A Test Facility for the Measurement of Torques at the Shaft to Seal Interface in Brush Seals

1999 ◽  
Vol 121 (1) ◽  
pp. 160-166 ◽  
Author(s):  
P. E. Wood ◽  
T. V. Jones
Keyword(s):  
Contact Pressure ◽  
Indirect Measurement ◽  
Test Facility ◽  
Axial Loads ◽  
Rotating Shaft ◽  
Brush Seal ◽  
Wide Range ◽  
Bearing Assembly ◽  
Brush Seals ◽  
Wide Speed Range

An important factor in the performance of brush seals for a wide range of gas turbine applications is the rate of wear at the seal to shaft interface, which is dependent on the contact pressure that exists between the bristles and rubbing surface. This is dependent on a variety of effects. Principally, these are the aerodynamic forces bending the bristles onto the rubbing surface, frictional effects within the bristle pack and at the backing ring that arise with the application of pressure differential, geometrical changes due to centrifugal and thermal growths, and transient differential movements of the rotor that develop in flight manoeuvres. In order to investigate the effect of these phenomena on contact pressure, a test facility has been devised in which the torque exerted by a brush seal on a rotating shaft is used as an indirect measurement of contact pressure. This has necessitated the design of a test facility in which all system torques can be fully calibrated. Consequently, a pressure balanced design has been adopted in which applied seal differential and pressure levels have a minimal effect on axial loads at the rotor bearing assembly. The primary method of torque measurement is the instantaneous deceleration of the rotor. Thus, measurements over a wide speed range are acquired with high frequency instrumentation. The means whereby small parasitic torques are evaluated and corrected is given. Results demonstrating the dependence of contact pressure on seal differential and pressure levels are presented.

scholarly journals A Test Facility for the Measurement of Torques at the Shaft to Seal Interface in Brush Seals

1997 ◽  
Author(s):  
P. E. Wood ◽  
T. V. Jones
Keyword(s):  
Contact Pressure ◽  
Indirect Measurement ◽  
Test Facility ◽  
Axial Loads ◽  
Rotating Shaft ◽  
Brush Seal ◽  
Wide Range ◽  
Bearing Assembly ◽  
Brush Seals ◽  
Wide Speed Range

An important factor in the performance of brush seals for a wide range of gas turbine applications is the rate of wear at the seal to shaft interface, which is dependant on the contact pressure that exists between the bristles and rubbing surface. This is dependent on a variety of effects. Principally these are; the aerodynamic forces bending the bristles onto the rubbing surface; frictional effects within the bristle pack, and at the backing ring, that arise with the application of pressure differential; geometrical changes due to centrifugal and thermal growths and transient differential movements of the rotor that develop in flight manoeuvres. In order to investigate the effect of these phenomena on contact pressure, a test facility has been devised in which the torque exerted by a brush seal on a rotating shaft is used as an indirect measurement of contact pressure. This has necessitated the design of a test facility in which all system torques can be fully calibrated. Consequently, a pressure balanced design has been adopted, in which applied seal differential and pressure levels have a minimal effect on axial loads at the rotor bearing assembly. The primary method of torque measurement is the instantaneous deceleration of the rotor. Thus measurements over a wide speed range are acquired with high frequency instrumentation. The means whereby small parasitic torques are evaluated and corrected is given. Results demonstrating the dependence of contact pressure on seal differential and pressure levels are presented.

An Experimental and Theoretical Study of Brush Seal and Shaft Thermal Interaction

2003 ◽  
Author(s):  
Andrew K. Owen ◽  
Terry V. Jones ◽  
S. M. Guo ◽  
Simon Hogg
Keyword(s):  
Theoretical Analysis ◽  
Test Facility ◽  
Thermal Interaction ◽  
Steam Turbines ◽  
Element Analysis ◽  
Oxford University ◽  
Brush Seal ◽  
Aerodynamic Parameters ◽  
Brush Seals ◽  
Seal Shaft

This paper presents a detailed experimental study and theoretical analysis of the thermal interactions of brush seal, shaft and airflow. The tests were performed in the Oxford University Brush Seal Test Facility. The facility, which was originally designed for the brush seal aerodynamic study, has been enhanced for thermal measurements. A variety of brush seals, typically applicable to aero and power generation gas and steam turbines, have been tested. The thermal interaction caused by changes in rotor and housing alignment was also studied. In the tests, in addition to the conventional aerodynamic parameters, such as the pressure, mass flow and torque, the temperatures of the rotor were measured and heat generated in the bristle/rotor contact were deduced using the finite element analysis. A theoretical analysis of the system was developed which predicts the heat transfer to the airflow from the bristle pack. This analysis is used to give a correlation to predict heat input to the rotor. The study provides valuable design information for the use of brush seals.

