Dynamics of ignition kernel in a liquid-fueled gas turbine model combustor studied via time-resolved 3D measurements

This work aims to study the ignition kernel dynamics with spatial-temporal resolved experimental measurements in spark-ignition processes of a liquid-fueled gas turbine model combustor. For this purpose, tomographic chemiluminescence combined with fiber endoscopes are used to measure the time-varying, volumetric CH* distribution of the ignition kernel in different combustor operating conditions at 10 kHz. Based on the time-varying 3D measurements, key properties of ignition kernels, including the 3D size, structure, orientation, growth direction, 3D and 3C (three-component) movement velocity, flame propagation speed, and their temporal evolutions are extracted to provide important insights into the kernel dynamics in such a highly localized transient process. Results show that the growth of the kernel is very sensitive to its motion trajectory. Generally, the kernels move following the flow rotation in the tangential direction, but are oriented along the radial direction and temporally evolve toward the radial direction as the ignition event progresses. Splitting and moving inward are also observed in the radial direction, which is not beneficial to the kernel growth. The evolution of flame propagation speed (S-T) during the ignition process shows two distinct stages. In the first stage, ST increases following the power-law of S-T = alpha At alpha-1. The rapid growing kernels are with the higher A and lower alpha. While in the second stage, ST oscillates around a mean value. The transition between the two stages is associated with the corrugation levels of the kernel. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.