Flame-Kernel Model for Analysis of Fiber-Optic Instrumented Spark Plug Data

A flame-kernel model is formulated for the analysis of data obtained using a recently developed spark plug equipped with fiber-optic flame-arrival detectors. The detectors measure the elapsed time from ignition to flame arrival at the detector locations for each engine cycle. The model, which assumes a flame kernel of elliptical cross section undergoing growth and convective displacement at constant rates, is used to estimate those rates from cycle-resolved measurements. It is shown that convection-rate estimation, ostensibly an interpolation of detector signals, in some cases involves an extrapolation that is sensitive to model assumptions. Implications concerning experimental procedure and data interpretation are discussed.