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.

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.

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.

Unsteady Numerical Simulation of the Flow in a Direct Transfer Pre-Swirl System

2008 ◽  
Author(s):  
Fabio Ciampoli ◽  
Nicholas J. Hills ◽  
John W. Chew ◽  
Timothy Scanlon
Keyword(s):  
Discharge Coefficient ◽  
Direct Transfer ◽  
Elementary Model ◽  
Discharge Coefficients ◽  
Significant Difference ◽  
Aero Engine ◽  
Velocity Coefficient ◽  
Unsteady Numerical Simulation ◽  
Unsteady Effects ◽  
Cooling Air

Results of fully unsteady numerical simulations of the flow in a direct transfer pre-swirl system are presented and compared with previously published experimental data from an aero-engine representative rig. The conditions considered include those where strong unsteady effects were observed experimentally. Two different rig builds are considered, with the main difference being in the design of the pre-swirl nozzles. The agreement between calculation and experiment is very good in terms of nozzle and receiver hole discharge coefficients and in identifying significant unsteady effects at certain conditions. Predicted cooling air delivery temperatures are lower than those measured. This may be due to heat transfer and other effects in the rig which have not been modelled. Present unsteady results also show agreement, where appropriate, with earlier steady CFD and an elementary model. Both calculations and measurements show similar performance in terms of delivery temperature for the two different builds studied, despite significant difference in pre-swirl nozzle discharge coefficients for the two builds. The calculations indicate that this is associated with the nozzle velocity coefficient being considerably higher than the discharge coefficient in one case.

Experimental Results of Flow Nozzle Based on PTC 6 for High Reynolds Number

2014 ◽  
Author(s):  
Noriyuki Furuichi ◽  
Kar-Hooi Cheong ◽  
Yoshiya Terao ◽  
Shinichi Nakao ◽  
Keiji Fujita ◽  
...  
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Discharge Coefficient ◽  
Experimental Results ◽  
Flow Conditions ◽  
Number Range ◽  
Discharge Coefficients ◽  
Reynolds Number Range ◽  
Lower Reynolds Number ◽  
High Reynolds

Discharge coefficients for three flow nozzles based on ASME PTC 6 are measured under many flow conditions at AIST, NMIJ and PTB. The uncertainty of the measurements is from 0.04% to 0.1% and the Reynolds number range is from 1.3×105 to 1.4×107. The discharge coefficients obtained by these experiments is not exactly consistent to one given by PTC 6 for all examined Reynolds number range. The discharge coefficient is influenced by the size of tap diameter even if at the lower Reynolds number region. Experimental results for the tap of 5 mm and 6 mm diameter do not satisfy the requirements based on the validation procedures and the criteria given by PTC 6. The limit of the size of tap diameter determined in PTC 6 is inconsistent with the validation check procedures of the calibration result. An enhanced methodology including the term of the tap diameter is recommended. Otherwise, it is recommended that the calibration test should be performed at as high Reynolds number as possible and the size of tap diameter is desirable to be as small as possible to obtain the discharge coefficient with high accuracy.

Discharge Coefficients of Rotating Short Orifices With Radiused and Chamfered Inlets

2004 ◽  
Vol 126 (4) ◽  
pp. 803-808 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Reynolds Numbers ◽  
Frame Of Reference ◽  
Efficient Operation ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Secondary Air ◽  
Cooling Air ◽  
Actual Geometry

The secondary air system of modern gas turbine engines consists of numerous stationary or rotating passages to transport the cooling air, taken from the compressor, to thermally high loaded components that need cooling. Thereby the cooling air has to be metered by orifices to control the mass flow rate. Especially the discharge behavior of rotating holes may vary in a wide range depending on the actual geometry and the operating point. The exact knowledge of the discharge coefficients of these orifices is essential during the design process in order to guarantee a well adapted distribution of the cooling air inside the engine. This is crucial not only for a safe and efficient operation but also fundamental to predict the component’s life and reliability. In this paper two different methods to correlate discharge coefficients of rotating orifices are described and compared, both in the stationary and rotating frame of reference. The benefits of defining the discharge coefficient in the relative frame of reference will be pointed out. Measurements were conducted for two different length-to-diameter ratios of the orifices with varying inlet geometries. The pressure ratio across the rotor was varied for rotational Reynolds numbers up to ReΦ=8.6×105. The results demonstrate the strong influence of rotation on the discharge coefficient. An analysis of the complete data shows significant optimizing capabilities depending on the orifice geometry.

