Numerical study on mixing and ignition enhancement characteristics in an air-intake strut supersonic combustor

• A novel mixing enhancement method of the supersonic combustor based on air-intake strut was proposed. • The mixing enhancement characteristics of the air-intake strut combustor under the effect of injection schemes and intake channel profiles were investigated. • The ignition enhancement characteristics of the air-intake strut combustor under the effect of injection schemes and intake channel profiles were discussed. • The mixing and ignition enhancement mechanism of the air-intake strut combustor were revealed. Numerical simulations were conducted on an air-intake strut supersonic combustor under the flight condition of Mach 6. The combustor inlet Mach number is Ma 0 = 2.8, the combustor inlet total temperature is T t 0 = 1680 K, and the combustor inlet total pressure is P t 0 = 1.68 MPa. The mixing characteristics of the air-intake strut combustor were analyzed. The results show that, compared to the wedge strut, the air-intake strut achieves mixing enhancement, and the mixing enhancement effect is affected by both the kerosene injection schemes and the profile of the air-intake channel. For kerosene injection schemes, the use of Injector 1 leads to the most significant mixing enhancement, while the use of Injector 2 leads to the least improvement. For the profile of the air-intake channel, the mixing enhancement effect can be improved when a converging outlet section is used. Further, the ignition enhancement characteristics were evaluated based on residence time and ignition delay time. The results show that, compared to the wedge strut, the air-intake strut achieves ignition enhancement, and the ignition enhancement effect is also affected by the kerosene injection schemes and the profile of the air-intake channel. Specifically, the use of Injector 3 or Injector 4 leads to the most significant ignition enhancement, while the use of Injector 2 fails to achieve ignition enhancement. For the profile of the air-intake channel, the ignition enhancement effect can be improved when a straight or diverging outlet section is used. Overall, the combustor exhibits the best comprehensive mixing enhancement and ignition enhancement when a straight ( c = 6 mm) or a divergent ( c = 8 mm) outlet section of air-intake strut is employed and Injector 1/Injector 3 combined kerosene injection scheme is adopted. Finally, the mechanisms of mixing enhancement and ignition enhancement of the air-intake strut combustor were analyzed. The results show that the air-intake strut achieves the mixing enhancement through staged mixing and the additional momentum imparted by the kerosene-air mixture intake jet. By regulating the kerosene distribution within the subsonic recirculation zone at the strut trailing edge, the ignition environment is improved, and a region where short ignition delay time region intersects with long residence time region is established, thereby achieving ignition enhancement in the combustor.