scholarly journals Modeling Film-Coolant Flow Characteristics at the Exit of Shower-Head Holes

2000 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Coolant Flow ◽  
The Heat Transfer Coefficient

Abstract The coolant flow characteristics at the hole exits of a film-cooled blade are derived from an earlier analysis where the hole pipes and coolant plenum were also discretized. The blade chosen is the VKI rotor with three staggered rows of shower-head holes. The present analysis applies these flow characteristics at the shower-head hole exits. A multi-block three-dimensional Navier-Stokes code with Wilcox’s k-ω model is used to compute the heat transfer coefficient on the film-cooled turbine blade. A reasonably good comparison with the experimental data as well as with the more complete earlier analysis where the hole pipes and coolant plenum were also gridded is obtained. If the 1/7th power law is assumed for the coolant flow characteristics at the hole exits, considerable differences in the heat transfer coefficient on the blade surface, specially in the leading-edge region, are observed even though the span-averaged values of h match well with the experimental data. This calls for span-resolved experimental data near film-cooling holes on a blade for better validation of the code.

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.

scholarly journals Heat Transfer on a Film-Cooled Rotating Blade

1999 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

A multi-block, three-dimensional Navier-Stokes code has been used to compute heat transfer coefficient on the blade, hub and shroud for a rotating high-pressure turbine blade with 172 film-cooling holes in eight rows. Film cooling effectiveness is also computed on the adiabatic blade. Wilcox’s k-ω model is used for modeling the turbulence. Of the eight rows of holes, three are staggered on the shower-head with compound-angled holes. With so many holes on the blade it was somewhat of a challenge to get a good quality grid on and around the blade and in the tip clearance region. The final multi-block grid consists of 4784 elementary blocks which were merged into 276 super blocks. The viscous grid has over 2.2 million cells. Each hole exit, in its true oval shape, has 80 cells within it so that coolant velocity, temperature, k and ω distributions can be specified at these hole exits. It is found that for the given parameters, heat transfer coefficient on the cooled, isothermal blade is highest in the leading edge region and in the tip region. Also, the effectiveness over the cooled, adiabatic blade is the lowest in these regions. Results for an uncooled blade are also shown, providing a direct comparison with those for the cooled blade. Also, the heat transfer coefficient is much higher on the shroud as compared to that on the hub for both the cooled and the uncooled cases.

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.

Leading-Edge Film-Cooling Physics: Part II — Heat Transfer Coefficient

2002 ◽  
Author(s):  
William D. York ◽  
James H. Leylek
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Numerical Predictions ◽  
Validation Experiment ◽  
Computational Methodology ◽  
Near Wall

A comprehensive study of film cooling on a turbine airfoil leading edge was performed with a documented, well-tested computational methodology. In this paper, numerically predicted heat transfer coefficients on the film-cooled leading edge are compared with experimental data from the open literature. The results are presented as the ratio of heat transfer coefficient with film cooling to that without film cooling, and the physics behind the surface results are discussed. The leading edge model was a half-cylinder in shape with a bluff afterbody to match the validation experiment, and other geometric parameters matched those of Part I of this study. Coolant at a density equal to that of the mainstream flow was injected through three rows of cylindrical film-cooling holes. One row of holes was centered on the stagnation line of the cylinder, and the other two rows were located ±3.5 hole diameters off stagnation. The downstream rows were staggered such that they were centered laterally between holes in the stagnation row. The holes were inclined at 20° with the surface, and made a 90° angle with the streamwise direction (radial injection). Four average blowing ratios were simulated in the range of 0.75 to 1.9, corresponding to the same momentum flux ratios as in Part I of this work. The multi-block, unstructured numerical grid was characterized by high quality and density, especially in the near wall region, in order to minimize error in predictions of the heat transfer. A fully-implicit scheme was used to solve the steady Reynolds-averaged Navier-Stokes equations, and a realizable k-ε model provided turbulence closure. A two-layer near-wall treatment allowed the resolution of the viscous sublayer for maximum accuracy in the prediction of the wall heat transfer coefficient. The numerical predictions exhibited generally good agreement with experimental data. The heat transfer coefficient was observed to increase sharply aft of the holes in the downstream rows. When coupled with the adiabatic effectiveness results of the first paper in this series, it is evident that a systematic computational methodology may be effectively applied to investigate and understand the complicated leading edge film-cooling problem.

Conjugate heat transfer from surface-mounted finite blunt plates

2006 ◽  
Vol 220 (1) ◽  
pp. 83-94 ◽  
Author(s):  
M Yaghoubi ◽  
E Velayati
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Leading Edge ◽  
Fin Efficiency ◽  
Flow And Heat Transfer ◽  
Flow Reynolds Number ◽  
The Heat Transfer Coefficient

Numerical studies of fluid flow and heat transfer are made in the separated, reattached, and redeveloped regions of the three-dimensional air flow on an array of finite plates with blunt leading edge. The flow reattachment occurs at a place downstream from the leading edge and the heat transfer coefficient becomes maximum around this region. The heat transfer coefficient is found to increase sharply near the leading edge and reduces in the wake. For the range of the parameters investigated in this study, some correlations have been developed for the length of reattachment region and variation of overall heat transfer coefficient for the considered bluff obstacles with various geometry and flow Reynolds number. For such blunt plates, when they are acting like fins, fin efficiency is determined and a relation based on flow Reynolds number and geometric parameters is developed to predict variation of the overall fin efficiency.

