scholarly journals Discharge Coefficients of Ports with Stepped Inlets

Aerospace ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 97
Author(s):  
Adrian Spencer
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Empirical Correlations ◽  
Equivalent Radius ◽  
One Dimensional ◽  
Vena Contracta ◽  
Discharge Coefficients ◽  
The Subject

Components of aeronautical gas turbines are increasingly being constructed from two layers, including a pressure containing skin, which is then protected by a thermal tile. Between them, pedestals and/or other heat transfer enhancing features are often employed. This results in air admission ports through the dual skin having a step feature at the inlet. Experimental data have been captured for stepped ports with a cross flow approach, which show a marked increase of 20% to 25% in discharge coefficient due to inlet step sizes typical of combustion chamber configurations. In this respect, the step behaves in a fashion comparable to ports with inlet chamfering or radiusing; the discharge coefficient is increased as a result of a reduction in the size of the vena contracta brought about by changes to the flow at inlet to the port. Radiused and chamfered ports have been the subject of previous studies, and empirical correlations exist to predict their discharge coefficient as used in many one-dimensional flow network tools. A method to predict the discharge coefficient change due to a step is suggested: converting the effect of the step into an equivalent radius to diameter ratio available in existing correlation approaches. An additional factor of eccentricity between the hole in the two skins is also considered. Eccentricity is shown to reduce discharge coefficient by up to 10% for some configurations, which is more pronounced at higher port mass flow ingestion fraction.

Experimental Study on Orifice Discharge Coefficients in Impingement Cooling With Confined Cross Flow

2015 ◽  
Author(s):  
Andre Schellenberg ◽  
Mats Kinell ◽  
Daniel Eriksson
Keyword(s):  
Discharge Coefficient ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Measured Data ◽  
Diameter Ratio ◽  
Maximum Deviation ◽  
Geometrical Parameters ◽  
Target Plate ◽  
Impingement Cooling ◽  
Discharge Coefficients

This work experimentally investigates the effects of confined cross flow and geometrical parameters in impingement flows on the jet discharge coefficient, Cd. Such cooling configurations are common in the gas turbine industry and all properties were chosen to be applicable in real applications. The effect on Cd was studied for square edged orifices with thickness to diameter ratio l/d = 1 in the range of jet to cross flow mass velocity ratio 0 ≤ Gc/Gj ≤ 6 at a jet Reynolds number of 104. The distance between orifices in the span wise yn/d = 2.5–8 and stream wise xn/d = 2.5–7 directions as well as the spacing to the target plate z/d = 1–3 were investigated. Generally, the conclusions from previous studies were confirmed. An exception to this was the observed increase of Cd with increasing Gc/Gj for Gc/Gj < 0.5. A correlation was developed for the discharge coefficient with the new experimental data as function of z/d, yn/d and Gc/Gj. The resemblance to the measured data was excellent with a maximum deviation of 4%.

scholarly journals Discharge Coefficients of Cooling Holes With Radiused and Chamfered Inlets

1991 ◽  
Author(s):  
N. Hay ◽  
A. Spencer
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Practical Interest ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Discharge Coefficients ◽  
The Subject ◽  
Cooling Air

The flow of cooling air within the internal passages of gas turbines is controlled and metered using orifices formed of holes in discs and casings. The effects of inlet radiusing and chamfering of these holes on the discharge coefficient forms the subject of this paper. Experimental results for a range of radiusing and chamfering ratios for holes of different length to diameter ratios are presented covering the range of pressure ratios of practical interest. The results indicate that radiusing and chamfering are both beneficial in increasing the discharge coefficient. Increases of 10–30% are possible. Chamfered holes give the more desirable performance characteristics in addition to being easier to produce than radiused holes.

Discharge Coefficients of Cooling Holes With Radiused and Chamfered Inlets

1992 ◽  
Vol 114 (4) ◽  
pp. 701-706 ◽  
Author(s):  
N. Hay ◽  
A. Spencer
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Practical Interest ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Discharge Coefficients ◽  
The Subject ◽  
Cooling Air

The flow of cooling air within the internal passages of gas turbines is controlled and metered using orifices formed of holes in disks and casings. The effects of inlet radiusing and chamfering of these holes on the discharge coefficients forms the subject of this paper. Experimental results for a range of radiusing and chamfering ratios for holes of different length-to-diameter ratios are presented covering the range of pressure ratios of practical Interest. The results indicate that radiusing and chamfering are both beneficial in increasing the discharge coefficient. Increases of 10–30 percent are possible. Chamfered holes give the more desirable performance characteristics in addition to being easier to produce than radiused holes.

