scholarly journals Experimentally Measured Effects of Incidence Angle on the Adiabatic and Overall Effectiveness of a Fully Cooled Turbine Airfoil With Shaped Showerhead Holes

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Kyle Chavez ◽  
Thomas N. Slavens ◽  
David Bogard
Keyword(s):  
Incidence Angle ◽  
Density Ratio ◽  
Leading Edge ◽  
Inlet Flow ◽  
Flow Angle ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Adiabatic Effectiveness ◽  
Inlet Conditions ◽  
Overall Effectiveness

Manufacturing and assembly variation can lead to shifts in the inlet flow incidence angles of a rotating turbine airfoil row. Understanding the sensitivity of the adiabatic film cooling effectiveness to a range of inlet conditions is necessary to verify the robustness of a cooling design. In order to investigate the effects of inlet flow incidence angles, adiabatic and overall effectiveness data were measured in a low speed linear cascade at 0 deg and 10 deg of the designed operating condition. Tests were completed at an inlet Reynolds number of Re = 120,000 and a turbulence intensity of Tu = 5% at the leading edge of the test article. Particle image velocimetry was used to verify the incident flow angle for each angle studied. The test section was first adjusted so that the pressure distribution and stagnation line of the airfoil matched those predicted by an aerodynamic computational fluid dynamics (CFD) model. IR thermography was then used to measure the adiabatic effectiveness levels of the fully cooled airfoil model with nine rows of shaped holes of varying construction and feed delivery. Measurements were taken over a range of blowing ratios and at a density ratio of DR = 1.23. This process was repeated for the two incidence angles measured, while the inlet pressure to the airfoil model was held constant for these incidence angle changes. Differences in laterally adiabatic effectiveness across the airfoil model were most evident in the showerhead, with changes as large as 0.2. The effect persisted most strongly at s/D = ±35 downstream of the stagnation row of holes, but was visible over the whole viewable area of 160 s/D. The effect was due to the stagnation line affecting the film at the showerhead row. Due to this effect, the showerhead was investigated in detail, including the effects of the stagnation line shift as well as the influence of the incidence angle on the overall effectiveness of the showerhead region. It was found that the stagnation line has the tendency to dramatically increase the near-hole adiabatic effectiveness levels when positioned within the breakout footprint of the hole. The effect persisted for the overall effectiveness study, since the hole spacing for this particular configuration was wide enough that the through hole convection was not completely dominant. This is the first study to present measured effectiveness values over both the pressure- and suction-side surfaces of a fully cooled airfoil for appreciably off-nominal incidence angles as well as examine adiabatic and overall effectiveness levels for a conical stagnation row of holes.

Experimentally Measured Effects of Incidence Angle on the Adiabatic and Overall Effectiveness of a Fully Cooled Turbine Airfoil With Showerhead Shaped Holes

2016 ◽  
Author(s):  
Kyle Chavez ◽  
Thomas N. Slavens ◽  
David Bogard
Keyword(s):  
Incidence Angle ◽  
Density Ratio ◽  
Leading Edge ◽  
Inlet Flow ◽  
Flow Angle ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Adiabatic Effectiveness ◽  
Inlet Conditions ◽  
Overall Effectiveness

Manufacturing and assembly variation can lead to shifts in the inlet flow incidence angles of a rotating turbine airfoil row. Understanding the sensitivity of the adiabatic film cooling effectiveness to a range of inlet conditions is necessary to verifying the robustness of a cooling design. In order to investigate the effects of inlet flow incidence angles, adiabatic and overall effectiveness data were measured in a low speed linear cascade at 0° and 10° of the designed operating condition. Tests were completed at an inlet Reynolds number of Re=120000 and a turbulence intensity of Tu = 5% at the leading edge of the test article. Particle Image Velocimetry was used to verify the incident flow angle for each angle studied. The test section was first adjusted so that the pressure distribution and stagnation line of the airfoil matched those predicted by an aerodynamic CFD model. IR thermography was then used to measure the adiabatic effectiveness levels of the fully-cooled airfoil model with nine rows of shaped holes of varying construction and feed delivery. Measurements were taken over a range of blowing ratios and at a density ratio of DR=1.23. This process was repeated for the two incidence angles measured, while the inlet pressure to the airfoil model was held constant for these incidence angle changes. Differences in laterally adiabatic effectiveness across the airfoil model were most evident in the showerhead, with changes as large as 0.2. The effect persisted most strongly at s/D=±35 downstream of the stagnation row of holes, but was visible over the whole viewable area of 160 s/D. The effect was due to the stagnation line affecting the film at the showerhead row. Due to this effect, the showerhead was investigated in detail, including effects of the stagnation line shift as well as the influence of the incidence angle on the overall effectiveness of the showerhead region. It was found that the stagnation line has the tendency to dramatically increase the near-hole adiabatic effectiveness levels when positioned within the breakout footprint of the hole. The effect persisted for the overall effectiveness study, since the hole spacing for this particular configuration was wide enough that the through hole convection was not completely dominant. This is the first study to present measured effectiveness values over both the pressure- and suction-side surfaces of a fully-cooled airfoil for appreciably off-nominal incidence angles as well as examine adiabatic and overall effectiveness levels for a conical stagnation row of holes.

