Film Cooling In A Pulsating Wall Jet
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Film Cooling In A Pulsating Wall Jet
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Author :
language : en
Publisher:
Release Date : 2000
Film Cooling In A Pulsating Wall Jet written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Turbulent wall jets have many important engineering applications. Much effort has been spent to investigate the plane turbulent wall jet without external stream (Launder and Rodi 1981,1983, Katz et al 1992, Wygnanski et al 1992) and with a relatively slow external stream (Zhou and Wygnanski 1993, Zhou et al 1996). However, many engineering applications seem to be described better by a wall jet embedded in a uniform stream of comparable velocity (the weak wall jet), for example, the cooling turbine blades and the flows over a wing equipped with a slotted flap (Fig. 1) represents such flows. The recently developed technique for separation control by periodic blowing/suction on the flap also belongs to category (Fig. 2). Thus, it is important to provide a better understanding of the development of these flows. For example: the possibility of flow similarity, normalization of the mean velocity fields, scaling laws for the governing parameters, as well as the various responses to external excitations. This report represents but a single facet of the general effort endeavoring to use the wall jet for boundary layer control, film cooling and the exertion of force on a body through the use of what is commonly known as the Coanda Effect.
Film Cooling In A Pulsating Wall Jet
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Author :
language : en
Publisher:
Release Date : 2000
Film Cooling In A Pulsating Wall Jet written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Turbulent wall jets have many important engineering applications. Much effort has been spent to investigate the plane turbulent wall jet without external stream (Launder and Rodi 1981,1983, Katz et al 1992, Wygnanski et al 1992) and with a relatively slow external stream (Zhou and Wygnanski 1993, Zhou et al 1996). However, many engineering applications seem to be described better by a wall jet embedded in a uniform stream of comparable velocity (the weak wall jet), for example, the cooling turbine blades and the flows over a wing equipped with a slotted flap (Fig. 1) represents such flows. The recently developed technique for separation control by periodic blowing/suction on the flap also belongs to category (Fig. 2). Thus, it is important to provide a better understanding of the development of these flows. For example: the possibility of flow similarity, normalization of the mean velocity fields, scaling laws for the governing parameters, as well as the various responses to external excitations. This report represents but a single facet of the general effort endeavoring to use the wall jet for boundary layer control, film cooling and the exertion of force on a body through the use of what is commonly known as the Coanda Effect.
Active Control Of Transverse Jets For Film Cooling Applications A Limited Statement Of Work
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Author :
language : en
Publisher:
Release Date : 2006
Active Control Of Transverse Jets For Film Cooling Applications A Limited Statement Of Work written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
The objective of this project was to initiate investigation of film cooling flow control in order to improve its performance through active excitation of the film-cooling jet. A theoretical analysis was conducted and mechanisms that can play a defining role in film cooling control were identified on the basis of fundamental fluid-dynamics, prior experiments and preliminary numerical simulations. A cold flow wind-tunnel experiment incorporating a scaled-up, single film-cooling jet on a flat wall with a 90 deg injection angle was designed and built. The theoretical analysis was used to identify a window of essential flow-modulation parameters (frequency, duty cycle, mean blowing ratio, blowing ratio amplitude) within which film-cooling flow performance is expected to improve. A flow-pulsing system was designed, built and dynamically characterized. Both the wind tunnel boundary layer and jet exit flows were characterized using constant temperature anemometry. A series of preliminary experiments were conducted using reactive, Mie-scattering, laser-sheet visualizations for three mean blowing ratios with nearly zero low blowing ratio in the cycle, two duty cycles and four pulsing frequencies. The visualization results indicate that for the transverse jet with 90 deg injection angle, low frequency pulsations of the jet flow tend to increase the lateral coverage of the jet relative to the benchmark steady case without causing substantial lift-off at a blowing ratio of 0.5 and duty cycle of 50%. The observations are encouraging as to the feasibility of controlling the film cooling jet through mass flow pulsation and are consistent with predictions from fundamental analysis in terms of anticipated favorable operating conditions.
Combined Effects Of Pulsed Film Cooling And Upstream Wakes On Gas Turbine Airfoil Heat Transfer
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Author : Kristofer Michal Womack
language : en
Publisher:
Release Date : 2006
Combined Effects Of Pulsed Film Cooling And Upstream Wakes On Gas Turbine Airfoil Heat Transfer written by Kristofer Michal Womack and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Marine engines categories.