Experimental Characterization of Variable Bristle Diameter Brush Seal Leakage, Stiffness and Wear

2013 ◽  
Author(s):  
Deepak Trivedi ◽  
Binayak Roy ◽  
Mehmet Demiroglu ◽  
Xiaoqing Zheng
Keyword(s):  
Wear Behavior ◽  
Pressure Loading ◽  
Blow Down ◽  
Friction Forces ◽  
Brush Seal ◽  
Wide Range ◽  
Successful Design ◽  
Brush Seals ◽  
And Performance

Brush seals are used in a wide variety of turbomachinery for sealing rotor-stator and stator-stator clearances. Application of traditional brush seals is limited by their life and performance at high differential pressures. GE’s patent-pending Variable Bristle Diameter (VBD) brush seal overcomes the limitations of the traditional brush seal by sandwiching a layer of fine bristles, with better sealing capability, between adjacent rows of stiffer bristles capable of withstanding larger differential pressure and flow disturbance. The General Electric VBD design uses thick bristles both in front and back rows. In addition to leakage performance, for successful design it is important to understand the force interactions between a brush seal bristle pack and the rotor. The important failure mechanisms to avoid include overheating and rotor dynamic instabilities caused by excessive brush seal forces. Brush seal stiffness, defined as brush seal force per unit circumferential length per unit incursion of the rotor, depends on the complex interaction of the pressure-dependent inter-bristle forces, the blow-down forces and the friction forces between the backplate and the bristle pack. Furthermore, brush seals exhibit different hysteresis and wear behavior under different pressure loading conditions. In this article, we present experimentally measured leakage, stiffness and wear characteristics of three different VBD brush seal designs subjected to a wide range of pressure loading.

Experimental Investigation of Oil Shedding From an Aero-Engine Ball Bearing at Moderate Speeds

2017 ◽  
Author(s):  
R. Santhosh ◽  
Jee Loong Hee ◽  
Kathy Simmons ◽  
Graham Johnson ◽  
David Hann ◽  
...  
Keyword(s):  
High Speed ◽  
Ball Bearing ◽  
Flow Regimes ◽  
Test Facility ◽  
Research Centre ◽  
Rotating Disks ◽  
Axial Loads ◽  
Aero Engine ◽  
Bearing Assembly ◽  
The University

In civil aero-engine transmission system bearings are used for shaft location and load support. An experimental test facility in the University of Nottingham’s Gas Turbine Transmissions Research Centre (G2TRC) was designed and commissioned to investigate oil behaviour as it exits an engine-representative ball bearing. In the rig, oil is delivered to the bearing inner race and cage via under-race feed at three delivery locations i.e. front, mid and rear of the bearing assembly. An electromagnetic load system is designed and implemented to allow engine representative axial loads up to 35 kN to be applied to the bearing. This paper details the rig design including the load and under-race lubrication systems and gives information about bearing oil shedding mechanisms observed. In this phase of testing high speed images are acquired at shaft speeds between 1000 and 7000 rpm at an oil flowrate of 5.2 litres per minute and bearing axial load of 10 kN. The work presented here focusses on oil shedding from the bearing cage. Oil shedding behaviour from aeroengine ball bearing is identified to share many similarities to that observed in the past for shedding from rotating disks and cups. However, it is shown that it not possible to predict the conditions at which transition in flow regimes will occur for the aeroengine bearing on the basis of correlations for simpler geometries (spinning disks and cups). The work presented here is the first observation of flow regimes in an aeroengine ball bearing involving high-resolution highspeed imaging.

A Slow-Speed Rotating Test Facility for Characterising the Stiffness of Brush Seals

2006 ◽  
Author(s):  
Gervas Franceschini ◽  
Jonathan J. Morgan ◽  
Terry V. Jones ◽  
David R. H. Gillespie
Keyword(s):  
Test Facility ◽  
Slow Speed ◽  
Blow Down ◽  
Eccentric Rotor ◽  
Brush Seal ◽  
Speed Rotation ◽  
Central Shaft ◽  
Computer Controlled ◽  
Brush Seals ◽  
Stiffness Characteristics

An appreciation of the importance of bristle stiffening and hysteresis in brush seals has led to the development of a test facility capable of making stiffness measurements at different seal pressures. Engine scale seals are tested under engine representative differential pressures and eccentric movements in the test facility. To cover current and future sealing requirements the facility is capable of up to 12,5 bar differential pressures across the seal and eccentric rotor to casing movements of 2,5 mm. A slow-speed rotating rotor allows the dynamic friction directions of the contacting seal elements to be matched with the engine application. Both the eccentric cycle through which the seal is driven and the low-speed rotation of the central shaft are computer controlled to ensure known conditions are obtained and experimental repeatability. It has not been necessary to simulate engine temperatures, rotor speeds and radial growth between the engine and test facility. In this paper the test facility is fully described. Experimental results, showing torque, flow and stiffness characteristics from a typical prototype engine brush seal are reported, with full details of the experimental uncertainties. The effects of bristle stiffening, seal hysteresis, and bristle blow-down on the quantities above are detailed in the results.

