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.

Experimental Flow Field Investigations of Nozzle Film Cooling Scheme on a Flat Plate Using Stereo PIV

2013 ◽  
Author(s):  
Yingjie Zheng ◽  
Ibrahim Hassan
Keyword(s):  
Flow Field ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Field Investigations ◽  
Nozzle Hole

This paper presents experimental flow field investigations of a film cooling scheme, referred to as nozzle scheme, on a flat plate using stereo PIV. The nozzle scheme has a cylindrical hole and internal obstacles to change the velocity distribution near the hole exit and hence the jet-mainstream interaction. Counter-rotating vortex pair (CRVP) is known to be one of the detrimental effects that affect the film cooling effectiveness. Previous CFD simulations demonstrated nozzle hole’s capability of reducing CRVP strength and enhancing film cooling effectiveness in comparison with a normal cylindrical hole. The present study examines the nozzle hole flow filed experimentally at blowing ratio ranged from 0.5 to 2.0 and compares with cylindrical hole. The experiments were conducted in a low-speed wind tunnel with a mainstream Reynolds number of 115,000 and the density ratio was 1.0 during all the investigations. The experimental results show that nozzle hole reduces streamwise vorticity of CRVP by an average of 55% at low blowing ratio, and 34%–40% at high blowing ratios. The velocity field and vorticity field of nozzle jet are compared with cylindrical jet. The result reveals that the nozzle jet forms a round bulk in contrast to the kidney shape jet core in cylindrical hole case. In addition, it is found that CRVP strength may not be a primary contributor to the jet lift-off.

Aerothermal Investigations on Mixing Flow Field of Film Cooling With Swirling Coolant Flow

2011 ◽  
Author(s):  
K. Takeishi ◽  
M. Komiyama ◽  
Y. Oda ◽  
Y. Egawa ◽  
T. Kitamura
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Film Cooling ◽  
Vertical Direction ◽  
Coolant Flow ◽  
Bottom Surface ◽  
Cooling Effectiveness ◽  
Slant Angle ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper describes the experimental results of a new film cooling method blowing through circular and shaped film cooling holes with swirling coolant flow. The experiments have been conducted by using a scale-up model of a film cooling hole installed on the bottom surface of a low-speed wind tunnel. Swirling motion of film coolant was induced inside a hexagonal plenum by two slant impingement jets, which are inclined at α degree toward the vertical direction and installed in a staggered position. The two impingement jets generate swirling flows inside the plenum, and this swirling flow enters into a film cooling hole keeping the angular momentum until the exit of the film cooling hole. The slant angle of the impingement jets was changed as α = 0°, 10°, 20°, 30° in their wind tunnel tests. The film cooling effectiveness on the flat wall was measured by using pressure sensitive paint (PSP) technique. In addition, the spatial distribution of non-dimensional concentration (or temperature) and flow field were measured by laser induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. In case of the circular film cooling hole, the coolant jet penetration into mainstream is suppressed by swirling motion of the coolant. As a result, though the coolant jet is deflected in the pitch direction, the film cooling effectiveness distribution on the wall keeps higher value behind the cooling hole over a long range. Additionally, kidney vortex structure disappeared. For the shaped cooling hole, the coolant jet spreads wider in spanwise direction at the downstream. Thus, the pitch averaged film cooling effectiveness at the downstream was 50% higher than that of the non-swirling case.

Experimental and Numerical Investigation of Flow Field and Downstream Surface Temperatures of Cylindrical and Diffuser Shaped Film Cooling Holes

2011 ◽  
Author(s):  
Tilman auf dem Kampe ◽  
Stefan Vo¨lker ◽  
Torsten Sa¨mel ◽  
Christian Heneka ◽  
Helge Ladisch ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Quantitative Agreement ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Contour Plots ◽  
Cooling Hole

An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.

