Effect of Wake-Disturbed Flow on Heat (Mass) Transfer to a Turbine Blade

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
S. Olson ◽  
S. Sanitjai ◽  
K. Ghosh ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Heat Mass Transfer ◽  
Turbine Blades ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Disturbed Flow ◽  
Linear Cascade ◽  
Naphthalene Sublimation Technique

This study investigates the effect of wakes in the presence of varying levels of background freestream turbulence on the heat (mass) transfer from gas turbine blades. Measurements using the naphthalene sublimation technique provide local values of the mass transfer coefficient on the pressure and suction surfaces of a simulated turbine blade in a linear cascade. Experimental parameters studied include the pitch of the wake-generating blades (vanes), blade-row separation, Reynolds number, and the freestream turbulence level. The disturbed flow strongly affects the mass transfer Stanton number on both sides of the blade, particularly along the suction surface. An earlier transition to a turbulent boundary layer occurs with increased background turbulence, higher Reynolds number, and from wakes shed from vanes placed upstream of the linear cascade. Note that once the effects on mass transfer are known, similar variation on heat transfer can be inferred from the heat/mass transfer analogy.

Effect of Wake-Disturbed Flow on Heat (Mass) Transfer to a Turbine Blade

2009 ◽  
Author(s):  
S. J. Olson ◽  
S. Sanitjai ◽  
K. Ghosh ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Heat Mass Transfer ◽  
Turbine Blades ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Disturbed Flow ◽  
Linear Cascade ◽  
Naphthalene Sublimation Technique

This study investigates the effect of wakes in the presence of varying levels of background freestream turbulence on the heat (mass) transfer from gas turbine blades. Measurements using the naphthalene sublimation technique provide local values of the mass transfer coefficient on the pressure and suction surfaces of a simulated turbine blade in a linear cascade. Experimental parameters studied include the pitch of the wake-generating blades (vanes), blade-row separation, Reynolds number and the freestream turbulence level. The disturbed flow strongly affects the mass transfer Stanton number on both sides of the blade, particularly along the suction surface. An earlier transition to a turbulent boundary layer occurs with increased background turbulence, higher Reynolds number and from wakes shed from vanes placed upstream of the linear cascade. Note that once the effects on mass transfer are known, similar variation on heat transfer can be inferred from the heat/mass transfer analogy.

Experimental Study of the Unsteady Aerodynamics in a Linear Cascade With Low Reynolds Number Low Pressure Turbine Blades

1997 ◽  
Author(s):  
Christopher G. Murawski ◽  
Rolf Sondergaard ◽  
Richard B. Rivir ◽  
Kambiz Vafai ◽  
Terrence W. Simon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Linear Cascade ◽  
Low Pressure Turbine ◽  
Flow Reynolds Number

Low pressure turbines in aircraft experience large changes in flow Reynolds number as the gas turbine engine operates from takeoff to high altitude cruise. Low pressure turbine blades are also subject to regions of strong acceleration and diffusion. These changes in Reynolds number, strong acceleration, as well as elevated levels of turbulence can result in unsteady separation and transition zones on the surface of the blade. An experimental study was conducted in a two-dimensional linear cascade, focusing on the suction surface of a low pressure turbine blade. The intent was to assess the effects of changes in Reynolds number, and freestream turbulence intensity. Flow Reynolds numbers, based on exit velocity and suction surface length, have been varied from 50,000 to 300,000. The freestream turbulence intensity was varied from 1.1 to 8.1 percent. Separation was observed at all test Reynolds numbers. Increasing the flow Reynolds number, without changing freestream turbulence, resulted in a slightly rearward movement of the onset of separation and shrinkage of the separation zone. Increasing the freestream turbulence intensity, without changing Reynolds number resulted in a shrinkage of the separation region on the suction surface. Increasing both flow Reynolds numbers and freestream turbulence intensity compounded these effects such that at a Reynolds number of 300,000 and a freestream turbulence intensity of 8.1%, the separation zone was almost nonexistent. The influences on the blade’s wake from altering freestream turbulence and Reynolds number are also documented. The width of the wake and velocity defect rise with a decrease in either turbulence level or chord Reynolds number. Numerical simulations were performed in support of experimental results. The numerical results compare well qualitatively with the low freestream turbulence experimental cases.

