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1
Khan, Mohammed Ajaz. "Leakage flow in labyrinth seals." Thesis, University of Bradford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482781.
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2
Allcock, D. C. J. "Abradable stator gas turbine labyrinth seals." Thesis, Cranfield University, 1999. http://dspace.lib.cranfield.ac.uk/handle/1826/10702.
Full textAbstract:
This is a detailed
study into the internal aerodynamics of labyrinth seals, with pmic|
reference to the effects of abradable
honeycomb stators on labyrinth seal leakage.-
A extensive
experimental programme established tables of friction factor for three
different
grades of honeycomb used by industry, and examined the effect of both
Reynolds number and clearance on these friction factors. The friction factor associated
with a
aerodynamically smooth surface was also experimentally determined in order to
establish the
experimental method.
The
experimental data was used to model the different grades of honeycomb used as
stator material in numerical simulations of a number
labyrinth seals, and allowed for
comparison of the leakage associated with both smooth and abradable stator straight
through labyrinth seals. Step-up and step-down seal geometries were also considered,
and the effects of pressure ratio, clearance and rotation on labyrinth seal leakage was
examined on all modelled seal
types.
This
numerically generated leakage data was comprehensive enough to allow for the
creation of a
second-generation one-dimensional labyrinth seal leakage predictor tool of
the
type used by design engineers in network models. This tool accounts for stator
material, seal clearance, overall pressure ratio, rotation and seal geometry, and the
accuracy associated with this tool allows labyrinth seal leakage to b predicted to within
10%. Functions of discharge coefficient and carry-over factor obtained from the
numerical
predictions are used by this tool, and as such it is capable of dealing with a
large number of different operating conditions for all the seal types modelled.
3
Gamal, Eldin Ahmed Mohamed. "Leakage and rotordynamic effects of pocket damper seals and see-through labyrinth seals." Texas A&M University, 2007. http://hdl.handle.net/1969.1/85848.
Full textAbstract:
This dissertation discusses research on the leakage and rotordynamic characteristics
of pocket damper seals (PDS) and see-through labyrinth seals, presents and evaluates
models for labyrinth seal and PDS leakage and PDS force coefficients, and compares
these seals to other annular gas seals. Low-pressure experimental results are used
alongside previously-published high-pressure labyrinth and PDS data to evaluate the
models. Effects of major seal design parameters; blade thickness, blade spacing, blade
profile, and cavity depth; on seal leakage, as well as the effect of operating a seal in an
off-center position, are examined through a series of non-rotating tests. Two
reconfigurable seal designs were used, which enabled testing labyrinth seals and PDS
with two to six blades.
Leakage and pressure measurements were made with air as the working fluid on
twenty-two seal configurations. Increasing seal blade thickness reduced leakage by the
largest amount. Blade profile results were more equivocal, indicating that both profile
and thickness affected leakage, but that the influence of one factor partially negated the
influence of the other. Seal leakage increased with increased eccentricity at lower
supply pressures, but that this effect was attenuated for higher pressure drops. While
cavity depth effects were minor, reducing depths reduced leakage up to a point beyond
which leakage increased, indicating that an optimum cavity depth existed. Changing
blade spacing produced results almost as significant as those for blade thickness,
showing that reducing spacing can detrimentally affect leakage to the point of negating the benefit of inserting additional blades. Tests to determine the effect of PDS partition
walls showed that they reduce axial leakage. The pressure drop was found to be highest
across the first blade of a seal for low pressure drops, but the pressure drop distribution
became parabolic for high pressure drops with the largest drop across the last blade.
Thirteen leakage equations made up of a base equations, a flow factor, and a kinetic
energy carryover factor were examined. The importance of the carryover coefficient
was made evident and a modified carryover coefficient is suggested. Existing fullypartitioned
PDS models were expanded to accommodate seals of various geometries.
4
Collins, Dermot. "The effects of wear on abradable honeycomb labyrinth seals." Thesis, Cranfield University, 2007. http://hdl.handle.net/1826/1756.
