Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements: Part I — Showerhead Effects

2002 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Leading Edge ◽  
Field Measurements ◽  
Companion Paper ◽  
Hole Diameter ◽  
Pressure Side ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
High Turbulence

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e. flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.

Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part I: Showerhead Effects

2002 ◽  
Vol 124 (4) ◽  
pp. 670-677 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Leading Edge ◽  
Field Measurements ◽  
Companion Paper ◽  
Hole Diameter ◽  
Pressure Side ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
High Turbulence

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e., flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.

Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements: Part II — Turbulence Effects

2002 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Large Scale ◽  
Field Measurements ◽  
Pressure Side ◽  
Thermal Fields ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
Average Distribution ◽  
Adiabatic Effectiveness

This study focused on the film cooling performance on the pressure side of a turbine vane subjected to high mainstream turbulence levels, with and without showerhead blowing. Whereas previous studies have measured the adiabatic effectiveness and heat transfer at the surface of the airfoil, the goal of this study was to examine the flow and thermal fields above the surface. These measurements included flow visualization, thermal profiles, and laser Doppler velocimetry. For comparison, adiabatic effectiveness was also measured. A mainstream turbulence level of Tu∞ = 20%, with integral length scale of seven hole diameters, was used. Particularly insightful is the discovery that the large scale high mainstream turbulence causes a lateral oscillation of coolant jet resulting in a much wider time average distribution of coolant. Even with high mainstream turbulence, showerhead blowing was found to still cause a significantly increased dispersion of the pressure side coolant jets.

Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part II: Turbulence Effects

2002 ◽  
Vol 124 (4) ◽  
pp. 678-685 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Large Scale ◽  
Field Measurements ◽  
Pressure Side ◽  
Thermal Fields ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
Average Distribution ◽  
Adiabatic Effectiveness

This study focused on the film cooling performance on the pressure side of a turbine vane subjected to high mainstream turbulence levels, with and without showerhead blowing. Whereas previous studies have measured the adiabatic effectiveness and heat transfer at the surface of the airfoil, the goal of this study was to examine the flow and thermal fields above the surface. These measurements included flow visualization, thermal profiles, and laser Doppler velocimetry. For comparison, adiabatic effectiveness was also measured. A mainstream turbulence level of Tu∞=20%, with integral length scale of seven hole diameters, was used. Particularly insightful is the discovery that the large-scale high mainstream turbulence causes a lateral oscillation of coolant jet resulting in a much wider time average distribution of coolant. Even with high mainstream turbulence, showerhead blowing was found to still cause a significantly increased dispersion of the pressure side coolant jets.

Evaluation of Superposition Predictions for Showerhead Film Cooling on a Vane

2014 ◽  
Author(s):  
Joshua B. Anderson ◽  
James R. Winka ◽  
David G. Bogard ◽  
Michael E. Crawford
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Edge Region ◽  
Current Investigation ◽  
Engine Design ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

The leading edge of a turbine vane is subject to some of the highest temperature loading within an engine, and an accurate understanding of leading edge film coolant behavior is essential for modern engine design. Although there have been many investigations of the adiabatic effectiveness for showerhead film cooling of a vane leading edge region, there have been no previous studies in which individual rows of the showerhead were tested with the explicit intent of validating superposition models. For the current investigation, a series of adiabatic effectiveness experiments were performed with a five-row and three-row showerhead. The experiments were repeated separately with each individual row of holes active. This allowed evaluation of superposition methods on both the suction side of the vane, which was moderately convex, and the pressure side of the vane, which was mildly concave. Superposition was found to accurately predict performance on the suction side of the vane at lower momentum flux ratios, but not at higher momentum flux ratios. On the pressure side of the vane the superposition predictions were consistently lower than measured values, with significant errors occurring at the higher momentum flux ratios. Reasons for the under-prediction by superposition analysis are presented.

Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade

2012 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Ranjan Saha ◽  
Jens Fridh ◽  
Torsten Fransson
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Film Cooling ◽  
Guide Vane ◽  
Leading Edge ◽  
Field Measurements ◽  
Co2 Concentration ◽  
Pressure Side ◽  
Trailing Edge ◽  
Nozzle Guide

An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge can be used to visualize the mixing of the coolant flow with the mainstream. Flow field measurements are performed in the downstream plane with a 5-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side of the vane trailing edge where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge does not reach the pressure side endwall, potentially creating a local hotspot.

Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane

2014 ◽  
Author(s):  
Hossein Nadali Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell ◽  
Esa Utriainen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Time Resolved ◽  
Turbine Vane

Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge. The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.

Experimental Simulation of Contaminant Deposition on a Film Cooled Turbine Vane Pressure Side With a Trench

2011 ◽  
Author(s):  
Jason E. Albert ◽  
David G. Bogard
Keyword(s):  
Surface Temperature ◽  
Film Cooling ◽  
Leading Edge ◽  
Stokes Number ◽  
Experimental Simulation ◽  
Pressure Side ◽  
Standard Design ◽  
Turbine Vane ◽  
Side Body ◽  
Film Cooling Holes

