Heat Transfer Coefficients of Film Cooling on a Rotating Turbine Blade Model—Part I: Effect of Blowing Ratio

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Zhi Tao ◽  
Zhenming Zhao ◽  
Shuiting Ding ◽  
Guoqiang Xu ◽  
Bin Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Co2 Injection ◽  
Spanwise Direction ◽  
Stationary Case ◽  
Suction Surface ◽  
Pressure Surface ◽  
Blowing Ratio

Experimental investigations were performed to measure the local heat transfer coefficient (hg) distributions of film cooling over a flat blade under both stationary and rotating conditions. Film cooling was via a straight circular hole of 4 mm in diameter located in the middle section of the blade angled 30 deg along the streamwise direction and 90 deg along the spanwise direction. The Reynolds (ReD) number based on the mainstream velocity and the film hole diameter was fixed at 3191, and the rotating speed (ω) was either 0 rpm or 800 rpm; the film cooling blowing ratios ranged from 0.4 to 2.0, and two averaged density ratios of 1.02 and 1.53 were employed with air and carbon dioxide (CO2) as the coolant, respectively. Thermochromic liquid crystal was used to measure the solid surface temperature distributions. Experimental results showed the following: (1) In the stationary case, the blowing ratio has a significant influence on the nondimensional heat transfer coefficient (hg/h0) especially in the near hole region. (2) The film trajectory in rotation had an obvious deflection in the spanwise direction, and the deflection angles on the suction surface are larger than those on the pressure surface. This was attributed to the combined action of the Coriolis force and centrifugal force. (3) In the rotating case, for CO2 injection, the magnitude of heat transfer coefficient on the pressure surface is reduced compared with the stationary case, and the blowing ratio has smaller effects on hg/h0 distribution. However, on the suction surface, the heat transfer coefficient at x/D<1.0 is enhanced and then rapidly reduced to be also below the stationary values. For air injection, rotation also depresses the hg/h0 for both the pressure and the suction surface. (4) The density ratio shows a considerable effect on the streamwise heat transfer coefficient distributions especially for the rotating cases.

Heat Transfer Coefficients of Film Cooling on a Rotating Turbine Blade Model: Part I—Effect of Blowing Ratio

2008 ◽  
Author(s):  
Zhi Tao ◽  
Zhenming Zhao ◽  
Shuiting Ding ◽  
Guoqiang Xu ◽  
Bin Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Co2 Injection ◽  
Spanwise Direction ◽  
Stationary Case ◽  
Suction Surface ◽  
Pressure Surface ◽  
Blowing Ratio

Experimental investigations were performed to measure the local heat transfer coefficient (hg) distributions of film cooling over a flat blade under both stationary and rotating conditions. Film cooling was via a straight circular hole of 4 mm in diameter located in the middle section of the blade angled 30° along the streamwise direction and 90° along the spanwise direction. The Reynolds (ReD) number based on the mainstream velocity and the film hole diameter was fixed to be 3191 and the rotating speeds (ω) were either 0 and 800 rpm; the film cooling blowing ratios ranged from 0.4 to 2.0 and two averaged density ratios of 1.02 and 1.53 were employed with air and carbon dioxide (CO2) as the coolant respectively. Thermochromic liquid crystal (TLC) was used to measure the solid surface temperature distributions. Experimental results showed that (1) in the stationary case, the blowing ratio has a significant influence on the non-dimensional heat transfer coefficient (hg/h0) especially in the near hole region. (2) the film trajectory in rotation had an obvious deflection in the spanwise direction, and the deflection angles on the suction surface are larger than that on the pressure surface. This was attributed to the combined action of the Coriolis force and centrifugal force. (3) in the rotating case, for CO2 injection, the magnitude of heat transfer coefficient on the pressure surface is reduced compared with the stationary case and the blowing ratio has smaller effects on hg/h0 distribution. However, on the suction surface, the heat transfer coefficient at x/D&lt;1.0 is enhanced and then rapidly reduced to be also below the stationary values. For air injection, rotation also depresses the hg/h0 for both the pressure and the suction surface. (4) the density ratio shows a considerable effect on the streamwise heat transfer coefficient distributions especially for the rotating cases.

