The benefits of wave rotor-topping in small (400 to 600 hp-class) and intermediate (3000 to 4000 hp-class) turboshaft engines, and large (80,000 to 100,000 lb, class) high bypass ratio turbofan engines are evaluated. Wave rotor performance levels are calculated using a one-dimensional design/analysis code. Baseline and wave rotor-enhanced engine performance levels are obtained from a cycle deck in which the wave rotor is represented as a burner with pressure gain. Wave rotor-topping is shown to significantly enhance the specific fuel consumption and specific power of small and intermediate size turboshaft engines. The specific fuel consumption of the wave rotor-enhanced large turbofan engine can be reduced while operating at significantly reduced turbine inlet temperature. The wave rotor-enhanced engine is shown to behave offdesign like a conventional engine. Discussion concerning the impact of the wave rotor/gas turbine engine integration identifies tenable technical challenges.

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A numerical model has been developed which can predict the dynamic (and steady state) performance of a wave rotor, given the geometry and time dependent boundary conditions. The one-dimensional, perfect gas, CFD based code tracks the gas dynamics in each of the wave rotor passages as they rotate past the various ducts. The model can operate both on and off-design, allowing dynamic behavior to be studied throughout the operating range of the wave rotor. The model accounts for several major loss mechanisms including finite passage opening time, fluid friction, heat transfer to and from the passage walls, and leakage to and from the passage ends. In addition it can calculate the amount of work transferred to or from the fluid when the flow in the ducts is not aligned with the passages such as occurs in off-design operation. Since it is one-dimensional, the model runs reasonably fast on a typical workstation. This paper will describe the model and present the results of some transient calculations for a conceptual four port wave rotor designed as a topping cycle for a small gas turbine engine. The wave rotor is being investigated for use as a core gas generator in future multi-spool gas turbine engines in order to achieve high peak cycle temperatures and pressures with conventional materials technology. The device, shown schematically in Fig. 1 uses gasdynamic waves to transfer energy directly to and from the working fluid through which the waves travel. Many descriptions of wave rotor operating principles exist in the literature (see Ref. 1 for a list), and one will not be provided here. The wave rotor is inherently an unsteady device in that gasdynamic waves are continually traversing the passages as they rotate within the casing. However, aside from the periodic fluctuations arising from the opening and closing of the passages as they enter and exit port regions, the flows in the ports are steady as long as the external boundary conditions are constant in time. This condition shall be referred to as steady state operation. Referring to Fig. 1, the external boundaries would include the combustor fuel flow, the upstream compressor discharge state, the downstream turbine inlet state, and the rotor speed.

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Over the past few decades, there has been significant research into propulsion concepts attempting to employ pressure gain combustion. Pressure gain combustion concepts to date have resulted in dynamic, non-uniform gas flows which are difficult to characterize and compare with more conventional forms of propulsion. This paper proposes a technique to derive for the pressure gain combustion device an equivalent, steady, uniform gas pressure that is available to do work or provide thrust, thereby providing a direct comparison with conventional propulsive devices.