Wave Rotor Topping Cycles
for Gas Turbine Engines

1-D Multi-Passage Simulation

Although the steady-state performance of the wave rotor appears promising for topping conventional gas turbine engines, critical questions concerning transient and dynamic performance remain. For example, how does the wave rotor respond to fuel flow changes? Does a wave rotor exhibit instabilities such as surge? How does transient behavior compare with that of conventional turbomachinery? How does a wave rotor start? In order to answer these and other questions, a numerical model has been developed which predicts the dynamic state of the fluid in all of the passages of the wave rotor as they are exposed to time dependent conditions in the various ports. The passages are assumed to have uniform properties at any cross section (i.e. one dimensional flow), and the gas is assumed calorically and thermally perfect.

Like the one-dimensional Single Passage Simulation , the multi-passage simulation is capable of predicting the not only unsteady gas dynamics which govern the wave rotor operation, but also the losses induced by viscosity, heat transfer to and from the passage walls, the finite opening time of the passages as they enter and exit port regions, non-uniformities in the port flows, and gas leakage between the passage ends and the stationary walls to and from the cavity in the center of the rotor. It is also capable of calculating the off-design work transfer which occurs when the flow in the ducts is not aligned with the rotor passages (i.e. flow turning). Since all of the passages are tracked simultaneously it is also possible to calculate the instantaneous torque on the drive shaft (and the acceleration of the rotor shaft if no drive motor is present). The combustor, the cavity in the center of the wave rotor, and the rotor wall metal have much longer response times than the gasdynamic waves in the rotor passages and have thus been modeled using lumped volume techniques.

full size - 615x769 (29K)

The multi-passage simulation has been coupled to the component based Generic Engine Transient Simulation (GETRAN) code developed at Texas A and M University to produce a first-ever dynamic, integrated wave rotor topped turboshaft engine simulation. Results from several transient simulations including rapid fuel flow changes and perturbations in engine inlet conditions indicate that there are no adverse interactions between the wave rotor component and surrounding turbomachinery. In fact, the wave rotor component may enhance stability during rapid engine acceleration. In particular, the compressor in the wave rotor topped engine configuration does not exhibit the tendency toward surge that an untopped engine does following rapid increases in fuel flow rate.

Contact: Daniel E.Paxson
email: dpaxson@grc.nasa.gov

Project Contact: Daniel E. Paxson
Phone: (216) 433-8334
email: dpaxson@grc.nasa.gov

responsible official: sanjay garg
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last updated: 2.29.08