Stiffness Measurement for Pressure-Loaded Brush Seals

2011 ◽  
Author(s):  
Rahul A. Bidkar ◽  
Xiaoqing Zheng ◽  
Mehmet Demiroglu ◽  
Norman Turnquist
Keyword(s):  
Gas Turbines ◽  
Design Parameters ◽  
Test Results ◽  
Pressure Loading ◽  
Friction Forces ◽  
Test Fixture ◽  
Hysteresis Behavior ◽  
Brush Seal ◽  
Wide Range ◽  
Brush Seals

Brush seals are widely used as flexible seals for rotor-stator and stator-stator gaps in power generation turbo-machinery like steam turbines, gas turbines, generators and aircraft engines. Understanding the force interactions between a brush seal bristle pack and the rotor is important for avoiding overheating and rotor dynamic instabilities caused by excessive brush seal forces. Brush seal stiffness (i.e. brush seal force per unit circumferential length per unit incursion of the rotor) is usually measured and characterized at atmospheric pressure conditions. However, the inter-bristle forces, the blow-down forces and the friction forces between the backplate and the bristle pack change in the presence of a pressure loading, thereby changing the stiffness of the brush seal in the presence of this pressure loading. Furthermore, brush seals exhibit different hysteresis behavior under different pressure loading conditions. Understanding the increased brush seal stiffness and the increased hysteresis behavior of brush seals in the presence of a pressure loading is important for designing brush seals for higher pressure applications. In this article, we present the development of a test fixture for measuring the stiffness of brush seals subjected to a pressure loading. The fixture allows for measurement of the bristle pack forces in the presence of a pressure loading on the seal while the rotor is incrementally pushed (radially) into the bristle pack. Following the development of this test fixture, we present representative test results on three sample seals to show the trends in brush seal stiffness as the pressure loading is increased. Specifically, we study the effect of different brush seal design parameters on the stiffness of brush seals over a wide range of pressure loadings. These test data can be used for developing predictive models for brush seal stiffness under pressure loading. Furthermore, we demonstrate the utility of this fixture in studying the hysteresis exhibited by brush seals along with the importance of the backplate pressure balance feature present in several brush seal designs. The test results validate the bilinear force-displacement curves previously reported in the literature.

Porosity Modeling of Brush Seals

1997 ◽  
Vol 119 (4) ◽  
pp. 769-775 ◽  
Author(s):  
J. W. Chew ◽  
S. I. Hogg
Keyword(s):  
Resistance Coefficient ◽  
Linear Superposition ◽  
One Dimensional ◽  
Leakage Flows ◽  
Brush Seal ◽  
Multiple Dimensions ◽  
Wide Range ◽  
Brush Seals ◽  
The One ◽  
Resistance Coefficients

A new model for predicting leakage flows through the bristle pack of brush seals is developed. In the model, the bristle pack is treated as a porous medium. Good agreement is demonstrated between predictions from a one-dimensional form of the model and a wide range of experimental data available from the literature, for seals with a bristle pack to rotor interference fit. The results demonstrate that both viscous and inviscid effects contribute significantly to the drag on the bristles within the pack. The model uses a linear superposition of viscous and inertial losses, with a resistance coefficient assigned to each contribution. Formulas that have been deduced for flow in packed beds, are adapted for use in assigning values to the resistance coefficients in the one-dimensional model. Finally, extension of the method to multiple dimensions is discussed, with a view to incorporating the model into a CFD code to form a general predictive capability for brush seal flows.

Operating Performance and Wear Investigations of Brush Seals for Steam Turbine Applications

2013 ◽  
Author(s):  
M. Raben ◽  
H. Schwarz ◽  
J. Friedrichs
Keyword(s):  
Operating Performance ◽  
Operating Time ◽  
Operation Time ◽  
Operating Conditions ◽  
Live Steam ◽  
Test Facility ◽  
Measurement Unit ◽  
Test Rig ◽  
Brush Seal ◽  
Brush Seals