An Experimental Investigation of the Effect of Freestream Turbulence on the Wake of a Separated Low-Pressure Turbine Blade at Low Reynolds Numbers

1999 ◽  
Vol 122 (2) ◽  
pp. 431-433 ◽  
Author(s):  
C. G. Murawski ◽  
K. Vafai
Keyword(s):  
Reynolds Number ◽  
Turbine Blade ◽  
Turbulence Intensity ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Low Reynolds Numbers ◽  
Low Pressure Turbine ◽  
Flow Reynolds Number

An experimental study was conducted in a two-dimensional linear cascade, focusing on the suction surface of a low pressure turbine blade. Flow Reynolds numbers, based on exit velocity and suction length, have been varied from 50,000 to 300,000. The freestream turbulence intensity was varied from 1.1 to 8.1 percent. Separation was observed at all test Reynolds numbers. Increasing the flow Reynolds number, without changing freestream turbulence, resulted in a rearward movement of the onset of separation and shrinkage of the separation zone. Increasing the freestream turbulence intensity, without changing Reynolds number, resulted in shrinkage of the separation region on the suction surface. The influences on the blade’s wake from altering freestream turbulence and Reynolds number are also documented. It is shown that width of the wake and velocity defect rise with a decrease in either turbulence level or chord Reynolds number. [S0098-2202(00)00202-9]

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

Effect of Inlet Skew on Heat/Mass Transfer From a Simulated Turbine Blade

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Kalyanjit Ghosh ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Turbine Blade ◽  
Sherwood Number ◽  
Heat Mass Transfer ◽  
Velocity Ratio ◽  
Transition To Turbulence ◽  
Suction Surface ◽  
Freestream Velocity ◽  
Pressure Surface ◽  
Passage Vortex

Heat (mass) transfer experiments are conducted to study the effect of an inlet skew on a simulated gas-turbine blade placed in a linear cascade. The inlet skew simulates the relative motion between rotor and stator endwalls in a single turbine stage. The transverse motion of a belt, placed parallel to and upstream of the turbine cascade, generates the inlet skew. With the freestream velocity constant at approximately 16 m/s, which results in a Reynolds number (based on the blade chord length of 0.184 m) of 1.8 × 105, a parametric study was conducted for three belt-to-freestream velocity ratios. The distribution of the Sherwood number on the suction surface of the blade shows that the inlet skew intensifies the generation of the horseshoe vortex close to the endwall region. This is associated with the development of a stronger passage vortex for a higher velocity ratio, which causes an earlier transition to turbulence. Corresponding higher mass transfer coefficients are measured between the midheight of the blade and the endwall, at a midchord downstream location. However, a negligible variation in transport properties is measured above the two-dimensional region of the blade at the higher velocity ratios. In contrast, the inlet skew has a negligible effect on the distribution of the Sherwood number on the entire pressure surface of the blade. This is mainly because the skew is directed along the passage vortex, which is from the pressure surface of the airfoil to the suction surface of the adjacent airfoil.

An Examination of the Contributions to Loss on a Transonic Turbine Blade in Cascade

1990 ◽  
Author(s):  
D. J. Mee ◽  
N. C. Baines ◽  
M. L. G. Oldfield ◽  
T. E. Dickens
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Suction Surface ◽  
Near Wake ◽  
Linear Cascade ◽  
Transonic Turbine ◽  
The Individual ◽  
The Way

Experiments to measure losses of a linear cascade of transonic turbine blades are reported. Detailed measurements of the boundary layer at the rear of the suction surface of a blade and examination of wake traverse data enable the individual components of boundary layer, shock and mixing loss to be determined. Results indicate that each component contributes significantly to the overall loss in different Mach number regimes. Traverses in the near wake of the blade indicate the way in which the wake develops and facilitate examination of the development of the mixing loss.