Heat Transfer and Effectiveness for a Turbulent Boundary Layer With Tangential Fluid Injection

1960 ◽  
Vol 82 (4) ◽  
pp. 303-312 ◽  
Author(s):  
R. A. Seban
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Free Stream ◽  
Cooling System ◽  
Leading Edge ◽  
Free Stream Velocity ◽  
Stream Velocity ◽  
The Heat Transfer Coefficient

Experimental results are presented for the effectiveness and for the heat-transfer coefficient for a film cooling system in which air was used both for the film and for the free-stream fluids. Injection occurred at a single tangential slot near the leading edge of the plate and the slot size was varied. All flows were turbulent and the injection velocities covered a range from much less to much greater than the free-stream velocity. Correlations are realized for both the effectiveness and for the heat-transfer coefficient and, as in the past experience with such systems, separate specifications are needed for injection velocities greater and less than the free-stream velocity.

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.

Influence of High Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer

1992 ◽  
Vol 114 (4) ◽  
pp. 707-715 ◽  
Author(s):  
A. B. Mehendale ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Blunt Body ◽  
Leading Edge ◽  
Surface Heat ◽  
Blowing Ratio ◽  
Turbulence Effect ◽  
The Heat Transfer Coefficient

The influence of high mainstream turbulence on leading edge film effectiveness and heat transfer coefficient was studied. High mainstream turbulence was produced by a passive grid and a jet grid. Experiments were performed using a blunt body with a semicylinder leading edge with a flat afterbody. The mainstream Reynolds number based on leading edge diameter was about 100,000. Spanwise and streamwise distributions of film effectiveness and heat transfer coefficient in the leading edge and on the flat sidewall were obtained for three blowing ratios, through rows of holes located at ±15 and ±40 deg from stagnation. The holes in each row were spaced three hole diameters apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. The results indicate that the film effectiveness decreases with increasing blowing ratio, but the reverse is true for the heat transfer coefficient. The leading edge film effectiveness for low blowing ratio (B = 0.4) is significantly reduced by high mainstream turbulence (Tu = 9.67 and 12.9 percent). The mainstream turbulence effect is diminished in the leading edge for higher blowing ratios (B = 0.8 and 1.2) but still exists on the flat sidewall region. Also, the leading edge heat transfer coefficient for blowing ratio of 0.8 increases with increasing mainstream turbulence; but the effect for other blowing ratios [B = 0.4 and 1.2) is not as systematic as for B = 0.8. Surface heat load is significantly reduced with leading edge film cooling.

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

2019 ◽  
Vol 141 (7) ◽  
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 plane (PLN) tip near the leading edge and the double side squealer (DSS) tip near the mid-chord region. However, the overall average film cooling effectiveness of the DSS tip was higher than that of the D10 tip.

Influence of Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer Through Two Rows of Inclined Film Slots

1991 ◽  
Author(s):  
S. Ou ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Heat Load ◽  
Leading Edge ◽  
Cross Sectional ◽  
Stagnation Line ◽  
Blowing Ratio ◽  
The Heat Transfer Coefficient

The effect of film slot injection on leading edge heat transfer coefficient and film cooling effectiveness under high mainstream turbulence conditions was experimentally studied for flow across a blunt body with a semi-cylinder leading edge and a flat afterbody. High mainstream turbulence levels were generated by a bar grid (Tu = 5.07%) and a passive grid (Tu = 9.67%). The incident mainstream Reynolds number based on the cylinder diameter was about 100,000. The spanwise and streamwise distributions of the heat transfer coefficient and film effectiveness in the leading edge and on the flat sidewall were obtained for three blowing ratios (B = 0.4, 0.8 and 1.2) with two rows of film slots located at ±15° and ±40° from stagnation line. The cross-sectional slot length-to-width ratio was two. The slots in each row were spaced three cross-sectional slot lengths apart and were angled 30° and 90° to the surface in the spanwise and streamwise direction, respectively. The results show that the heat transfer coefficient increases with increasing blowing ratio, but the film effectiveness reaches the maximum at an intermediate blowing ratio of B = 0.8 for both low (Tu = 0.75%) and high (Tu = 9.67%) mainstream turbulence conditions. The leading edge heat transfer coefficient increases and the film effectiveness decreases with mainstream turbulence level for the low blowing ratio; however, the mainstream turbulence effect reduces for the high blowing ratio. The leading edge heat load is significantly reduced with two rows of film slot injection. The blowing ratio of B = 0.4 provides the lowest heat load in the leading edge region for the low mainstream turbulence but B = 0.8 gives the lowest heat load for the high mainstream turbulence conditions.

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