Advanced Combustor Concepts for Low Emissions Supersonic Propulsion

Abstract

Novel leanburn combustor concepts were designed and evaluated for supersonic aircraft propulsion, with a focus on cruise NOx emissions. Premixing to lean conditions is especially challenging at supersonic cruise because combustor inlet temperatures are high and autoignition times are short. However, combustor pressure is significantly lower than at takeoff, so at cruise this allows heated jet fuel to be vaporized before injection as an aid to mixing. Two concepts—differentiated by swirler aerodynamics, swirler size, and staging method—were evaluated in the work reported here, both using injection of vaporized jet fuel. Computational fluid dynamics (CFD) calculations of mixing and combustion were used to design hardware for each concept. Injectors for each were fabricated using stereolithography (SLA) for coldflow mixing tests, and using metal fabrication for subsequent combustion tests. Combustion test results show that emissions index for NOx (EINOx) < 5 was achieved for both concepts in singlesector tests at supersonic cruise combustor conditions.