Effects of Density Ratio on the Hydrodynamics of Film Cooling

1990 ◽  
Vol 112 (3) ◽  
pp. 437-443 ◽  
Author(s):  
J. R. Pietrzyk ◽  
D. G. Bogard ◽  
M. E. Crawford
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Laser Doppler Anemometry ◽  
Density Ratio ◽  
Vertical Plane ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Entire Flow ◽  
Hydrodynamic Study

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow with a density ratio of injectant to free stream of 2. Laser-Doppler anemometry was used to measure the vertical and streamwise components of velocity for a jet-to-free stream mass flux ratio of 0.5. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and free stream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer.

Effects of Density Ratio on the Hydrodynamics of Film Cooling

1989 ◽  
Author(s):  
J. R. Pietrzyk ◽  
D. G. Bogard ◽  
M. E. Crawford
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Laser Doppler Anemometry ◽  
Density Ratio ◽  
Vertical Plane ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Entire Flow ◽  
Hydrodynamic Study ◽  
Field Approaches

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow with a density ratio of injectant to freestream of two. Laser Doppler anemometry was used to measure the vertical and streamwise components of velocity for a jet-to-freestream mass flux ratio of 0.5. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and freestream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer.

Hydrodynamic Measurements of Jets in Crossflow for Gas Turbine Film Cooling Applications

1989 ◽  
Vol 111 (2) ◽  
pp. 139-145 ◽  
Author(s):  
J. R. Pietrzyk ◽  
D. G. Bogard ◽  
M. E. Crawford
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Laser Doppler Anemometry ◽  
Vertical Plane ◽  
Separation Region ◽  
Mean Velocity ◽  
Stress Components ◽  
Entire Flow ◽  
Hydrodynamic Study ◽  
Field Approaches

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow. Laser-Doppler anemometry was used to measure the vertical and streamwise components of velocity for three jet-to-mainstream velocity ratios: 0.25, 0.5, and 1.0. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and mainstream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer. The data indicate the existence of a separation region in the hole from which the jet issues, causing high levels of turbulence and a relatively uniform mean velocity profile at the jet exit.

Experimental Validation of Quasisteady Assumption in Modeling of Unsteady Film-Cooling

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Stefan Bernsdorf ◽  
Martin G. Rose ◽  
Reza S. Abhari
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Three Dimensional ◽  
Flow Region ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Jet Trajectory ◽  
Air Streams

This paper reports on the validation of the assumption of quasisteady behavior of pulsating cooling injection in the near hole flow region. The respective experimental data are taken in a flat plate wind tunnel at ETH Zürich. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative nondimensionals are achieved, providing a faithful model at a larger scale. Heating the free stream air and strongly cooling the coolant gives the required density ratio between coolant and free-stream. The coolant is injected with different frequency and amplitude. The three-dimensional velocities are recorded using nonintrusive PIV, and seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The general flow field, the jet trajectory, and the streamwise circulation are utilized in the validation of the quasisteady assumption.

Adiabatic Effectiveness, Thermal Fields, and Velocity Fields for Film Cooling With Large Angle Injection

1997 ◽  
Vol 119 (2) ◽  
pp. 352-358 ◽  
Author(s):  
A. Kohli ◽  
D. G. Bogard
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Thermal Field ◽  
Density Ratio ◽  
Large Angle ◽  
Flux Ratio ◽  
Cryogenic Cooling ◽  
Round Hole ◽  
Mean Velocity ◽  
Injection Angle

The film cooling performance and velocity field were investigated for discrete round holes inclined at an injection angle of 55 deg. Results are compared to typical round film cooling holes, with an injection angle of 35 deg. All experiments in this study were performed at a density ratio of DR = 1.6, using cryogenic cooling of the injected air. Centerline and lateral distributions of effectiveness were obtained for a range of momentum flux ratios. Thermal field and two component mean velocity and turbulence intensity measurements were made at a momentum flux ratio that was within the range of maximum spatially averaged effectiveness. Compared to round holes with 35 deg injection angle, the 55 deg holes showed only a slight degradation in centerline effectiveness for low momentum flux ratios, while a significant reduction in effectiveness was seen at high momentum flux ratios. The thermal field for the 55 deg round holes indicated a faster decay of cooling capacity for the 55 deg round holes. The high turbulence levels for the 55 deg round hole coincided with the sharp velocity gradients between the jet and free stream, and the decay of turbulence levels with downstream distance was found to be similar to those for a 35 deg hole.

