Turbine Vane Endwall Film Cooling Study From Axial-Row Configuration With Simulated Upstream Leakage Flow

2017 ◽  
Author(s):  
Nafiz H. K. Chowdhury ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Axial Direction ◽  
Coverage Area ◽  
Blow Down ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Design ◽  
Exit Mach Number ◽  
Endwall Film Cooling

Endwall film cooling can be greatly improved if the leakage coolant flow from the upstream gap between the combustor and vane endwall is effectively engaged. In this study, such a full coverage film cooling design, called axial-row configuration, is considered and the performance is studied by measuring the film cooling effectiveness distribution using PSP technique. Experiments were performed in a blow-down wind tunnel cascade facility at the isentropic exit Mach number of 0.5 corresponding to inlet Reynolds number of 3.8 × 105, based on the axial chord. Passive turbulence grid was used to generate freestream turbulence level about 19 % with a length scale of 1.7 cm. The results are presented as two-dimensional film cooling effectiveness distributions on the endwall surface with pitchwise averaged distributions in the axial direction. The focus of this study is evaluating the effect of coolant-to-mainstream mass flow ratio (MFR) and density ratio (DR) on a particular endwall cooling design. Increasing coolant amount for the upstream leakage exhibited increased local adiabatic cooling effectiveness levels with relatively uniform coverage area. However, the passage cooling was not improved at highest coolant MFR = 1.5% rather indicated an optimum value of MFR = 1% based on better coolant coverage on the endwall surface. For density ratio effect, results indicated the best performance at DR = 1.5.

Influence of Coolant Density on Turbine Platform Film-Cooling With Stator–Rotor Purge Flow and Compound-Angle Holes

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Kevin Liu ◽  
Shang-Feng Yang ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Fundamental Parameters ◽  
Blowing Ratio ◽  
Purge Flow ◽  
Cylindrical Holes ◽  
Exit Mach Number ◽  
Compound Angle

A detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform. The platform was cooled by purge flow from a simulated stator–rotor seal combined with discrete hole film-cooling. The cylindrical holes and laidback fan-shaped holes were accessed in terms of film-cooling effectiveness. This paper focuses on the effect of coolant-to-mainstream density ratio on platform film-cooling (DR = 1 to 2). Other fundamental parameters were also examined in this study—a fixed purge flow of 0.5%, three discrete-hole film-cooling blowing ratios between 1.0 and 2.0, and two freestream turbulence intensities of 4.2% and 10.5%. Experiments were done in a five-blade linear cascade with inlet and exit Mach number of 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 750,000 and was based on the exit velocity and chord length of the blade. The measurement technique adopted was the conduction-free pressure sensitive paint (PSP) technique. Results indicated that with the same density ratio, shaped holes present higher film-cooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The optimum blowing ratio of 1.5 exists for the cylindrical holes, whereas the effectiveness for the shaped holes increases with an increase of blowing ratio. Results also indicate that the platform film-cooling effectiveness increases with density ratio but decreases with turbulence intensity.

Numerical Investigation of Effects of Blockage, Inclination Angle, and Hole-Size on Film Cooling Effectiveness at Concave Surface

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
Fu-qiang Wang ◽  
Jian Pu ◽  
Jian-hua Wang ◽  
Wei-dong Xia
Keyword(s):  
Film Cooling ◽  
Pressure Loss ◽  
Numerical Study ◽  
Density Ratio ◽  
Concave Surface ◽  
Blockage Ratio ◽  
Coverage Area ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

Abstract Film-hole can be often blocked by thermal-barrier coatings (TBCs) spraying, resulting in the variations of aerodynamic and thermal performances of film cooling. In this study, a numerical study of the blockage effect on the film cooling effectiveness of inclined cylindrical-holes was carried out on a concave surface to simulate the airfoil pressure side. Three typical blowing ratios (BRs) of 0.5, 1.0, and 1.5 were chosen at an engine-similar density ratio (DR) of 2.0. Two common inclination angles of 30 deg and 45 deg were designed. The blockage ratios were adjusted from 0 to 20%. The results indicated the blockage could enhance the penetration of film cooling flow to the mainstream. Thus, the averaged effectiveness and coolant coverage area were reduced. Moreover, the pressure loss inside of the hole was increased. With the increase of BR, the decrement of film cooling effectiveness caused by blockage rapidly increased. At BR = 1.5, the decrement could be acquired up to 70% for a blockage ratio of 20%. The decrement of film cooling effectiveness caused by blockage was nearly nonsensitive to the injection angle; however, the larger angle could generate the higher increment of pressure loss caused by blockage. A new design method for the couple scheme of film cooling and TBC was proposed, i.e., increasing the inlet diameter according to the blockage ratio before TBC spraying. In comparison with the original unblocked-hole, the enlarged blocked-hole not only kept the nearly same area-averaged effectiveness but also reduced slightly the pressure loss inside of the hole. Unfortunately, application of enlarged blocked-hole at large BR could lead to a more obvious reduction of effectiveness near hole-exit, in comparison with the original common-hole.

