The Influence of Turbulence and Reynolds Number on Multiple Slot Film Cooling Over the Suction Surface

2021 ◽  
Author(s):  
Loren Soma ◽  
Forrest Ames ◽  
Sumanta Acharya
Keyword(s):  
Reynolds Number ◽  
Film Cooling ◽  
Suction Surface ◽  
Slot Film Cooling

Letterbox Trailing Edge Heat Transfer: Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
N. J. Fiala ◽  
I. Jaswal ◽  
F. E. Ames
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Suction Surface ◽  
Trailing Edge ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Heat transfer and film cooling distributions have been acquired for a vane trailing edge with letterbox partitions. Additionally, pressure drop data have been experimentally determined across a pin fin array and a trailing edge slot with letterbox partitions. The pressure drop across the array and letterbox trailing edge arrangement was measurably higher than for the gill slot geometry. Experimental data for the partitions and the inner suction surface region downstream from the slot have been acquired over a four-to-one range in vane exit condition Reynolds number (500,000, 1,000,000, and 2,000,000), with low (0.7%), grid (8.5%), and aerocombustor (13.5%) turbulence conditions. At these conditions, both heat transfer and adiabatic film cooling distributions have been documented over a range of blowing ratios (0.47≤M≤1.9). Heat transfer distributions on the inner suction surface downstream from the slot ejection were found to be dependent on both ejection flow rate and external conditions. Heat transfer on the partition side surfaces correlated with both exit Reynolds number and blowing ratio. Heat transfer on partition top surfaces largely correlated with exit Reynolds number but blowing ratio had a small effect at higher values. Generally, adiabatic film cooling levels on the inner suction surface are high but decrease near the trailing edge and provide some protection for the trailing edge. Adiabatic effectiveness levels on the partitions correlate with blowing ratio. On the partition sides adiabatic effectiveness is highest at low blowing ratios and decreases with increasing flow rate. On the partition tops adiabatic effectiveness increases with increasing blowing ratio but never exceeds the level on the sides. The present paper, together with a companion paper that documents letterbox trailing edge aerodynamics, is intended to provide engineers with the heat transfer and aerodynamic loss information needed to develop and compare competing trailing edge designs.

The Influence of Turbulence and Reynolds Number on Multiple Slot Film Cooling Over the Suction Surface

2020 ◽  
Author(s):  
L. W. Soma ◽  
F. E. Ames ◽  
S. Acharya
Keyword(s):  
Film Cooling ◽  
Surface Film ◽  
Secondary Flows ◽  
Internal Cooling ◽  
Suction Surface ◽  
Film Cooling Effectiveness ◽  
Cooling Method ◽  
Cooling Section ◽  
Slot Film Cooling ◽  
Cooling Air

Abstract Developing robust film cooling protection on the suction surface of a vane is critical to managing the high heat loads which exist there. Suction surface film cooling often produces high levels of film cooling but can be influenced by secondary flows and some dissipation due to free-stream turbulence. Directly downstream from suction surface film cooling, heat loads are often significantly mitigated and internal cooling levels can be modest. One thermodynamically efficient way to cool the suction surface of a vane is with a counter cooling scheme. This combined internal/external cooling method moves cooling air in a direction opposite to the external flow through an internal convection array. The coolant is then discharged upstream where the high level of film cooling can offset the reduced cooling potential of the spent cooling air. The present suction surface film cooling arrangement combines a slot film cooling discharge on the near suction surface from an incremental impingement cooling method with a second from a counter cooling section. A second counter cooling section is added further downstream on the suction surface. The internal cooling plenums replicate the geometry of the cooling methods to ensure the fluid dynamics of the flow discharging from the slots are representative of the actual internal cooling geometry. These film cooling flows have been tested at blowing ratios of 0.5 and 1.0 for the initial slot and blowing ratios of 0.15 and 0.3 for the two downstream slots. The measurements have been taken at exit chord Reynolds numbers of 500,000, 1,000,000, and 2,000,000 with inlet turbulence levels ranging from 0.7% to 12.6%. Film cooling effectiveness measurements were acquired using both thermocouples and infrared thermography. The infrared thermography shows the influence of secondary flows on film cooling coverage near the suction surface endwall junction. The film cooling effectiveness results at varied blowing ratios, turbulence levels and Reynolds numbers document the impact of these major variables on suction surface slot film cooling. The results provide a consistent picture of the slot film cooling for the present three slot arrangement on the suction surface and they support the development of an advanced double wall cooling method.

