## Wave Rotor Topping Cycles for Gas Turbine Engines

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### 1-D Single Passage Simulation

A numerical model has been developed at the NASA Glenn Research Center which follows a single wave rotor passage as it rotates past the various ports. The model can predict both the unsteady flow quantities within the passage and the steady averaged flow quantities in the ports. It is based on the assumptions of one-dimensional, unsteady, perfect gas flow.

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Under these assumptions the passage flow field is essentially governed by the Euler equations. The high resolution, CFD model integrates these equations in time, thereby tracking not only the dominant wave behavior including shock losses, but the loss effects of leakage from the passage ends, viscosity, heat transfer to and from the passages, mixing of non-uniform flows in the ports, and finite passage opening time. The losses due to leakage, viscosity, and heat transfer are accounted for using source terms in the governing equations. The finite passage opening time losses are accounted for using modified boundary conditions. The model operates in the rotor reference frame; however, modified boundary conditions are also used to account for the often significant circumferential velocity component of the rotor. This latter modification allows the internal computational scheme to remain in the rotor reference frame, while quantities such as inlet duct stagnation properties may be specified in the fixed or absolute reference frame. Accurate modelling of this effect is critical to successful wave rotor analysis and design, particularly in off-design predictions where the flows in the inlet ducts are mis- matched with the rotor passages and significant turning may take place (i.e. work is done on the gas). The relative simplicity of the model, combined with robust boundary condition procedures which allow either inflow, outflow or both in any given port, make it useful for design, optimization, and analysis, of wave rotor cycles for many applications.

External components such as valves and combustors, which supply boundary conditions to the single passage model are treated as lumped volumes and updated every complete cycle. Steady state convergence is considered achieved when the gas state in the volumes is no longer changing and the sum of the mass flows through either end of the passage are zero over the course of one cycle.

This model has been validated extensively using several past wave rotor experiments.

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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 site maintenance: edmond wong nasa privacy statement last updated: 2.29.08