Introducing a New Test Rig for Film Cooling Measurements With Realistic Hole Inflow Conditions

2017 ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Test Rig ◽  
Hot Gas ◽  
Cooling Hole ◽  
Measurement Principle ◽  
Density Ratios ◽  
Operational Range ◽  
Film Cooling Holes

Further improvements in film cooling require an in-depth understanding of the influencing parameters. Therefore, a new test rig has been designed and commissioned for the assessment of novel film cooling holes under realistic conditions. The test rig is designed for generic film cooling studies. External hot gas flow as well as internal coolant passage flow are simulated by two individual flow channels connected to each other by the cooling holes. Based on a similarity analysis, the geometry of the test rig is scaled up by a factor of about 20. It furthermore offers the possibility to conduct experiments at high density ratios and realistic approach flow conditions at both cooling hole exit and inlet. The operational range of the new test rig is presented and compared to real engine conditions. It is shown that the important parameters are met and the transfer-ability of the results is ensured. Special effort is put onto the uniformity of the approaching hot gas flow, which will be demonstrated by temperature and velocity profiles. A first measurement of the heat transfer coefficient without film cooling is used to demonstrate the quality of the measurement principle.

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Adiabatic Effectiveness Measurements for a Baseline Shaped Film Cooling Hole

2014 ◽  
Author(s):  
Robert P. Schroeder ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Freestream Turbulence ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Shaped Hole ◽  
Adiabatic Effectiveness ◽  
Improved Performance ◽  
Density Ratios ◽  
Film Cooling Holes

Film cooling on airfoils is a crucial cooling method as the gas turbine industry seeks higher turbine inlet temperatures. Shaped film cooling holes are widely used in many designs given the improved performance over that of cylindrical holes. Although there have been numerous studies of shaped holes, there is no established baseline shaped hole to which new cooling hole designs can be compared. The goal of this study is to offer the community a shaped hole design, representative of proprietary and open literature holes that serves as a baseline for comparison purposes. The baseline shaped cooling hole design includes the following features: hole inclination angle of 30° with a 7° expansion in the forward and lateral directions; hole length of 6 diameters; hole exit-to-inlet area ratio of 2.5; and lateral hole spacing of 6 diameters. Adiabatic effectiveness was measured with this new shaped hole and was found to peak near a blowing ratio of 1.5 at density ratios of 1.2 and 1.5 as well as at both low and moderate freestream turbulence of 5%. Reductions in area-averaged effectiveness due to freestream turbulence at low blowing ratios were as high as 10%.

scholarly journals A Numerical Study of Anti-Vortex Film Cooling Designs at High Blowing Ratio

2008 ◽  
Author(s):  
James D. Heidmann
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Experimental Studies ◽  
Navier Stokes ◽  
Round Hole ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Lift Off ◽  
Density Ratios ◽  
Film Cooling Holes

A concept for mitigating the adverse effects of jet vorticity and lift-off at high blowing ratios for turbine film cooling flows has been developed and studied at NASA Glenn Research Center. This “anti-vortex” film cooling concept proposes the addition of two branched holes from each primary hole in order to produce a vorticity counter to the detrimental kidney vortices from the main jet. These vortices typically entrain hot freestream gas and are associated with jet separation from the turbine blade surface. The anti-vortex design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30 degree angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A modification of the anti-vortex concept whereby the branched holes exit adjacent to the main hole has been studied computationally for blowing ratios of 1.0 and 2.0 and at density ratios of 1.0 and 2.0. This modified concept was selected because it has shown the most promise in recent experimental studies. The computational results show that the modified design improves the film cooling effectiveness relative to the round hole baseline and previous anti-vortex cases, in confirmation of the experimental studies.

Effect of Internal Coolant Crossflow Orientation on the Discharge Coefficient of Shaped Film Cooling Holes

1999 ◽  
Author(s):  
Michael Gritsch ◽  
Christian Saumweber ◽  
Achmed Schulz ◽  
Sigmar Wittig ◽  
Edwin Sharp
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Strong Impact ◽  
Hot Gas ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole

Discharge coefficients of three film-cooling hole geometries are presented over a wide range of engine like conditions. The hole geometries comprise a cylindrical hole and two holes with a diffuser shaped exit portion (a fanshaped and a laidback fanshaped hole). For all three hole geometries the hole axis was inclined 30° with respect to the direction of the external (hot gas) flow. The flow conditions considered were the hot gas crossflow Mach number (up to 0.6), the coolant crossflow Mach number (up to 0.6) and the pressure ratio across the hole (up to 2). The effect of internal crossflow approach direction, perpendicular or parallel to the main flow direction, is particularly addressed in the present study. Comparison is made of the results for a parallel and perpendicular orientation, showing that the coolant crossflow orientation has a strong impact on the discharge behavior of the different hole geometries. The discharge coefficients were found to strongly depend on both hole geometry and crossflow conditions. Furthermore, the effects of internal and external crossflow on the discharge coefficients were described by means of correlations used to derive a predicting scheme for discharge coefficients. A comparison between predictions and measurements reveals the capability of the method proposed.