In recent years brush seals have become more and more an established alternative to existing labyrinth seals due to their increased pressure difference capability per stage in combination with a radial adaptive characteristic. In general brush seal and shaft should be in a concentric position. To utilize the special advantages of a brush seal system the radial adaptive capability of the seal’s bristle pack has to be achieved and guaranteed for the entire operation time. Every mechanism leading to a contact between the rotor and the seal will potentially cause an abrasive wear on both sides. In order to reduce this wear and to improve the operating performance of the brush seal, the influencing parameters resulting from the rotor eccentricity, the thermal gradient and the blown down characteristic of the bristle pack itself have to be understood. For this purpose the TU Braunschweig developed a unique steam test rig for brush seal investigations which allows live steam operations of single and multi stage brush seals up to 50 bar and 450 °C. Equipped with a 300 mm motor driven shaft, long time endurance tests under varying, transient operating conditions can be carried out. In addition to the steam test rig a second cold air test facility with an optical access and a force-displacement measurement unit is used. To analyse the operating bristle pack the brush seal packages and their characteristics were tested in detail under pressure gradients up to 8 bar. The paper shows the results of different seal designs with regards to the blow-down characteristics during a live steam endurance test. Based on these results especially the axial design of the brush seal was found to be an important parameter, since it has a significant influence on potential vibration behaviour of the bristle pack under specific load conditions. In contrast, the transient live steam measurements have shown that a limited amount of movement and vibrations enables an improved radial adaptiveness, leading to reduced leakages during transient operations. Finally the paper introduces a new rotor concept for the steam test rig for further investigations of the brush seal - rotor interaction. It enables the utilization of new and especially varying rotor materials for increased steam parameters as well as the detection of the heat introduction into the rotor during the operating time by rotor-integrated temperature probes.

Preliminary Investigations for a Pressure Balanced Back Plate at Low Inclined Brush Seals

2015 ◽  
Author(s):  
H. Schwarz ◽  
J. Friedrichs
Keyword(s):  
Steam Turbine ◽  
Renewable Energy Sources ◽  
Test Facility ◽  
Design Parameters ◽  
Blow Down ◽  
Pressure Drops ◽  
Brush Seal ◽  
Plate Design ◽  
Back Plate ◽  
Brush Seals

Within this paper a continuation in brush seal testing for flexible load regimes in a steam turbine is given. Besides the well-known main design parameters of brush seals, e.g. the bristle pack thickness, the bristle diameter or the lay angle of the bristle pack, this paper focuses on the axial inclination of the bristle pack and particularly the affinity of bristle pack oscillations at low inclined bristle packs and small pressure differences. As it was presented in GT2014-26330, the axial inclination of the bristle pack is an important design parameter for brush seals. Along with a clearly increased blow-down capability and a reduced stiffness the seals tend to exhibit an enhanced axial bristle pack width during pressurization. It was previously shown that a low axial inclination of the bristle pack results in a loose package and in bristle pack oscillations until pressure differences of 10 bar. Above pressure drops of 10 bar the resulting higher abrasive behavior stops and a well sealing brush seal with a loose bristle pack is given. Regarding the renewable energy sources for necessary changes in steam turbine operations, a flexible sealing system with an enhanced wide operating range is requested. To capture all positive behaviors of low inclined brush seals for pressure differences until 10 bar, a design to safely avoid bristle pack oscillations is required. With this background low inclined brush seals with a new back plate design were tested at the Institute’s cold air test facility in Braunschweig up to a pressure difference of 4 bar. The facility allows detailed sealing performance investigations including real time bristle pack observations. The present paper shows and discusses overall experimental results of brush seals with different axial inclinations mounted with an adjustable back plate to determine the influence of the back plate design on the bristle pack oscillations. Furthermore, these new results together with older measurements from 2012 were used to develop a theory regarding the changes that result from contact between the bristle pack and the adjusted back plate. Finally, the design for a pressure balanced back plate will be shown.

Particle degradation in pneumatic conveyors: Use of data from a pilot-sized test facility to predict degradation in an industrial conveyor

2002 ◽  
Vol 216 (2) ◽  
pp. 65-71
Author(s):  
I Bridle ◽  
S R Woodhead
Keyword(s):  
Solid Material ◽  
Basmati Rice ◽  
Test Facility ◽  
Design Stage ◽  
Pneumatic Conveying ◽  
Process Industries ◽  
Industrial Practice ◽  
Use Of Data ◽  
Bulk Solid ◽  
Wide Range

Degradation of bulk solid product during pneumatic conveying is of concern in a range of process industries. However, prediction of product degradation levels at the conveyor design stage has proved challenging. This paper presents a proposed prediction technique, based on the use of a pilot-sized test facility to provide relevant empirical data. The results of experiments undertaken using malted barley, basmati rice, and granulated sugar are reported. For each bulk solid material, a wide range of conveying conditions have been examined, consistent with common industrial practice. Correlations between predictions and experimental data obtained in an industrial-scale conveyor are presented and discussed.

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