Turbine Blade Tip Heat Transfer in Low Speed and High Speed Flows

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Nicholas R. Atkins ◽  
Li He
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Mach Number ◽  
Transfer Coefficient ◽  
High Speed ◽  
Low Speed ◽  
Blade Tip ◽  
The Heat Transfer Coefficient ◽  
Recovery Temperature

In this paper, high and low speed tip flows are investigated for a high-pressure turbine blade. Previous experimental data are used to validate a computational fluid dynamics (CFD) code, which is then used to study the tip heat transfer in high and low speed cascades. The results show that at engine representative Mach numbers, the tip flow is predominantly transonic. Thus, compared with the low speed tip flow, the heat transfer is affected by reductions in both the heat-transfer coefficient and the recovery temperature. The high Mach numbers in the tip region (M>1.5) lead to large local variations in recovery temperature. Significant changes in the heat-transfer coefficient are also observed. These are due to changes in the structure of the tip flow at high speed. At high speeds, the pressure side corner separation bubble reattachment occurs through supersonic acceleration, which halves the length of the bubble when the tip-gap exit Mach number is increased from 0.1 to 1.0. In addition, shock/boundary-layer interactions within the tip gap lead to large changes in the tip boundary-layer thickness. These effects give rise to significant differences in the heat-transfer coefficient within the tip region compared with the low speed tip flow. Compared with the low speed tip flow, the high speed tip flow is much less dominated by turbulent dissipation and is thus less sensitive to the choice of turbulence model. These results clearly demonstrate that blade tip heat transfer is a strong function of Mach number, an important implication when considering the use of low speed experimental testing and associated CFD validation in engine blade tip design.

Turbine Blade Tip Heat Transfer in Low Speed and High Speed Flows

2009 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Nicholas R. Atkins ◽  
Li He
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Mach Number ◽  
Transfer Coefficient ◽  
High Speed ◽  
Low Speed ◽  
Blade Tip ◽  
The Heat Transfer Coefficient ◽  
Recovery Temperature

In this paper, high and low speed tip flows are investigated for a high-pressure turbine blade. Previous experimental data are used to validate a CFD code, which is then used to study the tip heat transfer in high and low speed cascades. The results show that at engine representative Mach numbers the tip flow is predominantly transonic. Thus, compared to the low speed tip flow, the heat transfer is affected by reductions in both the heat transfer coefficient and the recovery temperature. The high Mach numbers in the tip region (M>1.5) lead to large local variations in recovery temperature. Significant changes in the heat transfer coefficient are also observed. These are due to changes in the structure of the tip flow at high speed. At high speeds, the pressure side corner separation bubble reattachment occurs through supersonic acceleration which halves the length of the bubble when the tip gap exit Mach number is increased from 0.1 to 1.0. In addition, shock/boundary-layer interactions within the tip gap lead to large changes in the tip boundary-layer thickness. These effects give rise to significant differences in the heat-transfer coefficient within the tip region compared to the low-speed tip flow. Compared to the low speed tip flow, the high speed tip flow is much less dominated by turbulent dissipation and is thus less sensitive to the choice of turbulence model. These results clearly demonstrate that blade tip heat transfer is a strong function of Mach number, an important implication when considering the use of low speed experimental testing and associated CFD validation in engine blade tip design.

scholarly journals Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade

2000 ◽  
Author(s):  
Gm S. Azad ◽  
Je-Chin Han ◽  
Robert J. Boyle
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Static Pressure ◽  
Cavity Surface ◽  
Edge Region ◽  
Blade Tip ◽  
The Heat Transfer Coefficient

Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modern first stage gas turbine rotor blade with a blade tip profile of a GE-E3 aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1×106. A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. The heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1% case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.

