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  • 1
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    Influence of Turbulence Parameters, Reynolds Number, and Body Shape on Stagnation-Region Heat Transfer (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The purpose of the present work was threefold: (1) to determine if a free-stream turbulence length scale existed that would cause the greatest augmentation in stagnation-region heat transfer over laminar levels; (2) to investigate the effect of velocity gradient on stagnation-region heat transfer augmentation by free-stream turbulence; and (3) to develop a prediction tool for stagnation heat transfer in the presence of free-stream turbulence. Heat transfer was measured in the stagnation region of four models with elliptical leading edges that had ratios of major to minor axes of 1:1, 1.5:1, 2.25:1, and 3:1. Five turbulence-generating grids were fabricated; four were square mesh, biplane grids made from square bars. The fifth grid was an array of fine parallel wires that were perpendicular to the model spanwise direction. Heat transfer data were taken at Reynolds numbers ranging from 37 000 to 228 000. Turbulence intensities were in the range of 1.1 to 15.9% while the ratio of integral length scale to leading-edge diameter ranged from 0.05 to 0.30. Stagnation-point velocity gradient was varied by nearly 50%. Stagnation-region heat transfer augmentation was found to increase with decreasing length scale but no optimum length scale was found. Heat transfer augmentation due to turbulence was found to be unaffected by the velocity gradient near the leading edge. A correlation was developed that fit heat transfer data for the square-bar grids to within +/- 4%.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-3487 , E-8882 , NAS 1.60:3487
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  • 2
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    Measurement of local convective heat transfer coefficients from a smooth and roughened NACA-0012 airfoil: Flight test data (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Wind tunnels typically have higher free stream turbulence levels than are found in flight. Turbulence intensity was measured to be 0.5 percent in the NASA Lewis Icing Research Tunnel (IRT) with the cloud making sprays off and around 2 percent with cloud making equipment on. Turbulence intensity for flight conditions was found to be too low to make meaningful measurements for smooth air. This difference between free stream and wing tunnel conditions has raised questions as to the validity of results obtained in the IRT. One objective of these tests was to determine the effect of free stream turbulence on convective heat transfer for the NASA Lewis LEWICE ice growth prediction code. These tests provide in-flight heat transfer data for a NASA-0012 airfoil with a 533 cm chord. Future tests will measure heat transfer data from the same airfoil in the Lewis Icing Research Tunnel. Roughness was obtained by the attachment of small, 2 mm diameter hemispheres of uniform size to the airfoil in three different patterns. Heat transfer measurements were recorded in flight on the NASA Lewis Twin Otter Icing Research Aircraft. Measurements were taken for the smooth and roughened surfaces at various aircraft speeds and angles of attack up to four degrees. Results are presented as Frossling number versus position on the airfoil for various roughnesses and angles of attack.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-100284 , E-3924 , NAS 1.15:100284 , AIAA PAPER 88-0287
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  • 3
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    Experimental Technique and Assessment for Measuring the Convective Heat Transfer Coefficient from Natural Ice Accretions (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A technique was developed to cast frozen ice shapes that had been grown on a metal surface. This technique was applied to a series of ice shapes that were grown in the NASA Lewis Icing Research Tunnel on flat plates. Nine flat plates, 18 inches square, were obtained from which aluminum castings were made that gave good ice shape characterizations. Test strips taken from these plates were outfitted with heat flux gages, such that when placed in a dry wind tunnel, can be used to experimentally map out the convective heat transfer coefficient in the direction of flow from the roughened surfaces. The effects on the heat transfer coefficient for both parallel and accelerating flow will be studied. The smooth plate model verification baseline data as well as one ice roughened test case are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106864 , E-9476 , NAS 1.15:106864 , AIAA PAPER 95-0537 , Aerospace Sciences Meeting and Exhibit; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States
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  • 4
