A Numerical Study on the Effect of the Equivalence Ratio of Hydrogen/Air or Methane/Air Mixtures on Minimum Ignition Energy in Spark Ignition Process

Abstract

Two dimensional calculations of the spark ignition process for hydrogen/air or methane/air combustible mixtures were conducted. Two dimensional equations with chemical reactions were solved by fourth-order Runge-Kutta method in Cartesian coordinate system. Harten Yee's upwind TVD scheme was used to capture shock waves produced by a spark discharge. The spark energy was applied into the electrode gap for 1.0 micro second, which is equivalent to capacity spark discharge. Detailed reaction mechanisms for hydrogen and methane combustion chemistries were employed. Equivalence ratio of combustible mixtures were varied, and minimum ignition energy for hydrogen/air or methane/air combustible mixtures was calculated. Early stages of flame development were investigated. Success or failure of the ignition was measured by increase rate in the maxmum temperature after the end of spark discharge. The maximum temperature in the flame kernel decreases after the end of spark discharge and then reaches the minimum value. In the case of ignition, the maximum temperature increases after a certain period of time. In the success of ignitions in hydrogen/air and methane/air mixtures, the maximum temperature in methane/air mixtures is greater that in hydrogen/air ones. Profiles of minimum ignition energy as a function of the equivalence ratio of hydrogen/air and methane/air mixture gases were obtained. Peak values of minimum ignition energy for both of hydrogen/air and methane/air mixtures are observed under lean mixture conditions.