Influence of High Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer: Effect of Film Hole Row Location

1992 ◽  
Vol 114 (4) ◽  
pp. 716-723 ◽  
Author(s):  
S. Ou ◽  
A. B. Mehendale ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Turbulence Effect

The effect of film hole row location on leading edge film cooling effectiveness and heat transfer coefficient under high mainstream turbulence conditions was experimentally determined for flow over a blunt body with semicylinder leading edge and a flat afterbody. Two separate cases of film injection film holes located only at ± 15 or ± 40 deg were studied. The holes were spaced three hole diameters apart in the spanwise direction and inclined 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. A bar grid (Tu = 5.07 percent), a passive grid (Tu = 9.67 percent), and a jet grid (Tu = 12.9 percent) produced high mainstream turbulence. The incident mainstream Reynolds number based on cylinder diameter was 100,000. Spanwise and streamwise distributions of film effectiveness and heat transfer coefficient in the leading edge and the flat sidewall were obtained for three blowing ratios. The results show mainstream turbulence adversely affects leading edge film effectiveness for the low blowing ratio (B = 0.4), but the effect reduces for higher blowing ratios (B = 0.8 and 1.2). The leading edge heat transfer coefficient increases with mainstream turbulence level for B = 0.4 and 0.8, but the effect is not systematic for B = 1.2. Mainstream turbulence effect is more severe for ±15 deg one-row injection than for ± 40 deg one-row injection. The surface heat load reduction for ± 15 deg one-row injection or ± 40 deg one-row injection is smaller than that for two-row injection.

Heat Transfer Coefficient Measurements on the Film-Cooled Pressure Surface of a Transonic Airfoil

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Paul M. Kodzwa ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Wide Band ◽  
Heat Fluxes ◽  
Pressure Surface ◽  
Lift Off ◽  
Transonic Airfoil

This paper presents isoenergetic temperature and steady-state film-cooled heat transfer coefficient measurements on the pressure surface of a modern, highly cambered transonic airfoil. A single passage model simulated the idealized two-dimensional flow path between blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade but produced an equivalent flow condition. Furthermore, this model allowed the use of steady-state, constant surface heat fluxes. We used wide-band thermochromic liquid crystals (TLCs) viewed through a novel miniature periscope system to perform high-accuracy (±0.2 °C) thermography. The peak Mach number along the pressure surface was 1.5, and maximum turbulence intensity was 30%. We used air and carbon dioxide as injectant to simulate the density ratios characteristic of the film cooling problem. We found significant differences between isoenergetic and recovery temperature distributions with a strongly accelerated mainstream and detached coolant jets. Our heat transfer data showed some general similarities with lower-speed data immediately downstream of injection; however, we also observed significant heat transfer attenuation far downstream at high blowing conditions. Our measurements suggested that the momentum ratio was the most appropriate variable to parameterize the effect of injectant density once jet lift-off occurred. We noted several nonintuitive results in our turbulence effect studies. First, we found that increased mainstream turbulence can be overwhelmed by the local augmentation of coolant injection. Second, we observed complex interactions between turbulence level, coolant density, and blowing rate with an accelerating mainstream.

scholarly journals Comparison of Two-Equation Turbulence Models for Prediction of Heat Transfer on Film-Cooled Turbine Blades

1997 ◽  
Author(s):  
Vijay K. Garg ◽  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Time ◽  
Suction Surface ◽  
The Heat Transfer Coefficient

A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley’s q-ω model, Chien’s k-ε model and Wilcox’s k-ω model with Menter’s modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all two-equation models require 40% more computer core than the B-L model for solution, and while the q-ω and k-ε models need 40% more computer time than the B-L model, the k-ω model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

2017 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Trench Width

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

Investigations on the Influence of Rib Orientation Angle on Film Cooling Performance of Compound Holes

2018 ◽  
Author(s):  
Lin Ye ◽  
Cun-liang Liu ◽  
Hai-yong Liu ◽  
Hui-ren Zhu ◽  
Jian-xia Luo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Orientation Angle ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