Aerothermal Investigations on Mixing Flow Field of Film Cooling With Swirling Coolant Flow

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Kenichiro Takeishi ◽  
Masaharu Komiyama ◽  
Yutaka Oda ◽  
Yuta Egawa
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Film Cooling ◽  
Vertical Direction ◽  
Coolant Flow ◽  
Bottom Surface ◽  
Cooling Effectiveness ◽  
Slant Angle ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper describes the experimental results of a new film cooling method that utilizes swirling coolant flow through circular and shaped film cooling holes. The experiments were conducted by using a scale-up model of a film-cooling hole installed on the bottom surface of a low-speed wind tunnel. Swirling motion of the film coolant was induced inside a hexagonal plenum using two diagonal impingement jets, which were inclined at an angle of α toward the vertical direction and installed in staggered positions. These two impingement jets generated a swirling flow inside the plenum, which entered the film-cooling hole and maintained its angular momentum until exiting the film-cooling hole. The slant angle of the impingement jets was changed to α = 0 deg, 10 deg, 20 deg, and 30 deg in the wind tunnel tests. The film cooling effectiveness on a flat wall was measured by a pressure sensitive paint (PSP) technique. In addition, the spatial distributions of the nondimensional concentration (or temperature) and flow field were measured by laser-induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. In the case of a circular film-cooling hole, the penetration of the coolant jet into the mainstream was suppressed by the swirling motion of the coolant. As a result, although the coolant jet was deflected in the pitch direction, the film cooling effectiveness on the wall maintained a higher value behind the cooling hole over a long range. Additionally, the kidney vortex structure disappeared. For the shaped cooling hole, the coolant jet spread wider in the spanwise direction downstream. Thus, the pitch-averaged film cooling effectiveness downstream was 50% higher than that in the nonswirling case.

Numerical and Experimental Investigation of the Film Cooling Effectiveness and Temperature Fields Behind a Novel Trench Configuration at High Blowing Ratio

2012 ◽  
Author(s):  
Bernhard Kröss ◽  
Michael Pfitzner
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spreading ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Tetrahedral Elements

The present study is a numerical and an experimental investigation of film cooling from cylindrical holes embedded in a 0.75D deep transverse trench. Additionally, a new design with tetrahedral elements located upstream of the trench was examined. They interact with the approaching boundary layer and modify the flow field near the trench. Different heights of the tetrahedrons were considered. Results from all geometries were compared to those from a cylindrical hole. The experiments were performed in a heated closed loop wind tunnel with a coolant supply at cryogenic temperatures. The adiabatic film cooling effectiveness was obtained using infrared thermography. Temperatures within the flow field were measured using a cold-wire. The experiments were performed at four blowing ratios (1.0, 2.0, 3.0 and 4.0) and two density ratios (1.19 and 1.75). CFD simulations using FLUENT were carried out in order to investigate the developing flow field. The results show that the cooling effectiveness of the trench configuration increases with increasing blowing ratio. The coolant film remains attached to the surface even at the highest blowing ratio. In comparison to the original trench configuration the adiabatic effectiveness is enhanced by the tetrahedral elements due to reduced mixing of coolant and hot gas within the trench and improved lateral spreading of cooling air. The variation of the density ratio showed that the measurements can not be scaled with the blowing ratio alone without considering the density ratio.

Turbine Vane Endwall Film Cooling With Slashface Leakage and Discrete Hole Configuration

2016 ◽  
Author(s):  
Nafiz H. K. Chowdhury ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Density Ratio ◽  
Secondary Flows ◽  
Blow Down ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Leakage Flows ◽  
Turbine Vane ◽  
Inlet Conditions

