Heat Transfer Measurements in a Rotating Equilateral Triangular Channel With Various Rib Arrangements

2006 ◽  
Author(s):  
Dong Hyun Lee ◽  
Dong-Ho Rhee ◽  
Hyung Hee Cho ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Leading Edge ◽  
Side Surface ◽  
Suction Side ◽  
Stationary Case ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Ribbed Channel ◽  
Triangular Channel ◽  
Rotating Channel

The present research investigates the heat transfer characteristics in an equilateral triangular channel to simulate the leading edge cooling passage of a gas turbine blade. The experiments are conducted for the stationary and rotating ribbed channel with three different attack angles (45°, 90° and 135°). Square ribs are installed in a staggered manner on the pressure and suction side surfaces of the channel. The rib height to channel hydraulic diameter ratio (e/Dh) is 0.079 and the rib-to-rib pitch (p) is 8 times of the rib height. To measure regional-averaged heat transfer coefficients in the channel, two rows of copper blocks with heaters are installed on each surface. The rotation number ranges from 0.0 to 0.1 for the fixed Reynolds number of 10,000. Inlet coolant-to-surface density ratio is about 0.2. For the channel with 90° ribs, the heat transfer rates of all regions have similar values for stationary case. However, for the rotating channel, heat transfer coefficients on the pressure side surface are significantly increased while the suction side surface has quite low heat transfer coefficients due to a single rotating secondary flow induced by Coriolis force. For the channel with angled rib arrangements, a pair of counter-rotating vortices is induced by the angled rib arrangements. High heat transfer coefficients are obtained on the regions near the inner wall for 45° angled ribbed channel and near the leading edge for the 135° angled ribbed channel. The heat transfer coefficients in rotating channel with angled ribs are almost the same as those of stationary case for the tested conditions because the secondary flow dominates the heat transfer. The channel with angled ribs consistently yields better thermal performance than the transverse ribbed channel for the test conditions of the present study.

Experimental and Numerical Study of Impingement on an Airfoil Leading Edge With and Without Showerhead and Gill Film Holes

2005 ◽  
Vol 128 (2) ◽  
pp. 310-320 ◽  
Author(s):  
M. E. Taslim ◽  
A. Khanicheh
Keyword(s):  
Heat Transfer ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Impingement Heat Transfer

This experimental investigation deals with impingement on the leading edge of an airfoil with and without showerhead film holes and its effects on heat transfer coefficients on the airfoil nose area as well as the pressure and suction side areas. a comparison between the experimental and numerical results are also made. the tests were run for a range of flow conditions pertinent to common practice and at an elevated range of jet Reynolds numbers (8000–48,000). The major conclusions of this study were: (a) The presence of showerhead film holes along the leading edge enhances the internal impingement heat transfer coefficients significantly, and (b) while the numerical predictions of impingement heat transfer coefficients for the no-showerhead case were in good agreement with the measured values, the case with showerhead flow was under-predicted by as much as 30% indicating a need for a more elaborate turbulence modeling.

Multi-Pass Serpentine Cooling Designs for Negating Coriolis Force Effect on Heat Transfer: Smooth Channels

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Prashant Singh ◽  
Yongbin Ji ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Stationary Condition ◽  
Stationary Case ◽  
Transfer Coefficients ◽  
Liquid Crystal Thermography ◽  
Heat Transfer Coefficients ◽  
Stationary Conditions

The combined action of Coriolis and centrifugal buoyancy forces results in nonuniform heat transfer coefficient on pressure and suction side internal walls, hence leading to nonuniform metal temperatures and increased thermal stresses. The present study addresses the problem of nonuniform heat transfer distribution due to rotation effect and proposes novel designs for serpentine cooling passages, which are arranged along the chord of the blade. The two configurations were four-passage and six-passage serpentine smooth channels. Detailed heat transfer coefficients were measured using transient liquid crystal thermography under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 12,294 to 85,000 under stationary conditions. Rotation experiments were carried out for the Rotation numbers of 0.05 and 0.11. Heat transfer enhancement levels of approximately two times the Dittus–Boelter correlation (for developed flow in smooth tubes) were obtained under stationary conditions. Under rotating conditions, we found that the four-passage configuration had slightly lower heat transfer compared with the stationary case, and the six-passage configuration had higher heat transfer on both the leading and trailing sides compared with the stationary case. The leading and trailing side heat transfer characteristics were near-similar to each other for both the configurations, and the rotating heat transfer was near-similar to the stationary condition heat transfer.

