scholarly journals INVESTIGATION OF A NOVEL PRESSURE-ACTUATED BRUSH SEAL UNDER HOT STEAM CONDITIONS

2020 ◽  
Vol 4 ◽  
pp. 14-26
Author(s):  
Philip Reggentin ◽  
Jens Friedrichs ◽  
Johan Flegler ◽  
Ivan McBean
Keyword(s):  
Power Plants ◽  
The Novel ◽  
Basic Design ◽  
Test Rig ◽  
Brush Seal ◽  
Brush Seals ◽  
Increasing Demand ◽  
Improved Design ◽  
Flexible Operation ◽  
Novel Design

Due to the increasing demand towards flexible operation of conventional power plants also the seals of their turbines have to adapt to varying loads. Based on the basic design of a clamped brush seal, a novel seal with a pressure-actuated backplate is introduced which is capable of combining the advantages of low and high inclined brush seals while avoiding their undesired properties for flexible operation. During preliminary investigations on a test rig operated with compressed air and without rotation, the functionality of the improved design was demonstrated. It is shown that the leakage mass flow was lowered by up to 40% while undesired bristle oscillations were reduced by up to 90% at low pressure differences compared to conventional seal designs. After the adaption of the design for subsequent investigations under realistic conditions comparable to those in a steam turbine, further tests were conducted at TU Braunschweig´s hot steam test rig. Within these investigations the novel design showed improved properties regarding a high leakage performance and an advanced capability to avoid deterioration due to shaft excursions compared to brush seals with fixed backplate design.

Design Parameters of Brush Seals and Their Impact on Seal Performance

2012 ◽  
Author(s):  
H. Schwarz ◽  
J. Friedrichs ◽  
J. Flegler
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Large Scale ◽  
Design Parameters ◽  
Test Rig ◽  
Pressure Drops ◽  
Seal Design ◽  
Brush Seal ◽  
Extreme Load ◽  
Brush Seals

Brush seals, which were originally designed for gas turbine applications, have been successfully applied to large-scale steam turbines within the past decade. From gas turbine applications, the fundamental behavior and designing levers are known. However, the application of brush seals to a steam turbine is still a challenge. This challenge is mainly due to the extreme load on the brush seal while operating under steam. Furthermore, it is difficult to test brush seals under realistic conditions, i.e. under live steam conditions with high pressure drops. Due to these insufficiencies, 2 test rigs were developed at the University of Technology Braunschweig, Germany. The first test rig is operated under pressurized air and allows testing specific brush seal characteristics concerning their general behavior. The knowledge gained from these tests can be validated in the second test rig, which is operated under steam at pressure drops of 45 bar and temperatures up to 450 °C. Using both the air test rig and the steam test rig helps keep the testing effort comparably small. Design variants can be pre-tested with air, and promising brush seal designs can consequently be tested in the steam seal test rig. The paper focuses on a clamped brush seal design which, amongst others, is used in steam turbine blade paths and shaft seals of current Siemens turbines. The consequences of the brush assembly on the brush appearance and brush performance are shown. The clamped brush seal design reveals several particularities compared to welded brushes. It could be shown that the clamped bristle pack tends to gape when clamping forces rise. Gapping results in an axially expanding bristle pack, where the bristle density per unit area and the leakage flow vary. Furthermore, the brush elements are usually assembled with an axial lay angle, i.e. the bristles are reclined against the backing plate. Hence, the axial lay angle is also part of the investigation.

Design and Validation of a New Test Rig for Brush Seal Testing Under Engine Relevant Conditions

2011 ◽  
Author(s):  
D. Pfefferle ◽  
K. Dullenkopf ◽  
H.-J. Bauer
Keyword(s):  
High Surface ◽  
Test Rig ◽  
Friction Forces ◽  
Brush Seal ◽  
Main Emphasis ◽  
Rotor Surface ◽  
Brush Seals ◽  
Gap Height ◽  
Radial Gap ◽  
Gap Width

