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.

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.

scholarly journals Experimental and Numerical Investigation of Effect of Blowing Ratio on Film Cooling Effectiveness and Heat Transfer Coefficient Over a Gas Turbine Blade Leading Edge Film Cooling Configurations

2013 ◽  
Author(s):  
Yepuri Giridhara Babu ◽  
Gururaj Lalgi ◽  
Ashok Babu Talanki Puttarangasetty ◽  
Jesuraj Felix ◽  
Sreenivas Rao V. Kenkere ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Gas Turbine Blade ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

Film cooling is one of the cooling techniques to cool the hot section components of a gas turbine engines. The gas turbine blade leading edges are the vital parts in the turbines as they are directly hit by the hot gases, hence the optimized cooling of gas turbine blade surfaces is essential. This study aims at investigating the film cooling effectiveness and heat transfer coefficient experimentally and numerically for the three different gas turbine blade leading edge models each having the one row of film cooling holes at 15, 30 and 45 degrees hole orientation angle respectively from stagnation line. Each row has the five holes with the hole diameter of 3mm, pitch of 20mm and has the hole inclination angle of 20deg. in spanwise direction. Experiments are carried out using the subsonic cascade tunnel facility of National Aerospace Laboratories, Bangalore at a nominal flow Reynolds number of 1,00,000 based on the leading edge diameter, varying the blowing ratios of 1.2, 1.50, 1.75 and 2.0. In addition, an attempt has been made for the film cooling effectiveness using CFD simulation, using k-€ realizable turbulence model to solve the flow field. Among the considered 15, 30 and 45 deg. models, both the cooling effectiveness and heat transfer coefficient shown the increase with the increase in hole orientation angle from stagnation line. The film cooling effectiveness increases with the increase in blowing ratio upto 1.5 for the 15 and 30 deg. models, whereas on the 45 deg. model the increase in effectiveness shown upto the blowing ratio of 1.75. The heat transfer coefficient values showed the increase with the increase in blowing ratio for all the considered three models. The CFD results in the form of temperature, velocity contours and film cooling effectiveness values have shown the meaningful results with the experimental values.

On the effect of geometry of w-wave trenches on film cooling performance of gas turbine blades

2021 ◽  
pp. 095765092110082
Author(s):  
Alireza Bakhshinejad Bahambari ◽  
Mohammad Hassan Kayhani ◽  
Mahmood Norouzi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Stokes Equations ◽  
Uniform Structure ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

In the present study, three types of w-wave trenches with different amplitude configurations are compared with transverse trench (TT), and the use of variable radius fillet (VRF) on downstream lips at different blowing ratio is numerically investigated to measure heat transfer coefficient, and cooling effectiveness. The numerical results are obtained by three-dimensional Reynolds average Navier–Stokes equations (RANS) while employing shear stress transport turbulence models, which are validated by comparing with experimental data. The trench width is kept constant in all cases, yet the three different amplitudes and variable fillet radiuses offered a variety of designs in trench film cooling. The results showed that w-wave trenches impressively improved film cooling effectiveness over the transverse trench, and utilizing fillets at downstream lips of the trench caused significant enhancement on both lateral averaged and centerline cooling performance. Due to the w-wave trench configuration, anti-counter-rotating vortices responsible for pushing coolant film toward the near-wall were formed throughout of downstream wall of the trench, and the cooling flow thus had a more uniform structure. The heat transfer coefficient distributions of filleted w-wave trenches are observed to be more uniform than simple w-wave and transverse trench under all blowing ratio conditions. Moreover, enlargement of the fillet radius in Cases 2 and 3 yielded to the growth of centerline coolant flow, which in turn resulted in the improvement of film cooling effectiveness at all blowing ratios.

