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.

scholarly journals A bacteriological evaluation of laminar-flow systems for orthopaedic surgery

1973 ◽  
Vol 71 (3) ◽  
pp. 559-564 ◽  
Author(s):  
W. Whyte ◽  
B. H. Shaw ◽  
R. Barnes
Keyword(s):  
Laminar Flow ◽  
Operating Room ◽  
Orthopaedic Surgery ◽  
Flow System ◽  
Air Flow ◽  
Cross Flow ◽  
Operating Rooms ◽  
Airborne Bacteria ◽  
Flow Systems ◽  
Bacteriological Evaluation

SUMMARYAn evaluation has been undertaken of the efficiency of laminar-flow ventilation in operating-rooms in which conventional operating-room clothing was used. It has been demonstrated that velocities in the region of 0·3–0·4 m/sec. will give maximum returns for effort in both down-flow and cross-flow systems. At this velocity the laminar-flow system, in terms of airborne bacteria measured at the would site, was about 11 times more effients using horizontal air-flow and 35–90 times more efficient using vertical air-flow than a plenum-ventilated operating room.

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.

An Experimental Study of Sprays in Cross Flow Representative of Gas Turbine Engine Secondary Air Systems

2009 ◽  
Author(s):  
N. J. Regan ◽  
N. R. Atkins ◽  
C. A. Long ◽  
P. R. N. Childs ◽  
P. S. Hutcheson ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Droplet Size ◽  
Laser Sheet ◽  
Cross Flow ◽  
Flux Ratio ◽  
Gas Turbine Engine ◽  
Droplet Velocity ◽  
Turbine Engine ◽  
Jet Trajectory ◽  
Secondary Air

The flow in the secondary air system of a gas turbine engine passes over numerous oil supply and scavenge pipes and a fracture in such a pipe will cause a jet of oil to be ejected as a spray. This spray will disperse in the surrounding flow. Accurate and reliable numerical modelling of these sprays presents significant problems due in part to their complexity, but also the lack of experimental data available for model validation. This paper describes the design, manufacture, testing and results from an experimental test rig aimed at spray characterisation. The sprays considered were produced through a round sharp edged nozzle with a 0.57 mm diameter and a length to diameter ratio of 1.61. The spray was introduced normal to the cross flow. Phase Doppler Anemometry was used to determine droplet size and velocity for Weber numbers within the range of 13 < Weg < 580 and Momentum Flux Ratio within the range of 0.8 < q < 136, resulting in 19 different spray fields. Each of these spray fields has been characterised at three axial locations. Contours of droplet size, mass flux distribution, axial droplet velocity and transverse droplet velocity are presented. In addition, a pulsed laser sheet and CCD camera were used to analyse the jet behaviour in terms of break up length and jet trajectory.

Experimental and Numerical Investigation of the Flow Field at Radial Holes in High-Speed Rotating Shafts

2012 ◽  
Author(s):  
Jan Sousek ◽  
Daniel Riedmüller ◽  
Michael Pfitzner
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Phenomena ◽  
Rotating Shafts ◽  
Secondary Air ◽  
The One ◽  
Discharge Behaviour

Rotating and stationary orifices are used within the secondary air system to transport sealing/ cooling air to its consumers. This paper reports on measurements of the discharge coefficient of rotating radial holes as their aerodynamical behaviour is different from the one of axial or stationary holes due to the presence of centrifugal and Coriolis forces. A test rig containing two independently rotating shafts was designed to investigate the flow phenomena and the discharge behaviour of these orifices. The required air mass flow is delivered by a screw compressor and can be regulated independently to supply the inner and outer annular passages of the test rig. It allows measurements of the discharge coefficient with cross flow and co- and counter-rotating shafts with centrifugal and centripetal flow through the rotating holes. On the outer shaft, absolute and differential pressures and temperatures in the rotating frame of reference are measured via a telemetry system. Measurements of the discharge coefficient for sharp-edged and rounded shaft inserts at a variety of different flow conditions and with swirl added to the air upstream of the orifice are presented. Furthermore experiments were conducted to quantify the influence of the inner shaft (non-rotating and rotating) on the discharge behaviour of orifices in the outer shaft. To complement the data acquired from the experiments and to get a better understanding of the flow field near the rotating holes also numerical flow simulations were performed.

Experimental and Numerical Investigation of the Flow Field at Radial Holes in High-Speed Rotating Shafts

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Jan Sousek ◽  
Daniel Riedmüller ◽  
Michael Pfitzner
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Phenomena ◽  
Rotating Shafts ◽  
Discharge Behavior ◽  
Secondary Air ◽  
Cooling Air

Rotating and stationary orifices are used within the secondary air system to transport sealing/cooling air to its consumers. This paper reports on measurements of the discharge coefficient of rotating radial holes since their aerodynamical behavior is different from that of axial or stationary holes due to the presence of centrifugal and Coriolis forces. A test rig containing two independently rotating shafts was designed in order to investigate the flow phenomena and the discharge behavior of these orifices. The required air mass flow is delivered by a screw compressor and can be independently regulated to supply the inner and outer annular passages of the test rig. It allows for measurements of the discharge coefficient with cross flow and co- and counter-rotating shafts with centrifugal and centripetal flow through the rotating holes. On the outer shaft, absolute and differential pressures and temperatures in the rotating frame of reference are measured via a telemetry system. Measurements of the discharge coefficient for sharp-edged and rounded shaft inserts at a variety of different flow conditions and with swirl added to the air upstream of the orifice are presented. Furthermore, experiments were conducted to quantify the influence of the inner shaft (nonrotating and rotating) on the discharge behavior of orifices in the outer shaft. To complement the data acquired from the experiments and to obtain a better understanding of the flow field near the rotating holes numerical flow simulations were also performed.