The combined effects of pulsed film cooling and upstream wakes were studied. In film cooling, compressed air is routed around the combustion chamber of a gas turbine engine and bled through holes on the surface of the turbine blades. This compressed air creates a protective film of relatively cool air that reduces the heat transfer between the combustion gases and the blades. Diverting air from the combustor reduces the power and efficiency of the turbine; however, pulsing the air may provide equivalent or acceptable protection for the turbine blades with less cooling air. Previous pulsed film cooling studies have been completed with a simplified, continuous freestream flow. In an actual turbine, the combustion gases pass through a cascade of rotor blades and stator vanes, which interrupt the flow, sending wakes downstream to subsequent rows of turbine blades. In this study, periodic wakes were added to the mainstream flow. A large test plate was constructed with a row of holes through which film cooling air could be pulsed. A wind tunnel provided a wall jet at a controlled velocity across the test plate. A wake generator was located upstream of the test plate to simulate the effect of upstream turbine blades, so that the resulting flow field, film cooling effectiveness, and heat transfer could be studied. Continuous film cooling resulted in better blade protection than pulsed film cooling at equivalent wake frequencies. For the cases with a continuous freestream and the cases with lower wake frequencies, continuous film cooling jets blowing at half the freestream velocity provided the best protection. For the highest wake frequency tested, continuous film cooling jets blowing at a velocity equal to the freestream velocity provided the best protection. Finally, when comparing pulse timing relative to the wake passing, there was some improvement in blade protection when the cooling jet was on as the wake passed over the cooling holes; however in most cases, differences were small. This study suggests that, for the geometry tested, continuous film cooling provides better protection for gas turbine blades for the same amount of cooling air.
Combined Effects Of Wakes And Jet Pulsing On Film Cooling
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Author :
language : en
Publisher:
Release Date : 2008
Combined Effects Of Wakes And Jet Pulsing On Film Cooling written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Pulsed film cooling jets subject to periodic wakes were studied experimentally. The wakes were generated with a spoked wheel upstream of a flat plate. Cases with a single row of cylindrical film cooling holes inclined at 35 deg to the surface were considered at blowing ratios B of 0.50 and 1.0 with jet pulsing and wake Strouhal numbers of 0.15, 0.30, and 0.60. Wake timing was varied with respect to the pulsing. Temperature measurements were made using an infrared camera, thermocouples, and constant current (cold wire) anemometry. The local film cooling effectiveness and heat transfer coefficient were determined from the measured temperatures. Phase locked flow temperature fields were determined from cold-wire surveys. With B0.5, wakes and pulsing both lead to a reduction in film cooling effectiveness, and the reduction is larger when wakes and pulsing are combined. With B1.0, pulsing again causes a reduction in effectiveness, but wakes tend to counteract this effect somewhat by reducing jet lift-off. At low Strouhal numbers, wake timing had a significant effect on the instantaneous film cooling effectiveness, but wakes in general had very little effect on the time averaged effectiveness. At high Strouhal numbers, the wake effect was stronger, but the wake timing was less important. Wakes increased the heat transfer coefficient strongly and similarly in cases with and without film cooling, regardless of wake timing. Heat transfer coefficient ratios, similar to the time averaged film cooling effectiveness, did not depend strongly on wake timing for the cases considered.
The Turbulent Wall Jet Its Development And Film Cooling Effectiveness
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Author : William Burns Nicoll
language : en
Publisher:
Release Date : 1967
The Turbulent Wall Jet Its Development And Film Cooling Effectiveness written by William Burns Nicoll and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1967 with categories.
Advances In Heat Transfer
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Author :
language : en
Publisher: Academic Press
Release Date : 2017-11-11
Advances In Heat Transfer written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-11-11 with Science categories.
