scholarly journals Experimental heat transfer coefficients and friction factors in a rib-roughened leading-edge cooling cavity of a gas turbine airfoil

2013 ◽  
Author(s):  
Peter Hagan
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Friction Factors ◽  
Experimental Heat Transfer ◽  
Cooling Cavity ◽  
Rib Roughened

Experimental and Numerical Investigation of Impingement on a Rib-Roughened Leading-Edge Wall

2003 ◽  
Vol 125 (4) ◽  
pp. 682-691 ◽  
Author(s):  
M. E. Taslim ◽  
K. Bakhtari ◽  
H. Liu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Cross Flow ◽  
Heat Removal ◽  
Leading Edge ◽  
Target Surface ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Edge Surface ◽  
Rib Roughened

Effective cooling of the airfoil leading edge is imperative in gas turbine designs. Among several methods of cooling the leading edge, impingement cooling has been utilized in many modern designs. In this method, the cooling air enters the leading edge cavity from the adjacent cavity through a series of crossover holes on the partition wall between the two cavities. The crossover jets impinge on a smooth leading-edge wall and exit through the film holes, and, in some cases, form a cross flow in the leading-edge cavity and move toward the end of the cavity. It was the main objective of this investigation to measure the heat transfer coefficient on a smooth as well as rib-roughened leading-edge wall. Experimental data for impingement on a leading-edge surface roughened with different conical bumps and radial ribs have been reported by the same authors previously. This investigation, however, deals with impingement on different horseshoe ribs and makes a comparison between the experimental and numerical results. Three geometries representing the leading-edge cooling cavity of a modern gas turbine airfoil with crossover jets impinging on (1) a smooth wall, (2) a wall roughened with horseshoe ribs, and (3) a wall roughened with notched-horseshoe ribs were investigated. The tests were run for a range of flow arrangements and jet Reynolds numbers. The major conclusions of this study were: (a) Impingement on the smooth target surface produced the highest overall heat transfer coefficients followed by the notched-horseshoe and horseshoe geometries. (b) There is, however, a heat transfer enhancement benefit in roughening the target surface. Among the three target surface geometries, the notched-horseshoe ribs produced the highest heat removal from the target surface, which was attributed entirely to the area increase of the target surface. (c) CFD could be considered as a viable tool for the prediction of impingement heat transfer coefficients on an airfoil leading-edge wall.

Experimental and Numerical Investigation of Impingement on a Rib-Roughened Leading-Edge Wall

2003 ◽  
Author(s):  
M. E. Taslim ◽  
K. Bakhtari ◽  
H. Liu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Heat Removal ◽  
Leading Edge ◽  
Target Surface ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Edge Surface ◽  
Rib Roughened

Effective cooling of the airfoil leading-edge is imperative in gas turbine designs. Amongst several methods of cooling the leading edge, impingement cooling has been utilized in many modern designs. In this method, the cooling air enters the leading edge cavity from the adjacent cavity through a series of crossover holes on the partition wall between the two cavities. The crossover jets impinge on a smooth leading-edge wall and exit through the film holes, and, in some cases, form a crossflow in the leading-edge cavity and move toward the end of the cavity. It was the main objective of this investigation to measure the heat transfer coefficient on a smooth as well as rib-roughened leading-edge wall. Experimental data for impingement on a leading edge surface roughened with different conical bumps and radial ribs are reported by the same authors, previously. This investigation, however, deals with impingement on different horseshoe ribs and makes a comparison between the experimental and numerical results. Three geometries representing the leading-edge cooling cavity of a modern gas turbine airfoil with crossover jets impinging on 1) a smooth wall, 2) a wall roughened with horseshoe ribs, and 3) a wall roughened with notched-horseshoe ribs were investigated. The tests were run for a range of flow arrangements and jet Reynolds numbers. The major conclusions of this study were: a) Impingement on the smooth target surface produced the highest overall heat transfer coefficients followed by the notched-horseshoe and horseshoe geometries. b) There is, however, a heat transfer enhancement benefit in roughening the target surface. Amongst the three target surface geometries, the notched-horseshoe ribs produced the highest heat removal from the target surface which was attributed entirely to the area increase of the target surface. c) CFD could be considered as a viable tool for the prediction of impingement heat transfer coefficients on an airfoil leading-edge wall.

Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity With and Without the Trailing-Edge Cooling Holes

2014 ◽  
Author(s):  
Mohammad Taslim ◽  
Joseph S. Halabi
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Flow Direction ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Cfd Models ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides) with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. Realizable k–ε turbulence model in conjunction with enhanced wall treatment approach for the near wall regions, was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

Experimental Heat Transfer Coefficients from Ice-Roughened Surfaces for Aircraft Deicing Design

1999 ◽  
Vol 36 (6) ◽  
pp. 948-956 ◽  
Author(s):  
Nihad Dukhan ◽  
K. C. Masiulaniec ◽  
Kenneth J. De Witt ◽  
G. James Van Fossen
Keyword(s):  
Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Experimental Heat Transfer

scholarly journals Verification of Thermal Models of Internally Cooled Gas Turbine Blades

