Film-Cooling Effectiveness With Injection Through a Porous Section

1965 ◽  
Vol 87 (3) ◽  
pp. 353-359 ◽  
Author(s):  
R. J. Goldstein ◽  
G. Shavit ◽  
T. S. Chen
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Stream Velocity ◽  
Temperature Profiles ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Secondary Air Injection ◽  
Layer Velocity ◽  
Secondary Air

An experimental study of the effectiveness of film cooling following secondary air injection through a porous section into a turbulent free stream is presented. Boundary-layer velocity and temperature profiles are described. The adiabatic wall temperatures are presented in terms of the film-cooling effectiveness. The effects of varying the secondary air temperature, the blowing rate, and the free-stream velocity are studied. It is found that the protection given to a surface downstream of a porous section through which air is injected compares favorably to earlier studies where the secondary air was injected nearly tangential to the surface.

Effect of Streamline Curvature on Film Cooling

1977 ◽  
Vol 99 (1) ◽  
pp. 77-82 ◽  
Author(s):  
R. E. Mayle ◽  
F. C. Kopper ◽  
M. F. Blair ◽  
D. A. Bailey
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Film Cooling ◽  
Flat Surface ◽  
Temperature Measurements ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Streamline Curvature ◽  
Layer Velocity

The effects of streamline curvature on film cooling effectiveness are discussed. Experiments for air discharged through a slot and into a turbulent boundary layer along a flat, convex, and concave surface are described. Adiabatic wall effectiveness measurements on each surface for several blowing rates are presented. Boundary-layer velocity and temperature measurements are also presented for one of the blowing rates. Compared to the results for the flat surface, convex curvature is found to increase the adiabatic wall effectiveness whereas concave curvature is found to be detrimental.

Film Cooling With Injection Through Holes: Adiabatic Wall Temperatures Downstream of a Circular Hole

1968 ◽  
Vol 90 (4) ◽  
pp. 384-393 ◽  
Author(s):  
R. J. Goldstein ◽  
E. R. G. Eckert ◽  
J. W. Ramsey
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Turbulent Boundary Layer ◽  
Film Cooling ◽  
Main Flow ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Secondary Air ◽  
Secondary Fluid

An experimental investigation has been conducted to determine the film cooling effectiveness with injection of air through a discrete hole into a turbulent boundary layer of air on a flat plate. The secondary air enters at either an angle of 35 deg or an angle of 90 deg to the main flow. The film cooling effectiveness is found to be considerably different from that obtained in previous studies in which the secondary fluid was introduced through a continuous slot.

Film Cooling Performance of the Embedded Holes in Trenches With Compound Angles

2010 ◽  
Author(s):  
Jia Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Lateral Spreading ◽  
Stream Velocity ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Axial Ejection ◽  
Cooling Air ◽  
Compound Angle

Film cooling performance for a row of cylindrical holes can be enhanced by embedding the row in a suitable transverse slot. The compound angle of the holes can even more affects the cooling performance at downstream of the injections. In this study the cooling performance of the embedded holes in transverse trenches with different compound angles are explored both by pressure sensitive paint (PSP) experiment technology and RANS algorithm. A film cooling test rig was built up in Tsinghua University, which contains an accelerating free stream section to model the surface of a turbine airfoil. The PSP technology is applied in the tests to obtain the film cooling effectiveness. The experiments are performed for a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 4000. Considering three compound angles, 0°, 45° and 90°, and with or without transverse trenches. All six cases are tested at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. Meanwhile, the test cases are numerically simulated based on RANS with k-ε turbulence model to show the detail of the flow patterns. Both the experimental and numerical results show that the adiabatic film effectiveness is relative insensitive to the blowing ratio in the case of holes with trenches. Moreover, it could be improved with a more uniform spanwise distribution. It is mainly due to the blockage of the ejected coolant at the downstream edge of the trench, which forces a portion of the cooling air to spread laterally within the trench prior to issuing onto the upper surface. Both 45° and 90° compound angles can further enhance the film cooling effectiveness over the axial ejection, this is mainly due to the lateral momentum component of the ejection. A lateral passage vortex is formed inside the trench which strengthens the lateral spreading of the jets. The 45° compound angle gives a higher film cooling effectiveness overall.

