Effect of different auto-ignition modeson the formation of pressure waves

Abstract

In internal combustion engines, different combustion technologiescan result in different knocks, such as the conventional knock of gasoline engines, the super knock and the knock of HCCI engines.Though they are all caused by the auto-ignition of unburned mixture which leads to the oscillation burning, the rising rate and the oscillation amplitude of their pressure are totally different. In order to explore the inner mechanism working behind them, three kinds of auto-ignition modes were built up to illustrate the different phenomena of pressure oscillations under different combustion technologies. The differences of these three kinds of auto-ignition modes in engines were clarified. In the method of Energy Injected, the heat source term of the energy equation can be changed based on the heat release rate obtained from experiments, and then a series of numerical simulations were conducted to realize these three kinds of auto-ignition modes. The numerical simulation shows that different auto-ignition modes will lead to different pressure waves, which can explain the different pressure rising rate and pressure oscillation amplitude. The method of Energy Injection based on the experiment measured heat release rate can accurately and rapidly identify the formation and propagation of pressure waves in the engine combustion chamber.