scholarly journals Showerhead Film Cooling Performance of a Turbine Vane at High Freestream Turbulence in a Transonic Cascade

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Shakeel Nasir ◽  
Trey Bolchoz ◽  
Wing-Fai Ng ◽  
Luzeng J. Zhang ◽  
Hee Koo Moon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Mach Number ◽  
Film Cooling ◽  
Boundary Layer Transition ◽  
Suction Surface ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

This paper experimentally investigates the effect of blowing ratio and exit Reynolds number/Mach number on the film cooling performance of a showerhead film cooled first stage turbine vane. The vane midspan was instrumented with single-sided platinum thin film gauges to experimentally characterize the Nusselt number and film cooling effectiveness distributions over the surface. The vane was arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Three different exit Mach numbers of Mex = 0.57, 0.76 and 1.0—corresponding to exit Reynolds numbers based on vane chord of 9.7 × 105, 1.1 × 106 and 1.5 × 106, respectively—were tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx/P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0, 1.5, 2.0, and 2.5 and a density ratio of DR = 1.3. Nusselt number and adiabatic film cooling effectiveness distributions were presented on the vane surface over a range of s/C = −0.58 on the pressure side to s/C = 0.72 on the suction side of the vane. The primary effects of coolant injection were to augment the Nusselt number and reduce the adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at all exit Mach number conditions. In general, an increase in blowing ratio (BR = 1.5 to 2.5) showed noticeable Nusselt number augmentation on pressure surface as compared to suction surface at exit Mach 0.57 and 0.75; however, the Nusselt number augmentation for these blowing ratios was found to be negligible on the vane surface for exit Mach 1.0 case. At exit Mach 1.0, an increase in blowing ratio (BR = 1.5 to 2.5) was observed to have an adverse effect on the adiabatic effectiveness on the pressure surface but had negligible effect on suction surface. The effectiveness trend on the suction surface was also found to be influenced by a favorable pressure gradient due to Mach number and boundary layer transition in the region s/C = 0.28 to s/C = 0.45 at all blowing ratio and exit Mach number conditions. An increase in Reynolds number from exit Mach 0.76 to 1.0 increased heat transfer levels on the vane surface at all blowing ratio conditions. A large increase in Reynolds number adversely affected adiabatic effectiveness on the pressure surface at all blowing ratio conditions. On the suction surface, a large increase in Reynolds number also affected adiabatic effectiveness in the favorable pressure gradient and boundary layer transition region.

Gill Slot Trailing Edge Heat Transfer: Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness

2007 ◽  
Author(s):  
F. E. Ames ◽  
N. J. Fiala ◽  
J. D. Johnson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Film Cooling ◽  
Guide Vane ◽  
Surface Boundary ◽  
Suction Surface ◽  
Trailing Edge ◽  
Film Cooling Effectiveness ◽  
Pin Fin

Heat transfer and film cooling distributions have been acquired downstream from the exit of a nozzle guide vane gill slot (or cutback). Additionally, heat transfer and pressure drop data have been experimentally determined for a pin fin array within the gill slot geometry. Generally, average row pin fin heat transfer levels for the converging channel correlate quite well with archival literature. However, no generalized flow friction factor correlation was found to predict the pressure drop within the array. Experimental data for the region downstream from the gill slot have been acquired over a four to one range in vane exit condition Reynolds number, with low, grid, and aero-combustor turbulence conditions. At these conditions, both heat transfer and adiabatic film cooling distributions have been documented over a range of blowing ratios. Heat transfer distributions downstream from the gill slot ejection were found to be dependent on both ejection flow rate and external conditions. Generally, adiabatic film cooling levels are high but dissipate toward the trailing edge and provide some protection on the trailing edge. Heat transfer levels on the trailing edge are affected largely by the chord exit Reynolds number and the suction surface boundary layer condition. The present paper, together with a companion paper which documents gill slot aerodynamics, is intended to provide designers with the heat transfer and aerodynamic loss information needed to compare competing trailing edge designs.

