Parametric Numerical Study on the Performance Characteristics of a Micro-Wave Rotor Gas Turbine

Abstract

In this paper, an alternative micro-gas turbine is proposed, where the traditional compressor-turbine arrangement is replaced by an axial, throughflow wave rotor. The investigated wave rotor features symmetrically cambered wall profiles and angled port arrangement for shaft power extraction and uses shock and rarefaction waves for pressure exchange and to achieve gas compression and expansion within a single device. A validated quasi-one-dimensional model that solves the laminar Navier-Stokes equations using a two-step Richtmyer scheme with minmod flux limiter is employed to characterise and examine microgas turbine behaviour. The model accounts for wall heat transfer, flow leakage, wall friction and inviscid blade forces. In addition, modified boundary conditions consider finite passage opening effects and a simple steady-flow combustor model is defined that links the high pressure in- and outlet ports. The model is used to conduct a parametric study to investigate the effects of leakage gap, heat release rate, exhaust backpressure, as well as profile camber on gas turbine performance with a focus on generated combustor compression and expansion efficiency, shaft power and system efficiency. The implications of combustor pressure loss as well as effects of a potential recuperator are discussed as well. The results identify axial leakage and combustor pressure loss as primary drivers for enhanced performance. Finally, the results reinforce the capacity of wave rotors to compress and expand gas efficiently, while thermal efficiency remains below 10 percent.