scholarly journals Experimental Investigation on Flow Field Characteristics of Impinging-Film Cooling

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jingyu Zhang ◽  
Ping Jiang ◽  
Ce Yuan ◽  
Xiaomin He
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Film Cooling ◽  
Test Rig ◽  
Temperature Ratio ◽  
Blowing Ratio ◽  
Pressure Experiment ◽  
Flow Field Characteristics ◽  
Entrainment Effect ◽  
Near Wall

This paper describes an experimental investigation on flow field characteristics of impinging-film cooling. Particle Image Velocimetry (PIV) technology has been applied to observe the effect of blowing ratio ( 0.04 ≤ M ≤ 0.3 ), temperature ratio ( 0.73 ≤ T u ≤ 0.91 ), jet-to-plate pitch ( 1.6 ≤ Z n ≤ 3.2 ), and spacing of impinging holes ( 1.94 ≤ Y n ≤ 3.5 ) on the flow field patterns in an impinging-film cooling test rig under atmospheric pressure. Experiment results show that the near-wall entrained vortex at the downstream of the slit moves downstream of the test rig as the blowing ratio increases, which increases the effective protection length of the film. While the vortex at the end of the inducting slab is stronger, this will increase the mixing in the shear layer. The radial size of the near-wall entrained vortex tends to decrease as the temperature ratio increases at the low blow ratio, and the entrainment effect on the downstream of the slit becomes smaller, causing the separation zone to decrease. Increasing the jet-to-plate pitch, the size of the near-wall entrained vortex increases, and the thickness of the film layer increases, this strengthens the separation effect of the near-wall airflow from the wall surface. The larger the spacing of the impinging holes, the more uneven the velocity distribution of the film.

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.

Experimental Flow Field Investigations Downstream a Film Cooling Scheme Over a Flat Plate Using the PIV Technique

2013 ◽  
Author(s):  
O. Hassan ◽  
I. Hassan
Keyword(s):  
Flow Field ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Experimental Investigations ◽  
Material Strength ◽  
Lateral Direction ◽  
Blowing Ratio ◽  
Piv Technique ◽  
Flow Field Characteristics

This paper presents experimental investigations of the flow field characteristics downstream a Scaled-Up Micro-Tangential Jet (SUMTJ) film cooling scheme using the Particle Image Velocimetry (PIV) technique over a flat plate. The SUMTJ scheme is a shaped scheme designed so that the secondary jet is supplied tangentially to the surface. The scheme combines the thermal benefits of tangential injection and the enhanced material strength of discrete holes schemes, compared with continuous slot schemes. The flow field characteristics downstream one row of holes were investigated at three blowing ratios, 0.5, 1.0 and 1.5, calculated based on the scheme exit area. A density ratio of unity, a Reynolds Number of 1.16E+5 and an average turbulence intensity of 8%, were used throughout the investigations. The performance of the SUMTJ scheme was compared to that of the circular hole scheme, based line case, at the same test conditions and blowing ratios. From the investigations, it was noticeable that the SUMTJ scheme jet stays attached to the surface for long downstream distances at all investigated blowing ratios. Moreover, the lateral expansion angles of the scheme help perform a continuous film from adjacent jets close to the schemes exits; however, they have bad impact on the uniformity of the film thickness in the lateral direction. The vorticity strength downstream the SUMTJ scheme in the y-z plane was much less than the vorticity strength downstream the circular scheme at all blowing ratios. However, the vorticity behavior in the shear layer between the secondary SUMTJ scheme jet and the mainstream was changing dramatically with blowing ratio. The latter is expected to have a significant impact on the film cooling performance enhancement with blowing ratio increase.

Experimental Flow-Field Investigations Downstream a Scaled-Up Micro-Tangential-Jet Scheme Using the Particle Image Velocimetry Technique

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Othman Hassan ◽  
Ibrahim Hassan
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Film Cooling ◽  
Particle Image ◽  
Material Strength ◽  
Main Stream ◽  
Base Line ◽  
Blowing Ratio ◽  
Image Velocimetry ◽  
Flow Field Characteristics

This paper presents experimental investigations of the flow-field characteristics downstream a Scaled-Up Micro-Tangential-Jet (SUMTJ) film-cooling scheme using the particle image velocimetry (PIV) technique over a flat plate. The SUMTJ scheme is a shaped scheme designed so that the secondary jet is supplied tangentially to the surface. The scheme combines the thermal benefits of tangential injection and the enhanced material strength of discrete holes’ schemes compared with continuous slot schemes. The flow-field characteristics downstream one row of holes were investigated at three blowing ratios, 0.5, 1.0, and 1.5, and were calculated based on the scheme exit area. A density ratio of unity, a Reynolds number of 1.16 × 105, and an average turbulence intensity of 8% were used throughout the investigations. The performance of the SUMTJ scheme was compared to that of the circular hole scheme, base line case case, at the same test conditions and blowing ratios. From the investigations, it was noticeable that the SUMTJ scheme jet stays attached to the surface for long downstream distances at all investigated blowing ratios. Moreover, the lateral expansion angles of the scheme help perform a continuous film from adjacent jets close to the schemes’ exits; however, they have a negative impact on the uniformity of the film thickness in the lateral direction. The vorticity strength downstream the SUMTJ scheme in the y-z plane was much less than the vorticity strength downstream the circular scheme at all blowing ratios. However, the vorticity behavior in the shear layer between the secondary SUMTJ scheme jet and the main stream was changing dramatically with the blowing ratio. The latter is expected to have a significant impact on the film-cooling performance as the blowing ratio increases.

