High Rotation Number Effect on Heat Transfer in a Leading Edge Cooling Channel of Gas Turbine Blades With Three Channel Orientations

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Szu-Chi Huang ◽  
Yao-Hsien Liu
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Turbine Blades ◽  
Leading Edge ◽  
Cooling Channel ◽  
Number Range ◽  
Gas Turbine Blades ◽  
Rotation Numbers ◽  
Mainstream Flow ◽  
Channel Orientation

Heat transfer in a leading edge, triangular-shaped cooling channel with three channel orientations under high rotation numbers is investigated in this study. Continuous ribs and V-shaped ribs (P/e = 9, e/Dh = 0.085), both placed at an angle (α = 45 deg) to the mainstream flow, are applied on the leading and trailing surfaces. The Reynolds number range is 15,000–25,000 and the rotation number range is 0–0.65. Effects of high rotation number on heat transfer with three angles of rotation (90 deg, 67.5 deg, and 45 deg) are tested. Results show that heat transfer is influenced by the combined effects of rib and channel orientation. When the rotation number is smaller than 0.4, rotation causes a decrease in the average Nusselt number ratios on the leading surface at a channel orientation of 90 deg. Heat transfer is enhanced gradually on the leading surface when the channel orientation varies from 90 deg to 45 deg for both ribbed cases. The highest heat transfer enhancement due to rotation is found at the highest rotation number of 0.65.

High Rotation Number Effect on Heat Transfer in a Leading Edge Cooling Channel With Three Channel Orientations

2012 ◽  
Author(s):  
Szu-Chi Huang ◽  
Yao-Hsien Liu
Keyword(s):  
Heat Transfer ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Cooling Channel ◽  
Height Ratio ◽  
Triangular Channel ◽  
Rotation Numbers ◽  
Channel Orientation

Heat transfer in a leading edge, triangular shaped cooling channel with three channel orientations under high rotation numbers is experimentally studied. Continuous ribs and V-shaped ribs, both at 45° rib angle of attack, are applied on the leading and trailing surfaces. For each rib case, three channel orientations (90°, 67.5°, and 45°) with respect to the plane of rotation are tested. The rib height to hydraulic diameter ratio (e/Dh) is 0.085 and the rib pitch to height ratio (P/e) is 9. Reynolds numbers are from 15000 to 25000, and the rotation numbers are from 0 to 0.65. Results show that the heat transfer variation is influenced by the combined effects of rib configuration and channel orientation. Effect of channel orientation influences local heat transfer distribution inside this triangular channel, and heat transfer is enhanced gradually on the leading surface when the channel orientation varies from 90° to 45° for both ribbed cases in this study.

scholarly journals Effects of Rotation at Different Channel Orientations on the Flow Field inside a Trailing Edge Internal Cooling Channel

2013 ◽  
Vol 2013 ◽  
pp. 1-19 ◽  
Author(s):  
Matteo Pascotto ◽  
Alessandro Armellini ◽  
Luca Casarsa ◽  
Claudio Mucignat ◽  
Pietro Giannattasio
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Trailing Edge ◽  
Gas Turbine Blades ◽  
Sst Turbulence Model ◽  
Channel Orientation ◽  
Effects Of Rotation

The flow field inside a cooling channel for the trailing edge of gas turbine blades has been numerically investigated with the aim to highlight the effects of channel rotation and orientation. A commercial 3D RANS solver including a SST turbulence model has been used to compute the isothermal steady air flow inside both static and rotating passages. Simulations were performed at a Reynolds number equal to 20000, a rotation number (Ro) of 0, 0.23, and 0.46, and channel orientations ofγ=0∘, 22.5°, and 45°, extending previous results towards new engine-like working conditions. The numerical results have been carefully validated against experimental data obtained by the same authors for conditionsγ=0∘and Ro = 0, 0.23. Rotation effects are shown to alter significantly the flow field inside both inlet and trailing edge regions. These effects are attenuated by an increase of the channel orientation fromγ=0∘to 45°.