Experimental and Numerical Study of Impingement on an Airfoil Leading-Edge With and Without Showerhead and Gill Film Holes

2005 ◽  
Author(s):  
M. E. Taslim ◽  
A. Khanicheh
Keyword(s):  
Heat Transfer ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Impingement Heat Transfer

This experimental investigation deals with impingement on the leading-edge of an airfoil with and without showerhead film holes and its effects on heat transfer coefficients on the airfoil nose area as well as the pressure and suction side areas. A comparison between the experimental and numerical results are also made. The tests were run for a range of flow conditions pertinent to common practice and at an elevated range of jet Reynolds numbers (8000–48000). The major conclusions of this study were: a) the presence of showerhead film holes along the leading edge enhances the internal impingement heat transfer coefficients significantly, and b) while the numerical predictions of impingement heat transfer coefficients for the no-showerhead case were in good agreement with the measured values, the case with showerhead flow was underpredicted by as much as 30% indicating a need for a more elaborate turbulence modeling.

Predictions of the Effect of Roughness on Heat Transfer From Turbine Airfoils

1998 ◽  
Author(s):  
Anil K. Tolpadi ◽  
Michael E. Crawford
Keyword(s):  
Heat Transfer ◽  
Side Surface ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Surface Finishing ◽  
Transfer Coefficients ◽  
Average Roughness ◽  
Wide Range ◽  
Turbine Airfoils ◽  
Good Agreement

The heat transfer and aerodynamic performance of turbine airfoils are greatly influenced by the gas side surface finish. In order to operate at higher efficiencies and to have reduced cooling requirements, airfoil designs require better surface finishing processes to create smoother surfaces. In this paper, three different cast airfoils were analyzed: the first airfoil was grit blasted and codep coated, the second airfoil was tumbled and aluminide coated, and the third airfoil was polished further. Each of these airfoils had different levels of roughness. The TEXSTAN boundary layer code was used to make predictions of the heat transfer along both the pressure and suction sides of all three airfoils. These predictions have been compared to corresponding heat transfer data reported earlier by Abuaf et al. (1997). The data were obtained over a wide range of Reynolds numbers simulating typical aircraft engine conditions. A three-parameter full-cone based roughness model was implemented in TEXSTAN and used for the predictions. The three parameters were the centerline average roughness, the cone height and the cone-to-cone pitch. The heat transfer coefficient predictions indicated good agreement with the data over most Reynolds numbers and for all airfoils-both pressure and suction sides. The transition location on the pressure side was well predicted for all airfoils; on the suction side, transition was well predicted at the higher Reynolds numbers but was computed to be somewhat early at the lower Reynolds numbers. Also, at lower Reynolds numbers, the heat transfer coefficients were not in very good agreement with the data on the suction side.

Heat Transfer Enhancement in Triangular Ducts With an Array of Side-Entry Wall/Impinged Jets

1999 ◽  
Author(s):  
J.-J. Hwang ◽  
C.-S. Cheng ◽  
Y.-P. Tsia
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Inclined Angle

An experimental study has been performed to measure local heat transfer coefficients and static well pressure drops in leading-edge triangular ducts cooled by wall/impinged jets. Coolant provided by an array of equally spaced wall jets is aimed at the leading-edge apex and exits from the radial outlet. Detailed heat transfer coefficients are measured for the two walls forming the apex using transient liquid crystal technique. Secondary-flow structures are visualized to realize the mechanism of heat transfer enhancement by wall/impinged jets. Three right-triangular ducts of the same altitude and different apex angles of β = 30 deg (Duct A), 45 deg (Duct B) and 60 deg (Duct C) are tested for various jet Reynolds numbers (3000≦Rej≦12600) and jet spacings (s/d = 3.0 and 6.0). Results show that an increase in Rej increases the heat transfer on both walls. Local heat transfer on both walls gradually decreases downstream due to the crossflow effect. At the same Rej, the Duct C has the highest wall-averaged heat transfer because of the highest jet center velocity as well as the smallest jet inclined angle. Moreover, the distribution of static pressure drop based on the local through flow rate in the present triangular duct is similar to that that of developing straight pipe flows. Average jet Nusselt numbers on the both walls have been correlated with jet Reynolds number for three different duct shapes.

Heat Transfer in Rotating Multi-Pass Rectangular Ribbed Channel With and Without a Turning Vane

2012 ◽  
Author(s):  
Jiang Lei ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
Ribbed Channel ◽  
Rotation Numbers ◽  
Loss Coefficients ◽  
Channel Loss ◽  
Turn Region

This paper experimentally investigates the effect of turning vane on hub region heat transfer in a multi-pass rectangular channel with rib-roughed wall at high rotation numbers. The experimental data were taken in the second and the third passages (Aspect Ratio = 2:1) connected by 180° U-bend. The flow was radial inward in the second passage and was radial outward after the 180° U-bend in the third passage. The square-edged ribs with P/e = 8, e/Dh = 0.1, and α = 45° were applied on the leading and trailing surfaces of the second and third passages. Results showed that rotation increases heat transfer on the leading surface but decreases it on the trailing surface in the second passage. In the third passage, rotation decreases heat transfer on the leading surface but increases it on the trailing surface. Without a turning vane, rotation reduces heat transfer on the trailing surface and increases it on the leading surface in the hub 180° turn region. After adding a half-circle-shaped turning vane, heat transfer coefficients do not change in the second passage before-turn while they are different in the turn region and after-turn region in the third passage. Regional heat transfer coefficients and channel loss coefficients are correlated with rotation numbers for multi-pass rectangular ribbed channel with and without a turning vane.