Influence of Blade Leading Edge Geometry on Turbine Endwall Heat(Mass) Transfer

2005 ◽  
Author(s):  
S. Han ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Local Heat ◽  
Secondary Flows ◽  
Transfer Performance ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Naphthalene Sublimation Technique ◽  
Passage Vortex

The secondary flows, including passage and other vortices in a turbine cascade cause significant aerodynamic losses and thermal gradients. Leading-edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading-edge modified blade has not been investigated thoroughly. Since a fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a fillet geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having modified leading-edge by adding a fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the fillets. Apparently the corner vortices are intensified with the leading-edge modified blade.

Influence of Blade Leading Edge Geometry on Turbine Endwall Heat (Mass) Transfer

2005 ◽  
Vol 128 (4) ◽  
pp. 798-813 ◽  
Author(s):  
S. Han ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Local Heat ◽  
Secondary Flows ◽  
Transfer Performance ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Naphthalene Sublimation Technique ◽  
Passage Vortex

The secondary flows, including passage and other vortices in a turbine cascade, cause significant aerodynamic losses and thermal gradients. Leading edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading edge modified blade has not been investigated thoroughly. Since a fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a fillet geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having a modified leading edge by adding a fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the fillets. Apparently the corner vortices are intensified with the leading edge modified blade.

An Examination of the Contributions to Loss on a Transonic Turbine Blade in Cascade

1992 ◽  
Vol 114 (1) ◽  
pp. 155-162 ◽  
Author(s):  
D. J. Mee ◽  
N. C. Baines ◽  
M. L. G. Oldfield ◽  
T. E. Dickens
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Suction Surface ◽  
Near Wake ◽  
Linear Cascade ◽  
Transonic Turbine ◽  
The Individual ◽  
The Way

Experiments to measure losses of a linear cascade of transonic turbine blades are reported. Detailed measurements of the boundary layer at the rear of the suction surface of a blade and examination of wake traverse data enable the individual components of boundary layer, shock and mixing loss to be determined. Results indicate that each component contributes significantly to the overall loss in different Mach number regimes. Traverses in the near wake of the blade indicate the way in which the wake develops and facilitate examination of the development of the mixing loss.

Development of Taylor-Go¨rtler Vortices Over the Pressure Surface of a Turbine Blade

2005 ◽  
Vol 127 (5) ◽  
pp. 540-543 ◽  
Author(s):  
H. P. Wang ◽  
S. J. Olson ◽  
R. J. Goldstein
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Turbine Blade ◽  
Flow Direction ◽  
Mass Transfer Rate ◽  
Leading Edge ◽  
Flow Region ◽  
Freestream Turbulence ◽  
Pressure Surface ◽  
Naphthalene Sublimation Technique

The naphthalene sublimation technique is used to investigate the development of Taylor-Go¨rtler vortices over the pressure surface of a simulated high performance turbine blade. Large spanwise variation in mass transfer is observed downstream on the pressure surface in the two-dimensional flow region for cases with low freestream turbulence, indicating the existence of Taylor-Go¨rtler vortices. Different average and local mass transfer rates for the same flow conditions suggest that roughness variation near the leading edge affects the initial formation of Taylor-Go¨rtler vortices. Larger and more uniformly distributed roughness at the leading edge produces much stronger Taylor-Go¨rtler vortices downstream and greatly enhances the mass transfer rate. The variation between the vortices does not change appreciably along the flow direction. The flow in the boundary layer is laminar over the entire pressure surface. In the presence of external disturbances such as high freestream turbulence or a boundary layer trip, no Taylor-Go¨rtler vortices are observed.

Sign in / Sign up

Export Citation Format

Share Document