Experimental Investigation on Flow Field Characteristics by Drag Reducing Agent Additives in Stirred Vessel

2019 ◽  
Author(s):  
Xueyu Qi ◽  
Ting Wu ◽  
Yiming Chen ◽  
Ke Yang ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Energy Dissipation ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Dissipation Rate ◽  
Energy Dissipation Rate ◽  
High Concentration ◽  
Stirred Vessel ◽  
Inhibition Effect ◽  
Flow Field Characteristics

Abstract In this paper, experimental investigation on two oil-soluble DRAs were carried out in stirred vessel by standard six-blade Rushton, based on the application of particle image velocimeter (PIV). Two DRAs (1# and 2#) with different concentration from 3 ppm to 50 ppm were added into diesel respectively, and speed of impeller speed was set 400 rpm. Flow field characteristics including turbulence intensity, turbulent kinetic energy, energy dissipation rate influenced by those additives in stirred vessel were study. It was found that inhibition effect of turbulence intensity of the two DRAs is not obvious with concentration below 10 ppm. However, when concentration is above 10 ppm, turbulence inhibition effect become more obvious. Under low concentration, 1# has better turbulence inhibition effect in area near impeller, while 2# has better turbulence inhibition effect under high concentration. When the two DRAs are under the same concentration of 50ppm, turbulent flow energy and energy dissipation rate are obviously reduced.

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.

Single and Multiple Row Endwall Film-Cooling of a Highly Loaded First Turbine Vane With Variation of Loading

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Martin Kunze ◽  
Konrad Vogeler ◽  
Michael Crawford ◽  
Glenn Brown
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Film Cooling ◽  
Wall Material ◽  
Measured Temperature ◽  
Single Row ◽  
Wall Flow ◽  
Endwall Film Cooling ◽  
Highly Loaded ◽  
Near Wall

This paper reports endwall film-cooling investigations with single and multiple rows of fan-shaped film holes using temperature-sensitive paint (TSP). The experiments are carried out in a six-bladed linear cascade based on the geometry of a highly loaded gas turbine first vane. The film effectiveness performance of the cooling rows is investigated under the influence of enhanced near-wall secondary flow. Tests are conducted at three different loading conditions changing the profile incidence. Film-cooling injection is established at elevated coolant density ratios of 1.4 using heated carbon dioxide. Due to the finite thermal conductivity of the wall material, the heat conduction effects observed in the measured temperature fields are assessed by a newly developed data analysis based on a finite element thermal analysis and tracking algorithms along CFD-computed near-wall surface streamlines. The results showed that the coolant trajectories are visibly influenced revealing the intense interaction between the film jets and the near-wall flow field. These effects are certainly enhanced with higher incidence leading to increased streamwise coolant consumption and reduced wall coverage. At the cascade inlet, the film-cooling injection is significantly affected by the near-wall flow field showing distinct over- and undercooled regions. Due to the enhanced deflection and mixing of the film jets injected from a single row, area-averaged film effectiveness and wall coverage decreases about 9 and 11%, respectively. With adding more cooling holes to this endwall area, the influence of the enhanced secondary flow becomes more pronounced. Hence, larger reduction in film effectiveness of 23% and wall coverage with 28% is observed. For single row injection at the airfoil pressure side, the stronger secondary flow motion with intensified streamwise mixing leads to a visibly decreased endwall coverage ratio of about 38% and maximum flow path reduction of about 41%. In this case, film effectiveness is found to be reduced up to 47% due to the small amount of coolant injected through this row. This effect is significantly smaller when more cooling rows are added showing an almost constant cooling performance for all incidence cases.

Flow Dynamics and Film Cooling Effectiveness on a Non-Axisymmetric Contour Endwall in a Two-Dimensional Cascade Passage

2009 ◽  
Author(s):  
Gazi I. Mahmood ◽  
Ross Gustafson ◽  
Sumanta Acharya
Keyword(s):  
Temperature Field ◽  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Blowing Ratio

The measured flow field and temperature field near a three-dimensional asymmetric contour endwall employed in a linear blade cascade are presented with and without film-cooling flow on the endwall. Flow field temperature and Nusselt number distributions along the asymmetric endwall with wall heating and no film-cooling flow are also reported to show local high heat transfer region on the endwall and justify the locations of the coolant holes. Adiabatic film-cooling effectiveness along the endwall is then measured to indicate the local effects of the coolant jets. The near endwall flow field and temperature field provide the coolant flow behavior and the interaction of coolant jets with the boundary layer flow. Thus, the local film-cooling effectiveness can be explained with the coolant jet trajectories. The measurements are obtained at the Reynolds number of 2.30×105 based on blade actual chord and inlet velocity, coolant-to-free stream temperature ratio of 0.93, and coolant-to-free stream density ratio of 1.06. The cascade employs the hub side blade section and passage geometry of the first stage rotor of GE-E3 turbine engine. The contour endwall profile is employed on the bottom endwall only in the cascade. The blowing ratio of the film-cooling flow varies from 1.0 to 2.4 from 71 discrete cylindrical holes located in the contour endwall. The three-dimensional profile of the endwall varies in height in both the pitchwise and axial directions. The flow field is quantified with the streamwise vorticity and turbulent intensity, pitchwise static pressure difference, flow yaw angle, and pitchwise velocity. Both the flow field and temperature data indicate that the coolant jets cover more distance in the pitchwise and axial direction in the passage as the blowing ratio increases. Thus, the local and average film-cooling effectiveness increase with the blowing ratio.

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.

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