Discharge Coefficients of Rotating Short Orifices With Radiused and Chamfered Inlets

2003 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Reynolds Numbers ◽  
Frame Of Reference ◽  
Efficient Operation ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Secondary Air ◽  
Cooling Air ◽  
Actual Geometry

The secondary air system of modern gas turbine engines consists of numerous stationary or rotating passages to transport the cooling air, taken from the compressor, to thermally high loaded components that need cooling. Thereby the cooling air has to be metered by orifices to control the mass flow rate. Especially the discharge behavior of rotating holes may vary in a wide range depending on the actual geometry and the operating point. The exact knowledge of the discharge coefficients of these orifices is essential during the design process in order to guarantee a well adapted distribution of the cooling air inside the engine. This is crucial not only for a safe and efficient operation but also fundamental to predict the component’s life and reliability. In this paper two different methods to correlate discharge coefficients of rotating orifices are described and compared, both in the stationary and rotating frame of reference. The benefits of defining the discharge coefficient in the relative frame of reference will be pointed out. Measurements were conducted for two different length-to-diameter ratios of the orifices with varying inlet geometries. The pressure ratio across the rotor was varied for rotational Reynolds numbers up to Reφ = 8:6 × 105. The results demonstrate the strong influence of rotation on the discharge coefficient. An analysis of the complete data shows significant optimising capabilities depending on the orifice geometry.

scholarly journals Application of SVM, ANN, GRNN, RF, GP and RT models for predicting discharge coefficients of oblique sluice gates using experimental data

2020 ◽  
Author(s):  
Farzin Salmasi ◽  
Meysam Nouri ◽  
Parveen Sihag ◽  
John Abraham
Keyword(s):  
Discharge Coefficient ◽  
Performance Metrics ◽  
Experimental Results ◽  
Free Flow ◽  
Support Vector ◽  
Flow Conditions ◽  
Discharge Coefficients ◽  
Gate Opening ◽  
Experimental Apparatus ◽  
Inclined Angle

Abstract Gates are commonly used to adjust water flow in open channels. By using an oblique/inclined gate, the water transferring capacity of open irrigation canals can be increased. Investigation of free and submerged discharge coefficients for inclined sluice gates is the focus of the present study. First an experimental apparatus incorporating an inclined gate was created. The inclined angle (β) and gate opening (a) were experiment variables, and the five inclination angles include: 0° (vertical gate), 15°, 30°, 45° and 60°. Experimental results showed a greater convergence of flow lines under the gate and increasing the gate angle causes the discharge coefficient to increase. Also experiments showed that increasing the submergence rate (yt/a), decreases the inclined gate discharge coefficient. Performance metrics were created for the experimental results. The metrics utilized Gaussian process (GP) regression, Support Vector Machine (SVM), artificial neural networks (ANN), generalized regression neural network (GRNN), Random Forest (RF) regression and Random Tree (RT) based models which were used to predict discharge coefficients (Cd) in both submerged and free flow conditions. The model input parameters were the ratio of the upstream water depth to gate opening (y/a) and the inclined angle (β) for free flow and also the submergence rate (yt/a) for submerged flow. The prediction models show that the ANN model in free flow conditions has the following performance metrics: Coefficient of determination, R2= 0.9957, Root Mean Square Error (RMSE) = 0.0044, and Mean Absolute Error (MAE) = 0.0017. The performance metrics for submerged flow conditions were R2 = 0.9922, RMSE = 0.0079 and MAE = 0.0054. The ANN approach is the most accurate model compared to the others.

