An investigation of controlling two-peak heat release rate for combustion noise reduction in split-injection PCCI engine using numerical calculation

A combustion method called Noise Canceling Spike (NC-Spike) Combustion [1, 2] has been reported in the co-author's previous paper, which reduces combustion noise in PCCI with split injection. This NC-Spike Combustion uses interference of the following "spike" of pressure rise on the preceding peak of pressure rise. The overall combustion noise is reduced by lowering the maximum frequency component of the noise spectrum. The period of this frequency is two times of the time interval between the two peaks of the pressure rise rate. This maximum load range of conventional PCCI combustion is limited by the combustion noise, since the maximum pressure rise rate increases as the amount of injected fuel increases. The NC-Spike Combustion has a potential to extend of the operating range of PCCI combustion. In this paper, we investigated feasibility and controllability of the two-peak heat release rate during high temperature heat release by adding fuel in the adiabatic compression process of pre-mixed gas. Numerical calculation using a multi-zone model was performed in consideration of the fuel inhomogeneity. In this paper, 2 zone model was used for simplification. Pre-mixed gas was charged into one zone (zone-1) and air was charged into the other zone (zone-2), and fuel was added to zone-2 during adiabatic compression process. The controllability of the height and interval of heat release peaks by adding fuel was investigated. The results showed that the certain fuel addition timing generates the second heat release, and the interval of peak heat release rate could be controlled.