Impact of Fuel Conditioning and Combustor Injection Temperature on a Hydrogen Turboprop

Abstract Reducing aviation emissions demands revolutionary propulsive technologies, and gaseous hydrogen (H2) combustion offers high potential. However, using this fuel in aero engines requires complex fuel conditioning systems. Cryogenic liquid hydrogen stored in aircraft tanks must be warmed to an adequate temperature for injection in the combustor. Recuperating gas turbine heat via a heat exchanger around the exhaust conditions the fuel without hindering engine performance. This article examines the impact of combustor injection temperature of gaseous hydrogen on the performance of an H2-burn turboprop for a short-range subsonic application. Multipoint design and off-design modeling of the advanced hydrogen cycle enable identification of critical conditions in different flight phases. Different control strategies were used to evaluate tradeoffs between engine specific fuel consumption (SFC), weight, and fuel system complexity. To maintain aircraft performance, combustor fuel injection temperatures must be low. Analyses show that at injection temperatures of 400 K, even with low pressure drop in the engine nozzle, engine weight increases by 2.5% over a 200 K baseline. Without an integrated heat exchanger, the engine requires upsizing by 1.8%, 4%, and 9.9% for injection temperatures of 100 K, 200 K, and 400 K, respectively, increasing SFC by 3.7%, 8.6%, and 21%. However, low fuel injection temperatures and the reduction of fuel injection velocity could lead to flame stability issues. This research emphasizes the need to define feasible fuel injection temperatures and velocities, supporting fuel conditioning optimization for future H2 aircraft and affecting fuel burn.