Development of methodology for designing wave disk engine based on wave dynamics and thermodynamic analysis

Abstract Wave rotor technology is based on pressure wave compression and expansion wave scavenging in a compressible fluid. This can be used to realize compression and exhaust strokes of an IC engine in a rotating disk, power extraction is governed by turbo-machinery principle and constant volume combustion is achieved which makes the wave disk engine a highly fuel efficient devise for power extraction. Wave disk engine primarily consists of a rotor mounted in housing with inlet and outlet ports carved to implement given port timings. As the rotor revolves each channel outlet faces the housing wall for a fraction of revolution until it gets exposed to the outlet port opening in the housing. At high rpm this event is equivalent to sudden opening of valve in a channel filled with pressurized gases, which generates expansion waves. The gases coming out impart angular momentum to the rotor generating power very similar to a reaction turbine operation. As the rotor passes the opening port it faces the housing wall, this event is equivalent to sudden closing of valve which generates hammer shock compressing the air-fuel mixture. When both the ports are closed the spark ignition initiates constant volume combustion resulting in a pressure gain combustion which provides better fuel efficiency. The design principle of wave disk engine demands research in wave propagation in gases in a variable area channel and understanding of work done by unsteady flow of gases. Therefore this work focuses on understanding of wave dynamics in a variable area duct, generating corresponding thermodynamic process diagrams and estimating thermodynamic efficiency of overall cycle. Port timing is most crucial design parameter to realize the benefits of constant volume combustion and a design approach is developed to determine port timings for a given shape of channel by running numerical simulations and constructing cycle diagrams. Three different rotor shapes are analyzed using this approach and an optimized channel shape is suggested.