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Author: Mohammad Arif Hossain
Publisher:
ISBN:
Category : Gas-turbines
Languages : en
Pages : 242
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Book Description
Gas turbine is an integrated part of modern aviation and power generation industry. The thermal efficiency of a gas turbine strongly depends on the turbine inlet temperature (TIT), and the turbine designers are continuously pushing the TIT to a higher value. Due to the increased freedom in additive manufacturing, the complex internal and external geometries of the turbine blade can be leveraged to utilize innovative cooling designs to address some of the shortcomings of current cooling technologies. The sweeping jet film cooling has shown some promise to be an effective method of cooling where the coolant can be brought very close to the blade surface due to its sweeping nature. A series of experiments were performed using a row of fluidic oscillators on a flat plate. Adiabatic cooling effectiveness, convective heat transfer coefficient, thermal field, and discharge coefficient were measured over a range of blowing ratios and freestream turbulence. Results were compared with a conventional shaped hole (777-hole), and the sweeping jet hole shows improved cooling performance in the lateral direction. Numerical simulation also confirmed that the sweeping jet creates two alternating vortices that do not have mutual interaction in time. When the jet sweeps to one side of the hole exit, it acts as a vortex generator as it interacts with the mainstream ow. This prevents the formation of the counter-rotating vortex pair (CRVP) and allows the coolant to spread in the lateral direction. The results obtained from the low speed at plate tests were utilized to design the sweeping jet film cooling hole for more representative turbine vane geometry. Experiments were performed in a low-speed linear cascade facility. Results showed that the sweeping jet hole has higher cooling effectiveness in the near hole region compared to the shaped hole at high blowing ratios. Next, a detailed experimental investigation of sweeping jet film cooling on the suction surface of a near engine scale transonic nozzle guide vane at an engine relevant Mach number (Ma = 0.8) and Reynolds number (Re = 1x10e6) to determine the effect of compressibility. The heat transfer measurements were conducted with a transient IR method, and the convective heat transfer coefficient (HTC) and adiabatic film cooling effectiveness were estimated using a dual linear regression technique (DLRT). Aerodynamic loss measurements were also performed at an exit plane downstream of the vane cascade. Finally, a comprehensive design integration of sweeping jet film hole was carried out in a Direct Metal Laser Sintering (DMLS) enabled engine scale nozzle guide vane and experimental investigation of overall cooling effectiveness at engine relevant temperature conditions were assessed. The systematic evolution of a sweeping jet film cooling hole design from a large scale flat plate to an engine scale nozzle guide vane has been presented.
Author: Mohammad Arif Hossain
Publisher:
ISBN:
Category : Gas-turbines
Languages : en
Pages : 242
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Book Description
Gas turbine is an integrated part of modern aviation and power generation industry. The thermal efficiency of a gas turbine strongly depends on the turbine inlet temperature (TIT), and the turbine designers are continuously pushing the TIT to a higher value. Due to the increased freedom in additive manufacturing, the complex internal and external geometries of the turbine blade can be leveraged to utilize innovative cooling designs to address some of the shortcomings of current cooling technologies. The sweeping jet film cooling has shown some promise to be an effective method of cooling where the coolant can be brought very close to the blade surface due to its sweeping nature. A series of experiments were performed using a row of fluidic oscillators on a flat plate. Adiabatic cooling effectiveness, convective heat transfer coefficient, thermal field, and discharge coefficient were measured over a range of blowing ratios and freestream turbulence. Results were compared with a conventional shaped hole (777-hole), and the sweeping jet hole shows improved cooling performance in the lateral direction. Numerical simulation also confirmed that the sweeping jet creates two alternating vortices that do not have mutual interaction in time. When the jet sweeps to one side of the hole exit, it acts as a vortex generator as it interacts with the mainstream ow. This prevents the formation of the counter-rotating vortex pair (CRVP) and allows the coolant to spread in the lateral direction. The results obtained from the low speed at plate tests were utilized to design the sweeping jet film cooling hole for more representative turbine vane geometry. Experiments were performed in a low-speed linear cascade facility. Results showed that the sweeping jet hole has higher cooling effectiveness in the near hole region compared to the shaped hole at high blowing ratios. Next, a detailed experimental investigation of sweeping jet film cooling on the suction surface of a near engine scale transonic nozzle guide vane at an engine relevant Mach number (Ma = 0.8) and Reynolds number (Re = 1x10e6) to determine the effect of compressibility. The heat transfer measurements were conducted with a transient IR method, and the convective heat transfer coefficient (HTC) and adiabatic film cooling effectiveness were estimated using a dual linear regression technique (DLRT). Aerodynamic loss measurements were also performed at an exit plane downstream of the vane cascade. Finally, a comprehensive design integration of sweeping jet film hole was carried out in a Direct Metal Laser Sintering (DMLS) enabled engine scale nozzle guide vane and experimental investigation of overall cooling effectiveness at engine relevant temperature conditions were assessed. The systematic evolution of a sweeping jet film cooling hole design from a large scale flat plate to an engine scale nozzle guide vane has been presented.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 25
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Book Description
Physics of film cooling for shaped, inclined slot-jets with realistic slot-length-to-width ratios is studied for a range of blowing ratio and density ratio parameters typical of gas turbine operations. Effect of inlet and exit shaping of the slot-jet on both flow and thermal field is isolated, and the dominant mechanisms responsible for differences in these items are documented. A computation method was used to study 4 configurations. Field results and surface phenomena are presented. Both adiabatic film effectiveness and heat transfer coefficient are vital in assessing film cooling performance. Performance of two popular turbulence models were studied to evaluate ability to handle highly elliptic jet/crossflow interaction type processes. The simulations were consistent.
Author: Kevin Thomas McGovern
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Author: Harvey Michael Maclin
Publisher:
ISBN:
Category :
Languages : en
Pages : 200
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Author: M. Martiny
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Orlando, FL, Jun 2 - Jun 5, 1997.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 39
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Book Description
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.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 39
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Book Description
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.
Author: Jakob Woisetschlager
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Presented at the 1995 ASME Cogen-Turbo Power Conference, August 23-25, 1995 - Vienna, Austria.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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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.
Author: S. Stephen Papell
Publisher:
ISBN:
Category : Mach number
Languages : en
Pages : 68
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