Longitudinally Stratified Combustion in Wave Rotors

A wave rotor may be used as a pressure-gain combustor, effecting wave compression and expansion, and intermittent cone ned combustion, to enhance gas-turbine engine performance. It will be more compact than an equivalent pressure-exchange wave-rotor system, but will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel ‐air ratio to sube ammable values, premixed stratie cation techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperatures well below autoignition conditions. One-dimensional, nonsteady numerical simulations of stratie ed-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a e ammability limit temperature. For good combustion efe ciency, a stratie cation strategy is developed that concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature proe les and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. Theresults indicate thatpeak local gas temperatures will causeexcessivetemperaturesintherotorhousingunlessadditionalcoolingmethodsareused. Therotortemperaturewillbeacceptable,but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct ‐rotor interaction.

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