Endwall Heat Transfer and Cooling Performance of a Transonic Turbine Vane with Upstream Injection Flow

2021 ◽  
pp. 1-24
Author(s):  
Zhigang LI ◽  
Bo Bai ◽  
Jun Li ◽  
Shuo Mao ◽  
Wing Ng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Gas Temperature ◽  
Blow Down ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Flow ◽  
Coolant Injection ◽  
Exit Mach Number

Abstract Detailed experimental and numerical studies on endwall heat transfer and cooling performance with coolant injection flow through upstream discrete holes is presented in this paper. High resolution heat transfer coefficient (HTC) and adiabatic film cooling effectiveness values were measured using a transient infrared thermography technique on an axisymmetric contoured endwall. The tests were performed in a transonic linear cascade blow-down wind tunnel facility. Conditions were representative of a land-based power generation turbine with exit Mach number of 0.85 corresponding to exit Reynolds number of 1.5 × 106, based on exit condition and axial chord length. A high turbulence level of 16% with an integral length scale of 3.6%P was generated using inlet turbulence grid to reproduce the typical turbulence conditions in real turbine. Low temperature air was used to simulate the typical coolant-to-mainstream condition by controlling two parameters of the upstream coolant injection flow: mass flow rate to determine the coolant-to-mainstream blowing ratio (BR = 2.5, 3.5), and gas temperature to determine the density ratio (DR = 1.2). To highlight the interactions between the upstream coolant flow and the passage secondary flow combined with the influence on the endwall heat transfer and cooling performance, a comparison of CFD predictions to experimental results was performed by solving steady-state Reynolds-Averaged Navier-Stokes (RANS) using the commercial CFD solver ANSYS Fluent V.15.

Turbine Vane Endwall Film Cooling From Cross-Row Configuration With Simulated Upstream Leakage Flow

2017 ◽  
Author(s):  
Nafiz H. K. Chowdhury ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Companion Paper ◽  
Leakage Flow ◽  
Blow Down ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Lift Off ◽  
Endwall Cooling

The performance of a full coverage film cooling configuration called cross-row (CR) configuration including upstream inlet leakage flow was studied by measuring the adiabatic film cooling effectiveness distribution using PSP technique. Experiments were conducted in a blow-down wind tunnel cascade facility at the isentropic exit Mach number of 0.5 corresponding to inlet Reynolds number of 3.8 × 105, based on axial chord length. A free-stream turbulence level was generated as high as 19% with a length scale of 1.7 cm at the inlet. The results are presented as two-dimensional adiabatic film cooling effectiveness distributions on the endwall surface with corresponding spanwise averaged distributions. The focus of this study is to investigate the effect of coolant-to-mainstream mass flow ratio (MFR) and density ratio (DR) on the proposed endwall cooling design. Initially, increased MFR for the endwall cooling and upstream leakage levels up the local adiabatic cooling effectiveness and yields relatively uniform coverage on the entire endwall. However, in either case, highest MFR does not provide any improvement as endwall cooling suffered from the jet lift-off and leakage coolant coverage restricted by the downstream near-wall flow field. Results also indicated a density ratio of 1.5 provides the best performance. Finally, a fair comparison is made with another design called axial-row (AR) configuration from a companion paper.

Turbine Vane Endwall Film Cooling Effectiveness of Different Purge Slot Configurations in a Linear Cascade

2019 ◽  
Author(s):  
Gunther Müller ◽  
Christian Landfester ◽  
Martin Böhle ◽  
Robert Krewinkel
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Region Of Interest ◽  
Experimental Tests ◽  
Secondary Flows ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Density Ratios ◽  
Endwall Film Cooling

