DEPENDENCE OF MINIMUM IGNITION ENERGY ON IGNITION PARAMETERS

Using two mathematical models (one allowing for pressure variations, and the other assuming the pressure to be uniform), the minimum ignition energies of a stoichiometric methane-air mixture are calculated. The effect of the initial pressure wave generated by the spark on minimum ignition energy is studied by comparing the results of the two models. The pressure wave is found to affect the values of minimum ignition energy for ignition times shorter than 2 μs. The dependence of minimum ignition energy on the kernel radius and ignition time are also investigated. The results show that as the kernel radius is decreased to small values, the minimum ignition energy reaches a constant value. The ignition times that give an optimum value of minimum ignition energy are in the range of 3 μs to 100 μs.Our results show that minimum ignition energy is strongly dependent on the ignition parameters, and a minimum value of 0.005 mJ is found for an ignition kernel radius of 0.0635 mm and an ignition time of 27.5 μs. This value is 70 times lower than the experimentally reported values. When a kernel radius of 0.5 mm is used, fair agreement with experiments is obtained. © 1990, Taylor & Francis Group, LLC. All rights reserved.