Full textAbstract:
This thesis reports on work undertaken to understand the effects, due to wear,
on the performance of abradable honeycomb labyrinth seals. The phenomena studied
are aerodynamic in nature and include compressible flow, turbulent flow, recirculation
and separation at a range of pressure ratios from 1.20 up to 3.50. Four primary
methods of investigation were used: experimental, numerical using CFD, numerical
using theoretical derivations and numerical using established labyrinth seal specific
computer codes. Effects of seal clearance, pressure ratio and tooth to groove location
have been investigated with overall performance and inter-seal pressure distribution
recorded experimentally and numerically for comparison.
Worn experimental results, when compared to their unworn equivalent, recorded
large increases in mass flow of up to 50% when the labyrinth teeth are located centrally
in the groove. Significant performance enhancements were achieved through
offsetting the teeth with respect to the groove, particularly in an upstream sense.
There was a marked deterioration with the labyrinth teeth located at the groove
exit. Inter-seal pressure distributions showed that the first and final teeth did most
of the work achieving significantly larger pressure drops which goes against current
seal understanding of increasing pressure drop through the seal.
Numerical work was undertaken to further investigate these effects. However,
due to the complex 3-D geometry of an abradable honeycomb labyrinth seal a 2-D
simplification technique was developed to speed up the investigative process. Using
this technique CFD was found capable of replicating the experimental data regarding
overall seal performance and inter-seal pressure distributions. The pressure on
the final tooth proved to be the hardest experimental data to recreate using CFD,
particularly at high pressure ratios when shocks are likely to form.
Further numerical work was undertaken using computer codes and theoretical
derivations. This work proved that the understanding of the seal loss coefficients
used by both methods was not adequate for the current study with the experimental
data recreated least successfully.
Suggestions are given for enhancement of seal design, including axial location
and seal computational routines, which will limit the impact of a 1.5% increase in
operational cost that is likely to accrue from seal deterioration.
5
Joubert, Stephanus Lourens. "Mathematical modeling of leakage flow through labyrinth seals / Lourens Joubert." Thesis, North-West University, 2003. http://hdl.handle.net/10394/389.
Full textAbstract:
Optimization of gas turbine systems has identified the need for simplified mathematical
models to calculate the losses experienced within turbo machines. One such loss is that of
the flow through labyrinth seals. As part of a larger study, this study concentrates on the
development of such loss models to aid in the performance prediction of turbo machines.
The aim of this study was therefore firstly to understand the nature of labyrinth leakage
flows and secondly to investigate mathematical models to calculate or predict such
leakages through most common geometries. Finally the ability of these models was
evaluated by implementing the models into an "engineering tool" in Engineering
Equation Solver (EES).
From a detailed literature survey, a few models for calculating and describing labyrinth
seal leakages were identified. An "engineering tool" was subsequently developed by
combining these models and the governing coefficients in the EES software. Although
experimental validation would have been the optimum, a lack of such facilities together
with a limited budget required alternative methods to be investigated. It was therefore
decided to use Computational Fluid Dynamics (CFD) software such as Star-CD and
Fluent. These software packages are accepted by the industry as a design standard and
visualizing tool for validation. The results obtained compared favourably with that of the
"engineering tool". It therefore proved that the suggested models offer good potential to
be used for performance prediction of labyrinth seals.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.
6
Xi, Jinxiang. "Seal inlet disturbance boundary conditions for rotordynamic models and influence of some off-design conditions on labyrinth rotordynamic instability." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4971.
Full textAbstract:
Systematic parametric studies were performed to better understand seal-inlet rotordynamics.
A CFD-perturbation model was employed to compute the seal-inlet flow
disturbance quantities. Seal inlet disturbance boundary condition correlations were
proposed from the computed seal-inlet quantities using the important parameters. It
was found that the cosine component of the seal-inlet swirl velocity disturbance W1C
has a substantial impact on the cross-coupled stiffness, and that the correlations for
W1C and W1S should be used to replace the historical guess that seal inlet W1C = 0
and W1S = 0. Also, an extremely precise relationship was found between the swirl
disturbance W1C and the seal-inlet swirl velocity (ÃÂRsh â ïW0). Thus, the number
of experiments or computer runs needed to determine the effect of spin speed, shaft
radius and/or inlet swirl velocity on the cross-coupled stiffness is greatly reduced by
plotting the simplified relationship of the cross-coupled stiffness against the swirl slip
velocity. The benefits of using the new seal-inlet boundary condition correlations
were assessed by implementing them into a CFD-perturbation model. Consistently
improved agreement with measurements was obtained for both liquid annular seals
and gas labyrinth seals.
