The Effect of Manifold Cross-Flow on the Discharge Coefficient of Sharp-Edged Orifices

1997 ◽  
Vol 24 (1-3) ◽  
pp. 239-250 ◽  
Author(s):  
P. A. Strakey ◽  
K. M. Olson ◽  
Douglas G. Talley
Keyword(s):  
Discharge Coefficient ◽  
Cross Flow

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.

Investigation of the Prediction Correlations for the Flow Through Rotating Orifices in the Gas Turbine Secondary Air Flow System

2013 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Zain Dweik ◽  
A. Subramani ◽  
Murali Krishnan R.
Keyword(s):  
Gas Turbine ◽  
Discharge Coefficient ◽  
Flow System ◽  
Air Flow ◽  
Tangential Velocity ◽  
Cross Flow ◽  
Secondary System ◽  
Accurate Analysis ◽  
Secondary Air ◽  
Reliable Design

The secondary air flow system of a gas turbine cools and seals those parts of the turbine which would otherwise be exposed to the high temperatures, resulting in their life reduction or even failures. At the same time, excessive secondary air flow hinders the performance of the engine. Accurate analysis of the secondary system is therefore necessary to safeguard the reliable design of the engine and accurate life predictions. The secondary system is analyzed through the flow network analysis which comprises of chambers or cavities connected through flow passages or restrictions. There are significant number of locations where the air passes through stationary or rotating holes, e.g., the pre-swirl nozzles and the turbine blade receiver holes respectively. The accuracy of the flow prediction depends on the accuracy of the orifice discharge coefficient. This paper provides a detailed assessment of the available discharge coefficient correlations. The discharge coefficient has been found to be dependent on the geometric parameters (viz., length, inlet radius, chamfer), and the amount of cross-flow at the orifice entrance. The cross-flow may result from the relative tangential velocity between the orifice and the air or the inclination of the inlet flow with respect to the orifice axis. In this study, it was found that the discharge coefficient correlations provide similar predictions for flows without any cross-flow. However, significant deviations are seen in the predictions for the cases involving cross-flow. To identify the most accurate correlation for secondary flow application, a thorough assessment was performed using the static and the rotating test data available in the literature. In addition to the comparison using available experimental data, a CFD study was performed to independently assess the correlations. This exercise led to the identification of the most suitable correlation for our application.

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.

Investigations on the Influence of Rib Orientation Angle on Film Cooling Performance of Cylindrical Holes

2017 ◽  
Author(s):  
Lin Ye ◽  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Jian-xia Luo ◽  
Ying-ni Zhai
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow Channels ◽  
Cylindrical Holes

This paper presents an experimental and numerical investigation on the film cooling with different coolant feeding channel structures. Two ribbed cross-flow channels with rib-orientation of 135° and 45° respectively and the plenum coolant channel have been studied and compared to find out the effect of rib orientation on the film cooling performances of cylindrical holes. The film cooling effectiveness and heat transfer coefficient were measured by the transient heat transfer measurement technique with narrow-band thermochromic liquid crystal. Numerical simulations with realizable k-ε turbulence model were also performed to analyze the flow mechanism. The results show that the coolant channel structure has a notable effect on the flow structure of film jet which is the most significant mechanism affecting the film cooling performance. Generally, film cooling cases fed with ribbed cross-flow channels have asymmetric counter-rotating vortex structures and related asymmetric temperature distributions, which make the film cooling effectiveness and the heat transfer coefficient distributions asymmetric to the hole centerline. The discharge coefficient of the 45° rib case is the lowest among the three cases under all the blowing ratios. And the plenum case has higher discharge coefficient than the 135° rib case under low blowing ratio. With the increase of blowing ratio, the discharge coefficient of the 135° rib case gets larger than the plenum case gradually, because the vortex in the upper half region of the coolant channel rotates in the same direction with the film hole inclination direction and makes the jet easy to flow into the film hole in the 135° rib case.

Rotor-Tip Leakage: Part II — Design Optimization Through Viscous Analysis and Experiment

1981 ◽  
Author(s):  
A. R. Wadia ◽  
T. C. Booth
Keyword(s):  
Stream Function ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Turbine Rotor ◽  
Leakage Flow ◽  
Tip Leakage ◽  
Rotating Blades ◽  
Numerical Studies ◽  
Coolant Injection ◽  
Blade Tip

Blade tip losses represent a major efficiency penalty in a turbine rotor. These losses are presently controlled by maintaining close tolerances on tip clearances. This two-part paper outlines a new methodology for predicting and minimizing tip flows, and focuses on the control of tip leakage through minimization of the discharge coefficient to control the normal leakage flow component. Minimization of the discharge coefficient was achieved through viscous analysis and was supported by discharge-rig testing. The analysis for the discharge cross-flow used a stream function-vorticity formulation. Support testing was conducted with a newly developed water table discharge rig in which tip-coolant discharge could also be simulated. Experimental and numerical tip-leakage results are presented on a discharge coefficient parameter for five different tip configurations. In addition, numerical studies were conducted for stationary and rotating blades with and without tip coolant injection.

Numerical Study on Flow and Heat Transfer Characteristics of Discrete Film Cooling Holes of the Sinusoidal Longitudinal Corrugated Heat Liner

2019 ◽  
Author(s):  
Zhi-peng Xu ◽  
Hui-ren Zhu ◽  
Ya-zhou Wang ◽  
Xinyu Bian
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Pressure Gradient ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Windward Side ◽  
Heat Transfer Characteristics ◽  
Corrugated Surface ◽  
Film Cooling Holes

Abstract To understand film cooling flow fields and heat transfer characteristics of the longitudinal corrugated surface on afterburner heat liner, the numerical simulation was performed in approximate actual boundary conditions. The single hole and full film holes on the corrugated surface were investigated under different boundary conditions to study the heat transfer and discharge coefficient. The adverse pressure gradient on the leeward results in spanwise expansion of the airflow, while the favorable pressure gradient on the windward keeps the shape of the jet constant. The different hole spacing and hole row spacing in different positions of the corrugated surface should be considered due to the film covering characteristics. The film cooling holes at the same height on the leeward and windward share the similar laterally average effectiveness. The flow rate and discharge coefficient increase from crest to trough. Cross-flow has a negative influence on the discharge coefficient especially the inlet cross-flow. The cross-flow and discharge coefficient can be correlated with each other by a logarithmic function. The jet discharge coefficient on the windward surface is higher than that on the leeward surface, which is contrary to previous cognition. The reason is that the jet blocking causes the downstream pressure zone to advance, which counteracts and enhanced the siphon effect on the leeward and windward side respectively. As the inlet pressure of coolant increases, the film cooling effectiveness on the windward side is greatly improved in full film condition. However, it changes little on the leeward side.

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.

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