Effect of Hole Shape on Film Cooling Effectiveness Over a Flat Plate

2013 ◽  
Author(s):  
J. Felix ◽  
N. Harshavardhana ◽  
Y. Giridhara Babu ◽  
D. Rajanna ◽  
N. Vinod Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Film Cooling ◽  
Thermal Image ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
The Heat Transfer Coefficient

Film cooling method of hot section components in the gas turbine engines is under continuous optimization for the enhanced cooling performance. In the present study, film cooling performance for a row of different shaped holes like triangular, circular and extended triangular have been considered. The adiabatic film effectiveness and the convective heat transfer coefficients are found experimentally on a flat plate. All the three test models are having holes of 5 mm diameter drilled at 20 mm pitch and inclined at an angle of 22 degrees. At the immediate downstream of these models, a flat plate is attached for finding the effect of these hole configurations. This flat plate is made with the low conductivity substrate and the stainless sheet of 0.2 mm thick is pasted over it in the flow path. The test model along with the flat plate is placed to the side wall of the rectangular duct where the mainstream air is supplied. The setup is made in such a way that the coolant air passed through the holes will create a film over the flat plate downstream. Infra Red camera is used to capture the thermal image of the entire test plate. The flat plate is connected with six thermocouples to have the reference surface temperature to correct the IR thermal image data. K-type thermocouples are used to measure the coolant and mainstream air temperatures. In both the heat transfer coefficient and adiabatic film cooling effectiveness experiments the blowing ratio is varied by 0.5 to 2.0, by keeping the constant mainstream air velocity of 20 m/s at ambient temperature. In the heat transfer coefficient experiments, the flat plate is heated with the constant heat flux conditions. In the adiabatic film cooling experiments, the coolant air is maintained at the temperature of −50°C with the help of liquid nitrogen heat exchanger bath. Results are plotted by taking the adiabatic film cooling effectiveness and convective heat transfer coefficient values from the centerline of holes downstream along the flow direction. From the results, the triangular and extended triangular hole models shown higher heat transfer coefficient and adiabatic film cooling effectiveness than the circular hole model.

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.

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.

Film Cooling Performance of Waist-Shaped Slot Holes

2010 ◽  
Author(s):  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Jiang-tao Bai ◽  
Du-chun Xu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Thermal Protection ◽  
Upstream Region ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Shaped Hole ◽  
The Heat Transfer Coefficient

Film cooling performance of a new shaped hole: waist-shaped slot hole is studied in this paper. Experimental measurement and numerical simulation are carried out to investigate the film cooling character and physics of this new shaped hole. And comparisons between the waist-shaped slot hole and two kinds of console holes are also performed. Both the cooling effectiveness distribution and the heat transfer coefficient distribution of the waist-shaped slot hole are similar with those of the console hole with large divergence angle because of the effect of the waist-shaped slot hole’s structure. The middle constriction structure of the waist-shaped slot hole and the coupled vortices make jets from the waist-shaped slot holes produce higher cooling effectiveness in the midspan region between adjacent holes. And also due to the effect of the middle constriction structure, the heat transfer coefficient of the waist-shaped slot hole is very high in the upstream midspan region. However, the heat transfer coefficient in the downstream midspan region is lower than that in the region near the hole centerline because of the effect of the coupled vortices. The waist-shaped slot holes provide the surface with very good thermal protection, especially in the upstream region. Although the console holes with small exit-entry area ratio provide better thermal protection than the waist-shaped slot holes due to small turbulence intensity, the flow resistance characteristic of the waist-shaped slot hole is much better.

Numerical Study on the Effects of V-Shaped Rib Angle on Film Cooling Performance for Turbine Blade Trailing Edge

2018 ◽  
Author(s):  
Lin Ye ◽  
Cun-liang Liu ◽  
Hai-yong Liu ◽  
Qi-jiao He ◽  
Gang Xie
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Film Cooling ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

