AUTOIGNITION OF A TURBULENT PREMIXED GAS

Autoignition in a two-dimensional turbulent premixed gas at temperatures ranging from 1100 K to 1400 K was numerically simulated. Assuming one-step irreversible reaction, the physical parameters were arranged to simulate a 30% (2H-2 + O2) + 70% N2 gas mixture. The temperature initially fluctuated about 1% resulting from a given isotropic compressible turbulent flow with an intensity of 25 m/s. The temperature fluctuation affected the ignition delay time and the spacial heterogeneity of ignition. At low temperatures, the ignition occurred spottily and a propagating pressure wave appeared from the hot spot. The pressure wave completed the ignition process and strong pressure fluctuations remained. At high temperatures, almost homogeneous ignition occurred. The ignition delay time was decreased by the temperature fluctuations and showed a good agreement with the theoretical results of Arrhenius' law in homogeneous turbulent media. Large activation energy also contributed to heterogeneous autoignition.