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.

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.

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.

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 2 — Heat Transfer Measurements

2004 ◽  
Author(s):  
J. R. Christophel ◽  
K. A. Thole ◽  
F. J. Cunha
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbine Blade ◽  
Suction Side ◽  
Coolant Flow ◽  
Total Power ◽  
Leakage Flow ◽  
Pressure Side ◽  
Transfer Coefficients ◽  
Blade Tip

The clearance gap between a turbine blade tip and its associated shroud allows leakage flow across the tip gap from the pressure side to the suction side of the blade. Understanding how this leakage flow affects heat transfer is critical in extending blade tip durability in terms of oxidation, erosion, clearance, and overall turbine performance. This paper is the second of a two part series that discusses the augmentation of tip heat transfer as a result of blowing from the pressure side of the tip as well as 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 coolant flow rates. Heat transfer coefficients were quantified by measuring the total power supplied to a constant heat flux surface placed on the tip of the blade and measuring the tip temperatures. Results indicate that increased blowing leads to increased augmentations in tip heat transfer, particularly at the entrance region to the gap. When combined with adiabatic effectiveness measurements, the coolant from the pressure side holes provides an overall net heat flux reduction to the blade tip but is nearly independent of coolant flow levels.

scholarly journals Unsteady Analysis of Blade and Tip Heat Transfer as Influenced by the Upstream Momentum and Thermal Wakes

2008 ◽  
Author(s):  
Ali A. Ameri ◽  
David L. Rigby ◽  
Erlendur Steinthorsson ◽  
James Heidmann ◽  
John C. Fabian
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Wall Temperature ◽  
Tip Clearance ◽  
Wall Heat Flux ◽  
Transfer Coefficients ◽  
Adiabatic Wall

The effect of the upstream wake on the blade heat transfer has been numerically examined. The geometry and the flow conditions of the first stage turbine blade of GE’s E3 engine with a tip clearance equal to 2% of the span was utilized. Based on numerical calculations of the vane, a set of wake boundary conditions were approximated which were subsequently imposed upon the downstream blade. This set consisted of the momentum and thermal wakes as well as the variation in modeled turbulence quantities of turbulence intensity and the length scale. Using a one blade periodic domain, the distributions of unsteady heat transfer rate on the turbine blade and its tip, as affected by the wake, were determined. Such heat transfer coefficient distribution was computed using the wall heat flux and the adiabatic wall temperature to desensitize the heat transfer coefficient to the wall temperature. For the determination of the wall heat flux and the adiabatic wall temperatures, two set of computations were required. The results were used in a phase-locked manner to compute the unsteady or steady heat transfer coefficients. It has been found that the unsteady wake has some effect on the distribution of the time averaged heat transfer coefficient on the blade and that this distribution is different from the distribution that is obtainable from a steady computation. This difference was found to be as large as 20 percent of the average heat transfer on the blade surface. On the tip surface, this difference is comparatively smaller and can be as large as four percent of the average.

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 Operating temperatures of oil-lubricated medium-speed gears: Numerical models and experimental results

2003 ◽  
Vol 217 (2) ◽  
pp. 87-106 ◽  
Author(s):  
H Long ◽  
A A Lord ◽  
D T Gethin ◽  
B J Roylance
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Rotational Speed ◽  
High Speed ◽  
Applied Load ◽  
Frictional Heat ◽  
Transfer Coefficients ◽  
Gear Teeth ◽  
Heat Transfer Coefficients

This paper investigates the effects of gear geometry, rotational speed and applied load, as well as lubrication conditions on surface temperature of high-speed gear teeth. The analytical approach and procedure for estimating frictional heat flux and heat transfer coefficients of gear teeth in high-speed operational conditions was developed and accounts for the effect of oil mist as a cooling medium. Numerical simulations of tooth temperature based on finite element analysis were established to investigate temperature distributions and variations over a range of applied load and rotational speed, which compared well with experimental measurements. A sensitivity analysis of surface temperature to gear configuration, frictional heat flux, heat transfer coefficients, and oil and ambient temperatures was conducted and the major parameters influencing surface temperature were evaluated.

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