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

2017 ◽  
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 ◽  
Air System ◽  
Secondary Air

The cooling air in the secondary air system of gas turbines is controlled and metered by numerous restrictors, mainly in the shape of orifices. The ability to understand and predict the associated pressure losses are important in order to improve the air flow in 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 disc. 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 was used to develop two correlations for the discharge coefficient as a function of geometrical as well as flow properties.

Coupled Simulation of the Secondary Air Flow, Heat Transfer, and Structural Deflection of a Gas Turbine Engine

2012 ◽  
Author(s):  
Guilherme Tondello ◽  
Wolodymir Boruszewski ◽  
Fernando Mengele ◽  
Marcelo Assato ◽  
Silvio Shimizu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Model ◽  
Air Flow ◽  
Labyrinth Seal ◽  
Simulation Software ◽  
Thermal Loads ◽  
Labyrinth Seals ◽  
Secondary Air

In secondary air flow in gas turbines, labyrinth seals are used to control the flow to and from each cavity and to the rotor blades for cooling purposes. Those components and the final flow rate are very sensitive to gap clearance and displacement due to structural and thermal loads during operation, therefore designing those seals and knowing the resultant flow rates in each part of the circuit during the design phase is not an easy task, and tuning those gap values may bring significant increase in turbine efficiency. This paper describes the application of coupled commercial codes for secondary air flow and structural simulation for better evaluating temperature profiles and labyrinth seal behavior during operation. Flowmaster V7 was used for building a one dimensional model of the complete secondary air flow path including swirl effects and heat transfer phenomena, and ANSYS was used for building a structural model, taking into account both rotational and thermal loads. The labyrinth seals clearances, and thermal interactions between solid and fluid were coupled bi-directionally between the two simulation software. This simulation focused in the system, including the effects of each region, passage, seal and cavity in the calculations. The turbine model simulated was a VSE’s gas turbine under development, having a nominal rotation of 22600 rpm. This paper presents the numerical characteristics of each model, the details about the 1D fluid and 3D structural coupling, and the results obtained.

Comparison of Discharge Coefficient Measurements and Correlations for Orifices With Cross-Flow and Rotation

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Marcus Hüning
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Computer Network ◽  
Cross Flow ◽  
Angular Speed ◽  
Component Design ◽  
Contour Plots ◽  
Secondary Air ◽  
Temperature Levels ◽  
Asme Paper

Gas turbines and jet engines consist of a network of connected cavities beside the main gas path called the secondary air system. These cavities, which are often surrounded by stationary and high angular speed rotating walls are exposed to varying pressure and temperature levels of air or oil contaminated air and are connected to each other by orifices or restrictors. It is vital to control the secondary flow to enable a reliable and efficient engine design, which meets component durability with a minimum of parasitic air consumption. It is essential to understand the flow physics as well as network interdependency in order to minimize the flow consumption and yet meeting engine operating requirements, as well as practical parts component design or manufacturing needs. In this connection, computer network codes containing model conceptions, which can accurately predict orifice flows, are essential. In an effort to provide usable further insight into flows across restrictors, such as orifices, this publication compares test results and orifice loss calculation models from the open literature with the aid of transformation laws and contour plots. The influence of different geometric features is incorporated into a model for the calculation of discharge coefficients. This publication is an extract of the underlying widespread and more detailed ASME paper (Huening, 2008, “Comparison of Discharge Coefficient Measurements and Correlations for Several Orifice Designs With Cross-Flow and Rotation Around Several Axes,” ASME Paper No. GT2008-50976). Minor errors, noticed during adapting, are corrected.

Pressure Driven Temperature Field in a Combustion Chamber

2004 ◽  
Author(s):  
Fernando Z. Sierra ◽  
Janusz Kubiak ◽  
Gustavo Urquiza
Keyword(s):  
Temperature Field ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Numerical Computation ◽  
High Temperatures ◽  
Characteristic Temperature ◽  
Air Flow ◽  
Combined Cycle ◽  
Auxiliary Equipment ◽  
Secondary Air

In this work numerical computation has been applied to investigate the temperature field in a gas turbine combustion chamber. The simulation considered pressure imbalance conditions of air flow between primary and secondary inlets. The combustion chamber under study is part of a 70 MW gas turbine from an operating combined cycle power plant. The combustion was simulated with proper fuel-air flow rate assuming stoichiometric conditions. Characteristic temperature and pressure fields were obtained under constant boundary conditions of air inlet. However, with pressure distribution imbalances of the order of 3 kPa between primary and secondary air inlets, excessive heating in regions other than the combustion chamber core were obtained. Over heating in these regions helped to explain what was observed to produce permanent damage to auxiliary equipment surrounding the combustion chamber core, like the cross flame pipes. It is observed that high temperatures which normally develop in the central region of the combustion chamber may reach other surrounding upstream regions by modifying slightly the air pressure. Scanning microscope examination of the damaged material confirmed that it was exposed to high temperatures such as predicted through the numerical computation.

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