Abstract
It has been generally accepted that NOx formation increases as the maximum temperature or correspondingly the maximum pressure of a combustion system increases. Recently some exceptional experimental results have been reportes that under certain circumstance NOx formation could be reduced while the maximum pressure was increasing by varying the methods of combustion for the same kind of premixed gases. Until now that kind of results have been acquired only for the case of a dual opposed prechamber. But the mechanism has not been clearly understood yet. 3D computer simulation has been tried to clarify the mechanism. Flor this purpose KIVA-Ⅱ has been modified and applied to the model combustion chamber with which the same kind of experimental works have been done by the authors. A good agreement with the experimental results was achieved with the spatial and temporal resolution which is hard th be obtained by the experimental methods. And it was observed that for the dual opposed prechamber case the time for the NOx formation, which is non-equilibrium reaction, is shorter than any other case by an appropriate mixing process in the main combustion chamber. The shorter time reduceed heat loss through the combustion chamber walls and thereby obtaines the higher maximum pressure.