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    Measurements of the Influence of Integral Length Scale on Stagnation Region Heat Transfer (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The purpose was twofold: first, to determine if a length scale existed that would cause the greatest augmentation in stagnation region heat transfer for a given turbulence intensity and second, to develop a prediction tool for stagnation heat transfer in the presence of free stream turbulence. Toward this end, a model with a circular leading edge was fabricated with heat transfer gages in the stagnation region. The model was qualified in a low turbulence wind tunnel by comparing measurements with Frossling's solution for stagnation region heat transfer in a laminar free stream. Five turbulence generating grids were fabricated; four were square mesh, biplane grids made from square bars. Each had identical mesh to bar width ratio but different bar widths. The fifth grid was an array of fine parallel wires that were perpendicular to the axis of the cylindrical leading edge. Turbulence intensity and integral length scale were measured as a function of distance from the grids. Stagnation region heat transfer was measured at various distances downstream of each grid. Data were taken at cylinder Reynolds numbers ranging from 42,000 to 193,000. Turbulence intensities were in the range 1.1 to 15.9 percent while the ratio of integral length scale to cylinder diameter ranged from 0.05 to 0.30. Stagnation region heat transfer augmentation increased with decreasing length scale. An optimum scale was not found. A correlation was developed that fit heat transfer data for the square bar grids to within +4 percent. The data from the array of wires were not predicted by the correlation; augmentation was higher for this case indicating that the degree of isotropy in the turbulent flow field has a large effect on stagnation heat transfer. The data of other researchers are also compared with the correlation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106503 , E-8532 , NAS 1.15:106503 , Symposium on Transport Phenomena and Dynamics of Rotating Machinery; May 08, 1994 - May 11, 1994; Kaanapali, HI; United States
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  • 5
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    Augmentation of Stagnation Region Heat Transfer Due to Turbulence From a DLN Can Combustor (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Heat transfer measurements have been made in the stagnation region of a flat plate with a circular leading edge. Electrically heated aluminum strips placed symmetrically about the leading edge stagnation region were used to measure spanwise averaged heat transfer coefficients. The maximum Reynolds number obtained, based on leading edge diameter, was about 100,000. The model was immersed in the flow field downstream of an approximately half scale model of a can-type combustor from a low NO(x), ground based power-generating turbine. The tests were conducted with room temperature air; no fuel was added. Room air flowed into the combustor through six vane type fuel/air swirlers. The combustor can contained no dilution holes. The fuel/air swirlers all swirled the incoming airflow in a counter clockwise direction (facing downstream). A 5-hole probe flow field survey in the plane of the model stagnation point showed the flow was one big vortex with flow angles up to 36' at the outer edges of the rectangular test section. Hot wire measurements showed test section flow had very high levels of turbulence, around 28.5 percent, and had a relatively large axial-length scale-to-leading edge diameter ratio of 0.5. X-wire measurements showed the turbulence to be nearly isotropic. Stagnation heat transfer augmentation over laminar levels was around 77 percent and was about 14 percent higher than predicted by a previously developed correlation for isotropic grid generated turbulence.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210241 , E-12360 , NAS 1.15:210241 , ASME Paper 2000-GT-0215 , International Gas Turbine and Aeroengine Technical Congress; May 08, 2000 - May 11, 2000; Munich; Germany
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  • 6
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    Augmentation of Stagnation Region Heat Transfer Due to Turbulence from a DLN Can Combustor (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Heat transfer measurements have been made in the stagnation region of a flat plate with a circular leading edge. Electrically heated aluminum strips placed symmetrically about the leading edge stagnation region were used to measure spanwise-averaged heat transfer coefficients. The maximum Reynolds number obtained, based on leading edge diameter, was about 100,000. The model was immersed in the flow field downstream of an approximately half-scale model of a can-type combustor from a low NO(x), ground-based power-generating turbine. The tests were conducted with room temperature air; no fuel was added. Room air flowed into the combustor through six vane-type fuel/air swirlers. The combustor can contained no dilution holes. The fuel/air swirlers all swirled the incoming airflow in a counterclockwise direction (facing downstream). A five-hole probe flow field survey in the plane of the model stagnation point showed the flow was one big vortex with flow angles up to 36 deg at the outer edges of the rectangular test section. Hot-wire measurements showed test section flow had very high levels of turbulence, around 28.5%, and had a relatively large axial-length scale-to-leading edge diameter ratio of 0.5. X-wire measurements showed the turbulence to be nearly isotropic. Stagnation heat transfer augmentation over laminar levels was around 77% and was about 14% higher than predicted by a previously developed correlation for isotropic grid-generated turbulence.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: Paper-2000GT215 , 45th International Gas Turbine and Aeroengine Congress and Exhibition; May 08, 2000 - May 11, 2000; Munich; Germany|Transactions of the American Society of Mechanical Engineers; 123; 140-146
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  • 7