On the Modeling of Tip Leakage Flow in Axial Turbine Blade Rows

2000 ◽  
Author(s):  
Reinhard Willinger ◽  
Hermann Haselbacher
Keyword(s):  
Discharge Coefficient ◽  
Velocity Ratio ◽  
Length Ratio ◽  
Tip Leakage Flow ◽  
Vena Contracta ◽  
Tip Leakage ◽  
Discharge Coefficients ◽  
Gap Flow ◽  
Starting Point ◽  
Gap Width

The starting point of this paper is an established turbine tip leakage loss model based on energy considerations. The model requires a discharge coefficient as an empirical input. The discharge coefficient is the ratio of the actual to the theoretical tip gap mass flow rate, The nondimensional parameters influencing the discharge coefficient are determined by a dimensional analysis. These parameters are: gap width to length ratio, end wall speed to gap flow velocity ratio and gap Reynolds number. Ranges for these parameters, valid for typical turbine tip gap situations, are presented. The numerical investigation of the turbulent flow in a plane perpendicular to the blade chord line supplies the discharge coefficient versus the nondimensional gap width. Depending on the gap width to length ratio, various degrees of mixing of the flow downstream of the vena contracta can be detected. Based on these observations, a simple tip gap flow model is presented. The discharge coefficients computed by this model are compared with the numerical results as well as with experimental values from the literature. Finally, the model is used to calculate the discharge coefficients of improved tip gap geometries (squealers, winglets).

Steady Compressible Flow through a Single Row of Radial Holes in the Wall of a Pipeline

1970 ◽  
Vol 12 (4) ◽  
pp. 248-258 ◽  
Author(s):  
G. H. Trengrouse
Keyword(s):  
Discharge Coefficient ◽  
Pressure Change ◽  
Single Row ◽  
One Dimensional ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Flow Through ◽  
Flow Theories ◽  
Good Agreement

Measured values of discharge coefficient for air flow through a single row of radial holes in the wall of a pipeline are reported, together with the values of pipe Mach numbers in the immediate vicinity of the holes. A wide range of pressure and area ratios are considered, the flow through the holes being either into or out of the pipe. It is shown that the effects on the measured values of both the pressure level at discharge from the holes and the air temperature are negligible. The agreement between the pressure change in the pipeline due to the holes, obtained experimentally, and that predicted by simple, one-dimensional flow theories is generally unsatisfactory. However, theoretical predictions of the jet efflux angles based on two-dimensional, incompressible, non-viscous flow arguments are in good agreement with those measured, but discrepancies do arise in the prediction of discharge coefficients.

Numerical Study of Inlet and Geometry Effects on Discharge Coefficients for Liquid Jet Emanating From a Plain-Orifice Atomizer

2002 ◽  
Vol 18 (3) ◽  
pp. 153-161 ◽  
Author(s):  
Chun-Lang Yeh
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Discharge Coefficient ◽  
Numerical Study ◽  
Surface Force ◽  
Diameter Ratio ◽  
The Body ◽  
Liquid Jet ◽  
Discharge Coefficients ◽  
Geometry Effects

AbstractA computational model for flow in a plain-orifice atomizer is established to examine the inlet and geometry effects on discharge coefficients. The volume of fluid (VOF) method with finite volume formulation was employed to capture the liquid/gas interface. A continuum Surface Force (CSF) model was adopted to model the surface tension. The body-fitted coordinate system was used to facilitate the configuration of the atomizer. The influences of the inlet chamfer angle, the orifice length/diameter ratio, the Reynolds number, and the inlet turbulence intensity are analyzed. It is found that the optimum discharge coefficient occurs at a chamfer angle of about 50°. The discharge coefficient at first increases with the increase in the orifice length/diameter ratio and then it decreases. The discharge coefficient increases with the increase in the Reynolds number up to Re = 40000, after which it remains sensibly constant. The influence of the inlet turbulence intensity on discharge coefficient is not significant, especially for a longer orifice.

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.

