scholarly journals Adiabatic Effectiveness and Heat Transfer Coefficient of Shaped Film Cooling Holes on a Scaled Guide Vane Pressure Side Model

2004 ◽  
Vol 10 (5) ◽  
pp. 345-354 ◽  
Author(s):  
Jan Dittmar ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Guide Vane ◽  
Inlet Temperature ◽  
Test Model ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The demand of improved thermal efficiency and high power output of modern gas turbine engines leads to extremely high turbine inlet temperature and pressure ratios. Sophisticated cooling schemes including film cooling are widely used to protect the vanes and blades of the first stages from failure and to achieve high component lifetimes. In film cooling applications, injection from discrete holes is commonly used to generate a coolant film on the blade's surface.In the present experimental study, the film cooling performance in terms of the adiabatic film cooling effectiveness and the heat transfer coefficient of two different injection configurations are investigated. Measurements have been made using a single row of fanshaped holes and a double row of cylindrical holes in staggered arrangement. A scaled test model was designed in order to simulate a realistic distribution of Reynolds number and acceleration parameter along the pressure side surface of an actual turbine guide vane. An infrared thermography measurement system is used to determine highly resolved distribution of the models surface temperature. Anin-situcalibration procedure is applied using single embedded thermocouples inside the measuring plate in order to acquire accurate local temperature data.All holes are inclined 35° with respect to the model's surface and are oriented in a streamwise direction with no compound angle applied. During the measurements, the influence of blowing ratio and mainstream turbulence level on the adiabatic film cooling effectiveness and heat transfer coefficient is investigated for both of the injection configurations.

Comparison of Numerical Investigations With Measured Heat Transfer Performance of a Film Cooled Turbine Vane

2008 ◽  
Author(s):  
D. Charbonnier ◽  
P. Ott ◽  
M. Jonsson ◽  
Th. Ko¨bke ◽  
F. Cottier
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Measurement Data ◽  
External Flow ◽  
Test Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

Detailed surface measurements of the heat transfer coefficient and the film cooling effectiveness by application of the transient liquid crystal method were carried out on a heavily film cooled nozzle guide vane (NGV) in a linear cascade wind tunnel at the EPFL as part of the European Research Project TATEF2 (Turbine Aero-Thermal External Flows 2). The external cooling setup included a showerhead cooling scheme and suction and pressure side of the airfoil several rows of fan-shaped cooling holes. By testing two different cooling flow rates at a NGV exit Reynolds number of 1.46E+06, detailed aerodynamic and heat transfer measurement data were obtained that can be used for validation of numerical codes and design tools for cooled airfoils. The data include the NGV surface static pressure distribution and wall heat transfer and film cooling effectiveness obtained by application of the transient liquid crystal technique. An engine representative density ratio between the coolant and the external hot gas flow was achieved by using CO2 as coolant gas. For the coupled simulation of internal cooling and external flow the numerical model was composed of the cooling air feeding the internal plenum, the cooling holes, and the outer external flow domain. An unstructured mesh was generated for the simulations by applying two different commercial CFD codes (Fluent and CFX). Identical boundary conditions were chosen in order to allow for a direct comparison of both codes. The computations were carried in two ways, first using a built-in transition model and second by imposing fully turbulent flow starting at the leading edge. For both codes the same built-in turbulence models were applied. The computations were set up to solve for the aerodynamic flow quantities both within and around the test model and for the thermal quantities on the vane surface, i.e. heat transfer coefficient and film cooling effectiveness. The computational results from the two codes are compared and validated against the results from the experiments. The numerical results were able to confirm a suspicion that the cross flow in the feeding plenum causes an observed non-symmetry of the measured film cooling effectiveness at the outlet of some cooling holes.

Heat Transfer Coefficient and Film-Cooling Effectiveness on a Gas Turbine Blade Tip

2002 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Film Cooling ◽  
Rotor Blade ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blade Tip

The detailed distributions of heat transfer coefficient and film cooling effectiveness on a gas turbine blade tip were measured using a hue detection based transient liquid crystal technique. Tests were performed on a five-bladed linear cascade with blow down facility. The blade was a 2-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The Reynolds number based on cascade exit velocity and axial chord length was 1.1 × 106 and the total turning angle of the blade was 97.7°. The overall pressure ratio was 1.32 and the inlet and exit Mach number were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. The blade model was equipped with a single row of film cooling holes at both the tip portion along the camber line and near the tip region of the pressure-side. All measurements were made at the three different tip gap clearances of 1%, 1.5%, and 2.5% of blade span and the three blowing ratios of 0.5, 1.0, and 2.0. Results showed that, in general, heat transfer coefficient and film effectiveness increased with increasing tip gap clearance. As blowing ratio increased, heat transfer coefficient decreased, while film effectiveness increased. Results also showed that adding pressure-side coolant injection would further decrease blade tip heat transfer coefficient but increase film effectiveness.