Thermal Investigation of Integrated Combustor Vane Concept Under Engine-Realistic Conditions

2016 ◽  
Author(s):  
Simon Jacobi ◽  
Budimir Rosic
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
High Speed ◽  
Secondary Flows ◽  
Experimental Measurements ◽  
Thermal Investigation ◽  
Nozzle Guide ◽  
The Heat Transfer Coefficient

This paper presents a thermal investigation of the Integrated Combustor Vane concept for power generation gas turbines with individual can combustors. This concept has the potential to replace the high-pressure turbine’s first vanes by prolonged combustor walls. Experimental measurements are performed on a linear high-speed cascade consisting of two can combustors and two integrated vanes. The modularity of the facility allows for the testing at engine-realistic high turbulence levels, as well as swirl strengths with opposing swirl directions. The heat transfer characteristics of the integrated vanes are compared to conventional nozzle guide vanes. The experimental measurements are supported by detailed numerical simulations using the inhouse CFD code TBLOCK. Experimental as well as numerical results congruently indicate a considerable reduction of the heat transfer coefficient (HTC) on the integrated vanes surfaces and endwalls caused by a differing state of boundary layer thickness. The studies furthermore depict a slight, non-detrimental shift in the heat transfer coefficient distributions and the strength of the integrated vanes secondary flows as a result of engine-realistic combustor swirl.

The Deformation Rule of the Cooled U75V Heavy Rail Caused by the Different Heat Transfer Coefficient

2011 ◽  
Vol 299-300 ◽  
pp. 1005-1011 ◽  
Author(s):  
Ming Xin Gao ◽  
Pei Long Wang ◽  
Hao Jia ◽  
Shan Hu Tong ◽  
Hua Song ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Speed ◽  
Reference Value ◽  
Ansys Software ◽  
Cooling Process ◽  
Technological Parameters ◽  
The Heat Transfer Coefficient ◽  
Heavy Rail

When rolled heavy rail is on the cooling bed for natural cooling, the heat transfer coefficient has important effect on the bending and section sizes of cooled heavy rail. In the paper, the heat-stress couple module ofANSYS software is adopted to carry on numerical simulation on the cooling process of 60kg/m U75V heavy rail, and we obtain the change rule that heat transfer coefficient has effect on bending curvature and section sizes of cooled heavy rail. This study is of great reference value on cooling bed design and the formulation of cooling technological parameters for high speed heavy rail.

Detailed Heat Transfer Coefficient Distributions on a Large-Scale Gas Turbine Blade Tip

2000 ◽  
Vol 123 (4) ◽  
pp. 803-809 ◽  
Author(s):  
Shuye Teng ◽  
Je-Chin Han ◽  
G. M. S. Azad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Wind Tunnel ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Large Scale ◽  
Tip Clearance ◽  
Low Speed ◽  
Blade Tip ◽  
Low Speed Wind Tunnel

Measurements of detailed heat transfer coefficient distributions on a turbine blade tip were performed in a large-scale, low-speed wind tunnel facility. Tests were made on a five-blade linear cascade. The low-speed wind tunnel is designed to accommodate the 107.49 deg turn of the blade cascade. The mainstream Reynolds number based on cascade exit velocity was 5.3×105. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The wake Strouhal number was kept at 0 or 0.1. The central blade had a variable tip gap clearance. Measurements were made at three different tip gap clearances of about 1.1 percent, 2.1 percent, and 3 percent of the blade span. Static pressure distributions were measured in the blade mid-span and on the shroud surface. Detailed heat transfer coefficient distributions were measured on the blade tip surface using a transient liquid crystal technique. Results show that reduced tip clearance leads to reduced heat transfer coefficient over the blade tip surface. Results also show that reduced tip clearance tends to weaken the unsteady wake effect on blade tip 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.

