An Experimental Study of the Leakage Flow Effect on the Film Cooling Effectiveness of a Gas Turbine Shroud

2021 ◽  
pp. 1-18
Author(s):  
Gi Mun Kim ◽  
Soo In Lee ◽  
Jin Young Jeong ◽  
Jae Su Kwak ◽  
Seokbeom Kim ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Density Ratio ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
High Heat Transfer ◽  
Hole Configuration ◽  
Cooling Hole

Abstract In the vicinity of gas turbine blades, a complex flow field is formed due to the flow separation, reattachment, and secondary flows, and this results in a locally non-uniform and high heat transfer on the surfaces. The present study experimentally investigates the effects of leakage flow through the slot between the gas turbine vane and blade rows on the film cooling effectiveness of the forward region of the shroud ring segment. The experiment is carried out in a linear cascade with five blades. Instead of the vane, a row of rods at the location of the vane trailing edge is installed to consider the wake effect. The leakage flow is introduced through the slot between the vane and blade rows, and additional coolant air is injected from the cooling holes installed at the vane's outer zone. The effects of the slot geometry, cooling hole configuration, and blowing ratio on the film cooling effectiveness are experimentally investigated using the pressure sensitive paint (PSP) technique. CO2 gas and a mixture of SF6 and N2 (25%+75%) are used to simulate the leakage flow to the mainstream density ratios of 1.5 and 2.0, respectively. The results indicate that the area averaged film cooling effectiveness is affected more by the slot width than by the cooling hole configuration at the same injection conditions, and the lower density ratio cases show higher film cooling effectiveness than the higher density ratio case at the same cooling configuration.

An Experimental Study on the Leakage Flow on the Film Cooling Effectiveness of a Gas Turbine Shroud

2020 ◽  
Author(s):  
Gi Mun Kim ◽  
Soo In Lee ◽  
Jin Young Jeong ◽  
Jae Su Kwak ◽  
Seokbeom Kim ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Density Ratio ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Hole Size ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
High Heat Transfer

Abstract In the vicinity of gas turbine blades, a complex flow field is formed due to the flow separation, reattachment, and secondary flows, and results in locally non-uniform and high heat transfer on the surfaces. In this study, the effects of leakage flow through the slot between gas turbine vane and blade rows on the film cooling effectiveness of the forward region of the shroud ring segment were experimentally investigated. The experiment was carried out in a linear cascade with five blades. Instead of vane, a row of rods at the location of the vane trailing edge was installed to consider the wake effect. The leakage flow was introduced through the slot between vane and blade rows and additional coolant air was injected from the cooling holes installed at the vane outer zone. The effects of the slot geometry, hole size, and blowing ratio on the film cooling effectiveness were experimentally investigated by using a pressure sensitive paint technique. CO2 gas and the mixture of SF6 and N2 (25%+75%) were used as leakage flow in order to simulate leakage flow to mainstream density ratios of 1.5 and 2.0, respectively. Results showed that the area averaged film cooling effectiveness was more affected by the slot width than the cooling hole size at the same blowing ratio, and the lower density ratio cases showed higher film cooling effectiveness than that of higher density ratio case at the same cooling configuration.

Assessment of a Double Hole Film Cooling Geometry Using S-PIV and PSP

2013 ◽  
Author(s):  
Lesley M. Wright ◽  
Stephen T. McClain ◽  
Charles P. Brown ◽  
Weston V. Harmon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Field Measurements ◽  
Secondary Flows ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hole Geometry ◽  
Compound Angle

A novel, double hole film cooling configuration is investigated as an alternative to traditional cylindrical and fanshaped, laidback holes. This experimental investigation utilizes a Stereo-Particle Image Velocimetry (S-PIV) to quantitatively assess the ability of the proposed, double hole geometry to weaken or mitigate the counter-rotating vortices formed within the jet structure. The three-dimensional flow field measurements are combined with surface film cooling effectiveness measurements obtained using Pressure Sensitive Paint (PSP). The double hole geometry consists of two compound angle holes. The inclination of each hole is θ = 35°, and the compound angle of the holes is β = ± 45° (with the holes angled toward one another). The simple angle cylindrical and shaped holes both have an inclination angle of θ = 35°. The blowing ratio is varied from M = 0.5 to 1.5 for all three film cooling geometries while the density ratio is maintained at DR = 1.0. Time averaged velocity distributions are obtained for both the mainstream and coolant flows at five streamwise planes across the fluid domain (x/d = −4, 0, 1, 5, and 10). These transverse velocity distributions are combined with the detailed film cooling effectiveness distributions on the surface to evaluate the proposed double hole configuration (compared to the traditional hole designs). The fanshaped, laidback geometry effectively reduces the strength of the kidney-shaped vortices within the structure of the jet (over the entire range of blowing ratios considered). The three-dimensional velocity field measurements indicate the secondary flows formed from the double hole geometry strengthen in the plane perpendicular to the mainstream flow. At the exit of the double hole geometry, the streamwise momentum of the jets is reduced (compared to the single, cylindrical hole), and the geometry offers improved film cooling coverage. However, moving downstream in the steamwise direction, the two jets form a single jet, and the counter-rotating vortices are comparable to those formed within the jet from a single, cylindrical hole. These strong secondary flows lift the coolant off the surface, and the film cooling coverage offered by the double hole geometry is reduced.

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.

