The Experts below are selected from a list of 351 Experts worldwide ranked by ideXlab platform

Esa Utriainen - One of the best experts on this subject based on the ideXlab platform.

A J Rawlinson - One of the best experts on this subject based on the ideXlab platform.

  • prediction and augmentation of nozzle guide vane film Cooling Hole pressure margin
    12th European Conference on Turbomachinery Fluid dynamics & Thermodynamics, 2017
    Co-Authors: Nicholas E Holgate, Irene Cresci, Peter T Ireland, A J Rawlinson
    Abstract:

    To ensure adequate Cooling and avoidance of hot gas ingestion, a high pressure turbine nozzle guide vane must maintain a safe pressure margin by which the film coolant static feed pressure exceeds the hot gas total pressure. This pressure margin is lowest for Cooling Holes near the stagnation region, especially near the coolant inlet. This study investigates an insert device which increases the pressure margin in these ingestion risk regions by altering the coolant passage geometry, potentially allowing engine performance gains via reduced combustor pressure loss requirements. Seven parametrically varied inserts are compared within a pressure-tapped, cooled vane model, and design rules are suggested. For correctly designed inserts, pressure margin results show significant improvement in the ingestion risk region, without causing ingestion risks elsewhere. An analytical model of combined converging, diverging and prismatic coolant channels is validated by experimental data to be capable of accurately predicting coolant pressure margins.

  • the variation of heat transfer coefficient adiabatic effectiveness and aerodynamic loss with film Cooling Hole shape
    Annals of the New York Academy of Sciences, 2006
    Co-Authors: J E Sargison, M L G Oldfield, A J Rawlinson
    Abstract:

    : The heat transfer coefficient and adiabatic effectiveness of cylindrical, fan shaped Holes and a slot are presented for the region zero to 50 diameters downstream of the Holes. Narrow-band liquid crystals were used on a heated flat plate with heated air coolant. These parameters have been measured in a steady state, low speed facility at engine representative Reynolds number based on Hole diameter and pressure difference ratio (ideal momentum flux ratio). The aerodynamic loss due to each of the film Cooling geometries has been measured using a traverse of the boundary layer far downstream of the film Cooling Holes. Compared to the cylindrical Holes, the fan shaped Hole case showed an improvement in the uniformity of Cooling downstream of the Holes and in the level of laterally averaged film Cooling effectiveness. The fan effectiveness approached the slot level and both the fan and cylindrical Hole cases show lower heat transfer coefficients than the slot and non film cooled cases based on the laterally averaged results. The drawback to the fan shaped Hole was that the aerodynamic loss was significantly higher than both the slot and cylindrical Hole values due to inefficient diffusion in the Hole exit expansion.

  • a converging slot Hole film Cooling geometry part 2 transonic nozzle guide vane heat transfer and loss
    Journal of Turbomachinery-transactions of The Asme, 2002
    Co-Authors: J E Sargison, M L G Oldfield, Gary D Lock, A J Rawlinson
    Abstract:

    This paper presents the first experimental measurements on an engine representative nozzle guide vane, of a new film-Cooling Hole geometry, a convergingslot-Hole or console. The patented console geometry is designed to improve the heat transfer and aerodynamic performance of turbine vane and rotor blade Cooling systems. These experiments follow the successful validation of the console design in low-speed flat-plate tests described in Part 1 of this paper. Stereolithography was used to manufacture a resin model of a transonic, engine representative nozzle guide vane in which seven rows of previously tested fan-shaped film-Cooling Holes were replaced by four rows of consoles. This vane was mounted in the annular vane ring of the Oxford cold heat transfer tunnel for testing at engine Reynolds numbers, Mach numbers and coolant to mainstream momentum flux ratios using a heavy gas to simulate the correct coolant to mainstream density ratio. Heat transfer data were measured using wide-band thermochromic liquid crystals and a modified analysis technique. Both surface heat transfer coefficient and the adiabatic Cooling effectiveness were derived from computer-video records of hue changes during the transient tunnel run. The Cooling performance, quantified by the heat flux at engine temperature levels, of the console vane compares favourably with that of the previously tested vane with fan-shaped Holes. The new console film-Cooling Hole geometry offers advantages to the engine designer due to a superior aerodynamic efficiency over the fan-shaped Hole geometry. These efficiency measurements are demonstrated by results from midspan traverses of a four-Hole pyramid probe downstream of the nozzle guide vane.