Numerical Simulation of a Simulated Film Cooled Turbine Blade Leading Edge Including Conjugate Heat Transfer Effects

2009 ◽  
Author(s):  
Laurene D. Dobrowolski ◽  
David G. Bogard ◽  
Justin Piggush ◽  
Atul Kohli
Keyword(s):  
Turbine Blade ◽  
Computational Study ◽  
Computational Simulation ◽  
Density Ratio ◽  
Leading Edge ◽  
Metal Temperature ◽  
Stagnation Line ◽  
Adiabatic Effectiveness ◽  
Overall Effectiveness ◽  
Blade Leading Edge

A conjugate numerical method was used to predict the normalized “metal” temperature of a simulated turbine blade leading edge. This computational study was done in conjunction with a parallel effort to experimentally determine normalized metal temperature, i.e. overall effectiveness, using a specially designed model blade leading edge. Also examined in this study were adiabatic models which provided adiabatic effectiveness results. Two different film cooling configurations were employed. The first configuration consisted of one row of holes centered on the stagnation line. The second configuration had two additional rows located at ±25 degrees from the stagnation line. These simulations were run at two different blowing ratios, M = 1 and M = 2. The coolant to mainstream density ratio was 1.5. The computational simulation was conducted using the FLUENT code using the realizable k-ε turbulence model and with grid resolution within the viscous sublayer. Adiabatic effectiveness distributions were predicted well by the computational simulations, except for localized areas near the holes. Predictions of overall effectiveness were higher than experimentally measured values in the stagnation region, but lower along downstream section of the leading edge. Reasons for the differences between computational predictions and experimental measurements were examined.

Inlet Flow Incidence Effects on the Thermal Performance of Showerhead Cooling in a Nozzle Vane Cascade

2019 ◽  
Author(s):  
H. Abdeh ◽  
G. Barigozzi ◽  
A. Perdichizzi ◽  
M. Henze ◽  
J. Krueckels
Keyword(s):  
Thermal Performance ◽  
Thermal Protection ◽  
Cooling System ◽  
Incidence Angle ◽  
Leading Edge ◽  
Intensity Level ◽  
Inlet Flow ◽  
Flow Angle ◽  
Film Cooling Effectiveness ◽  
Nozzle Vane

Abstract In the present paper, the influence of inlet flow incidence on the thermal performance of a film cooled linear nozzle vane cascade is assessed. Tests have been carried out on a cooled cascade, featuring a showerhead cooling system made of 4 rows of cylindrical holes. The cascade was tested by varying the inlet flow angle in the range ±20° at a high inlet turbulence intensity level (Tu1 = 9%) and at a constant inlet Mach number of 0.12. The thermal characterization of vane leading edge region was obtained through adiabatic film cooling effectiveness measurements. Vane load distributions supported the discussion of the results. Varying the incidence angle in either positive or negative angles, the thermal protection on the vane is reduced while the maximum protection happened at 0° incidence case.

