Improving Film Cooling Performance Using Airfoil Contouring

2006 ◽  
Author(s):  
Atul Kohli ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Suction Side ◽  
Design Tool ◽  
Optimization Process ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Cfd Analyses ◽  
Low Speed Wind Tunnel

In this study, a CFD-based optimization process is used to change the contour of the airfoil near a suction side cooling hole in order to improve its film effectiveness characteristics. An overview of the optimization process, which includes automated geometry, grid generation and CFD analyses is provided. From the results for the optimized geometry it is clear that the detachment of the cooling jet is much reduced and the cooling jet spread in the spanwise direction is increased substantially. The new external contour was then tested in a low-speed wind tunnel to provide a direct measure of the predictive capability. Comparisons to verification test data indicate that good agreement was achieved for both pressure and film cooling effectiveness behavior. This study proves that despite its limitations, current RANS methodology can be used a viable design tool and lead to innovative concepts for improving film cooling effectiveness.

Improving Film Cooling Performance Using Airfoil Contouring

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Atul Kohli ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Suction Side ◽  
Design Tool ◽  
Optimization Process ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Cfd Analyses

In this study, a computational fluid dynamics (CFD)-based optimization process is used to change the contour of the airfoil near a suction-side cooling hole in order to improve its film effectiveness characteristics. An overview of the optimization process, which includes automated geometry, grid generation, and CFD analyses, is provided. From the results for the optimized geometry, it is clear that the detachment of the cooling jet is much reduced and the cooling jet spread in the spanwise direction is increased substantially. The new external contour was then tested in a low-speed wind tunnel to provide a direct measure of the predictive capability. Comparisons to verification test data indicate that good agreement was achieved for both pressure and film cooling effectiveness behavior. This study proves that despite its limitations, current Reynolds averaged Navier-Stokes (RANS) methodology can be used a viable design tool and lead to innovative concepts for improving film cooling effectiveness.

Effect of Rotation on Flow Field and Film Cooling Effectiveness in Film-Cooled Turbine Rotors

2014 ◽  
Vol 31 (4) ◽  
Author(s):  
Xiaocheng Zhu ◽  
Liangliang Liu ◽  
Feng Yuan
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Film Cooling ◽  
Suction Side ◽  
Wake Region ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Low Speed Wind Tunnel

AbstractExperimental and numerical investigations of flow field in a film-cooled turbine model under stationary and rotating conditions in a low-speed wind tunnel are conducted. The effects of different blowing ratios (M = 1.5, 2) on the flow field are studied. Results revealed a secondary flow near the blade surface in the wake region behind the jet hole. Compared with the stationary turbine, there exists centrifugal force and Coriolis force in the flow field of the rotating turbine, and these forces cause changes in the flow field in the rotating turbine. The effect of rotation on the flow field and film cooling effectiveness in the Y-Z planes on the pressure side is stronger than on the suction side, and results in lower film cooling effectiveness on the pressure surface of the rotating turbine blade compared with the stationary turbine. As the blowing ratio increases, the secondary flow in the wake region will become stronger, thereby enlarging the range of the wake.

Effects of Surface Roughness and Near Hole Obstructions on Film Cooling Effectiveness

2007 ◽  
Author(s):  
Ruwan P. Somawardhana ◽  
David G. Bogard
Keyword(s):  
Surface Roughness ◽  
Film Cooling ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

For a film cooled turbine airfoil, significant degradation of adiabatic effectiveness can be caused by near-hole obstructions formed from deposition of contaminants. Since obstructions are a randomly occurring event, there are many variables to consider, namely shape, width, length, height, and position in relation to a film cooling hole. In addition to this, the level of overall surface roughness also must be considered. An investigation was conducted on obstruction characteristics for a single row of holes on the suction side of a simulated turbine vane. It was found that degradation due to near-hole obstructions only occurred when upstream obstructions were present. When directly upstream, degradation levels around 40% were observed and obstruction height was the dominating characteristic.

