Browsing by Author "Paxson, Daniel E."

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    Modified Through-Flow Wave-Rotor Cycle with Combustor-Bypass Ducts
    (1999-05) Paxson, Daniel E.; Nalim, M. Razi
    A wave-rotor cycle is described that avoids the inherent problem of combustor exhaust gas recirculation (EGR) found in four-port, through-flow (uniflow) pressure-gain wave-rotor cycles currently under consideration for topping gas-turbine engines. The recirculated hot gas is eliminated by the judicious placement of a bypass duct that transfers gas from one end of the rotor to the other. The resulting cycle, when analyzed numerically, yields a mean absolute temperature for the rotor that is 18% below the already impressive value (approximately the turbine inlet temperature) predicted for the conventional four-port cycle. The absolute temperature of the gas leading to the combustor is also reduced from the conventional design by 17%. The overall design-point pressure ratio of this new bypass cycle is approximately the same as the conventional cycle. This paper will describe the EGR problem and the bypass-cycle solution, including relevant wave diagrams. Performance estimates of design and off-design operation of a specific wave rotor will be presented. The results were obtained using a one-dimensional numerical simulation and design code.
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    A Numerical Investigation of Premixed Combustion in Wave Rotors
    (1997-07) Nalim, M. Razi; Paxson, Daniel E.
    Wave rotor cycles that utilize premixed combustion processes within the passages are examined numerically using a one-dimensional CFD-based simulation. Internal-combustion wave rotors are envisioned for use as pressure-gain combustors in gas turbine engines. The simulation methodology is described, including a presentation of the assumed governing equations for the flow and reaction in the channels, the numerical integration method used, and the modeling of external components such as recirculation ducts. A number of cycle simulations are then presented that illustrate both turbulent-deflagration and detonation modes of combustion. Estimates of performance and rotor wall temperatures for the various cycles are made, and the advantages and disadvantages of each are discussed.