Influence of Turbine Blade Leading Edge Profile on Film Cooling With Shaped Holes

2017 ◽  
Author(s):  
Mingjie Zhang ◽  
Nian Wang ◽  
Andrew F. Chen ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Edge Profile ◽  
Elliptical Cylinders ◽  
Blade Leading Edge

This paper presents the turbine blade leading edge model film cooling effectiveness with shaped holes, using the pressure sensitive paint (PSP) mass transfer analogy method. The effects of leading edge profile, coolant to mainstream density ratio and blowing ratio are studied. Computational simulations are performed using the realizable k-ε turbulence model. Effectiveness obtained by CFD simulations are compared with experiments. Three leading edge profiles, including one semi-cylinder and two semi-elliptical cylinders with an after body, are investigated. The ratios of major to minor axis of two semi-elliptical cylinders are 1.5 and 2.0, respectively. The leading edge has three rows of shaped holes. For the semi-cylinder model, shaped holes are located at 0 degrees (stagnation line) and ± 30 degrees. Row spacing between cooling holes and the distance between impingement plate and stagnation line are the same for three leading edge models. The coolant to mainstream density ratio varies from 1.0 to 1.5 and 2.0, and the blowing ratio varies from 0.5 to 1.0 and 1.5. Mainstream Reynolds number is about 100,900 based on the diameter of the leading edge cylinder, and the mainstream turbulence intensity is about 7%. The results provide an understanding of the effects of leading edge profile and on turbine blade leading edge region film cooling with shaped-hole designs.

Experimental Study of the Effects of an Oscillating Approach Flow on Overall Cooling Performance of a Simulated Turbine Blade Leading Edge

2009 ◽  
Author(s):  
Ross Johnson ◽  
Jonathan Maikell ◽  
David Bogard ◽  
Justin Piggush ◽  
Atul Kohli ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Line ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Oscillation Frequencies ◽  
Overall Effectiveness ◽  
Blade Leading Edge

When a turbine blade passes through wakes from upstream vanes it is subjected to an oscillation of the direction of the approach flow resulting in the oscillation of the position of the stagnation line on the leading edge of the blade. In this study an experimental facility was developed that induced a similar oscillation of the stagnation line position on a simulated turbine blade leading edge. The overall effectiveness was evaluated at various blowing ratios and stagnation line oscillation frequencies. The location of the stagnation line on the leading edge was oscillated to simulate a change in angle of attack between α = ± 5° at a range of frequencies from 2 to 20 Hz. These frequencies were chosen based on matching a range of Strouhal numbers typically seen in an engine due to oscillations caused by passing wakes. The blowing ratio was varied between M = 1, M = 2, and M = 3. These experiments were carried out at a density ratio of DR = 1.5 and mainstream turbulence levels of Tu ≈ 6%. The leading edge model was made of high conductivity epoxy in order to match the Biot number of an actual engine airfoil. Results of these tests showed that the film cooling performance with an oscillating stagnation line was degraded by as much as 25% compared to the performance of a steady flow with the stagnation line aligned with the row of holes at the leading edge.

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.

Influence of Turbine Blade Leading Edge Profile on Film Cooling With Shaped Holes

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Mingjie Zhang ◽  
Nian Wang ◽  
Andrew F. Chen ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Edge Profile ◽  
Elliptical Cylinders ◽  
Blade Leading Edge

This paper presents the turbine blade leading edge model film cooling effectiveness with shaped holes, using the pressure sensitive paint (PSP) mass transfer analogy method. The effects of leading edge profile, coolant to mainstream density ratio, and blowing ratio are studied. Computational simulations are performed using the realizable k–ɛ (RKE) turbulence model. Effectiveness obtained by computational fluid dynamics (CFD) simulations is compared with experiments. Three leading edge profiles, including one semicylinder and two semi-elliptical cylinders with an after body, are investigated. The ratios of major to minor axis of two semi-elliptical cylinders are 1.5 and 2.0, respectively. The leading edge has three rows of shaped holes. For the semicylinder model, shaped holes are located at 0 deg (stagnation line) and ±30 deg. Row spacing between cooling holes and the distance between impingement plate and stagnation line are the same for three leading edge models. The coolant to mainstream density ratio varies from 1.0 to 1.5 and 2.0, and the blowing ratio varies from 0.5 to 1.0 and 1.5. Mainstream Reynolds number is about 100,000 based on the diameter of the leading edge cylinder, and the mainstream turbulence intensity is about 7%. The results provide an understanding of the effects of leading edge profile on turbine blade leading edge region film cooling with shaped hole designs.