Improved Trench Film Cooling With Shaped Trench Outlets

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Habeeb Idowu Oguntade ◽  
Gordon E. Andrews ◽  
A. D. Burns ◽  
Derek B. Ingham ◽  
Mohammed Pourkashanian
Keyword(s):  
Flat Plate ◽  
Mass Flow ◽  
Film Cooling ◽  
Cross Flow ◽  
Suction Side ◽  
Experimental Results ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Vertical Slot ◽  
Cooling Hole

The influence of the shape of the downstream edge of trench film cooling hole outlets on film cooling effectiveness was investigated using CFD for flat plate film cooling. A 90 deg trench outlet wall with impinging 30 deg film cooling jets results in improved transverse film cooling effectiveness but produces a vertical slot jet into the cross flow, which is not the best aerodynamics for optimum film cooling. It was considered that improvements in the cooling effectiveness would occur if the trailing edge of the trench outlet produced a flow that was inclined in the direction of the crossflow. Beveled and filleted trench outlet shapes were investigated. The CFD predictions were shown to predict well the conventional sharp edged trench outlet experimental results for a flat plate geometry. The flat plate CFD predictions were also shown to predict the experimental results for trench cooling on the suction side of a turbine vane, where the local curvature was small relative to the trench width. The beveled and filleted trench outlets were predicted to suppress the vertical jet momentum and give a Coanda effect that allowed the cooling air to attach to the downstream wall surface. This produced an improved transverse spread of the coolant. Also, it was predicted that reducing the coolant mass flow per hole and increasing the number of rows of holes gave, for the same total coolant mass flow and the same surface area, a superior surface averaged cooling effectiveness.

The Effects of Obstructions on Film Cooling Effectiveness on the Suction Side of a Gas Turbine Vane

2006 ◽  
Author(s):  
Patricia Demling ◽  
David G. Bogard
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Temperature Profiles ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

The effects of obstructions on film cooling performance on a scaled-up 1st stage turbine vane will be discussed. Experimental results show that obstructions located upstream or inside of a film cooling hole will degrade adiabatic effectiveness up to 80% of the levels found with no obstructions. Downstream obstructions had little effect on performance. The location where the upstream obstructions ceased to degrade adiabatic effectiveness was determined and temperature profiles were constructed to determine how the upstream obstructions were affecting the mainstream and coolant flow.

Investigations of improved cooling effectiveness for ramp film cooling with compound angle film cooling jets

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Krishna Anand Vasu Devan Nair Girija Kumari ◽  
Parammasivam Kanjikoil Mahali
Keyword(s):  
Film Cooling ◽  
Flat Surface ◽  
Flow Characteristics ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Content Type ◽  
Film Cooling Effectiveness ◽  
Ramp Test ◽  
Cooling Hole ◽  
Compound Angle

Purpose This paper aims to investigate the film cooling effectiveness (FCE) and mixing flow characteristics of the flat surface ramp model integrated with a compound angled film cooling jet. Design/methodology/approach Three-dimensional numerical simulation is performed on a flat surface ramp model with Reynolds Averaged Navier-Stokes approach using a finite volume solver. The tested model has a fixed ramp angle of 24° and a ramp width of two times the diameter of the film cooling hole. The coolant air is injected at 30° along the freestream direction. Three different film hole compound angles oriented to freestream direction at 0°, 90° and 180° were investigated for their performance on-ramp film cooling. The tested blowing ratios (BRs) are in the range of 0.9–2.0. Findings The film hole oriented at a compound angle of 180° has improved the area-averaged FCE on the ramp test surface by 86.74% at a mid-BR of 1.4% and 318.75% at higher BRs of 2.0. The 180° film hole compound angle has also produced higher local and spanwise averaged FCE on the ramp test surface. Originality/value According to the authors’ knowledge, this study is the first of its kind to investigate the ramp film cooling with a compound angle film cooling hole. The improved ramp model with a 180° film hole compound angle can be effectively applied for the end-wall surfaces of gas turbine film cooling.