Effect of Internal Coolant Crossflow Orientation on the Discharge Coefficient of Shaped Film-Cooling Holes

1999 ◽  
Vol 122 (1) ◽  
pp. 146-152 ◽  
Author(s):  
M. Gritsch ◽  
C. Saumweber ◽  
A. Schulz ◽  
S. Wittig ◽  
E. Sharp
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Strong Impact ◽  
Hot Gas ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole

Discharge coefficients of three film-cooling hole geometries are presented over a wide range of engine like conditions. The hole geometries comprise a cylindrical hole and two holes with a diffuser-shaped exit portion (a fanshaped and a laidback fanshaped hole). For all three hole geometries the hole axis was inclined 30 deg with respect to the direction of the external (hot gas) flow. The flow conditions considered were the hot gas crossflow Mach number (up to 0.6), the coolant crossflow Mach number (up to 0.6) and the pressure ratio across the hole (up to 2). The effect of internal crossflow approach direction, perpendicular or parallel to the main flow direction, is particularly addressed in the present study. Comparison is made of the results for a parallel and perpendicular orientation, showing that the coolant crossflow orientation has a strong impact on the discharge behavior of the different hole geometries. The discharge coefficients were found to strongly depend on both hole geometry and crossflow conditions. Furthermore, the effects of internal and external crossflow on the discharge coefficients were described by means of correlations used to derive a predicting scheme for discharge coefficients. A comparison between predictions and measurements reveals the capability of the method proposed. [S0889-504X(00)01601-9]

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2018 ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10-10-10deg laidback fan-shaped cooling hole are discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Computational Predictions of Endwall Film Cooling for a Turbine Nozzle Vane With an Asymmetric Contoured Passage

2008 ◽  
Author(s):  
Yoji Okita ◽  
Chiyuki Nakamata
Keyword(s):  
Film Cooling ◽  
Computational Study ◽  
Suction Side ◽  
Geometrical Parameters ◽  
Passage Vortex ◽  
Rear Part ◽  
Cooling Hole ◽  
Secondary Vortices ◽  
Endwall Film Cooling ◽  
Film Cooling Holes

This paper presents results of a computational study for the endwall film cooling of an annular nozzle cascade employing a circumferentially asymmetric contoured passage. The investigated geometrical parameters and the flow conditions are set consistent with a generic modern HP-turbine nozzle. Rows of cylindrical film cooling holes on the contoured endwall are arranged with a design practice for the ordinary axisymmetric endwall. The solution domain, which includes the mainflow, cooling hole paths, and the coolant plenum, is discretized in the RANS equations with the realizable k-epsilon model. The calculated flow field shows that the pressure gradients across the passage between the pressure and the suction side are reduced with the asymmetric endwall, and consequently, the rolling up of the inlet boundary layer into the passage vortex is delayed and the separation line has moved further downstream. With the asymmetric endwall, because of the effective suppression of the secondary flow, more uniform film coverage is achieved especially in the rear part of the passage and the laterally averaged effectiveness is also significantly improved in this region. The closer inspection of the calculated thermal field reveals that, with the asymmetric passage, the coolant ejected from the holes are less deflected by the secondary vortices, and it attaches better to the endwall in this rear part.

Shock Wave - Film Cooling Interactions in Transonic Flows

2001 ◽  
Author(s):  
P. M. Ligrani ◽  
C. Saumweber ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Shock Waves ◽  
Film Cooling ◽  
Cross Flow ◽  
Injection Velocity ◽  
Film Cooling Effectiveness ◽  
Mach Numbers ◽  
Density Ratios ◽  
Film Cooling Holes

Interactions between shock waves and film cooling are described as they affect magnitudes of local and spanwise-averaged adiabatic film cooling effectiveness distributions. A row of three cylindrical holes is employed. Spanwise spacing of holes is 4 diameters, and inclination angle is 30 degrees. Freestream Mach numbers of 0.8 and 1.10–1.12 are used, with coolant to freestream density ratios of 1.5–1.6. Shadowgraph images show different shock structures as the blowing ratio is changed, and as the condition employed for injection of film into the cooling holes is altered. Investigated are film plenum conditions, as well as perpendicular film injection cross-flow Mach numbers of 0.15, 0.3, and 0.6. Dramatic changes to local and spanwise-averaged adiabatic film effectiveness distributions are then observed as different shock wave structures develop in the immediate vicinity of the film-cooling holes. Variations are especially evident as the data obtained with a supersonic Mach number are compared to the data obtained with a freestream Mach number of 0.8. Local and spanwise-averaged effectiveness magnitudes are generally higher when shock waves are present when a film plenum condition (with zero cross-flow Mach number) is utilized. Effectiveness values measured with a supersonic approaching freestream and shock waves then decrease as the injection cross-flow Mach number increases. Such changes are due to altered flow separation regions in film holes, different injection velocity distributions at hole exits, and alterations of static pressures at film hole exits produced by different types of shock wave events.

Computational Analysis of Conjugate Heat Transfer and Particulate Deposition on a High Pressure Turbine Vane

2009 ◽  
Author(s):  
Weiguo Ai ◽  
Thomas H. Fletcher
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Particle Method ◽  
Experimental Results ◽  
Turbine Vane ◽  
Particulate Deposition ◽  
Cooling Hole ◽  
Lagrangian Particle Method ◽  
Film Cooling Holes

Numerical computations were conducted to simulate flyash deposition experiments on gas turbine disk samples with internal impingement and film cooling using a CFD code (FLUENT). The standard k-ω turbulence model and RANS were employed to compute the flow field and heat transfer. The boundary conditions were specified to be in agreement with the conditions measured in experiments performed in the BYU Turbine Accelerated Deposition Facility (TADF). A Lagrangian particle method was utilized to predict the ash particulate deposition. User-defined subroutines were linked with FLUENT to build the deposition model. The model includes particle sticking/rebounding and particle detachment, which are applied to the interaction of particles with the impinged wall surface to describe the particle behavior. Conjugate heat transfer calculations were performed to determine the temperature distribution and heat transfer coefficient in the region close to the film-cooling hole and in the regions further downstream of a row of film-cooling holes. Computational and experimental results were compared to understand the effect of film hole spacing, hole size and TBC on surface heat transfer. Calculated capture efficiencies compare well with experimental results.

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.

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