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In order to investigate the effects of split injection on emission formation and engine performance, experiments were carried out using a heavy duty single cylinder diesel engine. Split injections with varied dwell time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the selected parameters, other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezo-electric injector. To interpret the observed phenomena, engine CFD simulations using the KIVA-3V code were also made. The results show that reductions in NOx emissions and brake specific fuel consumption were achieved for short dwell times whereas they both were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of single injections.

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.

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.

The injection process plays an important role in Diesel engines in terms of future emission legislations. Higher injection pressures and multiple injection events every cycle are a reality. To be able to understand how the fuel injection process can be further improved studies are needed on how higher pressure, multiple injections and multi orifice nozzles affect the overall process. The objective of this study was to further develop a measurement technique to determine injection rates and discharge coefficient for multi orifice nozzles. The technique used is based on measuring the instantaneous force of a fuel jet for a non-stationary injection process. The technique is applicable for multi orifice nozzles at high injection pressures. Both single and multiple injections can be resolved.

Soot particle size, particle concentration and volume fraction were measured by laser based methods in optically dense, highly turbulent combusting diesel sprays under engine-like conditions. Experiments were done in the Chalmers High Pressure, High Temperature spray rig under isobaric conditions and combusting commercial diesel fuel. Laser Induced Incandescence (LII), Elastic Scattering and Light Extinction were combined quasi-simultaneously to quantify particle characteristics spatially resolved in the middle plane of a combusting spray at two instants after the start of combustion. The influence that fuel injection pressure, gas temperature and gas pressure exert on particle size, particle concentration and volume fraction were studied. Probability density functions of particle size and two-dimensional images of particle diameter, particle concentration and volume fraction concerning instantaneous single-shot cases and average measurements are presented.