Film Cooling Measurements for Novel Hole Configurations

2005 ◽  
Author(s):  
Yiping Lu ◽  
David Faucheaux ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Free Stream ◽  
Cylindrical Hole ◽  
Stream Velocity ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Cylindrical Holes

Film cooling performance for a row of cylindrical holes can be. The effect of the slot exit area and shape is investigated. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 7150 at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. Two designs with a crescent shaped exit and a slot exit are considered. The results show that the crescent shaped exits provide significantly higher film cooling effectiveness than the cylindrical hole exit at all blowing ratios. The converging slot exit provides similar effectiveness as the crescent for higher blowing ratios. However, the crescent shape also enhances heat transfer coefficients significantly. Overall effectiveness for both crescent and converging slot exits are clearly superior to the standard cylindrical hole.

scholarly journals Effects of Bulk Flow Pulsations on Film Cooling From Spanwise Oriented Holes

1998 ◽  
Author(s):  
I. S. Jung ◽  
J. S. Lee
Keyword(s):  
Film Cooling ◽  
Static Pressure ◽  
Free Stream ◽  
Free Stream Velocity ◽  
Bulk Flow ◽  
Stream Velocity ◽  
Pressure Pulsations ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Temperature Distributions

Experimental results are presented which describe the effect of bulk flow pulsations on film cooling from a single row of spanwise oriented holes. The film coolant is injected from the holes with 35 degree inclination angles and 90 degree orientation angles. Static pressure pulsations are produced by rotating vanes made of an array of six shutter blades, which are extended across the span of the exit of the wind tunnel test section. The free-stream velocity is in the form of near-sinusoidal variation and peak-to-peak amplitude is 11%. Changing two parameters which are time-averaged blowing ratio (M = 0.5, 1.0, 2.0) and frequency (f = 0, 36 Hz) gives the corresponding coolant Strouhal numbers in the range from 0 to 3.6. Time-averaged and phase-averaged temperature distributions are measured in spanwise/normal planes, and the adiabatic film cooling effectiveness is evaluated from the adiabatic wall temperature distributions. The results show that the imposed free-stream velocity pulsations generate static pressure difference variations between the plenum chamber and free-stream. These static pressure pulsations result in periodic variation of injectant flow rate and spanwise momentum which cause dramatic alterations in film coolant distributions, trajectories and corresponding adiabatic film cooling effectiveness distributions downstream of injection holes.

The Effect of High Free-Stream Turbulence on Film Cooling Effectiveness

1996 ◽  
Vol 118 (4) ◽  
pp. 814-825 ◽  
Author(s):  
J. P. Bons ◽  
C. D. MacArthur ◽  
R. B. Rivir
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Constant Density ◽  
Injection Hole ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Free Stream Turbulence

This study investigated the adiabatic wall cooling effectiveness of a single row of film cooling holes injecting into a turbulent flat plate boundary layer below a turbulent, zero pressure gradient free stream. Levels of free-stream turbulence (Tu) up to 17.4 percent were generated using a method that simulates conditions at a gas turbine combustor exit. Film cooling was injected from a single row of five 35 deg slant-hole injectors (length/diameter = 3.5, pitch/diameter = 3.0) at blowing ratios from 0.55 to 1.85 and at a nearly constant density ratio (coolant density/free-stream density) of 0.95. Film cooling effectiveness data are presented for Tu levels ranging from 0.9 to 17 percent at a constant free-stream Reynolds number based on injection hole diameter of 19,000. Results show that elevated levels of free-stream turbulence reduce film cooling effectiveness by up to 70 percent in the region directly downstream of the injection hole due to enhanced mixing. At the same time, high free-stream turbulence also produces a 50–100 percent increase in film cooling effectiveness in the region between injection holes. This is due to accelerated spanwise diffusion of the cooling fluid, which also produces an earlier merger of the coolant jets from adjacent holes.

Film Cooling With Normal Injection Into a Supersonic Flow

1968 ◽  
Vol 90 (4) ◽  
pp. 584-588 ◽  
Author(s):  
R. J. Goldstein ◽  
E. R. G. Eckert ◽  
D. J. Wilson
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
High Speed ◽  
Incompressible Flows ◽  
Free Stream ◽  
Gas Injection ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Good Agreement

An experimental study of film cooling with subsonic gas injection into a mainstream with a Mach number of 2.90 is reported. Air, used as both the mainstream and secondary fluids, is injected normal to the surface of a flat plate through a short porous section into a two-dimensional turbulent boundary layer. The secondary fluid enters the boundary layer with a mass velocity which ranges from 0.0085 to 0.0223 of the free-stream value. The adiabatic wall temperatures are presented as the film-cooling effectiveness. The results of the present study, when the proper choice is made for the reference state used to account for fluid property variations across the high-speed boundary layer, are in good agreement with previous investigations in incompressible flows.

