Numerical study of high-energy spark ignition characteristics in a scramjet combustor

Reliable ignition is a fundamental prerequisite for the scramjet engines. In order to improve the reliability of ignition, further enhance the application of spark ignition in engineering, and improve the ignition ability in the field of supersonic combustion, an innovative long electrode distance high-energy spark igniter (LHSI) system was proposed by our research team. To reveal the instantaneous ignition characteristics of the LHSI, a simulation model of the LHSI is established and verified by experiments. Based on this, the formation and development of the initial flame kernel of vaporized kerosene and the ignition characteristics of LHSI in a scramjet combustor were simulated and compared with the conventional high-energy spark igniter (HSI). The analysis revealed that the success of the cavity ignition is greatly influenced by the local equivalent ratio of the initial flow field and the penetration depth of the initial flame kernel. Meanwhile, the fore recirculation zone of the cavity plays a key role in stabilization and development of the initial flame kernel. Compared with the HSI, the LHSI can produce initial flame kernel with higher penetration and greater size, which is the main reason why LHSI has a broader ignition boundary. The simulation results show that the oil-rich and oil-lean ignition boundaries of LHSI are about 17 % and 55 % wider than those of HSI, respectively.