Effects of Shape and Arrangement of Dimples on Film Cooling Performance Over Cutback Surface at Airfoil Trailing Edge

2013 ◽  
Author(s):  
Satomi Nishida ◽  
Akira Murata ◽  
Hiroshi Saito ◽  
Yoji Okita ◽  
Chiyuki Nakamata ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Local Heat Transfer ◽  
Trailing Edge ◽  
Mean Velocity ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

Trailing edge of a gas turbine blade is under very high thermal load because both sides are exposed to hot mainstream. The cooling film ejected from slots has to protect the cutback surface from the hot mainstream, and remove the heat from the surface. In this study, the film cooling performance of cutback surfaces with two types of dimples, spherical and teardrop-shaped dimples, were experimentally investigated with a transient infrared thermography method. Also, to examine the effects of arrangements, two different arrangements of the teardrop-shaped dimples, which are parallel and inclined to mainstream, were investigated. The dimples were arranged in two rows on the cutback surfaces. The Reynolds number of mainstream defined by the mean velocity and hydraulic diameter was 20,000, and profiles of local heat transfer coefficient and film cooling effectiveness on the cutback surface were measured for blowing ratios of 0.5–2.0. With the parallel teardrop-shaped dimples, reduction of the heat transfer in the upstream portion was less than that of the spherical dimples, and the heat transfer at downstream rims was higher. In the case of the inclined teardrop-shaped dimples, heat transfer enhancement at the downstream rims was higher than that of parallel one, and overall heat transfer coefficient was also higher. The film cooling effectiveness of all cases are almost equal values, namely, the dimpled surfaces could enhance heat transfer without reduction of the film cooling effectiveness; consequently significant cooling performance improvement was obtained for the teardrop-shaped dimple cases, especially with the introduction of inclined arrangement.

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.

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.

Effects of Oscillations in the Mainstream on Film Cooling at Various Blowing Ratios

2017 ◽  
Author(s):  
Seung Il Baek ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Jet Flow ◽  
Main Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

The objective of this study is to understand the effects of flow oscillations in the mainstream and film cooling jets on film cooling at various blowing ratios (0.5, 0.78, 1.0 and 1.5). These oscillations could be caused by the combustion instabilities. They are approximated in sinusoidal form for the current study. The effects of different frequencies (0, 2, 16, 32 Hz) on film cooling are investigated. Simulations are performed using URANS Realizable k-epsilon and LES Smagorinsky-Lilly turbulence models. The results indicate that if the frequencies of the mainstream and the jet flow are increased at a low average blowing ratio of M = 0.5, the adiabatic film cooling effectiveness is decreased and the heat transfer coefficient is increased due to increased disturbance in jet and main flow interaction with increasing frequency. It was observed that when the frequency of the mainstream and the cooling jet flow is increased at M = 0.5, the amplitude of the pressure difference between the mainstream and the plenum is increased resulting in increased amplitude of coolant flow rate oscillations leading to more jet lift off and more disturbance in the main flow and coolant interaction. Consequently, adiabatic film cooling effectiveness is decreased and heat transfer coefficient is increased. If the frequency of the mainstream is increased from 0 Hz to 2, 16, or 32 Hz at M = 0.5, the centerline effectiveness is decreased about 10%, 12%, or 47% and the spanwise-averaged Stanton number ratio is increased about 4%, 5%, or 9% respectively. If the frequencies of the main flow and the jet flow are increased at higher blowing ratios of M = 1.0 and 1.5, adiabatic effectiveness is increased and the spanwise-averaged heat transfer coefficient are decreased. Under steady flow conditions jet lift off is generated for these high blowing ratios. If the frequency of the mainstream and the jet flow is increased, the amplitude of coolant jet flow rate oscillation is increased for the same reason as mentioned above for M = 0.5. This leads to less jet lift off during the cycle resulting in more frequent coolant contact with the wall and consequently increased centerline effectiveness as frequency increases. In addition, the entrainment of hot gases underneath the jet doesn’t lead to higher mixing between the hot mainstream and the coolant and this results in decreased heat transfer coefficient. This is also indicated by the turbulent kinetic energy levels. Some representative results are: when the frequency of the main flow is increased from 0 Hz to 2, 16, or 32 Hz at M = 1.0, the centerline effectiveness is increased about 8%, 19%, or 320%. Also, if the oscillation frequency is increased from 2 Hz to 16, or 32 Hz at M = 1.0, the spanwise-averaged Stanton number ratio is decreased around 2%, to 5% respectively. It seems like the cut off point for low and high blowing ratio behavior of cooling jets is around M = 0.78.

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.

Sign in / Sign up

Export Citation Format

Share Document