Heat Transfer in Leading Edge, Triangular Shaped Cooling Channels With Angled Ribs Under High Rotation Numbers

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Yao-Hsien Liu ◽  
Michael Huh ◽  
Dong-Ho Rhee ◽  
Je-Chin Han ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Rotation Number ◽  
Leading Edge ◽  
Gas Turbine Blade ◽  
Cooling Channels ◽  
Triangular Channel ◽  
Buoyancy Parameter ◽  
Rotation Numbers

The gas turbine blade/vane internal cooling is achieved by circulating compressed air through the cooling channels inside the turbine blade. Cooling channel geometries vary to fit the blade profile. This paper experimentally investigated the rotational effects on heat transfer in an equilateral triangular channel (Dh=1.83 cm). The triangular shaped channel is applicable to the leading edge of the gas turbine blade. Angled 45 deg ribs are placed on the leading and trailing surfaces of the test section to enhance heat transfer. The rib pitch-to-rib height ratio (P/e) is 8 and the rib height-to-channel hydraulic diameter ratio (e/Dh) is 0.087. Effect of the angled ribs under high rotation numbers and buoyancy parameters is also presented. Results show that due to the radially outward flow, heat transfer is enhanced with rotation on the trailing surface. By varying the Reynolds numbers (10,000–40,000) and the rotational speeds (0–400 rpm), the rotation number and buoyancy parameter reached in this study are 0–0.58 and 0–1.9, respectively. The higher rotation number and buoyancy parameter correlate very well and can be used to predict the rotational heat transfer in the equilateral triangular channel.

Effect of Channel Orientation on Heat Transfer in Rotating Smooth Square U-Duct at High Rotation Number

2014 ◽  
Author(s):  
Yang Li ◽  
Hongwu Deng ◽  
Guoqiang Xu ◽  
Lu Qiu ◽  
Shuqing Tian
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Flow Channel ◽  
Transfer Coefficients ◽  
Number Range ◽  
Average Heat ◽  
Critical Rotation ◽  
First Pass ◽  
Channel Orientation

The effect of channel orientation on heat transfer in a rotating, two-pass, square channel is experimentally investigated in current work. The classical copper plate technique is employed to measure the regional averaged heat transfer coefficients. The inlet Reynolds number and Rotation number range from 25000 to 35000 and 0 to 0.82, respectively. Five different channel angles (−45°, −22.5°, 0°, 22.5°, 45°) are selected to study the effect of channel orientation on heat transfer. In the radially outward flow channel, the surface average heat transfer in β = 0° channel are higher than those in angled-channel (±22.5°, ±45°) on the trailing surface at all Rotation number ranges (0–0.82). While on the leading surface, surface average heat transfer are lower before a critical Rotation number, and turn higher after the critical point. Channel orientations show less influence on heat transfer in the radially inward flow channel. Compared with their corresponding perpendicular channel orientation values (β = 0° channel), heat transfer in angled-channels decrease on the pressure side and increase on the suction side at a relatively lower Rotation number (Ro<0.4) for both inward and outward channels. While at higher Rotation number (Ro>0.4), heat transfer in angled-channel decrease on both the leading and trailing walls in the first pass, and increase on both the leading and trailing walls in the second pass. By considering the effect of channel orientations, the relation between critical Rotation number on the leading surface in the first pass and dimensionless location (X/D) obeys a simple rule: (Roc·X/D)·cosβ = 1.31. The trailing-to-leading heat transfer differences induced by rotation increase with the increasing of Rotation number in angled-channel, and they are larger than β = 0° channel after the critical Rotation number in both passages.

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.