Further, the well-established CFD-perturbation model with new boundary condition
correlations was employed to investigate the rotordynamics of two off-design situations. The first case considered the influence of labyrinth seal teeth damage on
the performance and the rotordynamic characteristics of impeller eye seals in centrifugal
compressors. The second case considered the influence of rotor-axial-shifting on
rotordynamic forces for high-low labyrinth seals in steam turbines during the start-up
and shut-down process. The results should provide useful information for labyrinth
seal design and fault diagnosis of stability problems in turbines and compressors.
7
Zhuang, Qingyuan. "Parametric Study on the Aeroelastic Stability of Rotor Seals." Thesis, KTH, Kraft- och värmeteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116689.
Full textAbstract:
Labyrinth seals are widely used in rotating machinery and have been shown to experience aeroelastic instabilities. The rapid development of computational fluid dynamics now provides a high fidelity approach for predicting the aeroelastic behavior of labyrinth seals in three dimension and exhibits great potential within industrial application, especially during the detailed design stages. In the current publication a time-marching unsteady Reynolds- averaged Navier-Stokes solver was employed to study the various historically identified parameters that have essential influence on the stability of labyrinth seals. Advances in understanding of the related aeroelastic (flutter) phenomenon were achieved based on extensive yet economical numerical analysis of a simplified seal model. Further, application of the same methodology to several realistic gas turbine labyrinth seal designs confirmed the perceived knowledge and received agreements from experimental indications. Abbott’s criteria in describing the labyrinth seal aeroelastic behaviors were reaffirmed and further developed.
8
Dai, Yushuang. "Large eddy simulation of labyrinth seals and rib shapes for internal cooling passges." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271753.
Full textAbstract:
The turbine is one of the key components in gas turbine engines. To prevent the turbine blades from being badly damaged by their harsh working environment, it is necessary to keep them cool. This can be achieved by enhancement of the heat transfer performance through internal cooling passages. However, the large quantity of flow within this internal cycle inevitably results in mass flow loss, which is a major source of loss in turbomachinery. Therefore labyrinth seals are also investigated in this study, attempting to reduce the flow leakage and further increase the turbine efficiency. Large Eddy Simulation ( LES ) is used for its capability to capture the complex unsteady flow features in this study. Different rib shapes in a fully developed ribbed channel are investigated, aiming to improve the heat transfer performance. An immersed boundary method ( IBM ) is used with LES to generate complex geometries. With the use of IBM , the range of geometries can be represented on a background Cartesian grid. To obtain the best sealing performance, an investigation is undertaken into the possibility of optimising labyrinth seal planforms using a genetic algorithm ( GA ). By making use of the large number of populations, a much faster calculation can be achieved toward the objective function. Three hundred LES calculations are carried out, and an optimised design is generated that maximises the sealing effectiveness. The optimised design shows a leakage reduction of about 27.6% compared to the baseline geometry. The optimisation process employing a GA will be continued. It is expected that automated optimisation as presented will become increasingly important in the design process of future turbomachines, particularly for flows with strong parameter interactions, with an aim to further improve the overall efficiency of gas turbines.
9
Choi, Dong Chun. "A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3799.
Full textAbstract:
A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling
as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on
the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal
honeycomb structure was modeled using the concept of the baffle (zero-thickness wall)
and the simplified 2-D fin, respectively. The 3-D model showed that even a small axial
change of the tooth (or honeycomb wall) location, or a small circumferential change of
the honeycomb wall location significantly affected the flow patterns and leakage
characteristics especially for small tooth tip clearance. Also, the local details of the flow
field were investigated.
