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.

Film Cooling Effectiveness and Mass/Heat Transfer Coefficient Downstream of One Row of Discrete Holes

1999 ◽  
Vol 121 (2) ◽  
pp. 225-232 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin ◽  
R. L. Olson
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle with 3d hole spacing and relatively small hole length to diameter ratio (L/d = 6.3). Both film cooling effectiveness and mass/heat transfer coefficient are determined for blowing rates from 0.5 to 2.0 with density ratio of 1.0. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with those from pure air injection. This technique enables one to obtain detailed local information on film cooling performance. The laterally averaged and local film cooling effectiveness agree with previous experiments. The difference between mass/heat transfer coefficients and previous heat transfer results indicates that conduction error may play an important role in the earlier heat transfer measurements.

Heat transfer characteristics analysis on a fully cooled vane with varied density ratios

2021 ◽  
pp. 1-19
Author(s):  
Chunyi Yao ◽  
Zheng Zhang ◽  
Bo-lun Zhang ◽  
Hui Ren Zhu ◽  
Cun Liang Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Coolant Injection ◽  
Density Ratios

Abstract The objective of this experimental investigation was to determine the cooling performance of a fully cooled vane with 18 rows of cylinder cooling holes. The exit Reynolds number in the wind tunnel normalized by the true chord was 500,000 with a turbulence intensity of 15%. The film cooling effectiveness and heat transfer coefficient distribution were obtained by the transient liquid crystal technology, three mass flow ratios (MFR=7.0%, 9.9%, 11%) and two density ratios (DR=1.0, 1.5) were tested. The results show that the film cooling effectiveness distribution on the suction side is more uniform and the coolant injection trajectory is much longer than that on the pressure side. As the density ratio increasing to 1.5, the more laterally uniform film cooling effectiveness contour on the pressure side is observed and the spatially averaged film cooling effectiveness is increased by 11%∼43%. For the MFR=7.0%, the coolant injection with low momentum thickens the boundary layer and reduces the heat transfer coefficient in the mid-chord region of the pressure side. Both the increased mass flow ratio and decreased density ratio result in a higher heat transfer coefficient, while do not alter the distribution trend. By calculating the heat flux ratio, the reduction in the heat flux at DR=1.5 is found to be within 20% in most areas than that of DR=1.0 on the vane surface.

scholarly journals Aerodynamic Performance of a Transonic Turbine Blade Passage in Presence of Upstream Slot and Mateface Gap With Endwall Contouring

2014 ◽  
Author(s):  
Sakshi Jain ◽  
Arnab Roy ◽  
Wing Ng ◽  
Srinath Ekkad ◽  
Andrew S. Lohaus ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Film Cooling ◽  
Operating Conditions ◽  
Blow Down ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Aerodynamic Loss ◽  
Exit Mach Number ◽  
The Heat Transfer Coefficient

The present article investigates mixed out aerodynamic loss coefficient measurements for a high turning, contoured endwall passage under transonic operating conditions in presence of upstream purge slot and mateface gap. The upstream purge slot represents the gap between stator-rotor interface and the mateface gap simulates the assembly feature between adjacent airfoils in an actual high pressure turbine stage. While the performance of the mateface and upstream slot has been studied for lower Mach number, no studies exist in literature for transonic flow conditions. Experiments were performed at the Virginia Tech’s linear, transonic blow down cascade facility. Measurements were carried out at design conditions (isentropic exit Mach number of 0.88, design incidence) without and with coolant blowing. Upstream leakage flow of 1.0% coolant to mainstream mass flow ratio (MFR) was considered with the presence of mateface gap. There was no coolant blowing through the mateface gap itself. Cascade exit pressure measurements were carried out using a 5-hole probe traverse at a plane 1.0-Cax downstream of the trailing edge. Spanwise measurements were performed to complete the entire 2D loss plane from endwall to midspan, which were used to plot pitchwise averaged losses for different span locations and loss contours for the passage. Results reveal significant reduction in aerodynamic losses using the contoured endwall due to the modification of flow physics compared to a non-contoured planar endwall. The heat transfer experiments, designed to find the heat transfer coefficient and the film cooling effectiveness are described in detail in a separate paper [1].

A New Test Facility to Investigate Film Cooling on a Non-Axisymmetric Contoured Turbine Endwall: Part II — Heat Transfer and Film Cooling Measurements

2015 ◽  
Author(s):  
Johannes Kneer ◽  
Franz Puetz ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Superposition Principle ◽  
Density Ratio ◽  
Open Loop ◽  
Test Facility ◽  
Gas Temperature ◽  
Test Rig ◽  
Linear Cascade ◽  
Exit Mach Number

The present work is part of a comprehensive heat transfer and film-cooling study on a locally cooled non-axisymmetric contoured turbine endwall. A new test rig consisting of a linear cascade of three prismatic vanes at unity scale and exchangeable endwall has been established. The rig is operated in an open-loop configuration at a reduced main gas temperature of 425 K, an exit Mach number of 0.5 and an exit Reynolds number of 1.6×106. Air is used both as main gas and coolant; a realistic density ratio is achieved by cooling the coolant below freezing. In Part I [1] of the study aerodynamic measurements are presented. This paper concentrates on film-cooling of the contoured endwall with special emphasis on data acquisition and reduction for the application of the superposition principle of film cooling. The first experimental results from thermographic measurements are discussed.