To investigate the effects of the inclined ribs on internal flow structure in film hole and the film cooling performance on outer surface, experimental and numerical studies are conducted on the effects of rib orientation angle on film cooling of compound cylindrical holes. Three coolant channel cases, including two ribbed cross-flow channels (135° and 45° angled ribs) and the plenum case, are studied under three blowing ratios (0.5, 1.0 and 2.0). 2D contours of film cooling effectiveness as well as heat transfer coefficient were measured by transient liquid crystal measurement technique (TLC). The steady RANS simulations with realizable k-ε turbulence model and enhanced wall treatment were performed. The results show that the spanwise width of film coverage is greatly influenced by the rib orientation angle. The spanwise width of the 45° rib case is obviously larger than that of the 135° rib case under lower blowing ratios. When the blowing ratio is 1.0, the area-averaged cooling effectiveness of the 135° rib case and the 45° rib case are higher than that of the plenum case by 38% and 107%, respectively. With the increase of blowing ratio, the film coverage difference between different rib orientation cases becomes smaller. The 45° rib case also produces higher heat transfer coefficient, which is higher than the 135° rib case by 3.4–8.7% within the studied blowing ratio range. Furthermore, the discharge coefficient of the 45° rib case is the lowest among the three cases. The helical motion of coolant flow is observed in the hole of 45° rib case. The jet divides into two parts after being blown out of the hole due to this motion, which induces strong velocity separation and loss. For the 135° rib case, the vortex in the upper half region of the secondary-flow channel rotates in the same direction with the hole inclination direction, which leads to the straight streamlines and thus results in lower loss and higher discharge coefficient.

SURFACE HEATER FABRICATION USING MICRO-LITHOGRAPHY FOR TRANSPIRATION COOLING HEAT TRANSFER COEFFICIENT MEASUREMENTS

2021 ◽  
pp. 1-23
Author(s):  
Zheng Min ◽  
Sarwesh Narayan Parbat ◽  
Qing-Ming Wang ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Target Surface ◽  
Transpiration Cooling ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Adiabatic Cooling

Abstract Transpiration cooling is able to provide more uniform coolant coverage than film cooling to effectively protect the component surface from contacting the hot gas. Due to numerous coolant ejection outlets within a small area at the target surface, the experimental thermo-fluid investigation on transpiration cooing becomes a significant challenge. Two classic methods to investigate film cooling, the steady-state foil heater method and the transient thermography technique, both fail for transpiration cooling because the foil heater would block numerous coolant outlets, and the semi-infinite solid conduction model no longer holds for porous plates. In this study, a micro-lithography method to fabricate a silver coil pattern on top of the additively manufactured polymer porous media as the surface heater was proposed. The circuit was deliberately designed to cover the solid surface in a combination of series connection and parallel connection to ensure the power in each unit cell area at the target surface was identical. With uniform heat flux generation, the steady-state tests were conducted to obtain distributions of a pair of parameters, adiabatic cooling effectiveness, and heat transfer coefficient (HTC). The results showed that the adiabatic cooling effectiveness could reach 0.65 with a blowing ratio lower than 0.5. Meanwhile, the heat transfer coefficient ratio (hf/h0) of transpiration cooling was close to 1 with a small blowing ratio at 0.125. A higher HTC ratio was observed for smaller pitch-to-diameter cases due to more turbulence intensity generated at the target surface.

Investigation on the Leading Edge Film Cooling of Counter-Inclined Cylindrical and Laid-Back Holes With and Without Impingement: Part II — Heat Transfer Coefficient

2018 ◽  
Author(s):  
Rui-dong Wang ◽  
Cun-liang Liu ◽  
Hai-yong Liu ◽  
Hui-ren Zhu ◽  
Qi-ling Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
The Heat Transfer Coefficient ◽  
Tube Structure

