Predictive Breakdown Modeling for Spark Plug Design 2020-01-0781

Spark-plug lifetime is limited by the ability of the ignition coil to generate a spark channel. Electrode erosion during operation causes the geometry to deform and the maximum voltage required to form a spark increases until the ignition coil is no longer able to form the spark channel. Numerical models that can analyze the breakdown of the plasma in a spark plug have typically been limited to vacuum electrical field simulations and full-fidelity plasma models. In the present work, we present a fast, predictive breakdown model that blends the speed and computational efficiency of electric field model and incorporates the essential physics of the breakdown event without having to pay the cost of solving the full set of plasma governing equations. The model is based on the Raether-Meeks criteria and estimates the breakdown probability at a spatial location as a function of the electric field, gas pressure and the total Townsend ionization coefficient at the point. 2D parametric studies are performed for different spark gaps and aspect ratios to assess the dependence of breakdown of these design parameters.