Experimental and Numerical Assessment of an Optimised, Non-Axial Wave Rotor Turbine

Wave rotors exchange energy between different fluid streams via unsteady shock and expansion waves without the application of mechanical parts. This offers potential efficiency gains for a variety of thermodynamic cycles and applications ranging from refrigeration cycles to micro-gas turbines. This study deals with the experimental and numerical examination of anoptimised, four-port wave rotor turbine that functions both as a pressure exchange device and a power generating turbine. The wave rotor channels were optimised for increased power output at a single operating point and was based on a baseline wave rotor of 60 mm in diameter, 30 mm in length with symmetrical channel camber. Both units were experimentally tested on a gas stand in open-loop configuration using electrical heaters as a source of heat for the high pressure inlet and pressurised air for both inlet ducts. Throughout testing, the mass flow rates among high pressure in- and outlet were balanced. To gain further insights into the physics within the rotor, numerical simulations using a quasi-one-dimensional unsteady model were used alongside the experiments. The experimental results indicate a power increase of 74% at the target operating conditions. The increase in shaft power results in a reduced capacity to exchange pressure yielding a 4% lower pressure ratio. The peak shaft power recorded reached approximately 730 W and the maximum pressure ratio of approximately 1.65. The numerical model indicates that the gas dynamics within the rotor channels prove to be largely insensitive to the changes in blade camber and effective channel length.