Letterbox Trailing Edge Heat Transfer: Effects of Blowing Rate, Reynolds Number, and External Turbulence on Heat Transfer and Film Cooling Effectiveness

2008 ◽  
Author(s):  
N. J. Fiala ◽  
I. Jaswal ◽  
F. E. Ames
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Suction Surface ◽  
Trailing Edge ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Heat transfer and film cooling distributions have been acquired for a vane trailing edge with letterbox partitions. Additionally, pressure drop data have been experimentally determined across a pin fin array and a trailing edge slot with letterbox partitions. The pressure drop across the array and letterbox trailing edge arrangement was measurably higher than for the gill slot geometry. Experimental data for the partitions and the inner suction surface region downstream from the slot have been acquired over a four to one range in vane exit condition Reynolds number (500,000, 1,000,000 and 2,000,000), with low (0.7%), grid (8.5%), and aero-combustor (13.5%) turbulence conditions. At these conditions, both heat transfer and adiabatic film cooling distributions have been documented over a range of blowing ratios (0.47 ≤ M ≤ 1.9). Heat transfer distributions on the inner suction surface downstream from the slot ejection were found to be dependent on both ejection flow rate and external conditions. Heat transfer on the partition side surfaces correlated on both exit Reynolds number and blowing ratio. Heat transfer on partition top surfaces largely correlated on exit Reynolds number but blowing ratio had a small effect at higher values. Generally, adiabatic film cooling levels on the inner suction surface are high but decrease near the trailing edge and provide some protection for the trailing edge. Adiabatic effectiveness levels on the partitions correlate with blowing ratio. On the partition sides adiabatic effectiveness is highest at low blowing ratios and decreases with increasing flow rate. On the partition tops adiabatic effectiveness increases with increasing blowing ratio but never exceeds the level on the sides. The present paper, together with a companion paper which documents letterbox trailing edge aerodynamics, is intended to provide engineers with the heat transfer and aerodynamic loss information needed to develop and compare competing trailing edge designs.

scholarly journals Turbine Nozzle Film Cooling Study Using the Pressure Sensitive Paint (PSP) Technique

1999 ◽  
Author(s):  
Luzeng Zhang ◽  
Michael Baltz ◽  
Ram Pudupatty ◽  
Michael Fox
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Film Cooling ◽  
High Speed ◽  
Surface Film ◽  
Pressure Sensitive Paint ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Sensitive

The use of pressure sensitive paint (PSP) to measure film cooling effectiveness on a turbine nozzle surface was demonstrated in a high speed wind tunnel. Film cooling effectiveness was measured from a single row of holes located on a turbine vane suction surface with a shaped exit. Nitrogen gas was used to simulate film cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Three blowing ratios were studied for each of the five freestream conditions: a reference condition, a reduced and an increased Reynolds number condition, and a reduced and an increased Mach number condition. The freestream turbulence intensity was kept at 12.0% for all the tests. The PSP was calibrated at various temperatures and pressures to obtain better accuracy before being applied to the airfoil surface. The film effectiveness increased with blowing ratio for all the freestream conditions. The effects of secondary flow and freestream Mach number and Reynolds number on turbine nozzle suction surface film cooling are also discussed.

scholarly journals Showerhead Film Cooling Performance of a Turbine Vane at High Freestream Turbulence in a Transonic Cascade

2008 ◽  
Author(s):  
S. Nasir ◽  
T. Bolchoz ◽  
W. F. Ng ◽  
L. J. Zhang ◽  
H. K. Moon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Mach Number ◽  
Film Cooling ◽  
Boundary Layer Transition ◽  
Suction Surface ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

This paper experimentally investigates the effect of blowing ratio and exit Reynolds number/Mach number on the film cooling performance of a showerhead film cooled first stage turbine vane. The vane midspan was instrumented with single-sided platinum thin film gauges to experimentally characterize the Nusselt number and film cooling effectiveness distributions over the surface. The vane was arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Three different exit Mach numbers of Mex = 0.57, 0.76 and 1.0—corresponding to exit Reynolds numbers based on vane chord of 9.7 × 105, 1.1 × 106 and 1.5 × 106, respectively—were tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx/P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0, 1.5, 2.0, and 2.5 and a density ratio of DR = 1.3. Nusselt number and adiabatic film cooling effectiveness distributions were presented on the vane surface over a range of s/C = −0.58 on the pressure side to s/C = 0.72 on the suction side of the vane. The primary effects of coolant injection were to augment the Nusselt number and reduce the adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at all exit Mach number conditions. In general, an increase in blowing ratio (BR = 1.5 to 2.5) showed noticeable Nusselt number augmentation on pressure surface as compared to suction surface at exit Mach 0.57 and 0.75; however, the Nusselt number augmentation for these blowing ratios was found to be negligible on the vane surface for exit Mach 1.0 case. At exit Mach 1.0, an increase in blowing ratio (BR = 1.5 to 2.5) was observed to have an adverse effect on the adiabatic effectiveness on the pressure surface but had negligible effect on suction surface. The effectiveness trend on the suction surface was also found to be influenced by a favorable pressure gradient due to Mach number and boundary layer transition in the region s/C = 0.28 to s/C = 0.45 at all blowing ratio and exit Mach number conditions. An increase in Reynolds number from exit Mach 0.76 to 1.0 increased heat transfer levels on the vane surface at all blowing ratio conditions. A large increase in Reynolds number adversely affected adiabatic effectiveness on the pressure surface at all blowing ratio conditions. On the suction surface, a large increase in Reynolds number also affected adiabatic effectiveness in the favorable pressure gradient and boundary layer transition region.