A Transient Calorimeter Technique for Determining Regional Heat Transfer Coefficients in the Three-Temperature Flowfield at a Turbine Airfoil Leading Edge

2005 ◽  
Author(s):  
Scott R. Nowlin ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Ralf Knoche ◽  
T. Robert Kingston
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Internal Flow ◽  
Leading Edge ◽  
Internal Surface ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Novel Method ◽  
Exposed Surface Area

In this paper, the authors develop a novel method of obtaining regionally-averaged heat transfer coefficients in flowfields characterized by three temperatures using the well-known transient calorimeter technique. The technique is used to determine heat transfer in aluminum models of idealized turbine blade leading edges cooled through internal surface impingement, film cooling feed passages, and external convective film cooling. The external surface is subject to a stagnating mainstream crossflow. Importantly, the contributions to heating from the external flow and cooling from the internal flow can be separately resolved solely by heating the internal flow. Results for a basic showerhead geometry and an advanced intersecting-passage cooling configuration are presented for a range of internal and external Reynolds numbers. The intersecting-passage model shows little improvement in heat transfer coefficient over the showerhead for the flow conditions tested; however, the total cooling carried out is improved by the increase in exposed surface area. The technique’s uncertainties are fully assessed.

Heat Transfer Augmentation in a Rectangular Channel With Slit Rib-Turbulators on Two Opposite Walls

1997 ◽  
Vol 119 (3) ◽  
pp. 617-623 ◽  
Author(s):  
Jenn-Jiang Hwang ◽  
Tong-Miin Liou
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Open Area ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients ◽  
Ribbed Channel ◽  
Rib Turbulators

The effect of slit ribs on heat transfer and friction in a rectangular channel is investigated experimentally. The slit ribs are arranged in-line on two opposite walls of the channel. Three rib open-area ratios (β = 24, 37, and 46 percent), three rib pitch-to-height ratios (Pi/H = 10, 20, and 30), and two rib height-to-channel hydraulic diameter ratios (H/De = 0.081, and 0.162) are examined. The Reynolds number ranges from 10,000 to 50,000. Laser holographic interferometry is employed to measure the local heat transfer coefficients of the ribbed wall quantitatively, and observe the flow over the ribbed wall qualitatively. The results show that the slit rib has an advantage of avoiding “hot spots.” In addition, the heat transfer performance of the slit-ribbed channel is much better than that of the solid-ribbed channel. Semi-empirical correlations for friction and heat transfer are developed to account for rib spacings and open-area ratios. These correlations may be used in the design of turbine blade cooling passages.

Experimental and Numerical Impingement Heat Transfer in an Airfoil Leading-Edge Cooling Channel With Crossflow

2007 ◽  
Author(s):  
M. E. Taslim ◽  
D. Bethka
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Convective Heat Transfer Coefficient ◽  
Internal Heat ◽  
Leading Edge ◽  
Impinging Jet ◽  
Suction Side ◽  
Experimental Results ◽  
Transfer Coefficients ◽  
Impingement Heat Transfer

To enhance the internal heat transfer around the airfoil leading-edge area, a combination of rib-roughened cooling channels, film cooling and impingement cooling is often employed. Experimental data for impingement on various leading-edge geometries are reported by these and other investigators. Effects of strong crossflows on the leading-edge impingement heat transfer, however, have not been studied to that extent. This investigation dealt with impingement on the leading-edge of an airfoil in the presence of crossflows beyond the crossflow created by the upstream jets (spent air). Measurements of heat transfer coefficients on the airfoil nose area as well as the pressure and suction side areas are reported. The tests were run for a range of axial to jet mass flow rates (Maxial/Mjet) ranging from 1.14 to 6.4 and and jet Reynolds numbers ranging from 8000 to 48000. Comparisons are also made between the experimental results of impingement with and without the presence of crossflow and between representative numerical and measured heat transfer results. It was concluded that the presence of the external crossflow reduces the impinging jet effectiveness both on the nose and side walls, even for an axial to jet mass flow ratio as high as 5, the convective heat transfer coefficient produced by the axial channel flow was less than that of the impinging jet without the presence of the external crossflow, and the agreement between the numerical and experimental results was reasonable with an average difference ranging from −8% to −20%.

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.

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