The effects of decreasing pressure on the spatial and temperature evolution of spark kernels are reported in this work. This effort is motivated by the need to ensure that combustors and augmentors consistently ignite at high altitudes, where the pressure is reduced. Spark kernels were produced in air at 300–1000 mbar. Infrared radiation emitted by the spark kernels was measured using an infrared camera (FLIR SC6700). Temperatures were determined from the radiation measurements using an inverse deconvolution technique. Spark kernels travel faster and further from the igniter as pressure is reduced. Radiation from spark kernels was detected up to three igniter diameters from the igniter tip at 1000 mbar, and at least 3.4 diameters at 300 mbar. Peak temperatures within kernels decrease with decreases in pressure. For example, peak temperatures (i.e., the 90th percentile temperatures) were 2070 and 2360 K at 380 and 1000 mbar, respectively. In contrast, average kernel temperatures increase with decreases in pressure. This trend is attributed to less mass in the spark kernel being heated as a result of the reduced density. The estimated sensible energy of the kernels decreased from 0.8 J at 1000 mbar to 0.25 J at 300 mbar.
Temperature Evolution of Spark Kernels at Subatmospheric Pressures
Journal of Propulsion and Power ; 38 , 3 ; 339-347
2021-11-24
9 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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