Numerical Assessment of Four-Port Through-Flow Wave Rotor Cycles With Passage Height Variation

The potential for improved performance of wave rotor cycles through the use of passage height variation is examined. A Quasi-one-dimensional CFD code with experimentally validated loss models is used to determine the flowfield in the wave rotor passages. Results indicate that a carefully chosen passage height profile can produce substantial performance gains. Numerical performance data are presented for a specific profile, in a four-port, through-flow cycle design which yielded a computed 4.6% increase in design point pressure ratio over a comparably sized rotor with constant passage height. In a small gas turbine topping cycle application, this increased pressure ratio would reduce specific fuel consumption to 22% below the un-topped engine; a significant improvement over the already impressive 18% reductions predicted for the constant passage height rotor. The simulation code is briefly described. The method used to obtain rotor passage height profiles with enhanced performance is presented. Design and off-design results are shown using two different computational techniques. The paper concludes with some recommendations for further work. Introduction Pressure-gain wave rotors represent a promising technology for use as high pressure, high temperature topping cycles in gas turbine engines. 1-3 These devices utilize unsteady gasdynamic waves, rather than the airfoils of their conventional turbomachinery counterparts, to transfer energy to and from the working fluid. Besides significantly improving the performance of gas turbine engines which they top, the potential advantages of wave rotors include rotor metal temperatures substantially below the combustor discharge temperature, rotational speeds which are approximately one third those of conventional turbomachinery for the same application, a wide operating range, 4 and relatively simple rotor geometry. Recent research efforts have focused largely on four-port, through-flow cycles with axially aligned passages