In the foreseeable future, the transportation sector will continue to rely on internal combustion engines. Therefore, reduction of engine-out emissions and increase in engine efficiency are important goals to meet future legislative regulations and restricted fuel resources. One viable option, which provides lower peak temperatures and increased mixture homogeneity and thus simultaneously reduces nitric oxide as well as soot, is a low-temperature combustion (LTC) concept. However, this might result in an increase of unburnt hydrocarbon, carbon monoxide, and combustion noise due to early combustion phasing and lower engine efficiency. Various studies show that these drawbacks can be compensated by advanced injection strategies, e.g. by employing multiple injections.
The aim of this work is to identify the optimum injection strategy, which enables a wide range of engine operating points in LTC mode with reduced engine-out emissions. To achieve this goal, experiments with variations in the maximum pressure rise rate, injection pressure, intake pressure, and the EGR-rate are carried out and analyzed. Numerical investigation is carried out by three dimensional (3D) computational fluid dynamics (CFD) simulations in CONVERGE software for several multiple injection strategy conditions. CFD could predict ignition delay, pressure rise and heat release rate of each injection and hence overall injection rate shaping combustion process with good accuracy.