Numerical Evaluation of Influence of Internal Ribs on Heat Transfer in Flat Plate Film Cooling

2013 ◽  
Author(s):  
Yukiko Agata ◽  
Toshihiko Takahashi ◽  
Eiji Sakai ◽  
Koichi Nishino
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Inlet

To augment the thermal efficiency of combined power generation plants, the turbine inlet temperature of an industrial gas turbine has been increased. Cooling technology plays a vital role in the durability of gas turbine blades in situations in which the turbine inlet temperature exceeds the allowable temperature of the blade material. Cooling air is also directly associated with the reduction in thermal efficiency because bleed air from the compressor is used for turbine cooling. Thus, improvement in cooling performance has a marked impact on the further augmentation of thermal efficiency by increasing turbine inlet temperature. To evaluate film cooling performance on the basis of heat flux reduction, it is necessary to accurately estimate both heat transfer coefficient and adiabatic film cooling effectiveness. Most studies of film cooling, however, have focused on improving adiabatic film cooling effectiveness. In contrast, there are few studies focusing on heat transfer coefficient. One of the reasons for this is that adiabatic film cooling effectiveness is a performance parameter unique to film cooling. To preliminarily estimate the heat flux through a blade, heat transfer coefficient without film cooling can still be used as substitute. Moreover, the accurate CFD prediction of heat transfer coefficient with film cooling is difficult, compared with the evaluation of adiabatic film cooling effectiveness. Therefore, in this study, we addressed the CFD prediction of heat transfer coefficient with film cooling on a flat plate, and discussed its feasibility. Recent gas turbine blades operated at a turbine inlet temperature of over 1300 degree Celsius employ internal convection cooling with ribbed passages and external film cooling. These cooling technologies have been studied extensively, particularly regarding their individual effects. On the other hand, there are few investigations on the interaction between internal convection cooling and the film cooling. Although most of such film-cooling studies employed stagnant plenums to bleed cooling air, some researchers including the present authors have shown the marked impact of the conditions for supplying coolant air on film cooling performance. In this study, we focus particularly on the influence of internal rib orientation on external film cooling performance along the blade outer surface. CFD analysis is used to resolve the flow fields of the flat plate film cooling and to clarify the influence of rib orientation on heat-transfer.

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.

An Experimental Investigation of Adiabatic Film Cooling Effectiveness and Heat Transfer Coefficient on a Transonic Squealer Tip

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Andrew J. Saul ◽  
Peter T. Ireland ◽  
John D. Coull ◽  
Tsun Holt Wong ◽  
Haidong Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Film Cooling ◽  
Leakage Flow ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The effect of film cooling on a transonic squealer tip has been examined in a high speed linear cascade, which operates at engine-realistic Mach and Reynolds numbers. Tests have been performed on two uncooled tip geometries with differing pressure side rim edge radii, and a cooled tip matching one of the uncooled cases. The pressure sensitive paint technique has been used to measure adiabatic film cooling effectiveness on the blade tip at a range of tip gaps and coolant mass flow rates. Complementary tip heat transfer coefficients have been measured using transient infrared thermography, and the effects of the coolant film on the tip heat transfer and engine heat flux were examined. The uncooled data show that the tip heat transfer coefficient distribution is governed by the nature of flow reattachments and impingements. The squealer tip can be broken down into three regions, each exhibiting a distinct response to a change in the tip gap, depending on the local behavior of the overtip leakage flow. Complementary computational fluid dynamics (CFD) shows that the addition of casing motion causes no change in the flow over the pressure side rim. Injected coolant interacts with the overtip leakage flow, which can locally enhance the tip heat transfer coefficient. The film effectiveness is dependent on both the coolant mass flow rate and tip clearance. At increased coolant mass flow, areas of high film effectiveness on the pressure side rim coincide strongly with a net heat flux reduction and in the subsonic tip region with low heat transfer coefficient.

An Experimental Investigation of Adiabatic Film Cooling Effectiveness and Heat Transfer Coefficient on a Transonic Squealer Tip

2018 ◽  
Author(s):  
Andrew J. Saul ◽  
Peter T. Ireland ◽  
John D. Coull ◽  
Tsun Holt Wong ◽  
Haidong Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Film Cooling ◽  
Leakage Flow ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blade Tip

The effect of film cooling on a high pressure turbine blade with an open squealer tip has been examined in a high speed linear cascade. The cascade operates at engine realistic Mach and Reynolds numbers, producing transonic flow conditions over the blade tip. Tests have been performed on two uncooled tip geometries with differing pressure side rim edge radii, and a cooled tip matching one of the uncooled cases. The pressure sensitive paint technique has been used to measure adiabatic film cooling effectiveness on the blade tip at a range of tip gaps and coolant mass flow rates. Complementary tip heat transfer coefficients (HTC) have been measured using transient infrared thermography, and the effects of the coolant film on the tip heat transfer and engine heat flux examined. The uncooled data show that the tip heat transfer coefficient distribution is governed by the nature of flow reattachments and impingements. The squealer tip can be broken down into three regions, each exhibiting a distinct response to a change in the tip gap, depending on the local behaviour of the overtip leakage flow. The edge radius of the pressure side rim causes the overtip leakage flow to change dramatically at low clearance. Complementary CFD shows that the addition of casing motion causes no further change on the pressure side rim. Injected coolant interacts with the overtip leakage flow, which can locally enhance the tip heat transfer coefficient compared to the uncooled tip. The film effectiveness is dependent on both the coolant mass flow rate and tip clearance. At increased coolant mass flow, areas of high film effectiveness on the pressure side rim coincide strongly with a net heat flux reduction and in the subsonic tip region with low heat transfer coefficient.