Effect of Blowing Ratio in the Near-Stagnation Region of a Three-Row Leading Edge Film Cooling Geometry Using Large Eddy Simulations

2009 ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Large Eddy Simulations ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Blowing Ratio ◽  
Large Eddy ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Computational studies are carried out using Large Eddy Simulations (LES) to investigate the effect of coolant to mainstream blowing ratio in a leading edge region of a film cooled vane. The three row leading edge vane geometry is modeled as a symmetric semi-cylinder with a flat afterbody. One row of coolant holes is located along the stagnation line and the other two rows of coolant holes are located at ±21.3° from the stagnation line. The coolant is injected at 45° to the vane surface with 90° compound angle injection. The coolant to mainstream density ratio is set to unity and the freestream Reynolds number based on leading edge diameter is 32000. Blowing ratios (B.R.) of 0.5, 1.0, 1.5, and 2.0 are investigated. It is found that the stagnation cooling jets penetrate much further into the mainstream, both in the normal and lateral directions, than the off-stagnation jets for all blowing ratios. Jet dilution is characterized by turbulent diffusion and entrainment. The strength of both mechanisms increases with blowing ratio. The adiabatic effectiveness in the stagnation region initially increases with blowing ratio but then generally decreases as the blowing ratio increases further. Immediately downstream of off-stagnation injection, the adiabatic effectiveness is highest at B.R. = 0.5. However, further downstream the larger mass of coolant injected at higher blowing ratios, in spite of the larger jet penetration and dilution, increases the effectiveness with blowing ratio.

Investigation of Various Parametric Influences on Leading Edge Film Cooling

1997 ◽  
Author(s):  
Michael W. Cruse ◽  
Ushio M. Yuki ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Free Stream ◽  
Density Ratio ◽  
Leading Edge ◽  
Line Position ◽  
Stagnation Line ◽  
Free Stream Turbulence ◽  
Adiabatic Effectiveness ◽  
Density Ratios

Film cooling adiabatic effectiveness of a simulated turbine airfoil leading edge was studied experimentally. The leading edge had two rows of holes, one at nominally the stagnation line position and the second a few hole diameters downstream. Hole positions at the leading edge, and inclination of the holes with respect to the surface, were different than typically used in previous studies, but were representative of current design practice. Various leading edge film cooling parameters were investigated including stagnation line position, free-stream turbulence level, leading edge geometry, and coolant to mainstream density ratio. Large density ratios were obtained by cooling the injected coolant to very low temperatures. Large scale, high level free-stream turbulence (Tu = 20%) was generated using a specially developed cross-jet turbulence generator. An infrared camera system was used to obtain well resolved surface temperature distributions around the coolant holes and across the leading edge. Results from the experiments showed considerably higher optimum blowing ratios than found in previous studies. The stagnation line position was found to be important in influencing the direction of coolant flow from the first row of holes. High free-stream turbulence levels were found to greatly decrease adiabatic effectiveness at low blowing ratios (M = 1.0), but had little effect at high blowing ratios (M = 2.0 and 2.5). Adiabatic effectiveness distributions were very similar for circular and elliptical leading edges. Experiments conducted at coolant to mainstream density ratios of 1.1 and 1.8 showed distinctly different flow characteristics in the stagnation line region for the different density ratio coolants.

Effect of Inlet Swirl on the Model Leading Edge of Turbine Vane

2013 ◽  
Author(s):  
Hong Yin ◽  
Yanmin Qin ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Leading Edge ◽  
Operating Conditions ◽  
Test Model ◽  
Angle Distribution ◽  
Middle Section ◽  
Flow Angle ◽  
Stagnation Line ◽  
Film Cooling Effectiveness

Lean premixed combustion technology has been widely adopted in heavy duty and industrial gas turbine combustor. To enhance mixing and stabilize the flame, the large recirculation zone is built up by introducing strong swirling flow, which causes non-uniform flow field and has effect on the first stage vane, especially the leading edge. This paper investigates the effect of swirling flow on the downstream vane film cooling. Test rig consists of a swirler nozzle (swirl number equals 0.45) and a model leading edge with three rows of film cooling holes. Five-hole probe and pressure sensitive paint measurements were carried out. The operating conditions range includes three blowing ratios, two density ratios of cooling flow and two distances between the swirler and the model leading edge. Numerical simulations were also conducted and compared with the accumulated experimental data. Results show that the stagnation line of the model leading edge under swirling inlet flow condition is obviously altered compared with uniform inflow. Dividing the test model into three sections, film cooling effectiveness distribution has distinct characteristics in each section. Both ends of the model are mainly influenced by the flow direction. However the middle section performs differently since the vortex core impingement directly disturbs the film cooling ejection. Furthermore, detailed computational analysis reveals the swirling flow character and that the combined effect of total pressure and flow angle distribution dominates the film cooling of middle section.

Sign in / Sign up

Export Citation Format

Share Document