Heat-Transfer Coefficients of a Turbine Blade-Tip and Near-Tip Regions

2003 ◽  
Vol 17 (3) ◽  
pp. 297-303 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Blade Tip

Comparison of Heat Transfer Measurement Techniques on a Transonic Turbine Blade Tip

2009 ◽  
Author(s):  
Devin O’Dowd ◽  
Qiang Zhang ◽  
Phil Ligrani ◽  
Li He ◽  
Stefan Friedrichs
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbine Blade ◽  
Transfer Coefficients ◽  
Adiabatic Wall ◽  
Steady State Condition ◽  
Heat Transfer Coefficients ◽  
Measure Surface Temperature ◽  
Blade Tip ◽  
Processing Techniques

The present study considers spatially-resolved surface heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade under transonic conditions. Six different measurement and processing techniques are considered and compared, including transient infrared thermography and thin-film heat flux gauges. Three methods use the same experimental setup, using a heater mesh to provide a near-instantaneous step-change in mainstream temperature, employing an infrared camera to measure surface temperature. The three methods use the same data but different processing techniques to determine the heat transfer coefficients and adiabatic wall temperatures. Two methods use different processing techniques to reconstruct heat flux from the temperature time trace measured. A plot of the heat flux versus temperature is used to determine the heat transfer coefficients and adiabatic wall temperatures. The third uses the classical solution to the 1-D non-steady Fourier equation to determine heat transfer coefficients and adiabatic wall temperatures. A fourth method uses regression analysis to calculate detailed heat transfer coefficients for a quasi-steady state condition using a thin-foil heater on the tip surface. The fifth method uses the infrared camera to measure the adiabatic wall temperature surface distribution of a blade tip after a quasi-steady state condition is present. Finally, the sixth method employs thin-film gauges to measure surface temperature histories at four discreet blade tip locations. With this approach, heat flux reconstruction is used to calculate the transient heat transfer coefficients and adiabatic wall temperatures. Overall, the present study shows that the infrared thermography technique with heat flux reconstruction using the Impulse method, is the most accurate and reliable method to obtain detailed, spatially-resolved heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade.

Comparison of Heat Transfer Measurement Techniques on a Transonic Turbine Blade Tip

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
D. O. O’Dowd ◽  
Q. Zhang ◽  
L. He ◽  
P. M. Ligrani ◽  
S. Friedrichs
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbine Blade ◽  
Infrared Camera ◽  
Transfer Coefficients ◽  
Adiabatic Wall ◽  
Steady State Condition ◽  
Heat Transfer Coefficients ◽  
Blade Tip ◽  
Processing Techniques

The present study considers spatially resolved surface heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade under transonic conditions. Five different measurement and processing techniques using infrared thermography are considered and compared. Three transient methods use the same experimental setup, using a heater mesh to provide a near-instantaneous step-change in mainstream temperature, employing an infrared camera to measure surface temperature. These three methods use the same data but different processing techniques to determine the heat transfer coefficients and adiabatic wall temperatures. Two of these methods use different processing techniques to reconstruct heat flux from the temperature time trace measured. A plot of the heat flux versus temperature is used to determine the heat transfer coefficients and adiabatic wall temperatures. The third uses the classical solution to the 1D nonsteady Fourier equation to determine heat transfer coefficients and adiabatic wall temperatures. The fourth method uses regression analysis to calculate detailed heat transfer coefficients for a quasi-steady-state condition using a thin-foil heater on the tip surface. Finally, the fifth method uses the infrared camera to measure the adiabatic wall temperature surface distribution of a blade tip after a quasi-steady-state condition is present. Overall, the present study shows that the infrared thermography technique with heat flux reconstruction using the impulse method is the most accurate, computationally efficient, and reliable method to obtain detailed, spatially resolved heat transfer coefficients and adiabatic wall temperatures on a transonic turbine blade tip in a linear cascade.

Average Nusselt Number for Pressure and Suction Sides of Squealer Turbine Blade Tip

2011 ◽  
Author(s):  
Chaouki Ghenai
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Cavity Depth ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Blade Tip

Numerical simulations of the flow field and heat transfer of squealer blade tip are performed in this study. The effect of Reynolds number (Re = 10000–40000), the clearance gap to width ratios (C/W = 5%–15%) and the cavity depth to width ratios (D/W = 10%, 20% and 50%) on fluid flow and heat transfer characteristics are obtained. The temperature and velocity distributions inside the cavity, the local heat transfer coefficients, and the average Nusselt numbers for the pressure and suction sides of the turbine blade tip are determined. This paper presents the results of the effects of Reynolds number, clearance gap and width ratios on the Nusslet number for the pressure and suction sides of squealer turbine blade tip. The results show a good agreement with the experimental data obtained by Metzger and Bunker. New correlations for the average Nusselt numbers for turbine blade tip pressure and suction sides are presented.

