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.

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

1997 ◽  
Vol 119 (3) ◽  
pp. 601-609 ◽  
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 shows 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 semicircular 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. Both straight and 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 deg. The ribs on the curved surface were of constant cross section with an angle of attack 90 deg 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.

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.

Measurements of Heat Transfer Coefficients and Friction Factors in Passages Rib-Roughened on All Walls

1998 ◽  
Vol 120 (3) ◽  
pp. 564-570 ◽  
Author(s):  
M. E. Taslim ◽  
T. Li ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
Full Length ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Important Conclusion ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Partition Walls ◽  
Half Length

A liquid crystal technique was used to measure heat transfer coefficients in twelve test sections with square and trapezoidal cross-sectional areas representing blade midchord cooling cavities in a modern gas turbine. Full-length ribs were configured on suction side as well as pressure side walls while half-length ribs were mounted on partition walls between adjacent cooling cavities. Ribs were in staggered arrangements with a nominal blockage ratio of 22 percent and an angle of attack to the mainstream flow, α, of 90 deg. Heat transfer measurements were performed on the roughened walls with full-length as well as half-length ribs. Nusselt numbers, friction factors, and thermal performances of all geometries are compared. The most important conclusion of this study is that the roughening of the partition walls enhances the heat transfer coefficients on those walls but, more importantly, enhances heat transfer coefficients on the primary walls considerably.

scholarly journals 45° Staggered Rib Heat Transfer Coefficient Measurements in a Square Channel

1996 ◽  
Author(s):  
M. E. Taslim ◽  
A. Lengkong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Turbine Blades ◽  
Transfer Coefficients ◽  
Height Ratio ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Friction Factors

For high blockage ribs with large heat transfer areas, commonly used in small gas turbine blades, the rib heat transfer is a significant portion of the overall heat transfer in the cooling passages. Three staggered 45° rib geometries corresponding to blockage ratios of 0.133, 0.167 and 0.25 were tested in a square channel for pitch-to-height ratios of 5, 8.5 and 10, and for two distinct thermal boundary conditions of heated and unheated channel walls. Comparisons were made between the surface averaged heat transfer coefficients and friction factors for 45° ribs, and 90° ribs reported previously. Heat transfer coefficients of the furthest upstream rib and that of a typical rib located in the middle of the rib-roughened region were also compared. It was concluded that: a) For the geometries tested, the rib average heat transfer coefficient was much higher than that for the area between the ribs. b) Except for two cases corresponding to the highest blockage ribs mounted at pitch-to-height ratios of 8.5 and 10 for which the heat transfer results of 45° ribs were very close to those of 90° ribs, 45° ribs produced higher heat transfer coefficients than 90° ribs. c) At pitch-to-height ratios of 8.5 and 10, all 45° ribs produced lower friction factors than 90° ribs. However, when they were brought closer to each other (S/e=5), they produced higher friction factors than 90° ribs. d) Heat transfer coefficients for the two smaller rib geometries (e/Dh=0.133 and 0.167) did not vary significantly with the pitch-to-height ratio in the range tested. However, the heat transfer coefficient for the high blockage rib geometry increased significantly as the ribs were brought closer to each other. e) Under otherwise identical conditions, ribs in the furthest upstream position produced lower heat transfer coefficients than those in the midstream position. f) Rib thermal performance decreased with the rib blockage ratio. For both angles of attack, the smallest rib geometry in the midstream position and at a pitch-to-height ratio of 10 had the highest thermal performance, and the highest blockage rib in the furthest upstream position produced the lowest thermal performance.

scholarly journals Measurements of Heat Transfer Coefficients and Friction Factors in Passages Rib-Roughened on All Walls

1996 ◽  
Author(s):  
M. E. Taslim ◽  
T. Li ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
Full Length ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Important Conclusion ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Partition Walls ◽  
Half Length

A liquid crystal technique was used to measure heat transfer coefficients in twelve test sections with square and trapezoidal cross-sectional areas representing blade midchord cooling cavities in a modern gas turbine. Full-length ribs were configured on suction side as well as pressure side walls while half-length ribs were mounted on partition walls between adjacent cooling cavities. Ribs were in staggered arrangements with a nominal blockage ratio of 22% and an angle of attack to the mainstream flow, α, of 90°. Heat transfer measurements were performed on the roughened walls with full-length as well as half-length ribs. Nusselt numbers, friction factors and thermal performances of all geometries are compared. The most important conclusion of this study is that the roughening of the partition walls enhances the heat transfer coefficients on those walls but, more importantly, enhances heat transfer coefficients on the primary walls considerably.