Heat Transfer Enhancement Using Angled Grooves as Turbulence Promoters

2013 ◽  
Author(s):  
Krishnendu Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement ◽  
Number Range ◽  
Pressure Drops ◽  
Friction Factors ◽  
Mainstream Flow ◽  
Turbine Airfoils

An experimental study is conducted on a simulated internal cooling channel of a turbine airfoil using angled grooves and combination of grooves-ribs to enhance the heat transfer from the wall. The grooves are angled at 45° to the mainstream flow direction and combinations of four different geometries are studied that include: (1) angled grooves with a pitch, p/δ = 10, (2) angled groove with a larger pitch, p/δ = 15, (3) combination of angled groove and 45° angled rib, and (4) combination of angled groove with transverse rib. Transient liquid crystal experiments are conducted for a Reynolds number range of 13,000–55,000, and local and averaged heat transfer coefficient values are presented for all the geometries. Pressure drops are measured between the inlet and the exit of the grooved channel and friction factors are calculated. The combination of the angled groove and 45° angled rib provided the highest performance factor of the four cases considered, and these values were higher or comparable to among the best-performing rib geometries (45-degree broken ribs) commonly used in gas turbine airfoils.

Effect of Channel Orientation in a Rotating Smooth Wedge-Shaped Cooling Channel With Lateral Ejection

2013 ◽  
Author(s):  
Lu Qiu ◽  
Hongwu Deng ◽  
Zhi Tao
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Bulk Temperature ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Critical Rotation ◽  
Fundamental Research ◽  
Channel Orientation ◽  
Better Than

The effect of channel orientation on heat transfer in a rotating wedge-shaped cooling channel is experimentally investigated in current work. In order to perform a fundamental research, all turbulators are removed away. The classical copper plate technique is employed to measure the regional averaged heater transfer coefficients. The inlet Reynolds number and rotational speed range from 5100 to 21000 and zero to 1000rpm respectively, which results in the inlet Rotation number varies from zero to 0.68. In order to study the effect of channel orientation, five different angles are selected in current study. Furthermore, details such as local bulk temperature calculation and local mass flow rate determination are discussed in current paper. Interestingly, a two-dimensional bulk temperature distribution is observed. Due to the experimental results, the most evident rotation effect on heat transfer happens in 90° configuration. Compared to the non-rotating condition, there is about 35% overall heat transfer enhancement under highest rotation number. However, the greatest leading-to-trailing heat transfer difference happens in 135° or 112.5° configuration which depends on Rotation number. The highest difference is up to 40%. Besides, at the realistic 135° channel orientation, a critical Rotation number is observed after which the decreasing trend of heat transfer is traversed. The inlet Rotation is better than local one to describe this critical point. With the inlet parameter, the critical Rotation number is about 0.3 at all the locations in this channel.

Experimental Investigation of Leading Edge Impingement Under High Rotation Numbers With Racetrack Shaped Jets

2014 ◽  
Author(s):  
Weston V. Harmon ◽  
Cassius A. Elston ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Cross Flow ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Transfer Coefficients ◽  
Round Jet ◽  
Rotation Numbers ◽  
Circular Target

The effect of rotation on leading edge jet impingement is experimentally investigated in this study. Cooling air travels radially outward through a square supply channel, turns 90° into a cross-over hole, and impinges on a semi-circular surface. To eliminate the effect of jet cross-flow, regionally averaged heat transfer coefficients are measured on the surface surrounding a single jet. The heat transfer performance of a round jet is compared to that afforded by a 2:1 racetrack shaped jet. Two jet Reynolds numbers were investigated, Rejet = 15,000 and Rejet = 25,000. This, in addition to a varying rotational speed, allows for the consideration of rotation numbers varying from 0.0–0.076 (based on the jet velocity and jet hydraulic diameter). The results obtained are benchmarked against stationary results to highlight enhancement due to rotation. It is shown that as the rotation number increases, the heat transfer is enhanced on all regions of the semi-circular target surface. For rotation numbers of less than 0.030, enhancement due to rotation is marginal. Once rotation numbers breach this value, heat transfer begins to increase significantly on all surfaces. Additionally, it was shown that a racetrack shaped jet consistently out performs a round jet at an equivalent rotation number. The racetrack jet offers better and more consistent coverage of the leading edge surface, yielding higher average heat transfer enhancement.