Film Cooling With Compound Angle Holes: Adiabatic Effectiveness

1996 ◽  
Vol 118 (4) ◽  
pp. 807-813 ◽  
Author(s):  
D. L. Schmidt ◽  
B. Sen ◽  
D. G. Bogard
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Free Stream ◽  
Density Ratio ◽  
Flux Ratio ◽  
Test Facility ◽  
Film Cooling Effectiveness ◽  
Baseline Case ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Film cooling effectiveness was studied experimentally in a flat plate test facility with zero pressure gradient using a single row of inclined holes, which injected high-density, cryogenically cooled air. Round holes and holes with a diffusing expanded exit were directed laterally away from the free-stream direction with a compound angle of 60 deg. Comparisons were made with a baseline case of round holes aligned with the free stream. The effects of doubling the hole spacing to six hole diameters for each geometry were also examined. Experiments were performed at a density ratio of 1.6 with a range of blowing ratios from 0.5 to 2.5 and momentum flux ratios from 0.16 to 3.9. Lateral distributions of adiabatic effectiveness results were determined at streamwise distances from 3 D to 15 D downstream of the injection holes. All hole geometries had similar maximum spatially averaged effectiveness at a low momentum flux ratio of I = 0.25, but the round and expanded exit holes with compound angle had significantly greater effectiveness at larger momentum flux ratios. The compound angle holes with expanded exits had a much improved lateral distribution of coolant near the hole for all momentum flux ratios.

Velocity Measurements Around Film Cooling Holes With Deposition

2010 ◽  
Author(s):  
Kristian Haase ◽  
Jeffrey P. Bons
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Flat Plate ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Leading Edge ◽  
Flow Structures ◽  
Particle Image Velocimetry Technique ◽  
Film Cooling Holes

The choice of synthetic fuels (synfuels) in order to achieve greater fuel flexibility may lead to unwanted solid depositions on the blades of turbomachines. The objective of this paper is to gain information of the flow field over a turbine blade with depositions around the film cooling holes. For the investigation the particle image velocimetry technique (PIV) is utilized. The experiments are conducted in a low speed wind tunnel at a Reynolds number of 300,000 based on the distance from the leading edge to the middle of the cooling holes and a Reynolds number of 9,200 based on the hole diameter. Three different simulation plates are tested in the tunnel—a flat plate for comparison, a plate with large depositions only upstream of the holes, and one with smaller depositions all around the holes. The two deposition configurations are scaled models of actual depositions formed at simulated engine flow conditions on a turbine test coupon. The experiments are conducted at four different coolant to free stream blowing ratios—0, 0.5, 1, and 2—and at a density ratio of 1.1. PIV images are taken in four planes from the side of the tunnel to record the main flow structures and in five planes from the end of the tunnel to record the secondary flow structures. The results show that the type of deposition has a large influence on the flow field. With the smaller depositions the penetration of the coolant jet into the free stream is significantly reduced but the dimension and strength of the kidney vortices is increased compared to the flat plate. With the large depositions, on the other hand, the penetration of the coolant jet is much higher due to the ramp effect and the dimension of the secondary vortices is also increased. It can also be seen that the coolant gathers and stays behind the large depositions and then flows off very slowly. Film effectiveness and surface heat flux data acquired with the same plates (and reported previously) allow the identification of flow features and their direct influence on the film cooling performance.

Measurement of Eddy Diffusivity of Momentum in Film Cooling Flows With Streamwise Injection

1999 ◽  
Vol 122 (1) ◽  
pp. 178-183 ◽  
Author(s):  
R. W. Kaszeta ◽  
T. W. Simon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Flux Ratio ◽  
Eddy Diffusivity ◽  
Turbulent Shear ◽  
Spanwise Direction ◽  
Intensity Level ◽  
Mean Velocity ◽  
Injection Angle ◽  
Free Stream Turbulence

