Spatial Development and Temperature of Spark Kernels Exiting into Quiescent Air

Abstract

Measurements of the trajectory, temporal development, and temperature of spark kernels are needed for understanding the ignition process in spark ignition and gas turbine engines. Motivated by this, an infrared camera was used to obtain narrowband radiation intensity measurements of spark kernels exiting into quiescent air. An inverse deconvolution technique was implemented to estimate the temperature and sensible energy of the kernels. This technique is evaluated by a sensitivity analysis and comparisons to measurements of a well characterized flame. Infrared images show that the kernels develop into a toroidal shape after exiting from the igniter. The statistical distribution of the spark kernel trajectory is symmetric. Buoyancy forces are negligible. Regions of high and low radiation intensity are observed in the kernels, indicating temperature gradients within the gases. The radiation intensity emitted by the kernels decreases by more than an order of magnitude after exiting the igniter. Average temperature values decrease by less than 30% over 2 cm of the spark trajectory. Over that same distance the sensible energy of the kernels decreases by 80%.