Brush seals play an increasing role in turbomachinery due to their improved behavior towards leakage and their capability to compensate for gap variations caused by thermal expansion and rotor excursions. The flexible bristles of brush seals are able to endure short-term reductions in gap width without severe damage. Consequently the necessary gap between the rotor and brush seal can virtually be reduced to zero, leading to a considerable reduction in air leakage of up to 80 percent. However the reduced gap height increases the probability of rubbing between the bristle package and the rotor surface. The friction forces generated can cause an unwanted heat load on the rotor, bristles and leakage air. In addition, the surfaces involved are exposed to abrasion effects. Especially in the thin and lightweight rotor structures of aircraft engines, the additional heat impact can lead to a problematic level of material stress. To study these effects and to give reliable quantitative design rules, a versatile test rig for brush seals was designed and built. The simulation of seal behavior under relevant engine conditions is the main emphasis of this rig, including high pressure drop, leakage flow and high surface speed. The key feature is the possibility to vary the axis symmetric radial gap width during the test rig operation by up to a 0.5 mm overlap. The so caused rubbing induces a transient rotor temperature rise which is measured via a set of 12 thermocouples embedded in the rotor. These temperature readings can be used to calculate the brush seal heat impact on the rotor structure. Preliminary results with moderate differential pressure and rotor speed proved the functionality of the test rig and confirmed the global approach of the project.

scholarly journals Shaft-Less Energy Storage Flywheel

2015 ◽  
Author(s):  
Xiaojun Li ◽  
Alan Palazzolo ◽  
Dustin Tingey ◽  
Xu Han ◽  
Patrick McMullen ◽  
...  
Keyword(s):  
Energy Source ◽  
Energy Storage ◽  
Power Plants ◽  
Data Centers ◽  
Department Of Energy ◽  
Regenerative Braking ◽  
Frequency Regulation ◽  
The Novel ◽  
Conventional Steel ◽  
Novel Design

This paper provides an overview of a 100 kw flywheel capable of 100 kW-Hr energy storage that is being built by Vibration Control and Electromechanical Lab (VCEL) at Texas A&M University and Calnetix Technologies. The novel design has a potential of nearly doubling the energy density of conventional steel flywheels. Applications include renewable energy source energy storage, frequency regulation at power plants, regenerative braking on vehicles and cranes and backup power at data centers and hospitals. The design and construction of this Department of Energy sponsored flywheel will be presented.

An Investigation of Flow, Mechanical and Thermal Performance of Conventional and Pressure-Balanced Brush Seals

2012 ◽  
Author(s):  
Michael J. Pekris ◽  
Gervas Franceschini ◽  
David R. H. Gillespie
Keyword(s):  
Test Rig ◽  
Blow Down ◽  
Active Pressure ◽  
University Of Oxford ◽  
Seal Design ◽  
Passive Pressure ◽  
Brush Seal ◽  
Fuel Consumption Benefit ◽  
Brush Seals ◽  
Secondary Air

Compliant contacting filament seals such as brush seals are well known to give improved leakage performance and hence specific fuel consumption benefit compared to labyrinth seals. The design of the brush seal must be robust across a range of operating pressures, rotor speeds and radial build-offset tolerances. Importantly the wear characteristics of the seal must be well understood to allow a secondary air system suitable for operation over the entire engine life to be designed. A test rig at the University of Oxford is described which was developed for the testing of brush seals at engine-representative speeds, pressures and seal housing eccentricities. The test rig allows the leakage, torque and temperature rise in the rotor to be characterized as functions of the differential pressure(s) across the seal and the speed of rotation. Tests were run on two different geometries of bristle-pack with conventional, passive and active pressure-balanced backing ring configurations. Comparison of the experimental results indicates that the hysteresis inherent in conventional brush seal design could compromise performance (due to increased leakage) or life (due to exacerbated wear) as a result of reduced compliance. The inclusion of active pressure-balanced backing rings in the seal designs are shown to alleviate the problem of bristle-backing ring friction, but this is associated with increased blow-down forces which could result in a significant seal-life penalty. The best performing seal was concluded to be the passive pressure-balanced configuration, which achieves the best compromise between leakage and seal torque. Seals incorporating passive pressure-balanced backing rings are also shown to have improved heat transfer performance in comparison to other designs.

Brush Seal Frictional Heat Generation: Test Rig Design and Validation Under Steam Environment

2016 ◽  
Author(s):  
M. Raben ◽  
J. Friedrichs ◽  
J. Flegler
Keyword(s):  
Steam Turbine ◽  
Heat Generation ◽  
Gas Turbines ◽  
Frictional Heat ◽  
Narrow Gap ◽  
Test Rig ◽  
Frictional Heat Generation ◽  
Brush Seal ◽  
Rotor Surface ◽  
Brush Seals