An important issue in the use of coal- or biomass-derived synthetic gaseous (syngas) fuels is the deposition of contaminants on film cooled turbine surfaces, which alter cooling and aerodynamic performance and increase material degradation. The current study applied a new experimental technique that simulated the key physical aspects of contaminant deposition on a film cooled turbine vane. The depositing contaminants were modeled in a wind tunnel facility with a spray of molten wax droplets of a size range that matched the Stokes number of the contaminant particles in engine conditions. Most experiments were performed using a vane model with a thermal conductivity selected such that the model had the same Biot number of an actual engine airfoil, resulting in a cooler surface temperature. Some experiments were performed using an approximately adiabatic model for comparison. The film cooling design consisted of three rows of showerhead cooling at the leading edge and one row of body film cooling holes on the pressure side. Two designs of pressure side body film cooling holes were considered: a standard design of straight, cylindrical holes and an advanced design of “trenched” cooling holes in which the hole exits were situated in a recessed, transverse trench. The results showed thin deposits formed in the trench, with the thickest deposits on its downstream wall between coolant jets. Adiabatic film effectiveness levels were essentially unchanged by the presence of deposits for either film configuration. Deposit formation was strongly influenced by the model surface temperature with cooler surfaces inhibiting deposition. There was evidence of a threshold surface temperature above which deposits became significantly thicker.

scholarly journals Conjugate Heat Transfer Investigation on Swirl-Film Cooling at the Leading Edge of a Gas Turbine Vane

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 1007 ◽  
Author(s):  
Du ◽  
Mei ◽  
Zou ◽  
Jiang ◽  
Xie
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Leading Edge ◽  
Pressure Side ◽  
Cooling Efficiency ◽  
Cooling Effectiveness ◽  
Turbine Vane ◽  
Cooling Chamber

Numerical calculation of conjugate heat transfer was carried out to study the effect of combined film and swirl cooling at the leading edge of a gas turbine vane with a cooling chamber inside. Two cooling chambers (C1 and C2 cases) were specially designed to generate swirl in the chamber, which could enhance overall cooling effectiveness at the leading edge. A simple cooling chamber (C0 case) was designed as a baseline. The effects of different cooling chambers were studied. Compared with the C0 case, the cooling chamber in the C1 case consists of a front cavity and a back cavity and two cavities are connected by a passage on the pressure side to improve the overall cooling effectiveness of the vane. The area-averaged overall cooling effectiveness of the leading edge () was improved by approximately 57%. Based on the C1 case, the passage along the vane was divided into nine segments in the C2 case to enhance the cooling effectiveness at the leading edge, and was enhanced by 75% compared with that in the C0 case. Additionally, the cooling efficiency on the pressure side was improved significantly by using swirl-cooling chambers. Pressure loss in the C2 and C1 cases was larger than that in the C0 case.

Effects of TBC Thickness on an Internally and Film Cooled Model Turbine Vane

2014 ◽  
Author(s):  
William R. Stewart ◽  
David A. Kistenmacher ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Convective Heat Transfer Coefficient ◽  
Hole Diameter ◽  
Thermal Barrier ◽  
Internal Cooling ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Barrier Coating ◽  
Turbine Vane ◽  
Overall Effectiveness

Previous tests simulating the effects of TBC (thermal barrier coating) on an internally and film cooled model turbine vane showed that the insulating effects of TBC dominate over variations in film cooling geometry and blowing ratio. In this study overall and external effectiveness were measured using a matched Biot number model vane simulating a TBC of thickness 0.6d, where d is the film cooing hole diameter. This was a 35% reduction in thermal resistance from previous tests. Overall effectiveness measurements were taken for an internal cooling only configuration, as well as for three rows of showerhead holes with a single row of holes on the pressure side of the vane. This pressure side row of holes was tested both as round holes and as round holes embedded in a realistic trench with a depth of 0.6 hole diameters. Even in the case of this thinner TBC, the insulating effects dominate over film cooling. In addition, using measurements of the convective heat transfer coefficient above the vane surface, and the thermal conductivities of the vane wall and simulated TBC material, the overall effectiveness of the thin TBC thickness can be predicted from the thick TBC data, for an internal cooling only configuration.

Flow Field Measurements on a Large Scale Turbine Cascade With Leading Edge Film Cooling by Two Rows of Holes

1997 ◽  
Author(s):  
Sabine Ardey ◽  
Leonhard Fottner
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Vortex Pair ◽  
Leading Edge ◽  
Field Measurements ◽  
Suction Side ◽  
Pressure Side ◽  
Turbine Cascade

To increase the understanding of the aerodynamic processes dominating the flow field of turbine bladings with leading edge film cooling, isothermal investigations were carried out on a large scale high pressure turbine cascade. Near the stagnation point the blades are equipped with one row of film cooling holes on the suction side and one on the pressure side. Blowing ratio, turbulence intensity, Mach number, and Reynolds number are set to values typically found in modern gas turbines. Experimental data of the cascade flow were obtained by pneumatic probes and static pressure tappings. The flow field was visualized by Schlieren and oil flow techniques. For detailed investigations near the blowing holes the Laser Transit Velocimetry and the three dimensional Hot Wire Anemometry were used. The flow field measurements in the near hole region of the suction side show the typical kidney shaped vortex pair. A local suction peak on the pressure side causes a large recirculation area behind the holes on the pressure side and induces separation bubbles in between the pressure side holes. This leads to the generation of two pairs of vortices: The kidney-vortex is located on top of a second vortex pair and a trough flow that fills up the deficit of the recirculation. Thus the film cooling air is detached from the pressure side surface. In addition to the mean flow vectors Reynolds stress components are a good means to judge the propagation of the jet. In spite of the complex flow pattern occurring on each single jet, the surveyed loss-increase due to the leading edge blowing can be predicted by the mixing layer model.

Sign in / Sign up

Export Citation Format

Share Document