Spatial Development and Temperature of Spark Kernels Exiting into Quiescent Air

Measurements of the spatial development and temperature of spark kernels are useful for understanding the ignition process in spark ignition and gas turbine engines. Motivated by this, an infrared camera was used to make narrowband radiation intensity measurements of spark kernels exiting into quiescent air. An inverse deconvolution technique was developed to estimate the sensible energy and the path-integrated temperature of the kernels. This technique was evaluated using a sensitivity analysis, comparing results to temperature data obtained using background-oriented schlieren, and using a well-characterized hydrogen flame. Infrared images show that the kernels develop into a toroidal shape after exiting the igniter. The average spatial distribution where radiation from kernels is detected 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 the kernels exit the igniter. The average temperature values decrease by 30%, and the sensible energy decreases by 80%, over 2 cm of the spark kernel movement downstream.