The seven basic procedural steps to develop a 2-D axisymmetric honeycomb
labyrinth seal leakage model were shown. Clearly demonstrated for varying test
conditions was the 2-D model capability to predict the 3-D honeycomb labyrinth flow
that had been measured at different operating conditions from that used in developing the
2-D model. Specifically, the 2-D model showed very close agreement with measurements. In addition, the 2-D model greatly reduced the computer resource
requirement needed to obtain a solution of the 3-D honeycomb labyrinth seal leakage.
The novel and advanced strategy to reduce the turbine ingress heating, and thus
the coolant requirement, by injecting a Âcoolant isolation curtain was developed
numerically using a 3-D CFD model. The coolant isolation curtain was applied under the
nozzle guide vane platform for the forward cavity of a turbine stage. Specifically, the
isolation curtain serves to isolate the hot mainstream gas from the turbine outer region.
The effect of the geometry change, the outer cavity axial gap clearance, the
circumferential location of the injection curtain slot and the injection fluid angle on the
ingress heating was investigated. Adding the chamfer to the baseline design gave a
similar or higher maximum temperature T*
max than did the baseline design without
chamfer, but implementation of the injection curtain slot reduced substantially T*
max of
the outer region. In addition, a more desirable uniform adiabatic wall temperature
distribution along the outer rotor and stator surfaces was observed due to the presence of
the isolation curtain.
10
Jin, Hanxiang. "Surface Patterning and Rotordynamic Response of Annular Pressure Seals Used in Turbomachinery." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96731.
Full textAbstract:
Rotordynamic instability problems in turbomachinery have become more important in recent years due to rotordynamic components with higher speeds and higher power densities. These features typically lead to increased instability risk in rotor dynamic components as fluids-structure interactions take place. In addition, critical damage of rotordynamic components can result from high level vibrations of supporting bearing system, where the reduced rotor speed can lead to system operating near the rotor critical speed. Therefore, increased accuracy in modeling of rotordynamic components is required to predict the potential instability issues in high performance rotordynamic design. The instability issue may potentially be eliminated in design stage by varying the characteristics of the unstable components. One such turbomachinery component is the annular pressure seal. The annular pressure seals are specifically designed to prevent the fluid leakage from high pressure stage to low pressure stage in turbomachinery. Typical annular pressure seals have two different flow regions, an annular jet-flow region between the rotor and stator, and cylindrical or circumferential indentions on the stator/rotor surface that serve as cavities where flow recirculation occurs. As the working fluid enters the cavities and recirculates, the kinetic energy is reduced, resulting in a reduction of leakage flow. The current challenge is to model with higher precision the interaction between the rotordynamic components and the working fluid. In this dissertation, this challenge was overcome by developing a hybrid Bulk Flow/CFD method to compute rotordynamic responses for the annular pressure seals. In addition, design of experiments studies were performed to relate the surface patterning with the resulting rotordynamic response for the annular pressure seals, in which several different geometry specifications were investigated. This study on annular pressure seal design generated regression models for rotordynamic coefficients that can be used as optimization guidelines. Research topics related to the annular pressure seals were presented in this dissertation as well. The reduced order model of both hole-pattern seals and labyrinth seals were investigated. The results showed that the flow field representing the flow dynamics in annular pressure seals can be expressed as a combination of first three proper orthogonal decomposition modes. In addition, supercritical state of carbon dioxide (sCO2) process fluid was examined as the working fluid in a preliminary study to better understand the effects on annular pressure seals. The results showed that the performance and stability in the annular pressure seals using sCO2 as process fluid can both be improved.Doctor of Philosophy
This dissertation focused on understanding the correlations between surface patterning and rotordynamic responses in the annular pressure seals. The annular pressure seals are a specific type of rotordynamic component that was designed to prevent the fluid leakage from high pressure stage to low pressure stage in turbomachinery. As the working fluid enters the cavities and recirculates, the kinetic energy is reduced, resulting in a reduction of leakage flow through the annular pressure seals. Rotordynamic instability becomes an issue that may be related to the annular pressure seals in some cases. In recent years, rotordynamic components with higher rotor speeds and higher power densities are commonly used in industrial applications. These features could lead to increased instability risk in rotor-bearing systems as fluids-structure interactions take place. Therefore, high precision modeling of the rotodynamic components is required to predict the instability issues in high performance rotordynamic design. The instability issue may potentially be eliminated in design stage by varying the characteristics of the potentially unstable components. In this study, the surface patterning and rotordynamic responses were investigated for several different annular pressure seal models with a hybrid Bulk Flow/Computational Fluid Dynamics method. This dissertation provides for the first time regression models for rotordynamic coefficients that can be used as optimization guidelines. Research topics related to the annular pressure seals were presented in this dissertation as well. The reduced order model of both hole-pattern seals and labyrinth seals were investigated. The results showed that the flow field representing the flow dynamics in annular pressure seals can be expressed as a combination of first three proper orthogonal decomposition modes. In addition, supercritical state of carbon dioxide (sCO2) process fluid was examined to better understand the effects of working fluid on annular pressure seals. The results showed that the performance and stability in the annular pressure seals using sCO2 as process fluid can both be improved.