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.

The Influence of a Laminar Boundary Layer and Laminar Injection on Film Cooling Performance

1982 ◽  
Vol 104 (2) ◽  
pp. 355-362 ◽  
Author(s):  
R. J. Goldstein ◽  
T. Yoshida
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Film Cooling ◽  
Transport Mechanisms ◽  
Flow Measurements ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Flow

Measurements are reported of the film cooling effectiveness and heat transfer following injection of air into a mainstream of air. A single row of circular injection holes inclined at an angle of 35 deg is used with a lateral spacing between the holes of 3 dia. Low Reynolds number mainstream and injection flow permit studying the influence of a laminar approaching boundary layer and laminar film coolant flow. Measurements of the surface heat transfer taken with no injection indicate that the hole openings can effectively trip the laminar boundary layer into a turbulent flow. The type of the approaching boundary layer has relatively little influence on either the adiabatic effectiveness or the heat transfer with film cooling. The importance of the nature of the injected flow on film cooling performance can at least be qualitatively explained by the differences in the transport mechanisms and in the penetration of the injected air into the mainstream.

A New Test Facility to Investigate Film Cooling on a Nonaxisymmetric Contoured Turbine Endwall—Part II: Heat Transfer and Film Cooling Measurements

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Johannes Kneer ◽  
Franz Puetz ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Superposition Principle ◽  
Density Ratio ◽  
Open Loop ◽  
Test Facility ◽  
Gas Temperature ◽  
Test Rig ◽  
Linear Cascade ◽  
Exit Mach Number

The present work is part of a comprehensive heat transfer and film-cooling study on a locally cooled nonaxisymmetric contoured turbine endwall. A new test rig consisting of a linear cascade of three prismatic vanes at unity scale and exchangeable endwall has been established. The rig is operated in an open-loop configuration at a reduced main gas temperature of 425 K, an exit Mach number of 0.5, and an exit Reynolds number of 1.6 × 106. Air is used both as main gas and coolant; a realistic density ratio is achieved by cooling the coolant below freezing. In the first part of the study, aerodynamic measurements are presented. This paper concentrates on film cooling of the contoured endwall with special emphasis on data acquisition and reduction for the application of the superposition principle of film cooling. The first experimental results from thermographic measurements are discussed.

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

2020 ◽  
Author(s):  
Zhigang Li ◽  
Bo Bai ◽  
Jun Li ◽  
Shuo Mao ◽  
Wing Ng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Film Cooling ◽  
Secondary Flows ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Injection Flow ◽  
Coolant Injection ◽  
Turbine Vane ◽  
Endwall Cooling

Abstract Flow fields near the turbine vane endwall region are very complicated due to the presence of highly three-dimensional passage vortices and endwall secondary flows. This makes it challenging for the endwall to be effectively cooled by employing traditional endwall cooling methods, such as impingement cooling combined with local film cooling inside the vane passage. One effective endwall cooling scheme: coolant injection flow through discrete holes upstream of the vane leading edge on the endwall, has been considered by many gas turbine companies. The present paper focuses on endwall film cooling effectiveness evaluation with upstream coolant injection through discrete holes. 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 endwall tested was a scaled up inner endwall of an industrial transonic turbine vane with double-row discrete cylindrical film cooling holes located 0.39Cx upstream of the vane leading edge. 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. A detailed numerical method validation was performed for four different Reynolds-averaged turbulence models. The Realizable κ-ϵ model was validated to be suitable to obtain reliable numerical solution. The influences of a wide range of coolant-to-mainstream blowing ratios (BR = 1.0, 1.5, 1.9, 2.5, 3.0, 3.5) were numerically studied. Complex interactions between coolant injections and secondary flows in vane passage were presented and discussed. Results indicate that for lower values of BR, the endwall coolant coverage from the upstream double-row discrete holes is strongly controlled by the passage secondary flow, thus the cooling effectiveness is very poor. As the BR increases, the strong secondary flow in vane passage can be suppressed by the coolant injections and begin to be almost eliminated when BR increases to a critical value (BR = 2.5 – 3.0). Beyond the critical BR, most of the injected coolant begins to lift off from the endwall and penetrate significantly into the mainstream flow, yielding inefficient endwall cooling performance.

scholarly journals Film Cooling Effectiveness and Mass/Heat Transfer Coefficient Downstream of One Row of Discrete Holes

1998 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin ◽  
R. L. Olson
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35° inclination angle with 3d hole spacing and relatively small hole length to diameter ratio (L/d = 6.3). Both film cooling effectiveness and mass/heat transfer coefficient are determined for blowing rates from 0.5 to 2.0 with density ratio of 1.0. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficient obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. The laterally-averaged and local film cooling effectiveness agree with previous experiments. The difference between mass/heat transfer coefficients and previous heat transfer results indicates that conduction error may play an important role in the earlier heat transfer measurements.

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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