Effects of the Condition of the Approach Boundary Layer and of Mainstream Pressure Gradients on the Heat Transfer Coefficient on Film-Cooled Surfaces

1985 ◽  
Vol 107 (1) ◽  
pp. 99-104 ◽  
Author(s):  
N. Hay ◽  
D. Lampard ◽  
C. L. Saluja
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Gradient ◽  
Transfer Coefficient ◽  
Adverse Pressure Gradient ◽  
Pressure Gradients ◽  
Favorable Pressure Gradient ◽  
The Heat Transfer Coefficient

This paper describes an investigation of the sensitivity of the heat transfer coefficient under the film to the state of the approach boundary layer for injection through a row of holes on a flat plate. The investigation is done for a range of blowing parameters using a heat-mass transfer analogy. Injection angles of 35 deg and 90 deg are covered. Additionally, for the same injection geometries, the effect of injection in the presence of mild adverse, mild favorable, and strong favorable mainstream pressure gradients is investigated. The results indicate that the heat transfer coefficient under the film is sensitive neither to the condition of the approach boundary layer nor to the presence of a mild adverse pressure gradient, but it is significantly lowered by a favorable pressure gradient, particularly at low blowing parameters.

Direct Experimental Measurements of Heat Transfer Coefficient Augmentation due to Approach Flow Effects

2018 ◽  
Author(s):  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Experimental Program ◽  
The Heat Transfer Coefficient

The injection of film cooling can have a strong impact on the heat transfer coefficient (HTC) between the overflowing freestream gas and the cooled surface. This study investigated the influence of approach flow characteristics, including the boundary layer thickness and character (laminar and turbulent), as well as the approach flow Reynolds number, on the HTC. The influence of these parameters was previously unreported in the open film cooling literature. The figure of merit for this study was the HTC augmentation, that is the ratio of heat transfer coefficients for a cooled vs. uncooled surface. For this work, a direct measurement of the heat transfer coefficient was made, using a heated foil surface which provided a known wall heat flux. Generally for this type of measurement, a flux foil is placed downstream of the coolant hole. However, for this experimental program a heat flux foil was also placed upstream of the film cooling holes, in order to generate an upstream thermal boundary layer which would be more representative of actual engine conditions. Such a configuration has rarely been seen in published studies. An open-literature shaped-hole design was used, known as the 7-7-7 hole, in order to compare with existing results in the literature. A variety of blowing conditions were tested from M = 0.5–3.0. Two elevated density ratios of DR = 1.20 and DR = 1.80 were used. High-resolution IR thermography was used for these measurements, providing a highly-accurate and spatially-resolved measurement of HTC augmentation. The results indicated that turbulent boundary layer thickness had a modest effect on HTC augmentation, whereas a very high level of augmentation was observed for a laminar approach boundary layer. The presence of upstream heating greatly increased the HTC augmentation in the near-hole region, although these effects died out by 10–15 diameters from the holes.

The Local Heat-Transfer Coefficient Around a Heated Horizontal Cylinder in an Intense Sound Field

1962 ◽  
Vol 84 (3) ◽  
pp. 245-250 ◽  
Author(s):  
R. M. Fand ◽  
J. Roos ◽  
P. Cheng ◽  
J. Kaye
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Sound Field ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Horizontal Cylinder ◽  
Local Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

In order to achieve a better understanding of the physical mechanism of interaction between free convection and sound, an experimental investigation of the local heat-transfer coefficient around the circumference of a heated horizontal cylinder, both in the presence and absence of a strong stationary sound field, has been carried out. The results show that superposition of intense sound upon the free-convection temperature-velocity field about a heated horizontal cylinder increases the heat-transfer coefficient both on the under and upper portions of the cylinder’s surface. In the presence of a sound field for which SPL = 146 db (re 0.0002 microbar) and f = 1500 cps, the maximum measured increases in the local heat-transfer coefficient on the under and upper portions of a 3/4-in-diam cylinder—relative to the free convection case at the same temperature potential—were found to be approximately 250 and 1200 per cent, respectively. A comparison of these results with earlier flow-visualization studies indicates that the relatively large percentage increase in the heat-transfer coefficient on the upper portion of the cylinder is caused by the oscillating vortex flow which is characteristic of thermoacoustic streaming. The reasons for the increase in the heat-transfer coefficient on the lower portion of the cylinder appear to be: (a) An increase in laminar boundary-layer velocities (steady components) in this region; and (b) modification of the boundary-layer temperature profile due to acoustically induced oscillations (unsteady components) within the laminar boundary layer. The experimental data presented can be used to check the validity of future analytical investigations of thermoacoustic phenomena.

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.

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