11
Thompson, Elizabeth Danielle. "Study of Forces and Dynamic Coefficients in Whirling and Eccentric Labyrinth Seals Using ANSYS-CFX." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32328.
Full textAbstract:
Labyrinth seal force estimates are important to the prediction of the stability of turbomachinery. The force prediction methods fall into several categories: experiments, bulk flow analysis, and finite volume analysis. Finite volume analysis can be split into two subcategories: self-developed and commercial.
In this research, a commercial computational fluid dynamics (CFD) program called ANSYS-CFX was used to predict the forces generated in a labyrinth seal whirling at specified speeds. The results were compared to data from VT-FAST, a bulk flow code, and TASCflow, another commercial CFD program. It was shown that there were discrepancies among the results, and several hypotheses were made as to the reason for these discrepancies.
Additionally, ANSYS-CFX was used to study the effect of labyrinth seal eccentricity ratio on the resultant force generated. It was shown that the radial force component within the seal behaved linearly with respect to eccentricity ratio. However, the tangential force component had no distinguishable relationship with the eccentricity ratio. It was hypothesized that the lack of a relationship was caused by the small fluctuations in the inlet swirl. Although the inlet swirl varied very little at each eccentricity ratio, it was shown there was a relationship between the tangential force and inlet swirl.Master of Science
12
Flores, Diego [Verfasser], and Jörg [Akademischer Betreuer] Seume. "Influence of labyrinth seals in cavities on the flow of an axial compressor / Diego Flores ; Betreuer: Jörg Seume." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2018. http://d-nb.info/1168379962/34.
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13
Millsaps, Knox Taylor. "Analysis of aero-elastic forces in labyrinth seals and the design of an experimental facility to measure them." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109622.
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14
Flores, Galindo Diego Rodrigo [Verfasser], and Jörg [Akademischer Betreuer] Seume. "Influence of labyrinth seals in cavities on the flow of an axial compressor / Diego Flores ; Betreuer: Jörg Seume." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2018. http://nbn-resolving.de/urn:nbn:de:101:1-2018100402081060711538.
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15
TAURINO, ROBERTO. "ENERGY-EFFICIENT INNOVATIVE SEAL FOR AIRCRAFT ENGINES." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2681688.
Full textAbstract:
The development of new Additive Manufacturing techniques helps to overtake design constrains characterizing the standard processes. This new reality can opens the space to the redesign of more efficient aircraft engine components. The engine turbine labyrinth seal honeycomb land is currently obtained shaping and welding a sheet metal to create an hexagon pattern. The employing of the DMLM additive manufacturing could led to the development of new geometries, different from the standard honeycomb land, able to increase the labyrinth sealing performances. In this research, innovative stator patterns, able to reduce the seal leakage mass flow rate, have been investigated. The identification of innovative lining pattern cell shapes has been performed by using numerical CFD analyses. The selection of the innovative lining pattern cell shapes has been performed among all numerical solutions investigated. The most promising solutions have been then experimentally verified.