Heat Transfer Coefficients of Film Cooling on a Rotating Turbine Blade Model: Part II—Effects of Reynolds Number and Rotation Number

2008 ◽  
Author(s):  
Hongwei Wu ◽  
Guoqiang Xu ◽  
Bin Yang ◽  
Zhi Tao ◽  
Shuiting Ding ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Rotation Number ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Blade Model

An experimental study was conducted to investigate the heat transfer characteristics of film cooling on a rotating turbine blade model with a single cylindrical injection hole. As an important supplement to the study of Tao et al. [Z. Tao, Z.M. Zhao, S.T. Ding, G.Q. Xu, B. Yang and H.W. Wu, Experimental investigation of film cooling on a rotating turbine blade model: Part I. Effect of blowing ratio on heat transfer coefficients], the effects of Reynolds number ReD and rotation number Rt on local heat transfer coefficient distributions are presented in this paper. A steady-state thermochromic liquid crystal technique was employed to measure the temperature distribution of test surface on the blade model, and a telemetering data acquisition system was used to collect the signals from the rotating blade model by wireless approach. During the experiments, the Reynolds number based on the mainstream velocity and film hole diameter varies from 1841 to 4296, and the rotation number ranges from 0 to 0.0249. Both the air and CO2 are used as coolant, yielding the averaged density ratio of DR = 1.02 and 1.53, respectively. Experimental results show that the rotational effect has a significant influence on the heat transfer coefficient distributions. The profiles of h/h0, which is the ratio of heat transfer coefficient with film cooling to that without film cooling, will deflect towards the high-radius locations due to the strong centrifugal effect as Rt increases, and the deflective tendency of h/h0 is more apparent on the suction surface. The h/h0 values augment with the incremental ReD on the pressure surface, but decline firstly and then increase again on the suction surface. Furthermore, the averaged values of h/h0 for CO2 injection presents lower magnitudes as compared to the air injection.

scholarly journals Comparison of Two-Equation Turbulence Models for Prediction of Heat Transfer on Film-Cooled Turbine Blades

1997 ◽  
Author(s):  
Vijay K. Garg ◽  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Time ◽  
Suction Surface ◽  
The Heat Transfer Coefficient

A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley’s q-ω model, Chien’s k-ε model and Wilcox’s k-ω model with Menter’s modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all two-equation models require 40% more computer core than the B-L model for solution, and while the q-ω and k-ε models need 40% more computer time than the B-L model, the k-ω model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models.

Experimental Comparison of DBD Plasma Actuators for Low Reynolds Number Separation Control

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Christopher R. Marks ◽  
Rolf Sondergaard ◽  
Mitch Wolff ◽  
Rich Anthony
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbine Blades ◽  
Plasma Actuators ◽  
Experimental Comparison ◽  
Separation Control ◽  
Suction Surface ◽  
Dbd Plasma ◽  
Low Reynolds ◽  
Low Reynolds Number Airfoil

This paper presents experimental work comparing several Dielectric Barrier Discharge (DBD) plasma actuator configurations for low Reynolds number separation control. Actuators studied here are being investigated for use in a closed loop separation control system. The plasma actuators were fabricated in the U.S. Air Force Research Laboratory Propulsion Directorate’s thin film laboratory and applied to a low Reynolds number airfoil that exhibits similar suction surface behavior to those observed on Low Pressure (LP) Turbine blades. In addition to typical asymmetric arrangements producing downstream jets, one electrode configurations was designed to produce an array of off axis jets, and one produced a spanwise array of linear vertical jets in order to generate vorticity and improved boundary layer to freestream mixing. The actuators were installed on an airfoil and their performance compared by flow visualization, surface stress sensitive film (S3F), and drag measurements. The experimental data provides a clear picture of the potential utility of each design. Experiments were carried out at four Reynolds numbers, 1.4 × 105, 1.0 × 105, 6.0 × 104, and 5.0 × 104 at a-1.5 deg angle of attack. Data was taken at the AFRL Propulsion Directorate’s Low Speed Wind Tunnel (LSWT) facility.

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