The stable combustion and blowout characteristics investigation of the water injection pre-cooling on the afterburners

Abstract

Mass Injection and Pre-compressor Cooling (MIPCC) technology is a promising approach to improve thrust performance, through extending the turbine mode upper operating limit in Turbine-Based Combined Cycle (TBCC) engines. However, The introduction of cooling media results in a lowered flame temperature inside the afterburner and a reduced oxygen content at its inlet, which might result in combustion instability and blowout. Employing both numerical simulations and experimental testing methods, the influences of water injection on the stable combustion characteristics and blowout behavior of the afterburner in the turbine mode of TBCC engine were investigated in this study. The numerical results indicated that the introduction of water injection reduced velocity and turbulence fluctuations within the recirculation zone behind the V-shaped blunt body flame stabilizer. The experimental results indicate that the combustion stability of the flame remains almost unaffected, with the maximal fluctuation rate increasing by about 2 % within the water injection range of up to 5 %. Moreover, the combustion stability is significantly enhanced and the flame combustion area is increased by 16.6 % at the water injection ratio of approximately 2 %, compared with the case without water injection under the incoming flow temperature condition of 900 K. Flame blowout behavior revealed the existence of an optimal water injection ratio (less than 2 %) that enhanced the flame’s resistance to disturbances near-blowout stage, and thereby improved the afterburner’s blowout performance. This study provides crucial theoretical support for the application of MIPCC technology in TBCC engines, offering significant implications for improving the combustion reliability of afterburners.