Turbine vanes are typically assembled as a section containing single or double airfoil units in an annular pattern. First stage guide vane assembly results in two common mating interfaces — a gap between combustor and vane endwall and another resulted from the adjacent sections, called slashface. High pressure coolant could leak through these gaps to reduce the ingestion of hot gas and achieve certain cooling benefit. As vane endwall region flow field is already very complicated due to highly three-dimensional secondary flows, then a significant influence on endwall cooling can be expected due to the gap leakage flows. To determine the effect of leakage flows from those gaps, film cooling effectiveness distributions were measured using Pressure Sensitive Paint (PSP) technique on the endwall of a scaled up, mid-range industrial turbine vane geometry with the multiple rows of discrete film cooling holes inside the passages. Experiments were performed in a blow-down wind tunnel cascade facility at the exit Mach number of 0.5 corresponding to Reynolds number of 3.8 × 105 based on inlet conditions and axial chord length. Passive turbulence grid was used to generate freestream turbulence level about 19% with an integral length scale of 1.7 cm. Two parameters, coolant-to-mainstream mass flow ratio and density ratio were studied. The results are presented as two-dimensional film cooling effectiveness distribution on the vane endwall surface and the corresponding spanwise averaged values along the axial direction are also demonstrated.

Experimental and Numerical Investigation of Flow Field and Downstream Surface Temperatures of Cylindrical and Diffuser Shaped Film Cooling Holes1

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Tilman auf dem Kampe ◽  
Stefan Völker ◽  
Torsten Sämel ◽  
Christian Heneka ◽  
Helge Ladisch ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Quantitative Agreement ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Contour Plots ◽  
Cooling Hole

An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.

scholarly journals Film-Cooling From Holes With Expanded Exits: A Comparison of Computational Results With Experiments

1997 ◽  
Author(s):  
D. Giebert ◽  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Numerical Code ◽  
Navier Stokes ◽  
Mean Velocity ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Jet In Crossflow ◽  
Film Cooling Holes

A 3D Navier-Stokes code, together with the standard k-ϵ model with wall function approach, was used to investigate the flowfield in the vicinity of three different single scaled-up film-cooling holes. The hole geometries include a cylindrical hole, a hole with laterally expanded exit, and a hole with forward-laterally expanded exit. Comparisons of numerical results with detailed flowfield measurements of mean velocity and turbulent quantities are presented for a blowing ratio and density ratio of unity. Additionally, experimental data for different blowing ratios and a density ratio of about two are taken to perform validation of the code for adiabatic film-cooling effectiveness prediction. Results show that for both the round and the expanded hole geometries the code is able to capture all dominating flow structures of this jet in crossflow problem. However, discrepancies are found when comparing the flowfield inside the hole and at the hole exit. In particular, jet location at the hole exit differs significantly from measurement for the expanded hole geometries. For the adiabatic film-cooling effectiveness, it is shown that for round and expanded hole exits the intensity of the shear regions and the source of turbulence, respectively, have a strong influence on the predictive capability of the numerical code.

Conjugate Heat Transfer and Film Cooling of a Multi-Stage Cooling Scheme

2008 ◽  
Author(s):  
M. Ghorab ◽  
S. I. Kim ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Design Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Multi Stage ◽  
Internal Gap

Cooling techniques play a key role in improving efficiency and power output of modern gas turbines. The conjugate technique of film and impingement cooling schemes is considered in this study. The Multi-Stage Cooling Scheme (MSCS) involves coolant passing from inside to outside turbine blade through two stages. The first stage; the coolant passes through first hole to internal gap where the impinging jet cools the external layer of the blade. Finally, the coolant passes through the internal gap to the second hole which has specific designed geometry for external film cooling. The effect of design parameters, such as, offset distance between two-stage holes, gap height, and inclination angle of the first hole, on upstream conjugate heat transfer rate and downstream film cooling effectiveness performance are investigated computationally. An Inconel 617 alloy with variable properties is selected for the solid material. The conjugate heat transfer and film cooling characteristics of MSCS are analyzed across blowing ratios of Br = 1 and 2 for density ratio, 2. This study presents upstream wall temperature distributions due to conjugate heat transfer for different gap design parameters. The maximum film cooling effectiveness with upstream conjugate heat transfer is less than adiabatic film cooling effectiveness by 24–34%. However, the full coverage of cooling effectiveness in spanwise direction can be obtained using internal cooling with conjugate heat transfer, whereas adiabatic film cooling effectiveness has narrow distribution.

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