Turbine Tip and Shroud Heat Transfer

1991 ◽  
Vol 113 (3) ◽  
pp. 502-507 ◽  
Author(s):  
D. E. Metzger ◽  
M. G. Dunn ◽  
C. Hah
Keyword(s):  
Heat Transfer ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Leakage Flow ◽  
Turbine Cooling ◽  
Structural Durability ◽  
Close Proximity ◽  
Turbine Housing ◽  
Blade Tip ◽  
Pressure Driven Flow

Unshrouded blades of axial turbine stages move in close proximity to the stationary outer seal, or shroud, of the turbine housing. The pressure difference between the concave and convex sides of the blade drives a leakage flow through the gap between the moving blade tip and adjacent wall. This clearance leakage flow and accompanying heat transfer are of interest because of long obvious effects on aerodynamic performance and structural durability, but understanding of its nature and influences has been elusive. Previous studies indicate that the leakage through the gap is mainly a pressure-driven flow whose magnitude is related strongly to the airfoil pressure loading distribution and only weakly, if at all, to the relative motion between blade tip and shroud. A simple flow and heat transfer model incorporating these features can be used to estimate both tip and shroud heat transfer provided that reasonable estimates of the clearance gap size and clearance leakage flow can be made. The present work uses a numerical computation of the leakage flow to link the model to a specific turbine geometry and operating point for which a unique set of measured local tip and shroud heat fluxes is available. The resulting comparisons between the model estimates and measured heat transfer are good. The model should thus prove useful in the understanding and interpretation of future measurements, and should additionally prove useful for providing early design estimates of the levels of tip and shroud heat transfer that need to be compensated for by active turbine cooling.

Turbine Tip and Shroud Heat Transfer

1990 ◽  
Author(s):  
D. E. Metzger ◽  
M. G. Dunn ◽  
C. Hah
Keyword(s):  
Heat Transfer ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Leakage Flow ◽  
Turbine Cooling ◽  
Structural Durability ◽  
Close Proximity ◽  
Turbine Housing ◽  
Blade Tip ◽  
Pressure Driven Flow

Unshrouded blades of axial turbine stages move in close proximity to the stationary outer seal, or shroud, of the turbine housing. The pressure difference between the concave and convex sides of the blade drives a leakage flow through the gap between the moving blade tip and adjacent wall. This clearance leakage flow and accompanying heat-transfer are of interest because of long obvious effects on aerodynamic performance and structural durability, but understanding of its nature and influences has been elusive. Previous studies indicate that the leakage through the gap is mainly a pressure-driven flow whose magnitude is related strongly to the airfoil pressure loading distribution and only weakly, if at all, to the relative motion between blade tip and shroud. A simple flow and heat-transfer model incorporating these features can be used to estimate both tip and shroud heat transfer provided that reasonable estimates of the clearance gap size and clearance leakage flow can be made. The present work uses a numerical computation of the leakage flow to link the model to a specific turbine geometry and operating point for which a unique set of measured local tip and shroud heat fluxes are available. The resulting comparisons between the model estimates and measured heat-transfer are good. The model should thus prove useful in the understanding and interpretation of future measurements, and should additionally prove useful for providing early design estimates of the levels of tip and shroud heat transfer that need to be compensated for by active turbine cooling.

Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation

2008 ◽  
Author(s):  
Dianliang Yang ◽  
Xiaobing Yu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Relative Motion ◽  
Turbulence Models ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Blade Height ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Rotation ◽  
Blade Tip

In this paper, numerical methods have been applied to the investigation of the effect of rotation on the blade tip leakage flow and heat transfer. Using the first stage rotor blade of GE-E3 engine high pressure turbine, both flat tip and squealer tip have been studied. The tip gap height is 1% of the blade height, and the groove depth of the squealer tip is 2% of the blade height. Heat transfer coefficient on tip surface obtained by using different turbulence models was compared with experimental results. And the grid independence study was carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: 1) blade domain is rotating and shroud is stationary; 2) blade domain is stationary and shroud is rotating; and 3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force and the Coriolis force can be investigated respectively. By comparing the results of the three cases discussed, the effects of the blade rotation on tip leakage flow and heat transfer are revealed. It indicated that the main effect of the rotation on the tip leakage flow and heat transfer is resulted from the relative motion of the shroud, especially for the squealer tip blade.

