Effect on Gaseous Film Cooling of Coolant Injection Through Angled Slots and Normal Holes PDF Download

Author: S. Stephen Papell
Publisher:
ISBN:
Category : Cooling
Languages : en
Pages : 32

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Author: David W. Luckey
Publisher:
ISBN:
Category :
Languages : en
Pages : 357

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This experimental investigation involved the study of gas film cooling from a single row of spanwise angled holes using the stagnation region of a cylinder in cross flow to model the leading edge of a turbine vane. The objective was to obtain data for the local convective heat transfer rates to a highly cooled, curved surface exposed to a turbulent hot mainstream flow and a secondary, film coolant flow. Since the leading edge of the first stage, inlet turbine vane experiences some of the most severe thermal loads found in the turbine engine, effective film cooling is most important in this area. Film cooling of the leading edge area was modeled by making heat transfer measurements on the front stagnation region of a cylinder in cross flow. Experiments were conducted in a rectangular duct using a film cooled cylindrical test surface normal to a two-dimensional freestream flow. A gas turbine combustor provided heated air flow to simulate a Reynolds number typical of a high pressure, high temperature turbine vane. Internal convection cooling of the cylinder allowed a gas-to-wall temperature ratio of 2.1 to be achieved while using a moderate freestream gas temperature (1000R; 555K. The film coolant was chilled to obtain a coolant-to-freestream density ratio of 2.2, representative of the gas turbine environment. The cylindrical test surface was instrumented with miniature heat flux gages, and wall thermocouples to determine the influence of the film coolant blowing ratio and the injection hole geometry on the film cooling performance.

Author: Y. G. Tsuei
Publisher:
ISBN:
Category :
Languages : en
Pages : 31

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Wall cooling effectiveness is investigated for tangential, inclined, and normal injection of coolant through single or multiple wall slots into a laminar compressible boundary layer. Numerical solutions of the boundary layer equations are obtained by a reliable finite difference method. A grid control procedure which maintains a constant flow rate between grid lines is applied to the injection calculations wherein the boundary layer growth in the slot is as much as hundred-fold and the longitudinal component of the injection velocity is in some cases as large as the free stream velocity. Film cooling effectiveness is reported for a variety of injection configurations so that the effects of injection angle, coolant mass flow rate, Mach number, upstream boundary layer thickness, slot width, and the presence of upstream cooling slots can be investigated.

Author: D. W. Luckey
Publisher:
ISBN:
Category : Gas-turbines
Languages : en
Pages : 388

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 574

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Author: United States. National Aeronautics and Space Administration
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 448

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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 450

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Author: United States. National Aeronautics and Space Administration
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: United States. Superintendent of Documents
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ISBN:
Category : Government publications
Languages : en
Pages : 1812

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Author: Shane Haydt
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Gas turbines are used around the world to provide thrust for airplanes and to generate electricity. Designers and operators are constantly chasing higher thermal efficiency, and even an incremental increase is considered an achievement. Higher thermal efficiency begets higher turbine inlet temperatures, and the parts that are exposed to these temperatures require sophisticated cooling technologies. One such cooling method is shaped film cooling, which ejects low momentum coolant with the goal of it staying attached to the wall, spreading laterally, and providing a lower driving temperature for convection.In some film cooling manufacturing processes, the meter and diffuser are created in separate steps with separate machines, and an offset can occur in that process. A study was designed to quantify the change in adiabatic effectiveness for five offset directions: fore, fore-left, left, aft-left, and aft. All offset directions caused a detriment to film cooling performance, except for the fore offset, which improved adiabatic effectiveness relative to a no offset case. CFD helped show that the fore offset created a separation in the region of the film cooling metering section where jetting occurs, which decreased the high momentum and made the cooling jet more likely to remain attached to the surface. This study resulted in a patent.A large range of area ratios and blowing ratios were examined in a study designed to isolate the effect of area ratio by lengthening the diffuser of a shaped hole. Very high area ratios were generated that resulted in significant cooling potential. It was shown that at each area ratio there is an optimal blowing ratio beyond which the effectiveness will decrease or plateau. This was reduced to an optimal effective blowing ratio, M/AR, which was shown through CFD to be the condition when the coolant jet core has similar velocity magnitude to the mainstream flow. This results in a weak shear layer and a weak counter-rotating vortex pair.In an axially oriented hole, the mainstream flows over the top of a cooling jet and around the sides, in equal measure, creating a symmetric flowfield. In a compound angled shaped hole, the mainstream flows primarily around the leeward side, creating a strong shear layer and an asymmetric streamwise vortex. Compound angled shaped holes are used commonly in gas turbines, but there has been no work examining the adiabatic effectiveness and heat transfer coefficient augmentation at a range of compound angles, and there are no flowfield measurements. A comprehensive study of the flowfield, cooling effectiveness, and heat transfer coefficient were obtained for compound angled shaped holes for compound angles ranging from 0-60 in 15 increments. It is shown that asymmetry and vorticity magnitude increase with increasing compound angle and increasing blowing ratio. Holes with high compound angles can maintain jet attachment at high blowing ratios because the streamwise component of blowing ratio is reduced, which leads to high effectiveness. The most important contribution of this work was showing that the streamwise vortex increases heat transfer coefficient in a region adjacent to the jet, where very little coolant coverage exists. For this reason, compound angled shaped holes can cause local regions of increased heat flux relative to an uncooled surface, which may be an issue for some designs if not properly accounted for. Heat transfer coefficient augmentation increases as compound angle and blowing ratio increase. Designs that promote jet interaction, such as holes with a smaller pitchwise spacing or holes with significant lateral motion, cover the entire endwall in coolant and lessen the negative effects of high heat transfer coefficient augmentation.