Leading Edge Impingement With Racetrack Shaped Jets and Varying Inlet Supply Conditions

2013 ◽  
Author(s):  
C. Neil Jordan ◽  
Cassius A. Elston ◽  
Lesley M. Wright ◽  
Daniel C. Crites
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Turbine Blades ◽  
Leading Edge ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Crossflow Velocity

Impinging jets are often employed within the leading edge of turbine blades and vanes to combat the tremendous heat loads incurred as the hot exhaust gases stagnate along the exterior of the airfoil. Relative to traditional cylindrical jets, racetrack shaped impinging jets have been shown to produce favorable cooling characteristics within the turbine airfoil. This investigation experimentally and numerically quantifies the cooling characteristics associated with a row of racetrack shaped jets impinging on a concave, cylindrical surface. Detailed Nusselt number distributions are obtained using both a transient liquid crystal technique and commercially available CFD software (Star CCM+ from CD-Adapco). Three geometrical jet inlet and exit conditions are experimentally investigated: a square edge, a partially filleted edge (r/dH,Jet = 0.25), and a fully filleted edge (r/dH,Jet = 0.667). Additionally, to investigate the effect of high crossflow velocities at the inlet of the jet, a portion of the flow supplied to the test apparatus radially bypasses the impingement section. Thus, the mass flow rate into the test section is varied to achieve the desired inlet crossflow conditions and jet Reynolds numbers. As a result, jet Reynolds numbers (ReJet) of 11500 and 23000 are investigated at supply duct Reynolds numbers (ReDuct) of 20000 and 30000. The results are compared to baseline cases where no mass bypasses the test section. Additionally, the relative jet – to – jet spacing (s/dH,Jet) is maintained at 8, the relative jet – to – target surface spacing (z/dH,Jet) is 4, the target surface curvature – to – jet hydraulic diameter (D/dH,Jet) is 5.33, and the relative thickness of the jet plate (t/dH,Jet) is 1.33. Measurements indicate that the addition of fillets at the edges of the jet orifice and the introduction of significant crossflow velocity at the inlet of the jet can significantly degrade the cooling characteristics on the leading edge of the turbine blade. The magnitude of such degradation generally increases with increasing fillet size and inlet crossflow velocity. The V2F model is adequate for predicting the flow field and target surface heat transfer in the absence of inlet crossflow; however, it is believed the turbulence within the jet is overpredicted by the CFD leading to elevated heat transfer coefficients (compared to the experimental results).

45 deg Staggered Rib Heat Transfer Coefficient Measurements in a Square Channel

1998 ◽  
Vol 120 (3) ◽  
pp. 571-580 ◽  
Author(s):  
M. E. Taslim ◽  
A. Lengkong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Turbine Blades ◽  
Transfer Coefficients ◽  
Height Ratio ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Friction Factors

For high-blockage ribs with large heat transfer areas, commonly used in small gas turbine blades, the rib heat transfer is a significant portion of the overall heat transfer in the cooling passages. Three staggered 45 deg rib geometries corresponding to blockage ratios of 0.133, 0.167, and 0.25 were tested in a square channel for pitch-to-height ratios of 5, 8.5, and 10, and for two distinct thermal boundary conditions of heated and unheated channel walls. Comparisons were made between the surface-averaged heat transfer coefficients and friction factors for 45 deg ribs, and 90 deg ribs reported previously. Heat transfer coefficients of the furthest upstream rib and that of a typical rib located in the middle of the rib-roughened region were also compared. It was concluded that: (a) For the geometries tested, the rib average heat transfer coefficient was much higher than that for the area between the ribs. (b) Except for two cases corresponding to the highest blockage ribs mounted at pitch-to-height ratios of 8.5 and 10 for which the heat transfer results of 45 deg ribs were very close to those of 90 deg ribs, 45 deg ribs produced higher heat transfer coefficients than 90 deg ribs. (c) At pitch-to-height ratios of 8.5 and 10, all 45 deg ribs produced lower friction factors than 90 deg ribs. However, when they were brought closer to each other (S/e = 5), they produced higher friction factors than 90 deg ribs. (d) Heat transfer coefficients for the two smaller rib geometries (e/Dh = 0.133 and 0.167) did not vary significantly with the pitch-to-height ratio in the range tested. However, the heat transfer coefficient for the high blockage rib geometry increased significantly as the ribs were brought closer to each other. (e) Under otherwise identical conditions, ribs in the furthest upstream position produced lower heat transfer coefficients than those in the midstream position. (f) Rib thermal performance decreased with the rib blockage ratio. For both angles of attack, the smallest rib geometry in the midstream position and at a pitch-to-height ratio of 10 had the highest thermal performance, and the highest blockage rib in the furthest upstream position produced the lowest thermal performance.

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