Experimental Study on Pressure Losses in Circular Orifices for the Application in Internal Cooling Systems

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Christian Binder ◽  
Mats Kinell ◽  
Esa Utriainen ◽  
Daniel Eriksson ◽  
Mehdi Bahador ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Air Flow ◽  
Internal Cooling ◽  
Cooling Systems ◽  
Pressure Losses ◽  
Flow Through ◽  
Cooling Air Flow ◽  
New Phenomena ◽  
Cooling Air

The cooling air flow in a gas turbine is governed by the flow through its internal passages and controlled by restrictors such as circular orifices. If the cooling air flow is incorrectly controlled, the durability and mechanical integrity of the whole turbine may be affected. Consequently, a good understanding of the orifices in the internal passages is important. This study presents experimental results for a range of pressure ratios and length-to-diameter ratios common in gas turbines including even very small pressure ratios. Additionally, the chamfer depth at the inlet was also varied. The results of the chamfer depth variation confirmed its beneficial influence on decreasing pressure losses. Moreover, important effects were noted when varying more than one parameter at a time. Besides earlier mentioned hysteresis at the threshold of choking, new phenomena were observed, e.g., a rise of the discharge coefficient for certain pressure and length-to-diameter ratios. A correlation for the discharge coefficient was attained based on the new experimental data with a generally lower error than previous studies.

New Discharge Coefficient of Throat Tap Nozzle Based on ASME Performance Test Code 6 for Reynolds Number From 2.4 × 105 to 1.4 × 107

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Noriyuki Furuichi ◽  
Kar-Hooi Cheong ◽  
Yoshiya Terao ◽  
Shinichi Nakao ◽  
Keiji Fujita ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Discharge Coefficient ◽  
Performance Test ◽  
Reynolds Numbers ◽  
Experimental Results ◽  
National Metrology Institute ◽  
Reference Curve ◽  
Number Range ◽  
Discharge Coefficients

The throat tap nozzle of the American Society of Mechanical Engineers performance test code (ASME PTC) 6 is widely used in engineering fields, and its discharge coefficient is normally estimated by an extrapolation in Reynolds number range higher than the order of 107. The purpose of this paper is to propose a new relation between the discharge coefficient of the throat tap nozzle and Reynolds number by a detailed analysis of the experimental data and the theoretical models, which can be applied to Reynolds numbers up to 1.5 × 107. The discharge coefficients are measured for several tap diameters in Reynolds numbers ranging from 2.4 × 105 to 1.4 × 107 using the high Reynolds number calibration rig of the National Metrology Institute of Japan (NMIJ). Experimental results show that the discharge coefficients depend on the tap diameter and the deviation between the experimental results and the reference curve of PTC 6 is 0.75% at maximum. New equations to estimate the discharge coefficient are developed based on the experimental results and the theoretical equations including the tap effects. The developed equations estimate the discharge coefficient of the present experimental data within 0.21%, and they are expected to estimate more accurately the discharge coefficient of the throat tap nozzle of PTC 6 than the reference curve of PTC 6.

Numerical Investigation of the Effect of an Axial Pre-Swirl Nozzle With a Radial Angle in a Pre-Swirl Rotor-Stator System

2021 ◽  
Author(s):  
Gang Zhao ◽  
Shuiting Ding ◽  
Tian Qiu ◽  
Shenghui Zhang
Keyword(s):  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Temperature Drop ◽  
Tangential Velocity ◽  
Total Pressure Loss ◽  
Adiabatic Effectiveness ◽  
Cooling Air

Abstract Pre-swirl nozzles are often used in gas turbines to deliver the cooling air to the turbine blades. The static axial nozzles swirl the cooling air in the direction of rotation of the turbine disk, thereby reducing the relative total temperature of the air. Most studies about nozzles focus on its shape, radial location, tangential angle to reduce the pressure loss and increase the temperature drop of the pre-swirl system, but few of them consider the benefit of a radial angle of nozzles. This paper investigated numerically the performance of a pre-swirl system whose pre-swirl nozzles have a radial angle. Six radial angles are selected to study the flow dynamics of a direct-transfer pre-swirl system in terms of the total pressure loss coefficient of the pre-swirl cavity, the discharge coefficient of the receiver holes, and the adiabatic effectiveness. It is shown that the nozzles with radial angles can adjust the tangential velocity and radial velocity and thus can influence the performance of a pre-swirl system. There is a lowerest value of total pressure loss in pre-swirl cavity, that is α = 90°, which can hardly be influenced by the radial angle of nozzle and pressure ratio π. For a specific swirl ratio β∞, there exists an optimal αopt where the discharge coefficient of receiver hole is maximum. Moreover, αopt decreases as pressure ratio π increases. And so is the adiabatic effectiveness Θad.

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