Heat transfer of the counter-inclined cylindrical and laid-back holes with and without impingement on the turbine vane leading edge model are investigated in this paper. To obtain the film cooling effectiveness and heat transfer coefficient, transient temperature measurement technique on complete surface based on double thermochromic liquid crystals is used in this research. A semi-cylinder model is used to model the vane leading edge which is arranged with two rows of holes. Four test models are measured under four blowing ratios including cylindrical film holes with and without impingement tube structure, laid-back film holes with and without impingement tube structure. This is the second part of a two-part paper, the first part paper GT2018-76061 focuses on film cooling effectiveness and this study will focus on heat transfer. Contours of surface heat transfer coefficient and laterally averaged result are presented in this paper. The result shows that the heat transfer coefficient on the surface of the leading edge is enhanced with the increase of blowing ratio for same structure. The shape of the high heat transfer coefficient region gradually inclines to span-wise direction as the blowing ratio increases. Heat transfer coefficient in the region where the jet core flows through is relatively lower, while in the jet edge region the heat transfer coefficient is relatively higher. Compared with cylindrical hole, laid-back holes give higher heat transfer coefficient. Meanwhile, the introduction of impingement also makes heat transfer coefficient higher compared with cross flow air intake. It is found that the heat transfer of the combination of laid-back hole and impingement tube can be very high under large blowing ratio which should get attention in the design process.

Effects of Surface Geometry on Film Cooling Performance at Airfoil Trailing Edge

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Akira Murata ◽  
Satomi Nishida ◽  
Hiroshi Saito ◽  
Kaoru Iwamoto ◽  
Yoji Okita ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Surface Geometry ◽  
Enhanced Heat Transfer ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
The Heat Transfer Coefficient

Cooling at the trailing edge of a gas turbine airfoil is one of the most difficult problems because of its thin shape, high thermal load from both surfaces, hard-to-cool geometry of narrow passages, and at the same time demand for structural strength. In this study, the heat transfer coefficient and film cooling effectiveness on the pressure-side cutback surface was measured by a transient infrared thermography method. Four different cutback geometries were examined: two smooth cutback surfaces with constant-width and converging lands (base and diffuser cases) and two roughened cutback surfaces with transverse ribs and spherical dimples. The Reynolds number of the main flow defined by the mean velocity and two times the channel height was 20,000, and the blowing ratio was varied among 0.5, 1.0, 1.5, and 2.0. The experimental results clearly showed spatial variation of the heat transfer coefficient and the film cooling effectiveness on the cutback and land top surfaces. The cutback surface results clearly showed periodically enhanced heat transfer due to the periodical surface geometry of ribs and dimples. Generally, the increase of the blowing ratio increased both the heat transfer coefficient and the film cooling effectiveness. Within the present experimental range, the dimple surface was a favorable cutback-surface geometry because it gave the enhanced heat transfer without deterioration of the high film cooling effectiveness.

scholarly journals Effect of Velocity and Temperature Distribution at the Hole Exit on Film Cooling of Turbine Blades

1997 ◽  
Vol 119 (2) ◽  
pp. 343-351 ◽  
Author(s):  
V. K. Garg ◽  
R. E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Suction Surface ◽  
Free Stream Turbulence ◽  
The Heat Transfer Coefficient ◽  
Coolant Velocity

An existing three-dimensional Navier–Stokes code (Arnone et al., 1991), modified to include film cooling considerations (Garg and Gaugler, 1994), has been used to study the effect of coolant velocity and temperature distribution at the hole exit on the heat transfer coefficient on three film-cooled turbine blades, namely, the C3X vane, the VKI rotor, and the ACE rotor. Results are also compared with the experimental data for all the blades. Moreover, Mayle’s transition criterion (1991), Forest’s model for augmentation of leading edge heat transfer due to free-stream turbulence (1977), and Crawford’s model for augmentation of eddy viscosity due to film cooling (Crawford et al., 1980) are used. Use of Mayle’s and Forest’s models is relevant only for the ACE rotor due to the absence of showerhead cooling on this rotor. It is found that, in some cases, the effect of distribution of coolant velocity and temperature at the hole exit can be as much as 60 percent on the heat transfer coefficient at the blade suction surface, and 50 percent at the pressure surface. Also, different effects are observed on the pressure and suction surface depending upon the blade as well as upon the hole shape, conical or cylindrical.

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