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Igor Shevchenko ◽  
Nikolay Rogalev ◽  
Andrey Rogalev ◽  
Andrey Vegera ◽  
Nikolay Bychkov
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Heat Removal ◽  
Leading Edge ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Transfer Coefficients ◽  
Single Experiment ◽  
Heat Transfer Coefficients

Numerical simulation of temperature field of cooled turbine blades is a required element of gas turbine engine design process. The verification is usually performed on the basis of results of test of full-size blade prototype on a gas-dynamic test bench. A method of calorimetric measurement in a molten metal thermostat for verification of a thermal model of cooled blade is proposed in this paper. The method allows obtaining local values of heat flux in each point of blade surface within a single experiment. The error of determination of local heat transfer coefficients using this method does not exceed 8% for blades with radial channels. An important feature of the method is that the heat load remains unchanged during the experiment and the blade outer surface temperature equals zinc melting point. The verification of thermal-hydraulic model of high-pressure turbine blade with cooling allowing asymmetrical heat removal from pressure and suction sides was carried out using the developed method. An analysis of heat transfer coefficients confirmed the high level of heat transfer in the leading edge, whose value is comparable with jet impingement heat transfer. The maximum of the heat transfer coefficients is shifted from the critical point of the leading edge to the pressure side.

scholarly journals Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity with and without the Trailing-Edge Cooling Holes

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
M. E. Taslim ◽  
J. S. Halabi
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Flow Direction ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Cfd Models ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing-edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross-sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides) with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing-edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs, and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. Realizablek-εturbulence model in conjunction with enhanced wall treatment approach for the near wall regions was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

Experimental Study of Condensation Inside a Horizontal Single Square Minichannel

2009 ◽  
Author(s):  
Marko Matkovic ◽  
Stefano Bortolin ◽  
Alberto Cavallini ◽  
Davide Del Col
Keyword(s):  
Heat Transfer ◽  
Mass Velocity ◽  
Saturation Temperature ◽  
External Heat ◽  
Copper Tube ◽  
Transfer Coefficients ◽  
External Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Experimental Heat Transfer

This work is aimed at presenting experimental heat transfer coefficients measured during condensation inside a single square cross section minichannel, having a 1.18 mm side length. The experimental heat transfer coefficients are compared to the ones previously obtained in a circular minitube. This subject is particularly interesting since most of the mini and microchannels used in practical applications have non circular cross sections. The test section used in the present work is obtained from a thick wall copper tube which is machined to draw a complex passage for the water; its geometry has been studied with the aim of increasing the external heat transfer area and thus decreasing the external heat transfer resistance. This experimental technique allows to measure directly the temperature in the tube wall and in the water channel. The heat flux is determined from the temperature profile of the coolant in the measuring sector. The wall temperature is measured by means of thermocouples embedded in the copper tube, while the saturation temperature is obtained from the saturation pressure measured at the inlet and outlet of the measuring sector. On the whole, more than seventy thermocouples have been placed in the 23 cm long measuring section. Tests have been performed with R134a at 40°C saturation temperature, at mass velocities ranging between 200 and 800 kg m−2s−1. As compared to the heat transfer coefficients measured in a circular minichannel, in the square minichannel the authors find a heat transfer enhancement at the lowest values of mass velocity; this must be due to the effect of the surface tension. No heat transfer coefficient increase has been found at the highest values of the mass velocity where condensation is shear stress dominated.

Measurements of Heat Transfer Coefficients and Friction Factors in Rib-Roughened Channels Simulating Leading-Edge Cavities of a Modern Turbine Blade

1995 ◽  
Author(s):  
M. E. Taslim ◽  
T. Li ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Mainstream Flow ◽  
Edge Temperature

Leading edge cooling cavities in modern gas turbine blades play an important role in maintaining the leading edge temperature at levels consistent with airfoil design life. These cavities often have a complex cross-sectional shape to be compatible with the external contour of the blade at the leading edge. A survey of many existing geometries show that, for analytical as well as experimental analyses, such cavities can be simplified in shape by a four-sided polygon with one curved side similar to the leading edge curvature, a rectangle with one semi-circular side (often the smaller side) or a trapezoid, the smaller base of which is replaced by a semicircle. Furthermore, to enhance the heat transfer coefficient in these cavities, they are mostly roughened on three sides with ribs of different geometries. Experimental data on friction factors and heat transfer coefficients in such cavities are rare if not nonexistent. A liquid crystal technique was used in this experimental investigation to measure heat transfer coefficients in six test sections representing the leading-edge cooling cavities. Straight as well as tapered ribs were configured on the two opposite sidewalls in a staggered arrangement with angles of attack to the mainstream flow, α, of 60° and 90°. The ribs on the curved surface were of constant cross section with an angle of attack 90° to the flow. Heat transfer measurements were performed on the straight sidewalls as well as on the round surface adjacent to the blade leading edge. Effects such as rib angle of attack to the mainstream flow and constant versus tapered rib cross-sectional areas were also investigated. Nusselt numbers, friction factors and thermal performances are reported for nine rib geometries in six test sections.

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