Longitudinally stratified combustion in wave rotors

A wave rotor may be used as a pressure-gain combustor, effecting wave compr ession and expansion, and Intermittent confined combustion, to enhance gas- turbine engine performance. It will be more compact than an equivalent pres sure-exchange wave-rotor system, but wilt have similar thermodynamic and me chanical characteristics. Because the allowable turbine blade temperature l imits overall fuel-air ratio to subflammable values, premixed stratificatio n techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperatures well below autoignition conditions. One-d imensional, nonsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reac tion model incorporating a flammability limit temperature. For good combust ion efficiency, a stratification strategy is developed that concentrates fu el at the leading and trailing edges of the inlet port. Rotor and exhaust t emperature profiles and performance predictions are presented at three repr esentative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak focal gas temperatures will cause excessive temperatures in the rotor housing unless additional cooling metho ds are used. The rotor temperature will be acceptable, but the pattern fact or presented to the turbine may be of concern, depending on exhaust duct de sign and duct-rotor interaction.