Comparison of Gas Turbine Vane Pressure Side and Suction Side Film Cooling Performance and the Applicability of Superposition

2012 ◽  
Author(s):  
Mats Kinell ◽  
Esa Utriainen ◽  
Hossein Nadali Najafabadi ◽  
Matts Karlsson ◽  
Botond Barabas
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Gas Turbines ◽  
Suction Side ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
The Impact

In order to protect a solid surface exposed to high temperature gaseous flows, e.g. gas turbines and rocket engines, a second gas at lower temperature may be introduced into the hot boundary layer, i.e. one obtains a three temperature problem. The impact of the film cooling on a prototype vane due to variation in blowing ratio, the shape of the hole-outlet and position has been experimentally investigated. The semi-infinite and low conductive test object, initially at a uniform temperature, was exposed to a sudden step change in main flow temperature and a time-resolved surface temperature was measured using an IR camera. By assuming constant values of the heat transfer coefficient and the film cooling effectiveness over time, the heat equation was solved using least squares. The prototype vane was tested for different film cooling row positions on the pressure and suction side. Both cylindrical as well as fan shaped holes were investigated with and without showerhead cooling. The resulting heat transfer coefficient and film cooling effectiveness on the pressure side is compared to flat plate studies and to the results from the suction side. Also, the applicability of using superposition on showerhead cooling and on single/double rows is investigated. Furthermore, the results are compared to other published airfoil film cooling experiments and to CFD analysis for which conclusions are drawn on quantitative and qualitative capabilities of this tool.

Heat Transfer Coefficients and Film-Cooling Effectiveness on a Gas Turbine Blade Tip

2003 ◽  
Vol 125 (3) ◽  
pp. 494-502 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blade Tip

The detailed distributions of heat transfer coefficient and film cooling effectiveness on a gas turbine blade tip were measured using a hue detection based transient liquid crystals technique. Tests were performed on a five-bladed linear cascade with blow-down facility. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.7°. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. The blade model was equipped with a single row of film cooling holes at both the tip portion along the camber line and near the tip region of the pressure side. All measurements were made at the three different tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span and the three blowing ratios of 0.5, 1, and 2. Results showed that, in general, heat transfer coefficient and film effectiveness increased with increasing tip gap clearance. As blowing ratio increased, heat transfer coefficient decreased, while film effectiveness increased. Results also showed that adding pressure side coolant injection would further decrease the blade tip heat transfer coefficient but increase film-cooling effectiveness.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

2017 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Trench Width

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

Investigations on the Influence of Rib Orientation Angle on Film Cooling Performance of Compound Holes

2018 ◽  
Author(s):  
Lin Ye ◽  
Cun-liang Liu ◽  
Hai-yong Liu ◽  
Hui-ren Zhu ◽  
Jian-xia Luo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Orientation Angle ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

To investigate the effects of the inclined ribs on internal flow structure in film hole and the film cooling performance on outer surface, experimental and numerical studies are conducted on the effects of rib orientation angle on film cooling of compound cylindrical holes. Three coolant channel cases, including two ribbed cross-flow channels (135° and 45° angled ribs) and the plenum case, are studied under three blowing ratios (0.5, 1.0 and 2.0). 2D contours of film cooling effectiveness as well as heat transfer coefficient were measured by transient liquid crystal measurement technique (TLC). The steady RANS simulations with realizable k-ε turbulence model and enhanced wall treatment were performed. The results show that the spanwise width of film coverage is greatly influenced by the rib orientation angle. The spanwise width of the 45° rib case is obviously larger than that of the 135° rib case under lower blowing ratios. When the blowing ratio is 1.0, the area-averaged cooling effectiveness of the 135° rib case and the 45° rib case are higher than that of the plenum case by 38% and 107%, respectively. With the increase of blowing ratio, the film coverage difference between different rib orientation cases becomes smaller. The 45° rib case also produces higher heat transfer coefficient, which is higher than the 135° rib case by 3.4–8.7% within the studied blowing ratio range. Furthermore, the discharge coefficient of the 45° rib case is the lowest among the three cases. The helical motion of coolant flow is observed in the hole of 45° rib case. The jet divides into two parts after being blown out of the hole due to this motion, which induces strong velocity separation and loss. For the 135° rib case, the vortex in the upper half region of the secondary-flow channel rotates in the same direction with the hole inclination direction, which leads to the straight streamlines and thus results in lower loss and higher discharge coefficient.

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