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    Heat Transfer Measurements and Predictions on a Power Generation Gas Turbine Blade (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 129 deg of nominal turning and an axial chord of 137 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the design point of 628,000, -20%, +20%, and +40%. Three ideal exit pressure ratios were examined including the design point of 1.378, -10%, and +10%. Inlet incidence angles of 0 deg and +/-2 deg were also examined. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/TM-2000-210021 , NAS1.15:210021 , E-12218 , ASME-2000-GT-0209 , 45th International Gas Turbine and Aeroengine Technical Congress; May 08, 2000 - May 11, 2000; Munich; Germany
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  • 8
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    Stagnation Region Heat Transfer: The Influence of Turbulence Parameters, Reynolds Number and Body Shape (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effect of velocity gradient on stagnation region heat transfer augmentation by free stream turbulence was investigated. Heat transfer was measured in the stagnation region of four models with elliptical leading edges with ratios of major to minor axes of 1:1, 1.5:1, 2.25:1, and 3:1. Four geometrically similar, square bar, square mesh, biplane grids were used to generate free stream turbulence with different intensities and length. Heat transfer measurements were made for the following ranges of parameters: Reynolds number, based on leading edge diameter, 37,000 to 228,000; dimensionless leading edge velocity gradient, 1.20 to 1.80; turbulence intensity, 1.1 to 15.9%; and length scale to leading edge diameter ratio, 0.05 to 0.30. Stagnation point heat transfer augmentation by free stream turbulence can be predicted using a modified version of a previously developed correlation for a circular leading edge. Heat transfer augmentation was independent of body shape at the stagnation point. The heat transfer distribution down-stream from the stagnation point can be predicted using the normalized laminar heat transfer distribution.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106504 , E-8534 , NAS 1.15:106504 , AIAA/ASME Thermophysics and Heat Transfer Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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  • 9
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    High Reynolds number and turbulence effects on aerodynamics and heat transfer in a turbine cascade (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Experimental data on pressure distribution and heat transfer on a turbine airfoil were obtained over a range of Reynolds numbers from 0.75 to 7.5 x 10 exp 6 and a range of turbulence intensities from 1.8 to about 15 percent. The purpose of this study was to obtain fundamental heat transfer and pressure distribution data over a wide range of high Reynolds numbers and to extend the heat transfer data base to include the range of Reynolds numbers encountered in the Space Shuttle main engine (SSME) turbopump turbines. Specifically, the study aimed to determine (1) the effect of Reynolds number on heat transfer, (2) the effect of upstream turbulence on heat transfer and pressure distribution, and (3) the relationship between heat transfer at high Reynolds numbers and the current data base. The results of this study indicated that Reynolds number and turbulence intensity have a large effect on both the transition from laminar to turbulent flow and the resulting heat transfer. For a given turbulence intensity, heat transfer for all Reynolds numbers at the leading edge can be correlated with the Frossling number developed for lower Reynolds numbers. For a given turbulence intensity, heat transfer for the airfoil surfaces downstream of the leading edge can be approximately correlated with a dimensionless parameter. Comparison of the experimental results were also made with a numerical solution from a two-dimensional Navier-Stokes code.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106187 , E-7791 , NAS 1.15:106187 , AIAA PAPER 93-2252 , Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States
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  • 10
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    Modelling and experimental verification of a water alleviation system for the NASP (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: One possible low speed propulsion system for the National Aerospace Plane is a liquid air cycle engine (LACE). The LACE system uses the heat sink in the liquid hydrogen propellant to liquefy air in a heat exchanger which is then pumped up to high pressure and used as the oxidizer in a hydrogen liquid air rocket. The inlet airstream must be dehumidified or moisture could freeze on the cryogenic heat exchangers and block them. The main objective of this research has been to develop a computer simulation of the cold tube/antifreeze-spray water alleviation system and to verify the model with experimental data. An experimental facility has been built and humid air tests were conducted on a generic heat exchanger to obtain condensing data for code development. The paper describes the experimental setup, outlines the method of calculation used in the code, and presents comparisons of the calculations and measurements. Cause of discrepancies between the model and data are explained.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-105661 , E-7026 , NAS 1.15:105661 , National Heat Transfer Conference; Aug 09, 1992 - Aug 12, 1992; San Diego, CA; United States
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