Comparison of RANS and DES Modeling Against Measurements of Leading Edge Film Cooling on a First-Stage Vane

2016 ◽  
Author(s):  
S. Ravelli ◽  
G. Barigozzi
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Leading Edge ◽  
Spanwise Direction ◽  
Intensity Level ◽  
Edge Region ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Adiabatic Effectiveness

The performance of a showerhead arrangement of film cooling in the leading edge region of a first stage nozzle guide vane was experimentally and numerically evaluated. A six-vane linear cascade was tested at an isentropic exit Mach number of Ma2s = 0.42, with a high inlet turbulence intensity level of 9%. The showerhead cooling scheme consists of four staggered rows of cylindrical holes evenly distributed around the stagnation line, angled at 45° towards the tip. The blowing ratios tested are BR = 2.0, 3.0 and 4.0. Adiabatic film cooling effectiveness distributions on the vane surface around the leading edge region were measured by means of Thermochromic Liquid Crystals technique. Since the experimental contours of adiabatic effectiveness showed that there is no periodicity across the span, the CFD calculations were conducted by simulating the whole vane. Within the RANS framework, the very widely used Realizable k-ε (Rke) and the Shear Stress Transport k-ω (SST) turbulence models were chosen for simulating the effect of the BR on the surface distribution of adiabatic effectiveness. The turbulence model which provided the most accurate steady prediction, i.e. Rke, was selected for running Detached Eddy Simulation at the intermediate value of BR = 3. Fluctuations of the local temperature were computed by DES, due to the vortex structures within the shear layers between the main flow and the coolant jets. Moreover, mixing was enhanced both in the wall-normal and spanwise direction, compared to RANS modeling. DES roughly halved the prediction error of laterally averaged film cooling effectiveness on the suction side of the leading edge. However, neither DES nor RANS provided the expected decay of effectiveness progressing downstream along the pressure side, with 15% overestimation of ηav at s/C =0.2.

Rib Turbulator Effects on Crossflow-Fed Shaped Film Cooling Holes

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Dale W. Fox ◽  
Fraser B. Jones ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
...  
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Smooth Channel ◽  
Cooling Hole ◽  
Film Cooling Holes ◽  
Inlet Position ◽  
The Impact

Most studies of turbine airfoil film cooling in laboratory test facilities have used relatively large plenums to feed flow into the coolant holes. However, a more realistic inlet condition for the film cooling holes is a relatively small channel. Previous studies have shown that the film cooling performance is significantly degraded when fed by perpendicular internal crossflow in a smooth channel. In this study, angled rib turbulators were installed in two geometric configurations inside the internal crossflow channel, at 45 deg and 135 deg, to assess the impact on film cooling effectiveness. Film cooling hole inlets were positioned in both prerib and postrib locations to test the effect of hole inlet position on film cooling performance. A test was performed independently varying channel velocity ratio and jet to mainstream velocity ratio. These results were compared to the film cooling performance of previously measured shaped holes fed by a smooth internal channel. The film cooling hole discharge coefficients and channel friction factors were also measured for both rib configurations with varying channel and inlet velocity ratios. Spatially averaged film cooling effectiveness is largely similar to the holes fed by the smooth internal crossflow channel, but hole-to-hole variation due to inlet position was observed.

scholarly journals Adiabatic Wall Effectiveness Measurements of Film-Cooling Holes With Expanded Exits

1997 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Thermal Protection ◽  
Lateral Spreading ◽  
Cylindrical Hole ◽  
Adiabatic Wall ◽  
Camera System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper presents detailed measurements of the film-cooling effectiveness for three single, scaled-up film-cooling hole geometries. The hole geometries investigated include a cylindrical hole and two holes with a diffuser shaped exit portion (i.e. a fanshaped and a laidback fanshaped hole). The flow conditions considered are the crossflow Mach number at the hole entrance side (up to 0.6), the crossflow Mach number at the hole exit side (up to 1.2), and the blowing ratio (up to 2). The coolant-to-mainflow temperature ratio is kept constant at 0.54. The measurements are performed by means of an infrared camera system which provides a two-dimensional distribution of the film-cooling effectiveness in the nearfield of the cooling hole down to x/D = 10. As compared to the cylindrical hole, both expanded holes show significantly improved thermal protection of the surface downstream of the ejection location, particularly at high blowing ratios. The laidback fanshaped hole provides a better lateral spreading of the ejected coolant than the fanshaped hole which leads to higher laterally averaged film-cooling effectiveness. Coolant passage crossflow Mach number and orientation strongly affect the flowfield of the jet being ejected from the hole and, therefore, have an important impact on film-cooling performance.

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