Influence of air-entraining intensity on the afterburner ignition, flame-holding and combustion characteristics

Reliable ignition, flame-holding, and efficient combustion are crucial, particularly for the newly designed afterburner in variable cycle engines (VCEs). Herein, the air-entraining parts are close-coupled with the cavity-strut structures to simulate the variable cycle conditions of afterburner for VCEs; further, the performances of the lean ignition, blowout, and combustion with air-entraining function are experimentally investigated. Furthermore, attempts have been made to provide reasonable explanations regarding the discrepancies aroused by altering air-entraining intensity. The results indicate that the air-entraining can compensate for the destruction of strut on flow patterns inside cavity, and widen the ignitable space for ignition and extend the flammable Ma number by slightly sacrificing the ignition performance near the leading edge of cavity. An air-entraining stream with an air-entraining rate of 3.77% can decrease the lean ignition and blowout fuel/air ratio (FAR) by 21.07% and 26.91%, respectively. Increasing the air-entraining intensity can accelerate the flamelet growth, but may conversely enforce the flame fluctuation, which is caused by flame quenching under intense turbulence. Moreover, the expansion of cavity flame towards the main-stream enhances with the increasing air-entraining intensity, resulting in an increment of over 200 K in temperature rise of cavity-strut combustor. (C) 2020 Elsevier Masson SAS. All rights reserved.