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.

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.

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.

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.

Adiabatic Wall Effectiveness Measurements of Film-Cooling Holes With Expanded Exits

1998 ◽  
Vol 120 (3) ◽  
pp. 549-556 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Thermal Protection ◽  
Lateral Spreading ◽  
Cylindrical Hole ◽  
Camera System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Shaped Hole

This paper presents detailed measurements of the film-cooling effectiveness for three single, scaled-up film-cooling hole geometries. The hole geometries investigated include a cylindrical hole and two holes with a diffuser-shaped exit portion (i.e., a fan-shaped and a laid-back fan-shaped hole). The flow conditions considered are 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 blowing ratio (up to 2). The coolant-to-mainflow temperature ratio is kept constant at 0.54. The measurements are performed by means of an infrared camera system, which provides a two-dimensional distribution of the film-cooling effectiveness in the near field of the cooling hole down to x/D = 10. As compared to the cylindrical hole, both expanded holes show significantly improved thermal protection of the surface downstream of the ejection location, particularly at high blowing ratios. The laidback fan-shaped hole provides a better lateral spreading of the ejected coolant than the fan-shaped hole, which leads to higher laterally averaged film-cooling effectiveness. Coolant passage cross-flow Mach number and orientation strongly affect the flowfield of the jet being ejected from the hole and, therefore, have an important impact on film-cooling performance.

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

1983 ◽  
Vol 105 (2) ◽  
pp. 243-248 ◽  
Author(s):  
N. Hay ◽  
D. Lampard ◽  
S. Benmansour
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Practical Importance ◽  
Design Stage ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Scant Attention ◽  
Cooling Hole ◽  
Film Cooling Holes

The strongest flow parameter governing the film cooling effectiveness provided by a row of holes is the blowing rate. Precise setting of the blowing rate at the design stage requires accurate data for the discharge coefficient of the holes. The effects of crossflow on the discharge coefficient have received scant attention in published work to date. In the present work, the discharge coefficient of single rows of holes has been measured in a specially constructed isothermal rig over a wide range of geometric and flow conditions. Mainstream and coolant Mach numbers have been varied independently over the range 0 to 0.4 for pressure ratios in the range 0 to 2. Cooling hole length to diameter ratios were varied between 2 and 6, and inclinations of 30, 60, and 90 deg were used. The results show that the influence of crossflow is strong and complex, particularly with regard to that on the coolant side. A large range of data is presented sufficient to permit the discharge coefficient to be inferred for many cases of practical importance. Suggestions are also made for a promising theoretical approach to this problem.

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]

scholarly journals Adiabatic Wall Effectiveness Measurements of Film-Cooling Holes With Expanded Exits

1997 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Thermal Protection ◽  
Lateral Spreading ◽  
Cylindrical Hole ◽  
Adiabatic Wall ◽  
Camera System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper presents detailed measurements of the film-cooling effectiveness for three single, scaled-up film-cooling hole geometries. The hole geometries investigated 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 are 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 blowing ratio (up to 2). The coolant-to-mainflow temperature ratio is kept constant at 0.54. The measurements are performed by means of an infrared camera system which provides a two-dimensional distribution of the film-cooling effectiveness in the nearfield of the cooling hole down to x/D = 10. As compared to the cylindrical hole, both expanded holes show significantly improved thermal protection of the surface downstream of the ejection location, particularly at high blowing ratios. The laidback fanshaped hole provides a better lateral spreading of the ejected coolant than the fanshaped hole which leads to higher laterally averaged film-cooling effectiveness. Coolant passage crossflow Mach number and orientation strongly affect the flowfield of the jet being ejected from the hole and, therefore, have an important impact on film-cooling performance.

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