Modeling of Film Cooling—Part I: Experimental Study of Flow Structure

2005 ◽  
Vol 128 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Stefan Bernsdorf ◽  
Martin G. Rose ◽  
Reza S. Abhari
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Flow Structures ◽  
Pressure Side ◽  
Three Dimensional Flow ◽  
Blowing Ratio ◽  
Air Streams ◽  
Cooling Part ◽  
Cooling Model

This paper, which is Part I of a two part paper, reports on experimental data taken in a steady flow, flat plate wind tunnel at ETH Zürich, while Part II utilizes this data for calibration and validation purpose of a film cooling model embedded in a 3D CFD code. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative nondimensionals are achieved, providing a faithful model at larger scale. Heating the freestream air and strongly cooling the coolant gives the required density ratio between coolant and freestream. The three dimensional velocities are recorded using nonintrusive PIV; seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The three dimensional flow structures are revealed.

Modelling of Film Cooling: Part I — Experimental Study of Flow Structure

2005 ◽  
Author(s):  
Stefan Bernsdorf ◽  
Martin G. Rose ◽  
Reza S. Abhari
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Three Dimensional ◽  
Pressure Side ◽  
Three Dimensional Flow ◽  
Blowing Ratio ◽  
Air Streams ◽  
Cooling Part ◽  
Cooling Model

This paper, which is Part I of a two part paper, reports on new experimental data taken in a steady flow, flat plate wind tunnel at ETH Zu¨rich, while Part II utilizes this data for calibration and validation purpose of a new film cooling model embedded in a 3D CFD code. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative non-dimensionals are achieved, providing a faithful model at larger scale. Heating the free stream air and strongly cooling the coolant gives the required density ratio between coolant and free-stream. The three dimensional velocities are recorded using non-intrusive PIV, seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The three dimensional flow structures are revealed.

Experimental Validation of Quasisteady Assumption in Modeling of Unsteady Film-Cooling

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Stefan Bernsdorf ◽  
Martin G. Rose ◽  
Reza S. Abhari
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Three Dimensional ◽  
Flow Region ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Jet Trajectory ◽  
Air Streams

This paper reports on the validation of the assumption of quasisteady behavior of pulsating cooling injection in the near hole flow region. The respective experimental data are taken in a flat plate wind tunnel at ETH Zürich. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative nondimensionals are achieved, providing a faithful model at a larger scale. Heating the free stream air and strongly cooling the coolant gives the required density ratio between coolant and free-stream. The coolant is injected with different frequency and amplitude. The three-dimensional velocities are recorded using nonintrusive PIV, and seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The general flow field, the jet trajectory, and the streamwise circulation are utilized in the validation of the quasisteady assumption.

Experimental Validation of Quasi-Steady Assumption in Modelling of Unsteady Film-Cooling

2006 ◽  
Author(s):  
Stefan Bernsdorf ◽  
Martin G. Rose ◽  
Reza S. Abhari
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Three Dimensional ◽  
Flow Region ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Jet Trajectory ◽  
Air Streams

This paper reports on the validation of the assumption of quasi steady behaviour of pulsating cooling injection in the near hole flow region. The respective experimental data are taken in a flat plate wind tunnel at ETH Zu¨rich. The facility simulates the film cooling row flow field on the pressure side of a turbine blade. Engine representative non-dimensionals are achieved, providing a faithful model at larger scale. Heating the free stream air and strongly cooling the coolant gives the required density ratio between coolant and free-stream. The coolant is injected with different frequency and amplitude. The three dimensional velocities are recorded using non-intrusive PIV, seeding is provided for both air streams. Two different cylindrical hole geometries are studied, with different angles. Blowing ratio is varied over a range to simulate pressure side film cooling. The general flow field, the jet trajectory and the streamwise circulation are utilized in the validation of the quasi steady assumption.

Numerical Investigation of Coolant-to-Mainstream Scaling Parameters With Film Cooling on Pressure and Suction Side of a Gas Turbine Blade

2017 ◽  
Author(s):  
Lingyu Zeng ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Momentum Flux ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Flux Ratio ◽  
Suction Side ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Most experiments of blade film cooling are conducted with density ratio lower than that of turbine conditions. In order to accurately model the performance of film cooling under a high density ratio, choosing an appropriate coolant to mainstream scaling parameter is necessary. The effect of density ratio on film cooling effectiveness on the surface of a gas turbine twisted blade is investigated from a numerical point of view. One row of film holes are arranged in the pressure side and two rows in the suction side. All the film holes are cylindrical holes with a pitch to diameter ratio P/d = 8.4. The inclined angle is 30°on the pressure side and 34° on the suction side. The steady solutions are obtained by solving Reynolds-Averaged-Navier-Stokes equations with a finite volume method. The SST turbulence model coupled with γ-θ transition model is applied for the present simulations. A film cooling experiment of a turbine vane was done to validate the turbulence model. Four different density ratios (DR) from 0.97 to 2.5 are studied. To independently vary the blowing ratio (M), momentum flux ratio (I) and velocity ratio (VR) of the coolant to the mainstream, seven conditions (M varying from 0.25 to 1.6 on the pressure side and from 0.25 to 1.4 on the suction side) are simulated for each density ratio. The results indicate that the adiabatic effectiveness increases with the increase of density ratio for a certain blowing ratio or a certain momentum flux ratio. Both on the pressure side and suction side, none of the three parameters listed above can serve as a scaling parameter independent of density ratio in the full range. The velocity ratio provides a relative better collapse of the adiabatic effectiveness than M and I for larger VRs. A new parameter describing the performance of film cooling is introduced. The new parameter is found to be scaled with VR for nearly the whole range.

