scholarly journals Discharge Coefficient Measurements of Film-Cooling Holes With Expanded Exits

1997 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Cylindrical Hole ◽  
Flow Conditions ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole ◽  
Film Cooling Holes

This paper presents the discharge coefficients of three film-cooling hole geometries tested over a wide range of flow conditions. The hole geometries 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 were 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 pressure ratio across the hole (up to 2). The results show that the discharge coefficient for all geometries tested strongly depends on the flow conditions (crossflows at hole inlet and exit, and pressure ratio). The discharge coefficient of both expanded holes was found to be higher than of the cylindrical hole, particularly at low pressure ratios and with a hole entrance side crossflow applied. The effect of the additional layback on the discharge coefficient is negligible.

Discharge Coefficient Measurements of Film-Cooling Holes With Expanded Exits

1998 ◽  
Vol 120 (3) ◽  
pp. 557-563 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Cylindrical Hole ◽  
Flow Conditions ◽  
Wide Range ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Film Cooling Holes

This paper presents the discharge coefficients of three film-cooling hole geometries tested over a wide range of flow conditions. The hole geometries include a cylindrical hole and two holes with a diffuser-shaped exit portion (i.e., a fan-shaped and a laidback fan-shaped hole). The flow conditions considered were 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 pressure ratio across the hole (up to 2). The results show that the discharge coefficient for all geometries tested strongly depends on the flow conditions (crossflows at hole inlet and exit, and pressure ratio). The discharge coefficient of both expanded holes was found to be higher than of the cylindrical hole, particularly at low pressure ratios and with a hole entrance side crossflow applied. The effect of the additional layback on the discharge coefficient is negligible.

Effect of Crossflows on the Discharge Coefficient of Film Cooling Holes With Varying Angles of Inclination and Orientation

2001 ◽  
Author(s):  
Michael Gritsch ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Inclination Angle ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Orientation Angle ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole ◽  
Discharge Behavior ◽  
Hole Geometry ◽  
Film Cooling Holes

Measurements of discharge coefficients for five configurations of cylindrical film cooling hole geometries are presented. These comprise holes of varying angles of inclination (α= 30, 45, and 90deg) and orientation (γ= 0, 45, and 90deg) which are tested over a wide range of engine like conditions in terms of internal and external crossflow Mach numbers (Mam=0…1.2, Mac=0…0.6) as well as pressure ratios (ptc/pm=1…2.25). Results show that discharge coefficients do not solely depend on hole geometry but are also profoundly affected by the internal and external crossflow conditions. The effect of increasing the orientation angle on the discharge behavior is very similar to the effect of increasing the inclination angle. Both result in higher losses particularly at the cooling hole inlet while the losses at the hole exit are only slightly affected.

Effect of Crossflows on the Discharge Coefficient of Film Cooling Holes With Varying Angles of Inclination and Orientation

2001 ◽  
Vol 123 (4) ◽  
pp. 781-787 ◽  
Author(s):  
Michael Gritsch ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Inclination Angle ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Orientation Angle ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole ◽  
Discharge Behavior ◽  
Hole Geometry ◽  
Film Cooling Holes

Measurements of discharge coefficients for five configurations of cylindrical film cooling hole geometries are presented. These comprise holes of varying angles of inclination (α=30, 45, and 90 deg) and orientation (γ=0, 45, and 90 deg), which are tested over a wide range of engine-like conditions in terms of internal and external crossflow Mach numbers (Mam=0…1.2,Mac=0…0.6) as well as pressure ratios ptc/pm=1…2.25. Results show that discharge coefficients do not depend solely on hole geometry, but are also profoundly affected by the internal and external crossflow conditions. The effect of increasing the orientation angle on the discharge behavior is very similar to the effect of increasing the inclination angle. Both result in higher losses, particularly at the cooling hole inlet while the losses at the hole exit are only slightly affected.