Abstract This study is concerned with the film cooling effectiveness of the flow issuing from the gap between the NGV and the transition duct on the NGV endwall, i.e. the purge slot. Different slot widths, positions and injection angles were examined in order to represent changes due to thermal expansion as well as design modifications. Apart from these geometric variations, different blowing ratios (BR) and density ratios (DR) were realized to investigate the effects of the interaction between secondary flow and film cooling effectiveness. The experimental tests were performed in a linear scale-1 cascade equipped with four highly loaded turbine vanes at the Institute of Fluid Mechanics and Fluid Machinery of the University of Kaiserslautern. The mainstream flow parameters were, with a Reynolds number of 300,000 and a Mach number (outlet) of 0.6, set to meet real engine conditions. By using various flow conditioners, periodic flow was obtained in the region of interest (ROI). The adiabatic film cooling effectiveness was determined by using the Pressure Sensitive Paint (PSP) technique. In this context, nitrogen and carbon dioxide were used as tracer gases realizing two different density ratios DR = 1.0 and 1.6. The investigation was conducted for a broad range of blowing ratios with 0.25 ≤ BR ≤ 1.50. In combination with 10 geometry variations and the aforementioned blowing and density ratio variations 100 single operating points were investigated. For a better understanding of the coolant distribution, the secondary flows on the endwall were visualized by oil dye. The measurement results will be discussed based on the areal distribution of film cooling effectiveness, its lateral spanwise as well as its area average. The results will provide a better insight into various parametric effects of gap variations on turbine vane endwall film cooling performance — notably under realistic engine conditions.

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

2017 ◽  
Vol 139 (6) ◽  
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 ◽  
Free Stream Turbulence ◽  
Leakage Flows ◽  
Turbine Vane

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, midrange industrial turbine vane geometry with the multiple rows of discrete film cooling (DFC) 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 free-stream turbulence (FST) level about 19% with an integral length scale of 1.7 cm. Two parameters, coolant-to-mainstream mass flow ratio (MFR) and density ratio (DR), were studied. The results are presented as two-dimensional film cooling effectiveness distribution on the vane endwall surface with the corresponding spanwise averaged values along the axial direction.

Transonic Turbine Vane Endwall Film Cooling Using PSP Measurement Technique

2019 ◽  
Author(s):  
Chao-Cheng Shiau ◽  
Izzet Sahin ◽  
Izhar Ullah ◽  
Je-Chin Han ◽  
Alexander V. Mirzamoghadam ◽  
...  
Keyword(s):  
Shock Wave ◽  
Film Cooling ◽  
Density Ratio ◽  
Cross Flow ◽  
Flow Conditions ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Turbine Vane ◽  
Endwall Film Cooling

Abstract This work focuses on the parametric study of film cooling effectiveness on turbine vane endwall under various flow conditions. The experiments were performed in a five-vane annular sector cascade facility in a blowdown wind tunnel. The controlled exit isentropic Mach numbers were 0.7, 0.9, and 1.0, from high subsonic to transonic conditions. The freestream turbulence intensity is estimated to be 12%. Three coolant-to-mainstream mass flow ratios (MFR) in the range 0.75%, 1.0%, and 1.25% are studied. N2, CO2, and Argon/SF6 mixture were used to investigate the effects of density ratio (DR), ranging from 1.0, 1.5 to 2.0. There are 8 cylindrical holes on the endwall inside the passage. Pressure-sensitive paint (PSP) technique was used to capture the endwall pressure distribution for shock wave visualization and obtain the detailed film cooling effectiveness distributions. Both the high-fidelity effectiveness contour and the laterally (spanwise) averaged effectiveness were measured to quantify the parametric effect. This study will provide the gas turbine designer more insight on how the endwall film cooling effectiveness varies with different cooling flow conditions including shock wave through the endwall cross-flow passage.

Numerical Investigation of Effects of Blockage, Inclination Angle and Hole-Size on Film Cooling Effectiveness at Concave Surface

2020 ◽  
Author(s):  
Fu-qiang Wang ◽  
Jian Pu ◽  
Jian-hua Wang ◽  
Wei-dong Xia
Keyword(s):  
Film Cooling ◽  
Pressure Loss ◽  
Numerical Study ◽  
Density Ratio ◽  
Concave Surface ◽  
Blockage Ratio ◽  
Coverage Area ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