Sealing technology is a key feature to improve efficiency of steam turbines for both new power stations and modernization projects. One of the most powerful sealing alternatives for reducing parasitic leakages in the blade path of a turbine as well as in shaft sealing areas is the use of brush seals, which are also widely used in gas turbines and turbo compressors. The advantage of brush seals over other sealing concepts is based on the narrow gap that is formed between the brush seal bristle tips and the mating rotor surface together with its radial adaptivity. While the narrow gap between the bristle tips and the rotor leads to a strongly decreased flow through the seal compared with conventional turbomachinery seals, it is important to be aware of the tight gap that can be bridged by relative motion between the rotor and the brush seal, leading to a contact of the bristles and the rotor surface. Besides abrasive wear occurrence, the friction between the bristles and the rotor leads to heat generation which can be detrimental to turbine operation due to thermal effects, leading to rotor bending connected to increasing shaft vibrations. In order to investigate the frictional heat generation of brush seals, different investigation concepts have been introduced through the past years. To broaden the knowledge about frictional heat generation and to make it applicable for steam turbine applications, a new testing setup was designed for the steam test rig of the Institute of Jet Propulsion and Turbomachinery - TU Braunschweig, Germany, enabling temperature measurements in the rotor body under stationary and transient operation in steam by using rotor-integrated thermocouples. Within this paper, the development of the instrumented new rotor design and all relevant parts of the new testing setup is shown along with the testing ability by means of the validation of the test rig concept and the achieved measurement accuracy. First results prove that the new system can be used to investigate frictional heat generation of brush seals under conditions relevant for steam turbine shaft seals.

scholarly journals Contamination of Brush Seals by Oil and Salt and Its Impact on Rubbing and Hysteresis Behaviour

2019 ◽  
Vol 4 (4) ◽  
pp. 40
Author(s):  
Manuel Hildebrandt ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Fluxes ◽  
Total Power ◽  
Steam Turbines ◽  
Power Losses ◽  
Test Rig ◽  
Degree Of Contamination ◽  
Brush Seal ◽  
Steady State Operation ◽  
Brush Seals ◽  
Hysteresis Behaviour

The literature already contains some experimental, analytical and numerical investigations on the rubbing and hysteresis behaviour of brush seals. What the investigations have in common is that they were carried out with new and uncontaminated seals, or that such a condition was assumed. The influence of contamination has not been explicitly investigated yet. Particularly in stationary gas and steam turbines, foreign substances can accumulate on and in the bristle package during steady-state operation. In the case of a rubbing event with a contaminated brush seal, e.g., during shutdown of the machine, the process is not expected to be comparable to that assumed in the presence of a new, uncontaminated seal. The present paper is dedicated to the question of the influence of contamination on the total frictional power loss generated during rubbing and the distribution of heat fluxes in friction contact. For this purpose, rub tests with two seals were carried out on the brush seal test rig of the Institute of Thermal Turbomachinery (ITS) in new conditions. Subsequently, the sealing packages were contaminated with oil or a salt mixture. After the treatment, the rub tests were repeated and compared with the previous tests. In addition, stiffness measurements were used to assess the degree of contamination. A strong influence on the rubbing behaviour by the contamination was detected. Contamination causes the flexibility of the bristle package to be greatly reduced. As a result, especially at the beginning of the first measurements, the total power losses and rotor heat inputs are strongly increased. This flexibility is partly regained in the course of the measurements. As expected, contamination also influences the hysteresis behaviour of the seal. A highly increased leakage rate after rubbing could be observed, because the bristles remained close to their deflected positions. In the case of the salted seal, however, an improvement in the leakage performance could be observed after several repeat tests.

Development of Brush Seal Technology for Steam Turbine Retrofit Applications

2003 ◽  
Author(s):  
Don Stephen ◽  
Simon I. Hogg
Keyword(s):  
Steam Turbine ◽  
Labyrinth Seal ◽  
Life Assessment ◽  
Seal Design ◽  
Brush Seal ◽  
New Concepts ◽  
Brush Seals ◽  
Improved Design ◽  
Aero Engines ◽  
Operational Issues

Increased cylinder efficiency is one of the main drivers in the steam turbine retrofit market, particularly for HP and IP modules. To-date most retrofit turbine suppliers have concentrated their efforts on improving the aerodynamic efficiency of blades and other steampath components, optimizing stage numbers and reducing leakage losses. Developments in all of these areas rely heavily on improved design and analysis tools to refine existing designs and evaluate new concepts. The opportunity exists to further reduce leakage losses by replacing conventional labyrinth seal designs by more advanced turbomachinery sealing technology. Brush seals, which have now been used successfully in some gas turbine (mainly aero-engines) applications for several years, are a natural candidate for steam turbine retrofits. Careful thought is needed when applying brush seals as the mechanical integrity of the cylinder needs to be maintained at all times. Attempts to increase performance should never be at the expense of availability and reliability. This paper describes the development work undertaken by the authors’ company and covers research in the areas of brush seal design, performance improvement, operational issues, and life assessment.