An Experimental Investigation of Heat Transfer in an Orthogonally Rotating Channel Roughened With 45 deg Criss-Cross Ribs on Two Opposite Walls

1991 ◽  
Vol 113 (3) ◽  
pp. 346-353 ◽  
Author(s):  
M. E. Taslim ◽  
L. A. Bondi ◽  
D. M. Kercher
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Rotation Number ◽  
Turbine Blades ◽  
Steady Increase ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios

Turbine blade cooling is imperative in advanced aircraft engines. The extremely hot gases that operate within the turbine section require turbine blades to be cooled by a complex cooling circuit. This cooling arrangement increases engine efficiency and ensures blade materials a longer creep life. One principle aspect of the circuit involves serpentine internal cooling passes throughout the core of the blade. Roughening the inside surfaces of these cooling passages with turbulence promoters provides enhanced heat transfer rates from the surface. The purpose of this investigation was to study the effect of rotation, aspect ratio, and turbulator roughness on heat transfer in these rib-roughened passages. The investigation was performed in an orthogonally rotating setup to simulate the actual rotation of the cooling passages. Single-pass channels, roughened on two opposite walls, with turbulators positioned at 45 deg angle to the flow, in a criss-cross arrangement, were studied throughout this experiment. The ribs were arranged such that their pitch-to-height ratio remained at a constant value of 10. An aspect ratio of unity was investigated under three different rib blockage ratios (turbulator height/channel hydraulic diameter) of 0.1333, 0.25, and 0.3333. A channel with an aspect ratio of 2 was also investigated for a blockage ratio of 0.25. Air was flown radially outward over a Reynolds number range of 15,000 to 50,000. The rotation number was varied from 0 to 0.3. Stationary and rotating cases of identical geometries were compared. Results indicated that rotational effects are more pronounced in turbulated passages of high aspect and low blockage ratios for which a steady increase in heat transfer coefficient is observed on the trailing side as rotation number increases while the heat transfer coefficient on the leading side shows a steady decrease with rotation number. However, the all-smooth-wall classical pattern of heat transfer coefficient variation on the leading and trailing sides is not followed for smaller aspect ratios and high blockage ratios when the relative artificial roughness is high.

Influence of Channel Orientation on Heat Transfer in a Two-Pass Smooth and Ribbed Rectangular Channel (AR=2:1) Under Large Rotation Numbers

2010 ◽  
Author(s):  
Michael Huh ◽  
Jiang Lei ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Surface Condition ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Large Rotation ◽  
Buoyancy Parameter ◽  
Rotation Numbers ◽  
Mainstream Flow ◽  
Channel Orientation ◽  
Good Agreement

Experiments were conducted in a rotating two-pass cooling channel with an aspect ratio of 2:1 (Dh = 16.9 mm). Results for two surface conditions are presented: smooth and one ribbed configuration. For the ribbed channel, the leading and trailing walls are roughened with ribs (P/e = 10, e/Dh = 0.094) and are placed at an angle (α = 45°) to the mainstream flow. For each surface condition, two angles of rotation (β = 90°, 135°) were studied. For each angle of rotation, five Reynolds numbers (Re = 10K–40K) were considered. At each Reynolds number, five rotational speeds (Ω = 0–400 rpm) were considered. The maximum rotation number and buoyancy parameter reached were 0.45 and 0.85, respectively. Results showed that rotation effects are minimal in ribbed channels, at both angles of rotation, due to the strong interaction of rib and Coriolis induced vortices. In the smooth case, the channel orientation proved to be important and a beneficial heat transfer increase on the leading surface in the first pass (radially outward flow) was observed at high rotation numbers. The correlations developed in this study for predicting heat transfer enhancement due to rotation using the buoyancy parameter showed markedly good agreement with experimental data (+/-10%). Finally, heat transfer under rotating conditions on the tip cap showed to be quite dependent on channel orientation. The maximum tip cap Nu/Nus ratio observed was 2.8.

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