The trailing edge of the high-pressure turbine blade presents significant challenges to cooling structure design. To achieve better cooling performance at turbine blade trailing edge, a novel ribbed cutback structure is proposed for trailing edge cooling, which has rib structures on the cutback surface for heat transfer enhancement. In this study, numerical simulations have been performed on the effects of V-shaped rib angle on the film cooling characteristics and flow physics. Three V-shaped rib angles of 30°, 45° and 60° are studied. The distributions of adiabatic cooling effectiveness and heat transfer coefficient are obtained under blowing ratios with the value of 0.5, 1.0 and 1.5 respectively. Due to the relatively small rib height, the effect of V-shaped ribs on the film cooling effectiveness is not notable. The disadvantage of V-shaped ribs mainly exhibits at the downstream area of cutback surface. With the increase of V-shaped rib angle, the film cooling effectiveness becomes lower, but the values are still above 0.9. The V-shaped ribs obviously enhance the heat transfer on trailing edge cutback surface. The area-averaged heat transfer coefficient of the V-rib case is higher than that of the smooth case by 26.3–41.2%. The 45° V-rib case has higher heat transfer intensity than the other two V-shaped rib cases under all the three blowing ratios. However, the heat transfer coefficient distribution of the 60° V-rib case is more uniform. The heat transfer intensity of the 30° V-rib case is higher in the downstream region than the other two cases, but lower in the upstream region in which the difference becomes smaller with the increase of blowing ratio. The 45° V-rib case and the 60° V-rib case both reach the maximum value of area-averaged heat transfer intensity under blowing ratio is 1.0. Under higher blowing ratio, the 30° V-rib case and the 45° V-rib case outperform 2.1% and 6.7% higher value relative to the 60° V-rib case respectively due to the smaller velocity gradient in the 60° V-rib case in the downstream.

Film Cooling Effectiveness and Mass/Heat Transfer Coefficient Downstream of One Row of Discrete Holes

1999 ◽  
Vol 121 (2) ◽  
pp. 225-232 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin ◽  
R. L. Olson
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle with 3d hole spacing and relatively small hole length to diameter ratio (L/d = 6.3). Both film cooling effectiveness and mass/heat transfer coefficient are determined for blowing rates from 0.5 to 2.0 with density ratio of 1.0. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with those from pure air injection. This technique enables one to obtain detailed local information on film cooling performance. The laterally averaged and local film cooling effectiveness agree with previous experiments. The difference between mass/heat transfer coefficients and previous heat transfer results indicates that conduction error may play an important role in the earlier heat transfer measurements.

Numerical Evaluation of Influence of Internal Ribs on Heat Transfer in Flat Plate Film Cooling

2013 ◽  
Author(s):  
Yukiko Agata ◽  
Toshihiko Takahashi ◽  
Eiji Sakai ◽  
Koichi Nishino
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Inlet

To augment the thermal efficiency of combined power generation plants, the turbine inlet temperature of an industrial gas turbine has been increased. Cooling technology plays a vital role in the durability of gas turbine blades in situations in which the turbine inlet temperature exceeds the allowable temperature of the blade material. Cooling air is also directly associated with the reduction in thermal efficiency because bleed air from the compressor is used for turbine cooling. Thus, improvement in cooling performance has a marked impact on the further augmentation of thermal efficiency by increasing turbine inlet temperature. To evaluate film cooling performance on the basis of heat flux reduction, it is necessary to accurately estimate both heat transfer coefficient and adiabatic film cooling effectiveness. Most studies of film cooling, however, have focused on improving adiabatic film cooling effectiveness. In contrast, there are few studies focusing on heat transfer coefficient. One of the reasons for this is that adiabatic film cooling effectiveness is a performance parameter unique to film cooling. To preliminarily estimate the heat flux through a blade, heat transfer coefficient without film cooling can still be used as substitute. Moreover, the accurate CFD prediction of heat transfer coefficient with film cooling is difficult, compared with the evaluation of adiabatic film cooling effectiveness. Therefore, in this study, we addressed the CFD prediction of heat transfer coefficient with film cooling on a flat plate, and discussed its feasibility. Recent gas turbine blades operated at a turbine inlet temperature of over 1300 degree Celsius employ internal convection cooling with ribbed passages and external film cooling. These cooling technologies have been studied extensively, particularly regarding their individual effects. On the other hand, there are few investigations on the interaction between internal convection cooling and the film cooling. Although most of such film-cooling studies employed stagnant plenums to bleed cooling air, some researchers including the present authors have shown the marked impact of the conditions for supplying coolant air on film cooling performance. In this study, we focus particularly on the influence of internal rib orientation on external film cooling performance along the blade outer surface. CFD analysis is used to resolve the flow fields of the flat plate film cooling and to clarify the influence of rib orientation on heat-transfer.

Heat Transfer Coefficient and Film Cooling Effectiveness on the Partial Cavity Tip of a Gas Turbine Blade

2018 ◽  
Author(s):  
Jin Young Jeong ◽  
Woobin Kim ◽  
Jae Su Kwak ◽  
Jung Shin Park
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cavity Shape ◽  
Blade Tip ◽  
The Heat Transfer Coefficient