Influence of Coolant Density on Turbine Blade Film Cooling at Transonic Cascade Flow Conditions Using the Pressure Sensitive Paint Technique

2021 ◽  
Author(s):  
Izhar Ullah ◽  
Sulaiman M. Alsaleem ◽  
Lesley M. Wright ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Pressure Side ◽  
Pressure Sensitive Paint ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Pressure Sensitive ◽  
Blade Tip ◽  
Film Cooling Holes

Abstract This work is an experimental study of film cooling effectiveness on a blade tip in a stationary, linear cascade. The cascade is mounted in a blowdown facility with controlled inlet and exit Mach numbers of 0.29 and 0.75, respectively. The free stream turbulence intensity is measured to be 13.5 % upstream of the blade’s leading edge. A flat tip design is studied, having a tip gap of 1.6%. The blade tip is designed to have 15 shaped film cooling holes along the near-tip pressure side (PS) surface. Fifteen vertical film cooling holes are placed on the tip near the pressure side. The cooling holes are divided into a 2-zone plenum to locally maintain the desired blowing ratios based on the external pressure field. Two coolant injection scenarios are considered by injecting coolant through the tip holes only and both tip and PS surface holes together. The blowing ratio (M) and density ratio (DR) effects are studied by testing at blowing ratios of 0.5, 1.0, and 1.5 and three density ratios of 1.0, 1.5, and 2.0. Three different foreign gases are used to create density ratio effect. Over-tip flow leakage is also studied by measuring the static pressure distributions on the blade tip using the pressure sensitive paint (PSP) measurement technique. In addition, detailed film cooling effectiveness is acquired to quantify the parametric effect of blowing ratio and density ratio on a plane tip design. Increasing the blowing ratio and density ratio resulted in increased film cooling effectiveness at all injection scenarios. Injecting coolant on the PS and the tip surface also resulted in reduced leakage over the tip. The conclusions from this study will provide the gas turbine designer with additional insight on controlling different parameters and strategically placing the holes during the design process.

Numerical Investigation on Film Cooling Effectiveness of Stator Blade with Different Density Ratio

2014 ◽  
Vol 521 ◽  
pp. 104-107
Author(s):  
Ling Zhang ◽  
Quan Heng Jin ◽  
Da Fei Guo
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Middle Section ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Stator Blade

The Realizable k-ε turbulence model was performed to investigate the film cooling effectiveness with different blowing ratio 1,1.5,2 and different density ratio 1,1.5,2.The results show that, cooling effectiveness increases with the augment of blowing ratio. On the pressure side, cooling effectiveness increases with the augment of density ratio. On the suction side, with higher density ratio the leading edge cooling increases, the middle section reduces, and the trailing edge cooling effectiveness increases first decreases.

Performance Evaluation of a Novel Film-Cooling Hole

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Ki-Don Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Lateral Spreading ◽  
The Novel ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Shaped Hole

This paper presents a numerical investigation of the film-cooling performance of a novel film-cooling hole in comparison with a fan-shaped hole. The novel shaped hole is designed to increase the lateral spreading of coolant on the cooling surface. The film-cooling performance of the novel shaped hole is evaluated at a density ratio of 1.75 and the range of the blowing ratio of 0.5–2.5. The simulations were performed using three-dimensional Reynolds-averaged Navier–Stokes analysis with the SST k-ω model. The numerical results for the fan-shaped hole show very good agreement with the experimental data. For the blowing ratio of 0.5, the novel shaped film-cooling hole shows a similar cooling performance as the fan-shaped hole. However, as the blowing ratio increases, the novel shaped hole shows greatly improved lateral spreading of the coolant and the cooling performance in terms of the film-cooling effectiveness in comparison with the fan-shaped hole.

Experimental Flow Structure Investigation of Compound Angled Film Cooling

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Vipluv Aga ◽  
Martin Rose ◽  
Reza S. Abhari
Keyword(s):  
Flat Plate ◽  
Flow Structure ◽  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Cooling Flow ◽  
Blowing Ratio ◽  
Single Compound

The experimental investigation of film-cooling flow structure provides reliable data for calibrating and validating a 3D feature based computational fluid dynamics (CFD) model being developed synchronously at the ETH Zurich. This paper reports on the flow structure of a film-cooling jet emanating from one hole in a row of holes angled 20 deg to the surface of a flat plate having a 45 deg lateral angle to the freestream flow in a steady flow, flat plate wind tunnel. This facility simulates a film-cooling row typically found on a turbine blade, giving engine representative nondimensionals in terms of geometry and operating conditions. The main flow is heated and the injected coolant is cooled strongly to obtain the requisite density ratio. All three velocity components were measured using a nonintrusive stereoscopic particle image velocimetry (PIV) system. The blowing ratio and density ratio are varied for a single compound angled geometry, and the complex three dimensional flow is investigated with special regard to vortical structure.