Measurement of mean velocity and turbulent shear stress are presented for the mixing region of a film cooling situation in which the coolant is streamwise injected with an injection angle of 35 deg. Measurements are performed using triple-sensor anemometry so that all three instantaneous velocity components are documented. The free-stream turbulence intensity level is 12 percent, the ratio of the integral length scale to injection hole diameter is 4.0, the coolant-to-mainstream momentum flux ratio is 1.0, and the density ratio is unity. From these measurements, values for the eddy diffusivities of momentum in the lateral and wall-normal directions are calculated. Additionally, calculated values of the ratio of eddy diffusivity in the spanwise direction to eddy diffusivity in the wall-normal direction are presented, which provide documentation of the anisotropy of turbulent transport in this film cooling flow. [S0889-504X(00)02001-8]

scholarly journals Adiabatic Effectiveness, Thermal Fields, and Velocity Fields for Film Cooling With Large Angle Injection

1995 ◽  
Author(s):  
Atul Kohli ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Thermal Field ◽  
Density Ratio ◽  
Large Angle ◽  
Flux Ratio ◽  
Cryogenic Cooling ◽  
Round Hole ◽  
Mean Velocity ◽  
Injection Angle

The film cooling performance and velocity field were investigated for discrete round holes inclined at an injection angle of 55°. Results are compared to typical round film cooling holes, with an injection angle of 35°. All experiments in this study were performed at a density ratio of DR = 1.6, using cryogenic cooling of the injected air. Centerline and lateral distributions of effectiveness, were obtained for a range of momentum flux ratios. Thermal field and two component mean velocity and turbulence intensity measurements were made at a momentum flux ratio which was within the range of maximum spatially averaged effectiveness. Compared to round holes with 35° injection angle, the 55° holes showed only a slight degradation in centerline effectiveness for low momentum flux ratios, while a significant reduction in effectiveness was seen at high momentum flux ratios. The thermal field for the 55° round holes indicated a faster decay of cooling capacity for the 55° round holes. The high turbulence levels for the 55° round hole coincided with the sharp velocity gradients between the jet and freestream, and the decay of turbulence levels with downstream distance was found to be similar to those for a 35° hole.

Jets in a Crossflow: Effects of Geometry and Blowing Ratio

1999 ◽  
Vol 121 (2) ◽  
pp. 373-378 ◽  
Author(s):  
M. J. Findlay ◽  
M. Salcudean ◽  
I. S. Gartshore
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Film Cooling ◽  
Density Ratio ◽  
Mean Velocity ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Field Characteristics ◽  
Square Jets ◽  
Inlet Conditions

The flow field characteristics of three different geometries of square jets in a crossflow at various blowing ratios are examined. The geometries considered are: perpendicular, streamwise-inclined, and spanwise-inclined jets. The inclined jets are at a 30 deg angle to the wind tunnel floor. Mean velocity and turbulence measurements along with film cooling effectiveness and scalar transport data were obtained. Jet-to-crossflow blowing ratios of 1.5, 1.0 and 0.5 are used with a density ratio of 1. It is shown that the flow field at the jet exit is strongly influenced by the crossflow as well as by the inlet conditions at the entrance to the jet orifice. The strong streamline curvature which is present in the perpendicular and spanwise injection cases appears to result in the greatest turbulence anisotropy. The film cooling effectiveness is best at the lowest blowing ratios as the jet is deflected strongly towards the floor of the wind tunnel, although the improvement is more significant for the streamwise injection case.

scholarly journals Measurement of Eddy Diffusivity of Momentum in Film Cooling Flows With Streamwise Injection

1999 ◽  
Author(s):  
Richard W. Kaszeta ◽  
Terrence W. Simon
Keyword(s):  
Film Cooling ◽  
Turbulent Transport ◽  
Density Ratio ◽  
Flux Ratio ◽  
Eddy Diffusivity ◽  
Turbulent Shear ◽  
Spanwise Direction ◽  
Intensity Level ◽  
Mean Velocity ◽  
Injection Angle

Measurements of mean velocity and turbulent shear stress are presented for the mixing region of a film cooling situation in which the coolant is streamwise injected with an injection angle of 35°. Measurements are performed using triple-sensor anemometry so that all three instantaneous velocity components are documented. The freestream turbulence intensity level is 12%, the ratio of the integral length scale to injection hole diameter is 4.0, the coolant-to-mainstream momentum flux ratio is 1.0, and the density ratio is unity. From these measurements, values for the eddy diffusivities of momentum in the lateral and wall-normal directions are calculated. Additionally, calculated values of the ratio of eddy diffusivity in the spanwise direction to eddy diffusivity in the wall-normal direction are presented, which provide documentation of the anisotropy of turbulent transport in this film cooling flow.

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