scholarly journals The Application of Adiabatic Film Cooling Effectiveness to Non-Adiabatic Blade Cooling Design

1983 ◽  
Author(s):  
C. P. Lee ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Heat Transfer Analysis ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Transfer Parameter ◽  
Adiabatic Effectiveness ◽  
C 32 ◽  
Heat Transfer Parameter

The effect of heat transfer on film cooling has been studied analytically. The proposed model shows that the non-adiabatic film cooling effectiveness will increase with increasing of the heat transfer parameter, Ū / (ρVCp)2, on the convex, the flat and the concave walls over the entire range of film cooling parameter, X/MS. On the convex wall with a blowing rate, M, of 0.51 and a heat transfer parameter of 10−3 at the typical engine conditions, the non-adiabatic effectiveness can be higher than the adiabatic effectiveness by 45% at a film cooling parameter of 103; while the film temperature can be lower than the adiabatic wall by 18°C (32°F) at a dimensionless distance of 500. The model can be extended and applied to the heat transfer analysis for any kind of turbine blade with film cooling.

scholarly journals Adiabatic Wall Effectiveness Measurements of Film-Cooling Holes With Expanded Exits

1997 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Thermal Protection ◽  
Lateral Spreading ◽  
Cylindrical Hole ◽  
Adiabatic Wall ◽  
Camera System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper presents detailed measurements of the film-cooling effectiveness for three single, scaled-up film-cooling hole geometries. The hole geometries investigated include a cylindrical hole and two holes with a diffuser shaped exit portion (i.e. a fanshaped and a laidback fanshaped hole). The flow conditions considered are the crossflow Mach number at the hole entrance side (up to 0.6), the crossflow Mach number at the hole exit side (up to 1.2), and the blowing ratio (up to 2). The coolant-to-mainflow temperature ratio is kept constant at 0.54. The measurements are performed by means of an infrared camera system which provides a two-dimensional distribution of the film-cooling effectiveness in the nearfield of the cooling hole down to x/D = 10. As compared to the cylindrical hole, both expanded holes show significantly improved thermal protection of the surface downstream of the ejection location, particularly at high blowing ratios. The laidback fanshaped hole provides a better lateral spreading of the ejected coolant than the fanshaped hole which leads to higher laterally averaged film-cooling effectiveness. Coolant passage crossflow Mach number and orientation strongly affect the flowfield of the jet being ejected from the hole and, therefore, have an important impact on film-cooling performance.

Effects of Double Wall Cooling Configuration and Conditions on Performance of Full-Coverage Effusion Cooling

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Nathan Rogers ◽  
Zhong Ren ◽  
Warren Buzzard ◽  
Brian Sweeney ◽  
Nathan Tinker ◽  
...  
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Hole Array ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Full Coverage ◽  
Cooling Hole ◽  
Double Wall

Experimental results are presented for a double wall cooling arrangement which simulates a portion of a combustor liner of a gas turbine engine. The results are collected using a new experimental facility designed to test full-coverage film cooling and impingement cooling effectiveness using either cross flow, impingement, or a combination of both to supply the film cooling flow. The present experiment primarily deals with cross flow supplied full-coverage film cooling for a sparse film cooling hole array that has not been previously tested. Data are provided for turbulent film cooling, contraction ratio of 1, blowing ratios ranging from 2.7 to 7.5, coolant Reynolds numbers based on film cooling hole diameter of about 5000–20,000, and mainstream temperature step during transient tests of 14 °C. The film cooling hole array consists of a film cooling hole diameter of 6.4 mm with nondimensional streamwise (X/de) and spanwise (Y/de) film cooling hole spacing of 15 and 4, respectively. The film cooling holes are streamwise inclined at an angle of 25 deg with respect to the test plate surface and have adjacent streamwise rows staggered with respect to each other. Data illustrating the effects of blowing ratio on adiabatic film cooling effectiveness and heat transfer coefficient are presented. For the arrangement and conditions considered, heat transfer coefficients generally increase with streamwise development and increase with increasing blowing ratio. The adiabatic film cooling effectiveness is determined from measurements of adiabatic wall temperature, coolant stagnation temperature, and mainstream recovery temperature. The adiabatic wall temperature and the adiabatic film cooling effectiveness generally decrease and increase, respectively, with streamwise position, and generally decrease and increase, respectively, as blowing ratio becomes larger.

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