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]

Experimental Study on Pressure Losses in Circular Orifices With Inlet Cross Flow

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Daniel Feseker ◽  
Mats Kinell ◽  
Matthias Neef
Keyword(s):  
Experimental Study ◽  
Film Cooling ◽  
Gas Turbines ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Cross Flow ◽  
Pressure Losses ◽  
Wide Range ◽  
Cooling Hole ◽  
Secondary Air

The ability to understand and predict the pressure losses of orifices is important in order to improve the air flow within the secondary air system. This experimental study investigates the behavior of the discharge coefficient for circular orifices with inlet cross flow which is a common flow case in gas turbines. Examples of this are at the inlet of a film cooling hole or the feeding of air to a blade through an orifice in a rotor disk. Measurements were conducted for a total number of 38 orifices, covering a wide range of length-to-diameter ratios, including short and long orifices with varying inlet geometries. Up to five different chamfer-to-diameter and radius-to-diameter ratios were tested per orifice length. Furthermore, the static pressure ratio across the orifice was varied between 1.05 and 1.6 for all examined orifices. The results of this comprehensive investigation demonstrate the beneficial influence of rounded inlet geometries and the ability to decrease pressure losses, which is especially true for higher cross flow ratios where the reduction of the pressure loss in comparison to sharp-edged holes can be as high as 54%. With some exceptions, the chamfered orifices show a similar behavior as the rounded ones but with generally lower discharge coefficients. Nevertheless, a chamfered inlet yields lower pressure losses than a sharp-edged inlet. The obtained experimental data were used to develop two correlations for the discharge coefficient as a function of geometrical as well as flow properties.

Large-Scale Testing to Validate the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes

2000 ◽  
Vol 123 (3) ◽  
pp. 593-600 ◽  
Author(s):  
D. A. Rowbury ◽  
M. L. G. Oldfield ◽  
G. D. Lock
Keyword(s):  
Film Cooling ◽  
Stream Flow ◽  
Large Scale ◽  
Discharge Coefficient ◽  
Static Pressure ◽  
Free Stream ◽  
Discharge Coefficients ◽  
Large Scale Testing ◽  
Cooling Hole ◽  
Film Cooling Holes

This paper discusses large-scale, low-speed experiments that explain unexpected flow-interaction phenomena witnessed during annular cascade studies into the influence of external crossflow on film cooling hole discharge coefficients. More specifically, the experiments throw light on the crossover phenomenon, where the presence of the external crossflow can, under certain circumstances, increase the discharge coefficient. This is contrary to most situations, where the external flow results in a decrease in discharge coefficient. The large-scale testing reported helps to explain this phenomenon through an increased understanding of the interaction between the emerging coolant jet and the free-stream flow. The crossover phenomenon came to light during an investigation into the influence of external crossflow on the discharge coefficients of nozzle guide vane film cooling holes. These experiments were performed in the Cold Heat Transfer Tunnel (CHTT), an annular blowdown cascade of film cooled vanes that models the three-dimensional external flow patterns found in modern aero-engines. (Rowbury et al., 1997, 1998). The variation in static pressure around the exit of film cooling holes under different flow conditions was investigated in the large-scale tests. The study centered on three holes whose geometries were based on those found in the leading edge region of the CHTT vanes, as the crossover phenomenon was witnessed for these rows during the initial testing. The experiments were carried out in a low-speed wind tunnel, with the tunnel free-stream flow velocity set to match the free-stream Reynolds number (based on the local radius of curvature) and the “coolant” flow velocity set to replicate the engine coolant-to-free-stream momentum flux ratio. It was found that the apparent enhancement of film cooling hole discharge coefficients with external crossflow was caused by a reduction in the static pressure around the hole exit, associated with the local acceleration of the free-stream around the emerging coolant jet. When these measured static pressures (rather than the free-stream static pressure) were used to calculate the discharge coefficient, the crossover effect was absent. The improved understanding of the crossover phenomenon and coolant-to-free-stream interactions that has been gained will be valuable in aiding the formulation of predictive discharge coefficient schemes.

