Spark ignition of combustible gas mixtures

A mathematical model is presented to simulate the evolution with time of a spark channel into a combustion wave. The model considers the phenomena associated with electrical breakdown and arc phases, the plasma conductivity and realistic transport coefficients at high temperatures, and a detailed chemical reaction scheme. The growth of the initial flame radius is calculated by a numerical integration of the model equations and compared with the experimental observation of Tagalian and Heywood. The time needed for the establishment of a flame propagation in the "like-laminar" regime was found to be strongly dependent on the breakdown energy and on the spark duration, and to a small extent on the initial pressure, temperature, and residual gas fraction. The model was used also to examine quantitatively the effect of some relevant parameters on the cycle-to-cycle variation in the steady-state burning velocity and it was concluded that the cycle-to-cycle variation is attributed mainly either to the inhomogeneity of the trapped mixture and/or to the cycle-to-cycle variation in trapped conditions; a variation of 5% of the volumetric efficiency affects the burning velocity by some ±13 %.