  • a converging slot Hole film Cooling geometry part 1 low speed flat plate heat transfer and loss
    Journal of Turbomachinery-transactions of The Asme, 2002
    Co-Authors: J E Sargison, M L G Oldfield, Gary D Lock, A J Rawlinson
    Abstract:

    This paper presents experimental measurements of the performance of a new film Cooling Hole geometry - the Converging Slot-Hole or Console. This novel, patented geometry has been designed to improve the heat transfer and aerodynamic loss performance of turbine vane and rotor blade Cooling systems. The physical principles embodied in the new Hole design are described, and a typical example of the console geometry is presented. The Cooling performance of a single row of consoles was compared experimentally with that of typical 35° cylindrical and fan-shaped Holes and a slot, on a large-scale, flat-plate model at engine representative Reynolds numbers in a low speed tunnel with ambient temperature main flow. The Hole throat area per unit width is matched for all four Hole geometries. By independently varying the temperature of the heated coolant and the heat flux from an electrically heated, thermally insulated, constant heat flux surface, both the heat transfer coefficient and the adiabatic Cooling effectiveness were deduced from digital photographs of the colour play of narrowband thermochromic liquid crystals on the model surface. A comparative measurement of the aerodynamic losses associated with each of the four film-Cooling geometries was made by traversing the boundary layer at the downstream end of the flat plate. The promising heat transfer and aerodynamic performance of the console geometry have justified further experiments on an engine representative nozzle guide vane in a transonic annular cascade presented in Part 2 of this paper [1].

  • a converging slot Hole film Cooling geometry part 1 low speed flat plate heat transfer and loss
    Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 2001
    Co-Authors: J E Sargison, M L G Oldfield, Gary D Lock, S M Guo, A J Rawlinson
    Abstract:

    This paper presents experimental measurements of the performance of a new film Cooling Hole geometry - the Converging Slot-Hole or Console. This novel, patented geometry has been designed to improve the heat transfer and aerodynamic loss performance of turbine vane and rotor blade Cooling systems. The physical principles embodied in the new Hole design are described, and a typical example of the console geometry is presented.The Cooling performance of a single row of consoles was compared experimentally with that of typical 35° cylindrical and fan-shaped Holes and a slot, on a large-scale, flat-plate model at engine representative Reynolds numbers in a low speed tunnel with ambient temperature main flow. The Hole throat area per unit width is matched for all four Hole geometries. By independently varying the temperature of the heated coolant and the heat flux from an electrically heated, thermally insulated, constant heat flux surface, both the heat transfer coefficient and the adiabatic Cooling effectiveness were deduced from digital photographs of the colour play of narrow-band thermochromic liquid crystals on the model surface.A comparative measurement of the aerodynamic losses associated with each of the four film-Cooling geometries was made by traversing the boundary layer at the downstream end of the flat plate.The promising heat transfer and aerodynamic performance of the console geometry have justified further experiments on an engine representative nozzle guide vane in a transonic annular cascade presented in Part 2 of this paper [1].Copyright © 2001 by ASME

Hossein Nadali Najafabadi - One of the best experts on this subject based on the ideXlab platform.

Heekoo Moon - One of the best experts on this subject based on the ideXlab platform.