Experimental Heat Transfer and Discharge Coefficients for Single Confined Jet Impingement Normal to a Surface at Close Distances

2008 ◽  
Author(s):  
J. D. Shapiro ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Discharge Coefficient ◽  
Jet Impingement ◽  
Ambient Air ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Gap Size ◽  
Discharge Coefficients

Heat transfer and flow discharge coefficients for confined jet impingement are being investigated for a single round jet impinging normal to a target surface less than one hole diameter from the jet origin. A search of open literature resulted in the availability of no discharge coefficient information, and limited heat transfer information, especially for the configuration of a confined jet in close surface impingement. The experiment has been conducted for a developing jet and utilizes liquid crystal thermography for heat transfer measurements. Nusselt numbers were obtained for jet Reynolds numbers between 15000 and 30000 with a gap to hole diameter ratio of 0.3 to 3. Discharge coefficient data were obtained for jet Reynolds numbers between 11000 and 59000, with a gap to hole diameter ratio of 0.2 to infinity. The heat transfer data obtained shows a secondary Nusselt number peak and similar trends to those seen in other close surface impingement studies. The data also show a crossover of Nusselt number at increasing radial distance from the jet stagnation point with increasing gap size which could be indicative of ambient air entrainment. The discharge coefficient data obtained show a decrease in discharge coefficient for a decrease in gap size. At constant pressure ratio conditions a large decrease in discharge coefficient is observed between pressure ratios of 1.05 and 1.11. The results of this study are applicable to many industrial applications. However, a discussion of close surface impingements applicability to gas turbines has been included, as well as a comparison of the experimental and numerical results.

scholarly journals Discharge Coefficient Measurements for Flow Through Compound-Angle Conical Holes with Cross-Flow

2004 ◽  
Vol 10 (2) ◽  
pp. 145-153 ◽  
Author(s):  
M. E. Taslim ◽  
S. Ugarte
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Flow Direction ◽  
Cross Flow ◽  
Discharge Coefficients ◽  
Flow Length ◽  
Cylindrical Holes ◽  
Flow Through ◽  
Compound Angle ◽  
Hole Axis

Diffusion-shaped film holes with compound angles are currently being investigated for high temperature gas turbine airfoil film cooling. An accurate prediction of the coolant blowing rate through these film holes is essential in determining the film effectiveness. Therefore, the discharge coefficients associated with these film holes for a range of hole pressure ratios is essential in designing airfoil cooling circuits. Most of the available discharge coefficient data in open literature has been for cylindrical holes. The main objective of this experimental investigation was to measure the discharge coefficients for subsonic as well as supersonic pressure ratios through a single conical-diffusion hole. The conical hole has an exit-to-inlet area ratio of 4, a nominal flow length-to-inlet diameter ratio of 4, and an angle with respect to the exit plane (inclination angle) of 0°, 30°, 45°, and 60°. Measurements were performed with and without a cross-flow. For the cases with a cross-flow, discharge coefficients were measured for each of the hole geometries and 5 angles between the projected conical hole axis and the cross-flow direction of 0°, 45°, 90°, 135°, and 180°. Results are compared with available data in open literature for cylindrical film holes as well as limited data for conical film holes.

Discharge Coefficient and Effectiveness Measurement for Conical Shaped Film Cooling Holes

2005 ◽  
Author(s):  
H. A. Zuniga ◽  
Vaidyanathan Krishnan ◽  
A. K. Sleiti ◽  
J. S. Kapat ◽  
Sanjeev Bharani
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Density Ratio ◽  
Diameter Ratio ◽  
Constant Density ◽  
Base Line ◽  
Blowing Ratio ◽  
Discharge Coefficients ◽  
Effectiveness Measurement ◽  
Film Cooling Holes

Experimental measurements of discharge coefficient and effectiveness of conical shaped film cooling holes with 1°, 2° and 3° uniform diffusion angle are presented. All film holes are inclined at 35° with hole length to diameter ratio, L/D = 3.5, pitch to diameter ratio, PI/D = 3 with a constant density ratio of 1.26 and with nitrogen as the coolant. Results show that conical film holes have higher discharge coefficients than their cylindrical counterparts. For conical holes, the local distribution and laterally averaged effectiveness values decrease with increasing blowing ratio from 0.45 to 1. The configuration with 3° uniform diffusion angle has the highest effectiveness values and outperforms the conical holes with 1°, 2° diffusion angles by 40% in the proximity of the holes (X/D ≪ 5) at a blowing ratio of 0.45. Results are compared to base line cylindrical as well as to fan shape film holes available in open literature. The average effectiveness of the conical holes can reach values comparable to those achieved by fan shaped film holes at the same blowing ratio.

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