Transient Three-Dimensional Heat Transfer Model of a Solar Thermochemical Reactor for H2O and CO2 Splitting via Nonstoichiometric Ceria Redox Cycling

2013 ◽  
Author(s):  
Justin Lapp ◽  
Wojciech Lipiński
Keyword(s):  
Heat Transfer ◽  
Heat Recovery ◽  
Fuel Efficiency ◽  
Three Dimensional ◽  
Reactor Design ◽  
Heat Transfer Model ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Rotating Cylinders ◽  
Solar Receiver

A transient heat transfer model is developed for a solar reactor prototype for H2O and CO2 splitting via two-step non-stoichiometric ceria cycling. Counter-rotating cylinders of reactive and inert materials cycling between high and low temperature zones permit continuous operation and heat recovery. To guide the reactor design a transient three-dimensional heat transfer model is developed based on transient energy conservation, accounting for conduction, convection, radiation, and chemical reactions. The model domain includes the rotating cylinders, a solar receiver cavity, and insulated reactor body. Radiative heat transfer is analyzed using a combination of the Monte Carlo method, Rosseland diffusion approximation, and the net radiation method. Quasi-steady state distributions of temperatures, heat fluxes, and the non-stoichiometric coefficient are reported. Ceria cycles between temperatures of 1708 K and 1376 K. A heat recovery effectiveness of 28% and solar-to-fuel efficiency of 5.2% are predicted for an unoptimized reactor design.

scholarly journals A Summary of the Cooled Turbine Blade Tip Heat Transfer and Film Effectiveness Investigations Performed by Dr. D. E. Metzger

1994 ◽  
Author(s):  
Y. W. Kim ◽  
W. Abdel-Messeh ◽  
J. P. Downs ◽  
F. O. Soechting ◽  
G. D. Steuber ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Convection Heat Transfer ◽  
Secondary Flows ◽  
Test Surface ◽  
Leakage Flow ◽  
Test Technique ◽  
Coolant Injection ◽  
Blade Tip

The clearance gap between the stationary outer air seal and blade tips of an axial turbine allows a clearance gap leakage flow to be driven through the gap by the pressure-to-suction side pressure difference. The presence of strong secondary flows on the pressure side of the airfoil tends to deliver air from the hottest regions of the mainstream to the clearance gap. The blade tip region, particularly near the trailing edge, is very difficult to cool adequately with blade internal coolant flow. In this case, film cooling injection directly onto the blade tip region can be used in an attempt to directly reduce the heat transfer rates from the hot gases in the clearance gap to the blade tip. The present paper is intended as a memorial tribute to the late Professor Darryl E. Metzger who has made significant contributions in this particular area over the past decade. A summary of this work is made to present the results of his more recent experimental work that has been performed to investigate the effects of film coolant injection on convection heat transfer to the turbine blade tip for a variety of tip shapes and coolant injection configurations. Experiments are conducted with blade tip models that are stationary relative to the simulated outer air seal based on the result of earlier works that found the leakage flow to be mainly a pressure-driven flow which is related strongly to the airfoil pressure loading distribution and only weakly, if at all, to the relative motion between blade tip and shroud. Both heat transfer and film effectiveness are measured locally over the test surface using a transient thermal liquid crystal test technique with a computer vision data acquisition and reduction system for various combinations of clearance heights, clearance flow Reynolds numbers, and film flow rates with different coolant injection configurations. The present results reveal a strong dependency of film cooling performance on the choice of the coolant supply hole shapes and injection locations for a given tip geometry.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low Speed Cascade

2003 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83 × 105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

Numerical Study of Heat Transfer and Cooling Effectiveness on a Flat-Tip Turbine Blade

2013 ◽  
Author(s):  
Qihe Huang ◽  
Jiao Wang ◽  
Lei He ◽  
Qiang Xu
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Numerical Study ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow And Heat Transfer ◽  
Blade Tip

A numerical study is performed to simulate the tip leakage flow and heat transfer on the first stage rotor blade tip of GE-E3 turbine, which represents a modern gas turbine blade geometry. Calculations consist of the flat blade tip without and with film cooling. For the flat tip without film cooling case, in order to investigate the effect of tip gap clearance on the leakage flow and heat transfer on the blade tip, three different tip gap clearances of 1.0%, 1.5% and 2.5% of the blade span are considered. And to assess the performance of the turbulence models in correctly predicting the blade tip heat transfer, the simulations have been performed by using four different models (the standard k-ε, the RNG k-ε, the standard k-ω and the SST models), and the comparison shows that the standard k-ω model provides the best results. All the calculations of the flat tip without film cooling have been compared and validated with the experimental data of Azad[1] and the predictions of Yang[2]. For the flat tip with film cooling case, three different blowing ratio (M = 0.5, 1.0, and 1.5) have been studied to the influence on the leakage flow in tip gap and the cooling effectiveness on the blade tip. Tip film cooling can largely reduce the overall heat transfer on the tip. And the blowing ratio M = 1.0, the cooling effect for the blade tip is the best.