Effect of Squealer Cavity Depth and Oxidation on Turbine Blade Tip Heat Transfer

2001 ◽  
Author(s):  
Ronald S. Bunker ◽  
Jeremy C. Bailey
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Turbine Blade ◽  
Surface Heat ◽  
Transfer Coefficients ◽  
Cavity Depth ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Blade Cascade ◽  
Blade Tip

An experimental study has been performed to investigate the effect of squealer cavity depth on the detailed distribution of convective heat transfer coefficients of a turbine blade tip surface. This paper presents full surface information on heat transfer coefficients within a blade cascade which develops an appropriate pressure distribution about an airfoil blade tip and shroud model. A stationary blade cascade experiment has been run consisting of three airfoils, the center airfoil having a variable tip gap clearance. The airfoil models the aerodynamic tip section of a high pressure turbine blade with inlet Mach number of 0.21, exit Mach number of 0.74, pressure ratio of 1.41, Reynolds number of 2.8•106, and total turning of about 100 degrees. The cascade inlet turbulence intensity level is 9%. Tip surface heat transfer coefficient distributions are first shown for a flat, square-edge tip with a clearance gap of 2.03 mm. Heat transfer distributions are then shown for full-perimeter squealer tip cavities having the same clearance gap above the squealer rim, and clearance-to-cavity depth ratios from 0.67 to 2. Regionally averaged heat transfer coefficients are analyzed to discern a relationship between tip heat transfer and cavity depth. Further tests demonstrate the effect of partial squealer rim oxidation, or material loss, on the surface heat transfer distributions.

Cooling the Tip of a Turbine Blade Using Pressure Side Holes—Part II: Heat Transfer Measurements

2005 ◽  
Vol 127 (2) ◽  
pp. 278-286 ◽  
Author(s):  
J. R. Christophel ◽  
K. A. Thole ◽  
F. J. Cunha
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbine Blade ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Net Heat Flux ◽  
Blade Tip

The clearance gap between a turbine blade tip and its associated shroud allows leakage flow across the tip from the pressure side to the suction side of the blade. Understanding how this leakage flow affects heat transfer is critical in extending the durability of a blade tip, which is subjected to effects of oxidation and erosion. This paper is the second of a two-part series that discusses the augmentation of tip heat transfer coefficients as a result of blowing from film-cooling holes placed along the pressure side of a blade and from dirt purge holes placed on the tip. For the experimental investigation, three scaled-up blades were used to form a two-passage, linear cascade in a low-speed wind tunnel. The rig was designed to simulate different tip gap sizes and film-coolant flow rates. Heat transfer coefficients were quantified by using a constant heat flux surface placed along the blade tip. Results indicate that increased film-coolant injection leads to increased augmentation levels of tip heat transfer coefficients, particularly at the entrance region to the gap. Despite increased heat transfer coefficients, an overall net heat flux reduction to the blade tip results from pressure-side cooling because of the increased adiabatic effectiveness levels. The area-averaged results of the net heat flux reduction for the tip indicate that there is (i) little dependence on coolant flows and (ii) more cooling benefit for a small tip gap relative to that of a large tip gap.

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

scholarly journals Heat Transfer and Flow on the Blade Tip of a Gas Turbine Equipped With a Mean-Camberline Strip

2001 ◽  
Vol 123 (4) ◽  
pp. 704-708 ◽  
Author(s):  
A. A. Ameri
Keyword(s):  
Heat Transfer ◽  
Sharp Edge ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Large Power ◽  
Tip Leakage ◽  
Numerical Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Blade Tip ◽  
Convective Heat Transfer Coefficients

Experimental and computational studies have been performed to investigate the detailed distribution of convective heat transfer coefficients on the first-stage blade tip surface for a geometry typical of large power generation turbines (>100 MW). In a previous work the numerical heat transfer results for a sharp edge blade tip and a radiused blade tip were presented. More recently several other tip treatments have been considered for which the tip heat transfer has been measured and documented. This paper is concerned with the numerical prediction of the tip surface heat transfer for radiused blade tip equipped with mean-camberline strip (or “squealer” as it is often called). The heat transfer results are compared with the experimental results and discussed. The effectiveness of the mean-camberline strip in reducing the tip leakage and the tip heat transfer as compared to a radiused edge tip and sharp edge tip was studied. The calculations show that the sharp edge tip works best (among the cases considered) in reducing the tip leakage flow and the tip heat transfer.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

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%.

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