  • full coverage film Cooling heat transfer coefficients and film effectiveness for a sparse Hole array at different blowing ratios and contraction ratios
    Journal of Heat Transfer-transactions of The Asme, 2015
    Co-Authors: Phil Ligrani, Matt Goodro, Michael Fox, Heekoo Moon
    Abstract:

    The present experimental investigation considers a full coverage film Cooling arrangement with different streamwise static pressure gradients. The film Cooling Holes in adjacent streamwise rows are staggered with respect to each other, with sharp edges and streamwise inclination angles of 20 deg with respect to the liner surface. Data are provided for turbulent film Cooling, contraction ratios of 1 and 4, blowing ratios (BRs) (at the test section entrance) of 2.0, 5.0, and 10.0, a coolant Reynolds number of 12,000, freestream temperatures from 75 °C to 115 °C, a film Hole diameter of 7 mm, and density ratios from 1.15 to 1.25. Nondimensional streamwise and spanwise film Cooling Hole spacings, X/D and Y/D, are 18 and 5, respectively. Data illustrating the effects of contraction ratio, BR, and streamwise location on local, line-averaged, and spatially averaged adiabatic film effectiveness data; and on local, line-averaged and spatially averaged heat transfer coefficient data are presented. Varying BR values are present along the length of the contraction passage, which contains the Cooling Hole arrangement, when contraction ratio is 4. Dependence on BR indicates important influences of coolant concentration and distribution. For example, line-averaged and spatially averaged adiabatic effectiveness data show vastly different changes with BR for the configurations with contraction ratios of 1 and 4. In addition, much larger effectiveness alterations are present as BR changes from 2.0 to 10.0, when significant acceleration is present and Cr = 4 (in comparison with the Cr = 1 data).

  • crossflows from jet array impingement Cooling Hole spacing target plate distance reynolds number effects
    International Journal of Thermal Sciences, 2015
    Co-Authors: Phillip M. Ligrani, Heekoo Moon
    Abstract:

    Abstract Data which illustrate the combined and separate effects of Hole array spacing, jet-to-target plate distance, and Reynolds number on cross-flows , and the resulting heat transfer, for an impingement jet array are presented. The array of impinging jets are directed to one flat surface of a channel which is bounded on three sides. Considered are Reynolds numbers ranging from 8000 to 50,000, jet-to-target plate distances of 1.5 D , 3.0 D , 5.0 D , and 8.0 D , and steamwise and spanwise Hole spacing of 5 D , 8 D , and 12 D , where D is the impingement Hole diameter. In general, the cumulative accumulations of cross-flows, from sequential rows of jets, reduce the effectiveness of each individual jet (especially for jets at larger streamwise locations). In other situations, the impingement cross-flow results in locally augmented Nusselt numbers. Such variations most often occur at larger downstream locations, as jet interactions are more vigorous, and local magnitudes of mixing and turbulent transport are augmented. This occurs in channels at lower Reynolds numbers, where impingement jets are confined by smaller Hole spacing, and smaller jet-to-target plate distance. The overall result is complex dependence of local, line-averaged, and spatially-averaged Nusselt numbers on Hole array spacing, jet-to-target plate distance, and impingement jet Reynolds number.

  • full coverage film Cooling heat transfer coefficients and film effectiveness for a sparse Hole array at different blowing ratios and contraction ratios
    ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, 2013
    Co-Authors: P M Ligrani, Michael Fox, Matt Goodro, Heekoo Moon
    Abstract:

    The present experimental investigation considers a full coverage film Cooling arrangement with differrent streamwise static pressure gradients. The film Cooling Holes in adjacent streamwise rows are staggered with respect to each other, with sharp edges, and streamwise inclination angles of 20 degrees with respect to the liner surface. Data are provided for turbulent film Cooling, contraction ratios of 1 and 4, blowing ratios (at the test section entrance) of 2.0, 5.0, and 10.0, coolant Reynolds numbers of 12,000, freestream temperatures from 75°C to 115°C, a film Hole diameter of 7 mm, and density ratios from 1.15 to 1.25. Non-dimensional streamwise and spanwise film Cooling Hole spacings, X/D and Y/D, are 18, and 5, respectively. Data illustrating the effects of contraction ratio, blowing ratio, and streamwise location on local, line-averaged and spatially-averaged adiabatic film effectiveness data, and on local, line-averaged and spatially-averaged heat transfer coefficient data are presented. Varying blowing ratio values are utilized along the length of the contraction passage, which contains the Cooling Hole arrangement, when contraction ratio is 4. Dependence on blowing ratio indicates important influences of coolant concentration and distribution. For example, line-averaged and spatially-averaged adiabatic effectiveness data show vastly different changes with blowing ratio BR for the configurations with contraction ratios of 1 and 4. These changes from acceleration are thus mostly due to different blowing ratio distributions along the test section. In particular, much larger effectiveness alterations are present as BR changes from 2.0 to 10.0, when significant acceleration is present and Cr = 4 (in comparison with the Cr = 1 data). When BR = 10.0, much smaller changes due to different contract ratios are present. This is because coolant distributions along the test surfaces are so abundant that magnitudes of streamwise acceleration (and different streamwise variations of blowing ratio) have little effect on near-wall film concentration distributions, or on variations of film Cooling effectiveness.Copyright © 2013 by ASME

  • full coverage film Cooling film effectiveness and heat transfer coefficients for dense Hole arrays at different Hole angles contraction ratios and blowing ratios
    Journal of Heat Transfer-transactions of The Asme, 2013
    Co-Authors: P M Ligrani, Matt Goodro, Mike Fox, Heekoo Moon
    Abstract:

    Experimental results are presented for a full-coverage film Cooling arrangement which simulates a portion of a gas turbine engine, with appropriate streamwise static pressure gradient. The test surface utilizes varying blowing ratio (BR) along the length of the contraction passage which contains the Cooling Hole arrangement. For the different experimental conditions examined, film Cooling Holes are sharp-edged and streamwise inclined either at 20 deg or 30 deg with respect to the liner surface. The film Cooling Holes in adjacent streamwise rows are staggered with respect to each other. Data are provided for turbulent film Cooling, contraction ratios of 1, 3, 4, and 5, blowing ratios (at the test section entrance) of 2.0, 5.0, and 10.0, coolant Reynolds numbers Re fc of 10,000―12,000, freestream temperatures from 75 °C to 115 °C, a film Hole diameter of 7 mm, and density ratios from 1.15 to 1.25. Nondimensional streamwise and spanwise film Cooling Hole spacings, X/D and Y/D, are 6, and 5, respectively. When the streamwise Hole inclination angle is 20deg spatially averaged and line-averaged adiabatic effectiveness values at each x/D location are about the same as the contraction ratio varies between 1,3, and 4, with slightly higher values at each x/D location when the contraction ratio Cr is 5. For each contraction ratio, there is a slight increase in effectiveness when the blowing ratio is increased from 2.0 to 5.0 but there is no further substantial improvement when the blowing ratio is increased to 10.0. Overall, line-averaged and spatially averaged-adiabatic film effectiveness data, and spatially averaged heat transfer coefficient data are described as they are affected by contraction ratio, blowing ratio, Hole angle α, and streamwise location x/D. For example, when α = 20 deg, the detrimental effects of mainstream acceleration are apparent since heat transfer coefficients for contraction ratios Cr of 3 and 5 are often higher than values for Cr = 1, especially for x/D > 100.

  • full coverage film Cooling film effectiveness and heat transfer coefficients for dense and sparse Hole arrays at different blowing ratios
    ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, 2011
    Co-Authors: Matt Goodro, P M Ligrani, Mike Fox, Heekoo Moon
    Abstract:

    Experimental results are presented for a full coverage film Cooling arrangement which simulates a portion of a gas turbine engine, with appropriate streamwise static pressure gradient and varying blowing ratio along the length of the contraction passage which contains the Cooling Hole arrangement. Film Cooling Holes are sharp-edged, streamwise inclined at 20° with respect to the liner surface, and are arranged with a length to diameter ratio of 8.35. The film Cooling Holes in adjacent streamwise rows are staggered with respect to each other. Data are provided for turbulent film Cooling, contraction ratios of 1 and 4, blowing ratios (at the test section entrance) of 2.0, 5.0, and 10.0, coolant Reynolds numbers Refc from 10,000 to 12,000, freestream temperatures from 75°C to 115°C, a film Hole diameter of 7 mm, and density ratios from 1.15 to 1.25. Changes to X/D and Y/D, non-dimensional streamwise and spanwise film Cooling Hole spacings, with Y/D of 3, 5, and 7, and with X/D of 6 and 18, are considered. For all X/D = 6 Hole spacings, only a slight increase in effectiveness (local, line-averaged, and spatially-averaged) values are present as the blowing ratio increases from 2.0 to 5.0, with no significant differences when the blowing ratio increases from 5.0 to 10.0. This lack of dependence on blowing ratio indicates a condition where excess coolant is injected into the mainstream flow, a situation not evidenced by data obtained with the X/D = 18 Hole spacing arrangement. With this sparse array configuration, local and spatially-averaged effectiveness generally increase continually as the blowing ratio becomes larger. Line-averaged and spatially-averaged heat transfer coefficients are generally higher at each streamwise location, also with larger variations with streamwise development, with the X/D = 6 Hole array, compared to the X/D = 18 array.Copyright © 2011 by ASME

Terrence W. Simon - One of the best experts on this subject based on the ideXlab platform.

  • Measurements in Film Cooling Flows: Hole L/D and Turbulence Intensity Effects
    Journal of Turbomachinery, 1998
    Co-Authors: Steven W. Burd, Richard W. Kaszeta, Terrence W. Simon
    Abstract:

    Hot-wire anemometry measurements of simulated film Cooling are presented to document the influence of the free-stream turbulence intensity and film Cooling Hole length-to-diameter ratio on mean velocity and on turbulence intensity. Measurements are taken in the zone where the coolant and free-stream flows mix. Flow from one row of film Cooling Holes with a streamwise injection of 35 deg and no lateral injection and with a coolant-to-free-stream flow velocity ratio of 1.0 is investigated under free-stream turbulence levels of 0.5 and 12 percent. The coolant-to-free-stream density ratio is unity. Two length-to-diameter ratios for the film Cooling Holes, 2.3 and 7.0, are tested. The measurements document that under low free-stream turbulence conditions pronounced differences exist in the flowfield between L/D = 7.0 and 2.3. The differences between L/D cases are less prominent at high free-stream turbulence intensities. Generally, short-L/D injection results in jetting of the coolant farther into the free-stream flow and enhanced mixing. Other changes in the flowfield attributable to a rise in free-stream turbulence intensity to engine-representative conditions are documented.

  • Measurements in film Cooling flows: Hole L/D and turbulence intensity effects
    1996
    Co-Authors: Steven W. Burd, Richard W. Kaszeta, Terrence W. Simon
    Abstract:

    Hot-wire anemometry of simulated film Cooling was used to study the influence of freestream turbulence intensity and film Cooling Hole length-to-diameter ratio on mean velocity and turbulence intensity. Measurements were made in the zone where the coolant and freestream flows mix. Flow from one row of film Cooling Holes with a streamwise injection of 35{degree} and no lateral injection and with a coolant- to-freestream flow velocity ratio of 1.0 was investigated under freestream turbulence levels of 0.5 and 12%. Coolant-to-freestream density ratio was unity. Two length-to-diameter ratios for the film Cooling Holes, 2.3 and 7.0, are tested. Results show that under low freestream turbulence conditions, pronounced differences exist in the flowfield between L/D=7.0 and 2.3; the differences are less prominent at high freestream turbulence intensities. Generally, short-L/D injection results in ``jetting`` of the coolant further into the freestream flow and enhanced mixing. Other changes in the flowfield attributable to a rise in freestream turbulence intensity to engine- representative conditions are documented. 15 figs, 2 tabs, refs.