Effect of Turbine Blade Tip Cooling Configuration on Tip Leakage Flow and Heat Transfer

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Sergen Sakaoglu ◽  
Harika S. Kahveci
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

Abstract The pressure difference between suction and pressure sides of a turbine blade leads to tip leakage flow, which adversely affects the first-stage high-pressure (HP) turbine blade tip aerodynamics. In modern gas turbines, HP turbine blade tips are exposed to extreme thermal conditions requiring cooling. If the coolant jet directed into the blade tip gap cannot counter the leakage flow, it will simply add up to the pressure losses due to leakage. Therefore, the compromise between the aerodynamic loss and the gain in tip-cooling effectiveness must be optimized. In this paper, the effect of tip-cooling configuration on the turbine blade tip is investigated numerically from both aerodynamics and thermal aspects to determine the optimum configuration. Computations are performed using the tip cross section of GE-E3 HP turbine first-stage blade for squealer and flat tips, where the number, location, and diameter of holes are varied. The study presents a discussion on the overall loss coefficient, total pressure loss across the tip clearance, and variation in heat transfer on the blade tip. Increasing the coolant mass flow rate using more holes or by increasing the hole diameter results in a decrease in the area-averaged Nusselt number on the tip floor. Both aerodynamic and thermal response of squealer tips to the implementation of cooling holes is superior to their flat counterparts. Among the studied configurations, the squealer tip with a larger number of cooling holes located toward the pressure side is highlighted to have the best cooling performance.

Numerical investigation of high pressure turbine blade tip-shaping effects on the aerothermal and dynamic performance

2019 ◽  
Vol 15 (6) ◽  
pp. 1121-1135
Author(s):  
Fujuan Tong ◽  
Wenxuan Gou ◽  
Lei Li ◽  
Zhufeng Yue ◽  
Wenjing Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Dynamic Performance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Local Pressure ◽  
Content Type ◽  
Turbine Efficiency ◽  
Flow Loss ◽  
Blade Tip

Purpose In order to improve the engine reliability and efficiency, an effective way is to reform the turbine blade tip conformation. The paper aims to discuss this issue. Design/methodology/approach The present research provides several novel tip-shaping structures, which are considered to control the blade tip loss. Four different tip geometries have been studied: flat tip, squealer tip, flat tip with streamwise ribs and squealer tip with streamwise ribs. The tip heat transfer and leakage flow are both analyzed in detail, for example the tip heat transfer coefficient, tip flow and local pressure distributions. Findings The results show that the squealer seal and streamwise rib can reduce the tip heat transfer and leakage loss, especially for the squealer tip with streamwise ribs. The tip and near-tip flow patterns at the different locations of axial chord reflect that both the squealer seal and streamwise rib structure can control the tip leakage flow loss. In addition, the analysis of the aerodynamic parameters (the static pressure and turbine efficiency) also indicates that the squealer tip with streamwise ribs obtains the highest adiabatic efficiency with an increase of 2.34 percent, compared with that of the flat tip case. Originality/value The analysis of aerothermal and dynamic performance can provide a reference for the blade tip design and treatment.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low-Speed Cascade

2004 ◽  
Vol 126 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the two-dimensional blade. The wind tunnel accommodates an 116 deg turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83×105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required freestream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady-state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

Tip Leakage Flow and Heat Transfer Characteristics on Rotor Casing and Blade Tip in an Axial Gas Turbine Engine: Steady Analysis

2008 ◽  
Author(s):  
Md Hamidur Rahman ◽  
Sung In Kim ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Heat Transfer Characteristics ◽  
Turbine Engine ◽  
Tip Leakage ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Blade Tip

Steady simulations have been performed to investigate tip leakage flow and heat transfer characteristics on the casing and rotor blade tip in a single stage turbine engine. A turbine stage of stator and rotor was modeled with a pressure ratio of 3.2. The predicted isentropic Mach number and adiabatic wall temperature on the casing showed good agreement with available experimental data. The effects of tip clearance height and rotor rotational speed on the blade tip and casing heat transfer characteristics are mainly considered. It is observed that the tip leakage flow structure is highly dependent on the height of the tip gap as well as speeds of the rotor blade. In all cases, flow separates just around the corner of the pressure side of the blade tip. The region of recirculating flow increases with the increase of the clearance height. Then the flow reattaches on the tip surface near the suction side beyond the flow separation. This flow reattachment enhances surface heat transfer. The leakage flow interaction with the reverse cross flow, induced by relative casing motion, is found to have significant effect on the blade tip and casing heat transfer distribution. Critical region of high heat transfer on the casing exists near the blade tip leading edge and along the pressure side edge at all clearance height. Whereas, at high speed rotation, it tends to move towards the trailing edge due to the change of inflow angle.

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