines, e.g. during the compression stroke. This action has been related to engine-out emissions in different ways, and an experimental investigation of impinging diesel sprays is thus made for a standard diesel fuel and a two-component model fuel (IDEA). The experiment was performed at conditions corresponding to those found during the compression stroke in a heavy duty diesel engine. The spray characteristics of two fuels were measured using two different optical methods: a Phase Doppler Particle Analyzer (PDPA) and high-speed imaging. A temperature controlled wall equipped with rapid, coaxial thermocouples was used to record the change in surface temperature from the heat transfer of the impinging sprays.

Both spray-wall and spray-spray interactions in direct injection diesel engines have been found to influence the rate of heat release and the formation of emissions. Simulations of these phenomena for diesel sprays need to be validated, and an issue is investigating what kind of fuels can be used in both experiments and spray calculations. The objective of this work is to compare numerical simulations with experimental data of sprays impinging on a temperature controlled wall with respect to spray characteristics and heat transfer. The numerical simulations were made using the STAR-CD and KIVA-3V codes. The CFD simulations accounted for the actual spray chamber geometry and operating conditions used in the experiments. Particular attention was paid to the fuel used for the simulations.