Leakage flow between the rotating turbine blade tip and the fixed casing causes high heat loads and thermal stress on the tip and near the tip region. For this study, new squealer tips called partial cavity tips, which combine the advantages of plane and squealer tips, were suggested, and the effects of the cavity shape on the tip heat transfer coefficient and film cooling effectiveness were investigated experimentally in a low speed linear cascade. The suggested blade tips had a flat surface near the leading edge and a squealer cavity from the mid-chord to trailing edge region to achieve the advantages of both blade tip types. The heat transfer coefficient was measured via the 1-D transient heat transfer technique using an IR camera, and the film cooling effectiveness was obtained via the pressure sensitive paint (PSP) technique. Results showed that the heat transfer coefficient and film cooling effectiveness on the partial cavity tips strongly depended on the cavity shape. Near the leading edge, the heat transfer coefficients for the partial cavity tip cases were lower than that for the squealer tip case. However, the heat transfer coefficient on the cavity surface was higher for the partial cavity tip cases. The D10 tip showed a similar distribution of film cooling effectiveness to that of the PLN tip near the leading edge and the DSS tip near the mid-chord region. However, the overall averaged film cooling effectiveness of the DSS tip was higher than that of the D10 tip.

EXPERIMENTAL INVESTIGATION ON COOLING PERFORMANCE OF IMPINGEMENT-EFFUSION FULL COVERAGE FILM ON SUCTION SURFACE OF A VANE

2021 ◽  
pp. 1-28
Author(s):  
Fan Zhang ◽  
Cun Liang Liu ◽  
Lin Ye ◽  
Bingran Li ◽  
Shuaiqi Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Net Benefit ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

Abstract This research experimentally investigated the net benefit of film cooling with 6 rows of impingement-effusion structures on the suction surface of a vane. The experiment obtained the film cooling effectiveness of double-walled system on the suction surface via the pressure-sensitive paint (PSP) technique. The film cooling effectiveness obtained by the PSP technique is coupled with the transient liquid crystal (TLC) technique to determine the heat transfer coefficient. This combination of techniques reduces the time required for the experiment and improves the efficiency of the experiment. Through the experimentally measured film cooling effectiveness and dimensionless heat transfer coefficient, the net heat flux reduction (NHFR) is calculated to comprehensively measure the net benefit of film cooling. At the same time, in view of the lower net benefit of film cooling of the film holes in the front of the suction surface under higher mass flux ratio, the study improved the cylindrical holes into fan-shaped holes, and proposed two improvement schemes: Vane A and Vane B. The findings show that using the coupling of PSP and TLC to determine the heat transfer coefficient can yield credible results. The improvement of the fan-shaped holes makes the film cooling effectiveness and heat transfer coefficient ratio improved compared with the baseline vane. Changing cylindrical holes to fan-shaped holes does not necessarily lead to better net benefit of film cooling. The fan-shaped holes should be arranged reasonably to obtain better net benefit of film cooling.

Experimental Investigation on Cooling Performance of Impingement-Effusion Full Coverage Film on Suction Surface of Vane

2020 ◽  
Author(s):  
Fan Zhang ◽  
Cunliang Liu ◽  
Shuaiqi Zhang ◽  
Lin Ye ◽  
Bingran Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbulence Intensity ◽  
Mass Flux ◽  
Film Cooling ◽  
Flux Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
The Heat Transfer Coefficient

Abstract To study the film cooling performance of impingement-effusion structures, it is important to study their adiabatic film cooling effectiveness. To improve the adiabatic film cooling effectiveness on a vane, some rows of cylindrical effusion holes are changed into fan-shaped holes. This experiment measured the adiabatic film cooling effectiveness of the double-walled system on the suction surface via the pressure-sensitive paint (PSP) technique. The film cooling effectiveness obtained by the PSP technique is coupled with the transient liquid crystal (TLC) technique to determine the heat transfer coefficient. This combination of techniques reduces the time required for the experiment and improves the efficiency of the experiment. The heat transfer coefficient ratio is used to evaluate the level of heating transfer. The net heat flux reduction (NHFR) is used to quantify the net benefit of film cooling. Two experimental vanes’ (A and B) film holes are both arranged in 6 rows of holes. There are 15 holes in each row. Only the positions of the fan-shaped holes are different. The experimental conditions include the mainstream Reynolds number (Re = 151,000) based on the chord length and inlet velocity, the turbulence intensities (Tu = 0.77%, 16.9%), and the mass flux ratios (ṁc/ṁg = 0.4%, 0.8%, 1.6%). The findings show that when the mass flux ratio increases to a point, the film cooling effectiveness does not improve. Increasing the turbulence intensity leads to a decrease in the film cooling effectiveness except for the region after Row 6 on Vane B. Using the coupling of PSP and TLC to determine the heat transfer coefficient can yield credible results. The turbulence intensity and the arrangement of the film holes have obvious effects on the distribution of the heat transfer coefficient ratio. The effects of turbulence intensity, mass flux ratio and hole arrangement on NHFR were studied.

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