Brush Seal Frictional Heat Generation—Test Rig Design and Validation Under Steam Environment

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Markus Raben ◽  
Jens Friedrichs ◽  
Johan Flegler
Keyword(s):  
Steam Turbine ◽  
Heat Generation ◽  
Gas Turbines ◽  
Frictional Heat ◽  
Narrow Gap ◽  
Test Rig ◽  
Frictional Heat Generation ◽  
Brush Seal ◽  
Rotor Surface ◽  
Brush Seals

Sealing technology is a key feature to improve efficiency of steam turbines for both new power stations and modernization projects. One of the most powerful sealing alternatives for reducing parasitic leakages in the blade path of a turbine as well as in shaft sealing areas is the use of brush seals, which are also widely used in gas turbines and turbo compressors. The advantage of brush seals over other sealing concepts is based on the narrow gap that is formed between the brush seal bristle tips and the mating rotor surface together with its radial adaptivity. While the narrow gap between the bristle tips and the rotor leads to a strongly decreased flow through the seal compared with conventional turbomachinery seals, it is important to be aware of the tight gap that can be bridged by relative motion between the rotor and the brush seal, leading to a contact of the bristles and the rotor surface. Besides abrasive wear occurrence, the friction between the bristles and the rotor leads to heat generation which can be detrimental to turbine operation due to thermal effects, leading to rotor bending connected to increasing shaft vibrations. In order to investigate the frictional heat generation of brush seals, different investigation concepts have been introduced through the past years. To broaden the knowledge about frictional heat generation and to make it applicable for steam turbine applications, a new testing setup was designed for the steam test rig of the Institute of Jet Propulsion and Turbomachinery—TU Braunschweig, Germany, enabling temperature measurements in the rotor body under stationary and transient operation in steam by using rotor-integrated thermocouples. Within this paper, the development of the instrumented new rotor design and all relevant parts of the new testing setup is shown along with the testing ability by means of the validation of the test rig concept and the achieved measurement accuracy. First results prove that the new system can be used to investigate frictional heat generation of brush seals under conditions relevant for steam turbine shaft seals.

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.

An Investigation of Flow, Mechanical, and Thermal Performance of Conventional and Pressure-Balanced Brush Seals

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Michael J. Pekris ◽  
Gervas Franceschini ◽  
David R. H. Gillespie
Keyword(s):  
Test Rig ◽  
Blow Down ◽  
Active Pressure ◽  
University Of Oxford ◽  
Seal Design ◽  
Passive Pressure ◽  
Brush Seal ◽  
Fuel Consumption Benefit ◽  
Brush Seals ◽  
Secondary Air

Compliant contacting filament seals such as brush seals are well known to give improved leakage performance and hence specific fuel consumption benefit compared to labyrinth seals. The design of the brush seal must be robust across a range of operating pressures, rotor speeds, and radial build-offset tolerances. Importantly the wear characteristics of the seal must be well understood to allow a secondary air system suitable for operation over the entire engine life to be designed. A test rig at the University of Oxford is described which was developed for the testing of brush seals at engine-representative speeds, pressures, and seal housing eccentricities. The test rig allows the leakage, torque, and temperature rise in the rotor to be characterized as functions of the differential pressure(s) across the seal and the speed of rotation. Tests were run on two different geometries of bristle pack with conventional, passive, and active pressure-balanced backing ring configurations. Comparison of the experimental results indicates that the hysteresis inherent in conventional brush seal design could compromise performance (due to increased leakage) or life (due to exacerbated wear) as a result of reduced compliance. The inclusion of active pressure-balanced backing rings in the seal designs are shown to alleviate the problem of bristle–backing ring friction, but this is associated with increased blow-down forces which could result in a significant seal-life penalty. The best performing seal was concluded to be the passive pressure-balanced configuration, which achieves the best compromise between leakage and seal torque. Seals incorporating passive pressure-balanced backing rings are also shown to have improved heat transfer performance in comparison to other designs.

Sign in / Sign up

Export Citation Format

Share Document