Abstract Film-hole can be often blocked by the thermal-barrier coatings (TBC) spraying, resulting in the variations of film cooling performance and pressure loss. In this work, a numerical study of the effect of blockage ratio on the film cooling effectiveness of inclined cylindrical-holes was carried out on a concave surface to simulate the airfoil pressure side. Three typical blowing ratios (BRs) of 0.5, 1.0 and 1.5 were chosen at an engine-similar density ratio (DR) of 2.0. Two common inclination angles of 30° and 45° were designed. The blockage ratios were adjusted from 0 to 20%. The results indicated that the blockage near the trailing edge of hole-exit could enhance the penetration of film cooling flow to the mainstream. Thus, the averaged effectiveness and coolant coverage area were reduced. Moreover, the pressure loss inside of hole was increased. With the increase of BR, the decrement of film cooling effectiveness caused by blockage rapidly enhanced. At BR = 1.5, the decrement could be acquired up to 70% for a blockage ratio of 20%. The decrement of film cooling effectiveness caused by blockage was nearly non-sensitive to the injection angle; however, the larger injection angle could generate the higher increment of pressure loss caused by blockage. A new design method for the couple scheme of film-cooling and TBC was proposed, i.e. increasing the inlet diameter according to the blockage ratio before TBC spraying. In comparison with the original unblocked-hole, the enlarged blocked-hole not only can keep the nearly same area-averaged effectiveness, but also can reduce slightly the pressure loss inside of hole. The smaller injection angle could obtain the larger reduction of pressure loss. Unfortunately, application of enlarged blocked-hole at large BR could lead to a more obvious reduction of effectiveness near hole-exit, in comparison with the original common-hole.

Numerical investigation of blowing ratio, density ratio and axial position of film holes on the vane endwall film cooling effectiveness with upstream step

2021 ◽  
pp. 095441002110165
Author(s):  
Qingzong Xu ◽  
Qiang Du ◽  
Pei Wang ◽  
Xiangtao Xiao ◽  
Jun Liu
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Pressure Loss ◽  
Total Pressure ◽  
Density Ratio ◽  
Total Pressure Loss ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Endwall Film Cooling

The aerothermal performance of interrupted slot and film holes was numerically investigated. Previous study indicates that the interrupted slot performs better compared to the conventional slot. In the meanwhile, the step formed along with the interrupted slot affects the film cooling characteristics. In this article, a row of film holes is arranged downstream of the step, and the mass flow rate for the interrupted slot is constant at 1%. Blowing ratio (BR) from 0.5 to 1.5 and density ratio from 1 to 2 were studied for the film holes. Endwall film cooling effectiveness distribution indicates that film cooling is easily affected by the secondary flow inside passage and the upstream step. Coolant traces are split into two parts due to the effects of step vortex and transverse flow. For different density ratios, increasing BR shows a different trend of film cooling effectiveness due to the variation of coolant momentum. The coolant jet is easily affected by the secondary flow when its momentum is low, but tends to liftoff when its momentum is too high. As a result, it is better to position the film holes far away from the upstream step. The total pressure loss coefficient distribution at the passage exit indicates that the coolant injection increases the total pressure loss. But density ratio has smaller effect on the loss variation. Besides, two axial positions of cooling holes were studied to improve the endwall cooling performance. Without the effect of step vortex, the film effectiveness of cooling holes is improved.

Film Cooling Effectiveness Comparison on Turbine Vane Endwall With Cluster Configurations Using PSP Measurement Technique

2017 ◽  
Author(s):  
Nafiz H. K. Chowdhury ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Hongzhou Xu ◽  
Michael Fox
Keyword(s):  
Measurement Technique ◽  
Film Cooling ◽  
Density Ratio ◽  
Blow Down ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Comparison Results ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Endwall Cooling

Film cooling performance comparison on a turbine vane endwall with two different cluster configurations incorporating upstream inlet leakage flow was studied by applying PSP measurement technique. Experiments were conducted in a blow-down wind tunnel cascade facility at the exit isentropic Mach number of 0.5 corresponding to inlet Reynolds number of 380,000, based on axial chord length. A freestream turbulence level was generated as high as 19% with an integral length scale of 1.7 cm at the inlet of vanes’ leading edge plane. The results of each design and the comparison are presented in two-dimensional adiabatic film cooling effectiveness distributions on the endwall surface as well as the corresponding laterally averaged distributions. The focus of this study is to compare two different endwall cooling designs by the parametric effect of coolant-to-mainstream mass flow ratio (MFR) and density ratio (DR) on film cooling effectiveness. Initially, increased MFR for the endwall cooling and upstream leakage levels up the local film cooling effectiveness and yields improved coverage on the endwall. However, the endwall and upstream leakage demonstrate different behavior, while highest MFR does not provide any improvement as endwall cooling is suffered from the jet lift-off, highest MFR from the upstream leakage shows a monotonic increasing effectiveness on the endwall. On the other hand, the DR effect on effectiveness reveals different trend at a different design. Under a given amount of coolant supply and a fixed number of cooling hole, the comparison results really emphasize the importance of the cooling hole arrangement as one of the proposed cluster design can properly cover the whole endwall area.

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