Implementation of Hole-Pair in Ramp to Improve Film Cooling Effectiveness on a Plain Surface

2020 ◽  
Author(s):  
Sadam Hussain ◽  
Xin Yan
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Hole Pair ◽  
Cooling Effect ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Plain Surface

Abstract Film cooling is one of the most critical technologies in modern gas turbine engine to protect the high temperature components from erosion. It allows gas turbines to operate above the thermal limits of blade materials by providing the protective cooling film layer on outer surfaces of blade against hot gases. To get a higher film cooling effect on plain surface, current study proposes a novel strategy with the implementation of hole-pair into ramp. To gain the film cooling effectiveness on the plain surface, RANS equations combined with k-ω turbulence model were solved with the commercial CFD solver ANSYS CFX11.0. In the numerical simulations, the density ratio (DR) is fixed at 1.6, and the film cooling effect on plain surface with different configurations (i.e. with only cooling hole, with only ramp, and with hole-pair in ramp) were numerically investigated at three blowing ratios M = 0.25, 0.5, and 0.75. The results show that the configuration with Hole-Pair in Ramp (HPR) upstream the cooling hole has a positive effect on film cooling enhancement on plain surface, especially along the spanwise direction. Compared with the baseline configuration, i.e. plain surface with cylindrical hole, the laterally-averaged film cooling effectiveness on plain surface with HPR is increased by 18%, while the laterally-averaged film cooling effectiveness on plain surface with only ramp is increased by 8% at M = 0.5. As the blowing ratio M increases from 0.25 to 0.75, the laterally-averaged film cooling effectiveness on plain surface with HPR is kept on increasing. At higher blowing ratio M = 0.75, film cooling effectiveness on plain surface with HPR is about 19% higher than the configuration with only ramp.

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.

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Film Cooling of Cylindrical Hole With a Downstream Short Crescent-Shaped Block

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Baitao An ◽  
Jianjun Liu ◽  
Chao Zhang ◽  
Sijing Zhou
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Vortex Pair ◽  
Cylindrical Hole ◽  
Test Case ◽  
Main Body ◽  
Lateral Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper presents a method to improve the film-cooling effectiveness of cylindrical holes. A short crescent-shaped block is placed at the downstream of a cylindrical cooling hole. The block shape is defined by a number of geometric parameters including block height, length and width, etc. The single row hole on a flat plate with inclination angle of 30 deg, pitch ratio of 3, and length-diameter ratio of 6.25 was chosen as the baseline test case. Film-cooling effectiveness for the cylindrical hole with or without the downstream short crescent-shaped block was measured by using the pressure sensitive paint (PSP) technique. The density ratio of coolant (argon) to mainstream air is 1.38. The blowing ratios vary from 0.5 to 1.25. The results showed that the lateral averaged cooling effectiveness is increased remarkably when the downstream block is present. The downstream short block allows the main body of the coolant jet to pass over the block top and to form a new down-wash vortex pair, which increases the coolant spread in the lateral direction. The effects of each geometrical parameter of the block on the film-cooling effectiveness were studied in detail.

Enhanced Film Cooling Effectiveness With Surface Trenches

2013 ◽  
Author(s):  
K. Vighneswara Rao ◽  
Jong S. Liu ◽  
Daniel C. Crites ◽  
Luis A. Tapia ◽  
Malak F. Malak ◽  
...  
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Operating Conditions ◽  
Airfoil Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Ansys Cfx ◽  
Cooling Hole ◽  
Computational Fluid Dynamics Cfd ◽  
Film Cooling Holes

In this study, cylindrical and fan shaped film cooling holes are evaluated on the blade surface numerically, using the Computational Fluid Dynamics (CFD) tool ANSYS-CFX, with the objective of improving cooling effectiveness by understanding the flow pattern at the cooling hole exit. The coolant flow rates are adjusted for blowing ratios of 0.5, 1.0 & 1.5 (momentum flux ratios of 0.125, 0.5 & 1.125 respectively). The density ratio is maintained at 2.0. New shaped holes viz. straight, concave and convex trench holes are introduced and are evaluated under similar operating conditions. Results are presented in terms of surface temperatures and adiabatic effectiveness at three different blowing ratios for the different film cooling hole shapes analyzed. Comparison is made with reference to the fan shaped film cooling hole to bring out relative merits of different shapes. The new trench holes improved the film cooling effectiveness by allowing more residence time for coolant to spread laterally while directing smoothly onto the airfoil surface. While convex trench improved the centre-line effectiveness, straight trench improved the laterally-averaged and overall effectiveness at all blowing ratios. Concave trench improved the effectiveness at blowing ratios 0.5 and 1.0.

Numerical Prediction of Film Cooling and Heat Transfer With Different Film-Hole Arrangements on the Plane and Squealer Tip of a Gas Turbine Blade

2004 ◽  
Author(s):  
Huitao Yang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Heat ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Tip Leakage ◽  
High Heat Transfer

The blade tip is one area that experiences high heat transfer due to the strong tip leakage flow. One of the common methods is to apply film cooling on tip to reduce the heat load. To get a better film cooling, different arrangements of film holes on the plane and squealer tips have been numerically studied with the Reynolds stress turbulence model and non-equilibrium wall function. The present study investigated three types of film-hole arrangements: 1) the camber arrangement: the film cooling holes are located on the mid-camber line of tips, 2) the upstream arrangement: the film holes are located upstream of the tip leakage flow and high heat transfer region, and 3) two rows arrangement: the camber and upstream arrangements are combined under the same amount of coolant. In addition, three different blowing ratios (M = 0.5, 1 and 1.5), are evaluated for film cooling effectiveness and heat transfer coefficient. The predicted heat transfer coefficients are in good agreement with the experimental data, but the film cooling effectiveness is over predicted on the blade tips.

Sign in / Sign up

Export Citation Format

Share Document