Analysis and evaluation of the low-temperature ignition performance of a gas-turbine can-annular combustor

Abstract

Abstract To clarify the low-temperature ignition characteristics of a gas-turbine can-annular combustor, a coupled numerical model of a torch igniter and combustor was established to examine ignition limits, torch-jet behavior, internal flow, fuel-droplet evaporation, and transient flame propagation. With an ignition energy of 4 J, the isolated torch igniter achieved successful ignition at 264 K but failed at 259 K and 234 K. In the coupled configuration, combustor ignition succeeded at 269 K but failed at 264 K. As the inlet-air temperature decreased from 334 K to 264 K, the area of the 1,500 K isosurface decreased from 0.0355 m2 to 0.0235 m2, a reduction of approximately 33.8 %, while the maximum flow velocity decreased only from 42 m/s to 41 m/s. Although the overall flow topology remained similar, lower temperature suppressed droplet evaporation, reduced vapor-phase fuel concentration, and increased the retention of relatively large droplets near the flame-tube head, primary holes, and walls. At 264 K, an initial ignition kernel still formed near the torch-igniter outlet, but insufficient thermal coverage, weakened evaporation, and deteriorated local mixing prevented sustained flame growth and propagation into the primary combustion zone.