Pressure-Side Bleed Film Cooling: Part II — Unsteady Framework for Experimental and Computational Results

2002 ◽  
Author(s):  
D. Scott Holloway ◽  
James H. Leylek ◽  
Frederick A. Buck
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Viscous Sublayer ◽  
Pressure Side ◽  
Unusual Behavior ◽  
High Quality ◽  
Injection Point ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Unsteady Simulation

This study examines the unsteady transonic pressure-side bleed film cooling on the trailing edge of a turbine blade and resolves the key mechanism responsible for the unusual relationship between film cooling effectiveness and increasing blowing ratio. This study is meant to show that unsteadiness is the key mechanism causing the unexpected results seen in the experiments. It is believed that this unsteadiness is highly dependent on the ratio of the lip thickness to slot height and the shedding frequencies of the passage and coolant vortices, which depend on blowing ratio. For low blowing ratio, hot passage flow has the dominant vortices. For high blowing ratio, coolant flow has the dominant vortices. For intermediate blowing ratio, the vortices have the potential to interact and cause the unusual behavior seen in pressure-side bleed film cooling. On the basis of these observations, experiments were repeated with pressure probes used to acquire the shedding frequencies at the effectiveness measurement location, which showed that unsteadiness was indeed present. Realistic engine conditions are considered with lip thickness to slot height ratio of 0.9 and mainstream Mach numbers of 0.7 at the coolant injection point and expanding to sonic conditions at the exit plane of the test section. Numerical results are from a 2-D mid-plane cut of the original geometry and a full-pitch 3-D model. Computations use high quality grids, high order discretization schemes, and an advanced turbulence model. The 3-D grid consists of 4.4 million cells and a high quality, unstructured, multi-topology mesh with resolution of the viscous sublayer and y+ < 1 on all surfaces. The simulations are fully converged, time accurate, and grid-independent. A novel methodology is used to introduce unsteadiness into the simulations. Effects of blowing ratio are examined, where blowing ratio is equal to 1.0 for 3-D and ranges from 0.3 to 1.5 for 2-D with a density ratio of 1.52. By performing an unsteady simulation, the unusual relationship between the effectiveness and blowing ratio is demonstrated in an unsteady framework.

Pressure-Side Bleed Film Cooling: Part I — Steady Framework for Experimental and Computational Results

2002 ◽  
Author(s):  
D. Scott Holloway ◽  
James H. Leylek ◽  
Frederick A. Buck
Keyword(s):  
Test Section ◽  
Film Cooling ◽  
Density Ratio ◽  
Experimental Results ◽  
Test Surface ◽  
Pressure Side ◽  
Computational Results ◽  
Height Ratio ◽  
High Quality ◽  
Blowing Ratio

This study combines both experiments and computations to investigate pressure-side bleed on the trailing edge of a turbine blade. Realistic engine conditions are considered with a lip thickness to slot height ratio of 0.9 and mainstream Mach numbers of 0.7 at the coolant injection point expanding to sonic conditions at the exit plane of the test section. The purpose of this study is to understand the complex physics of pressure-side bleed, in particular, the unusual behavior that occurs with increasing blowing ratio. Experimentally, it is shown that as the blowing ratio increases, the film cooling effectiveness at a point near the end of the test section increases for blowing ratios less than 0.8, while decreasing over the range of blowing ratios from 1.0 through 1.25. For blowing ratios higher than 1.25, effectiveness increases. This phenomenon has been repeated experimentally for many years without being fully understood. Parts I and II of this paper describe the mechanism responsible for the unusual experimental results. This mechanism is unsteady vortex shedding. Experimental results are from a row of jets with the use of foreign gas injection that simulates the engine conditions that would be seen by the pressure side of an airfoil with pressure-side bleed. These results consist of the pressure distribution due to the nozzle and the effectiveness along the test surface downstream of the injection site. The computational model is designed to replicate the experimental setup. High-quality grids, high-order discretization schemes, and an advanced turbulence model are employed to ensure that the computational results can be used to explain the complex physics of transonic pressure-side bleed film cooling. The grid consists of 2.2 million cells and a high-quality, unstructured, multi-topology, super-block mesh with the resolution of the viscous sub-layer and y+ < 1 on all surfaces. The simulations are fully converged and grid-independent. Effects of blowing ratio are examined, with blowing ratio ranging from 0.5 to 2.0 and a density ratio of 1.52. The geometry consists of not only the transonic mainstream flow and the jet, but also the creeping plenum flow. As a result of the significant lip thickness to slot height ratio, it is shown that unsteady effects are the dominant mechanism in the physics of pressure-side bleed film cooling.

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