CFD Predicted Discharge Coefficients of a Single Cylindrical Hole With Compressible External Cross-Flow

2009 ◽  
Author(s):  
L. Guo ◽  
Y. Y. Yan ◽  
J. D. Maltson
Keyword(s):  
Mach Number ◽  
Pressure Distribution ◽  
Inclination Angle ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Cylindrical Hole ◽  
Static Pressure Distribution ◽  
Mainstream Flow

A computational investigation on discharge coefficient (Cd) of a single cylindrical hole is presented in this paper. The numerical calculations are carried out on a 3-D compressible model. The Shear-Stress Transport (SST) k–ω model is used to simulate the turbulence in the flow. The inclination angle (α) of the film cooling hole varies from 20° to 30°, 45° and 90°, respectively. The diameter of the hole is fixed at 10mm, but different coolant to mainstream pressure ratios (ptc/pm) are examined. The coolant Mach number (Mac) is set at a constant value of 0.3 and the mainstream flow Mach number (Mam) varies from 0.3 to 1.4. The effects of Mam and α on the Cd value as well as the static pressure distribution at the jet exit are investigated. The numerical results show an acceptable agreement in the trend of the Cd variation compare with the available experimental data. It has been predicted that the static pressure distribution in the vicinity of the jet exit is influenced by a number of factors including the mainstream flow Mach number, shock wave, jet inclination angle and the pressure ratio of the coolant to the mainstream flow. And then the static pressure field near the hole can further give strong influence on the discharge coefficient.

A Method for Correlating the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes

2000 ◽  
Author(s):  
D. A. Rowbury ◽  
M. L. G. Oldfield ◽  
G. D. Lock
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Film Cooling ◽  
Guide Vane ◽  
Density Ratio ◽  
External Flow ◽  
Published Data ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Film Cooling Holes

An empirical means of predicting the discharge coefficients of film cooling holes in an operating engine has been developed. The method quantifies the influence of the major dimensionless parameters, namely hole geometry, pressure ratio across the hole, coolant Reynolds number, and the freestream Mach number. The method utilises discharge coefficient data measured on both a first-stage high-pressure nozzle guide vane from a modern aero-engine and a scale (1.4 times) replica of the vane. The vane has over 300 film cooling holes, arranged in 14 rows. Data was collected for both vanes in the absence of external flow. These non-crossflow experiments were conducted in a pressurised vessel in order to cover the wide range of pressure ratios and coolant Reynolds numbers found in the engine. Regrettably, the proprietary nature of the data collected on the engine vane prevents its publication, although its input to the derived correlation is discussed. Experiments were also conducted using the replica vanes in an annular blowdown cascade which models the external flow patterns found in the engine. The coolant system used a heavy foreign gas (SF6/Ar mixture) at ambient temperatures which allowed the coolant-to-mainstream density ratio and blowing parameters to be matched to engine values. These experiments matched the mainstream Reynolds and Mach numbers and the coolant Mach number to engine values, but the coolant Reynolds number was not engine representative (Rowbury et al., 1997 and 1998). A correlation for discharge coefficients in the absence of external crossflow has been derived from this data and other published data. An additive loss coefficient method is subsequently applied to the cascade data in order to assess the effect of the external crossflow. The correlation is used successfully to reconstruct the experimental data. It is further validated by successfully predicting data published by other researchers. The work presented is of considerable value to gas turbine design engineers as it provides an improved means of predicting the discharge coefficients of engine film cooling holes.

Discharge Coefficient of Turbine Cooling Holes: A Review

1998 ◽  
Vol 120 (2) ◽  
pp. 314-319 ◽  
Author(s):  
N. Hay ◽  
D. Lampard
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Correlated Data ◽  
Published Data ◽  
Flow Conditions ◽  
Turbine Cooling ◽  
Acceptable Accuracy ◽  
Discharge Coefficients ◽  
Method Of Evaluation ◽  
Film Cooling Holes

Published information on the discharge coefficient of film cooling holes is classified in terms of the hole geometry, the external flow conditions at inlet and outlet, and the method of evaluation. This may be either theoretical or experimental. The information is reviewed primarily in the context of its use for evaluating discharge coefficients for conditions not directly covered by published data. It is shown that potential flow analyses can give acceptable accuracy for simple geometries with crossflows, while more complex cases require the use of correlated data, which may be incorporated in a range of predictive schemes. Deficiencies and inconsistencies in the published information are highlighted, and future developments are discussed.

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