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Item Experimental Investigation on the Wave Rotor Constant Volume Combustor(AIAA, 2010-07-25) Matsutomi, Yu; Meyer, Scott; Wijeyakulasuriya, Sameera; Izzy, Zuhair; Nalim, M. Razi; Shimo, Masayoshi; Kowalkowski, Mike; Snyder, Philip; Mechanical Engineering, School of Engineering and TechnologyA wave rotor constant volume combustor was designed and built as a collaborative work of Rolls-Royce, Indiana University-Purdue University Indianapolis (IUPUI), and Purdue University. The experiment was designed to operate at rotational speeds of up to 4,200 rpm with air mass flow rates of approximately 18 lbm per second. Initial tests were conducted at 2,100 rpm with ethylene as fuel. The rig was operated with different fuel injection schemes to investigate operational characteristics of the combustor. Successful combustion and pressure gain were achieved over a range of operating conditions.Item Leakage Assessment of Pressure-Exchange Wave Rotors(2008-07) Akbari, Pezhman; Nalim, M. Razi; Donovan, ES; Snyder, PHControl of leakage within wave rotors is recognized as a key requirement for efficient operation. Previous studies suggest that experimentally observed performance degradation is substantially due to flow leakage. This work presents a leakage model for predicting leakage-attributed performance degradation of four-port pressure-exchange wave rotors more accurately than previous single-cavity leakage models. The methodology comprehensively considers the leakage paths of the entire device. It combines a wave-rotor quasi-one-dimensional computational fluid dynamics prediction code, experimentally validated for internal gas dynamics with the generalized flow-circuit-modeling capability of a leakage-flow network solver. The computational fluid dynamics program and the network solver step through a series of iterations by sharing common leakage information. Application to a well-instrumented wave-rotor rig is briefly summarized, providing important guidance for the improvement of leakage and performance. The new approach is anticipated to be useful in enhancing the design, operation, and efficiency of a broad class of wave rotors by better understanding leakage and hence designing sealing features to control leakage flows.Item Longitudinally Stratified Combustion in Wave Rotors(2000-11) Nalim, M. RaziA wave rotor may be used as a pressure-gain combustor, effecting wave compression and expansion, and intermittent confined combustion, to enhance gas-turbine engine performance. It will be more compact than an equivalent pressure-exchange wave-rotor system, but will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel-air ratio to subftammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperatures well below autoignition conditions. One-dimensional, nonsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed that concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will cause excessive temperatures in the rotor housing unless additional cooling methods are used. The rotor temperature will be acceptable, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction.Item 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.Item Performance Enhancement of Microturbine Engines Topped With Wave Rotors(2006-01) Akbari, Pezhman; Nalim, M. Razi; Mueller, NorbertSignificant performance enhancement of microturbines is predicted by implementing various wave-rotor-topping cycles. Five different advantageous cases are considered for implementation of a four-port wave rotor into two given baseline engines. In these thermodynamic analyses, the compressor and turbine pressure ratios and the turbine inlet temperatures are varied, according to the anticipated design objectives of the cases. Advantages and disadvantages are discussed. Comparison between the theoretic performance of wave-rotor-topped and baseline engines shows a performance enhancement up to 34%. General design maps are generated for the small gas turbines, showing the design space and optima for baseline and topped engines. Also, the impact of ambient temperature on the performance of both baseline and topped engines is investigated. It is shown that the wave-rotor-topped engines are less prone to performance degradation under hot-weather conditions than the baseline engines.