Advances in Heat Transfer, Volume 49 provides in-depth review articles from a broader scope than in traditional journals or texts. Topics covered in this new volume include Heat Transfer in Rotating Cooling Channel, Flow Boiling and Flow Condensation in Reduced Gravity, Advances in Gas Turbine Cooling, and Advanced Heat Transfer Topics in Complex Duct Flows. While the articles in this series will be of great interest to mechanical, chemical and industrial engineers working in the field of heat transfer, the book is also ideal for those in graduate schools or industry, and even non-specialists interested in the latest research. Compiles the expert opinions of leaders in the industry Fills the information gap between regularly scheduled journals and university-level textbooks by providing in-depth review articles over a broader scope than in traditional journals or texts Essential reading for all mechanical, chemical and industrial engineers working in the field of heat transfer, or in graduate schools or industry
Experimental Investigation Of Air Film Cooling Applied To An Adiabatic Wall By Means Of An Axially Discharging Slot
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Author : S. Stephen Papell
language : en
Publisher:
Release Date : 1959
Experimental Investigation Of Air Film Cooling Applied To An Adiabatic Wall By Means Of An Axially Discharging Slot written by S. Stephen Papell and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1959 with Mach number categories.
Laminar Turbulent Transition
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Author : H.F. Fasel
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-03-09
Laminar Turbulent Transition written by H.F. Fasel and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-03-09 with Science categories.
The origins of turbulent flow and the transition from laminar to turbulent flow are among the most important unsolved problems of fluid mechanics and aerodynamics. Besides being a fundamental question of fluid mechanics, there are any number of applications for information regarding transition location and the details of the subsequent turbulent flow. The JUT AM Symposium on Laminar-Turbulent Transition, co-hosted by Arizona State University and the University of Arizona, was held in Sedona, Arizona. Although four previous JUT AM Symposia bear the same appellation (Stuttgart 1979, Novosibirsk 1984, Toulouse 1989, and Sendai 1994) the topics that were emphasized at each were different and reflect the evolving nature of our understanding of the transition process. The major contributions of Stuttgart 1979 centered on nonlinear behavior and later stages of transition in two-dimensional boundary layers. Stability of closed systems was also included with Taylor vortices in different geometries. The topics of Novosibirsk 1984 shifted to resonant wave interactions and secondary instabilities in boundary layers. Pipe- and channel-flow transition were discussed as model problems for the boundary layer. Investigations of free shear layers were presented and a heavy dose of supersonic papers appeared for the first time. The character of Toulouse 1989 was also different in that 3-D boundary layers, numerical simulations, streamwise vortices, and foundation papers on receptivity were presented. Sendai 1994 saw a number of papers on swept wings and 3-D boundary layers. Numerical simulations attacked a broader range of problems.
Jet Rocket Nuclear Ion And Electric Propulsion
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Author : W.H.T. Loh
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Jet Rocket Nuclear Ion And Electric Propulsion written by W.H.T. Loh and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Technology & Engineering categories.
During the last decade, rapid growth of knowledge in the field of jet, rocket, nuclear, ion and electric propulsion has resulted in many advances useful to the student, engineer and scientist. The purpose for offering this course is to make available to them these recent advances in theory and design. Accordingly, this course is organized into seven parts: Part 1 Introduction; Part 2 Jet Propulsion; Part 3 Rocket Propulsion; Part 4 Nuclear Propulsion; Part 5 Electric and Ion Propulsion; Part 6 Theory on Combustion, Detonation and Fluid Injection; Part 7 Advanced Concepts and Mission Applications. It is written in such a way that it may easily be adopted by other universities as a textbook for a one semester senior or graduate course on the subject. In addition to the undersigned who served as the course instructor and wrote Chapter I, 2 and 3, guest lecturers included: DR. G. L. DUGGER who wrote Chapter 4 "Ram-jets and Air-Aug mented Rockets," DR. GEORGE P. SUTTON who wrote Chapter 5 "Rockets and Cooling Methods," DR . . MARTIN SUMMERFIELD who wrote Chapter 6 "Solid Propellant Rockets," DR. HOWARD S. SEIFERT who wrote Chapter 7 "Hybrid Rockets," DR. CHANDLER C. Ross who wrote Chapter 8 "Advanced Nuclear Rocket Design," MR. GEORGE H. McLAFFERTY who wrote Chapter 9 "Gaseous Nuclear Rockets," DR. S. G. FORBES who wrote Chapter 10 "Electric and Ion Propul sion," DR. R. H. BODEN who wrote Chapter 11 "Ion Propulsion," DR.