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In order to meet future emission regulations, various new combustion concepts are being developed, several of which incorporate advanced diesel injection strategies, e.g. multiple injections, offering attractive potential benefits. In this study the effects of split injections on soot evolution in diesel flames were investigated in a series of flame experiments performed using a high pressure, high temperature (HP/HT) spray chamber and laser-induced incandescence apparatus to measure soot volume fractions. The focus was on split injections with varied dwell times preceded by a short pilot. The results, which were analyzed and compared to results from engine tests, show that net soot production can be decreased by applying an appropriate split injection strategy.

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.

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.

The effects of multiple injections on engine-out emissions from a high-speed direct injection (HSDI) diesel engine were investigated in a series of experiments using a single cylinder research engine. Injection sequences in which the main injection was split into two, three and four pulses were tested and the resulting emissions (NOx, CO HC and particulate matter), torque and cylinder pressures were compared to those obtained with single injections. Together with the number of injections, the effects of varying the dwell time were also investigated. It was found that dividing the main injection into two parts lowered the engine-out particulate and CO emissions and increased fuel efficiency. However, it also resulted in increased NOx emissions.