Experimental investigation of compressible turbulent jets.
Item
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Title
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Experimental investigation of compressible turbulent jets.
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Identifier
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AAI3074692
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identifier
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3074692
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Creator
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Wang, Zhexuan.
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Contributor
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Adviser: Yiannis Andreopoulos
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Date
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2003
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Mechanical
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Abstract
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The motivation of this study is the important role of jets in subsonic and supersonic combustion. To understand the details of a jet mixing with the ambient air, an experimental study was conducted on subsonic compressible jet flows of different gases issued into the air. How quickly and how well a jet flow can be mixed with ambient flow will have a major influence on combustion efficiency, heat release rate, pollutant formation, jet noise suppression and size reduction of such functions.;The jet exit used in this work is circular in cross section with a diameter of 7mm. Three different gases were used, nitrogen, helium and krypton respectively at three distinct Mach numbers 0.3, 0.6, and 0.9, which lead to conclusions based on density and velocity variation. Total pressure, total temperature, and velocity measurements, were carried out with the aid of pressure transducers, thermocouples, and the well-known Particle Image Velocimetry (PIV) technique respectively. Compressibility effects combined with density effects were thus obtained.;Compressibility (based on Mach number) and density effects were found to be the key factors in this present work. The PIV scheme with the Cross-Correlation and Auto-Correlation methods was carried out with two pulsed-lasers, which provided the light source for visualization and quantitative measurements, and talcum powders, which seeded the jet flows for light scattering. The velocity distribution along the centerline obtained from experimental data indicated that the velocity decay of helium is the fastest, while the velocity decay of krypton is the slowest of the three used gases. Total pressure distribution along the centerline also showed the same results. Correspondingly, the level of turbulent fluctuations is also higher in the case of helium jets indicating better mixing with the ambient air. The centerline velocity decays in proportion to the inverse of location away from the jet exit, as well as velocity decay constants were obtained for different jet flows and compared with the existing information. The present results were found to be in good agreement with previous work. Total temperature results revealed that at a low subsonic Mach number range, the total temperature could be treated as a constant, which is equivalent to the ambient temperature.;By using helium, a lighter than air gas and krypton a heavier than air gas, density effects were studied in combination with compressibility effects. Distributions of mean concentration and mean density in the mixing zones were computed from the measurements of total pressure, total temperature and velocity with satisfactory accuracy.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