Firstly, a dedicated work has been accomplished, to verify whether ANSYS CFX code was capable of predicting labyrinth seal performances adequately in terms of mass flow leakage. Then, a dedicated simplified model has been developed, in order to explore the performances of new designs with a reasonable computational cost.
An extended CFD analysis, on the honeycomb stepped labyrinth seal, has been performed, in order to investigate the stator part geometrical parameters affecting the discharge coefficient. A one-at-a-time approach has been employed, to investigate: cell wall thickness, cell depth, cell diameter and fin tip thickness. Moreover, the effect of varying the fin tip and cell relative position has been evaluated. Numerical results, for both convergent and divergent flow conditions, have been obtained and analyzed in terms of leakage variations. The obtained results are in good agreement with the data available in the literature . The analysis has highlighted the cell diameter as the most influencing geometrical parameter, for honeycomb labyrinth seal stator part.
In order to define innovative stator lining cell shapes, some assumptions for the honeycomb labyrinth seal rubbing and thermal behaviors have been employed.
Nineteen solutions have been numerically investigated, by leveraging on the knowledge in simulations acquired from the previous activity. A numerical model, of a double fin straight honeycomb labyrinth seal, able to reproduce engine conditions, has been implemented. CFD results have shown how the rhomboidal geometry could give a sensible improvement in the sealing performances.
Two of the rhomboidal shapes analyzed have been flow tested, on a static rig, that was reproducing the same labyrinth seal geometry numerically investigated. The test samples have been manufactured by using the DMLM technique at 1x scale. The measurements performed, for several running clearances and pressure ratios, are then compared with the standard honeycomb seal data and numerical pre-test predictions.
The rhomboidal cells thermal response has been tested in a facility available at the Energy Department of the Politecnico di Torino. The test rig is able to reproduce the outer band static part of a low pressure turbine stage and the blade tip labyrinth seal. It is working at high temperature and has been dimensioned in order to reproduce, in engine similitude, the non-dimensional numbers ruling LPT turbines thermal phenomena. The test article has been designed by integrating the innovative cells into the complete stepped shroud design. The part has been manufactured by means of DMLM technique. The results of the heat transfer model, reproducing the low pressure turbine test rig thermal behavior, have been compared with experimental data.
Finally, the rubbing behavior, of innovative solutions, has been verified performing a rubbing test and comparing measurements with standard solution data.
16
Бага, Вадим Миколайович, Вадим Николаевич Бага, Vadym Mykolaiovych Baha, and Д. С. Мартиш. "Дослідження впливу масштабного фактору на характериститки лабіринтних ущільнень." Thesis, Сумський державний університет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/62583.
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17
Holík, Petr. "Úcpávky turbodmychadel." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230162.
Full textAbstract:
This master’s thesis deals with theme of turbocharger seals. The aims of a thesis are to compare a turbocharger seals used in PBS Turbo turbochargers and to describe a testing of a seals. Principle of turbocharging and types of turbocharger are described in fist part. Next point of the thesis is describing of a face seals and non-contacting seals. The main part of the thesis describes kinds and reasons of seals testing; also contains comparison between labyrinth seals and piston ring, comparison of seals of PBS Turbo’s turbochargers and assesses the impact of turbocharger angle on the tightness of the seal.
18
Бага, Вадим Миколайович, Вадим Николаевич Бага, Vadym Mykolaiovych Baha, and О. І. Подоляка. "Підвищення ефективності лабіринтних ущільнень." Thesis, Сумський державний університет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/62584.
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В данній роботі проводилися чисельні дослідження із застосуванням гідродинамічного програмного комплексу FlowVision для розрахунку течії у вузьких осьових зазорах лабіринтного ущільнення, за результатами яких одержані нові дані по детальному дослідженню ущільнення з гладким валом.
19
Вертепов, Юрий Михайлович, Юрій Михайлович Вертепов, Yurii Mykhailovych Vertepov, and А. А. Кривошеев. "Исследование процесса всасывания жидкостнокольцевой машины." Thesis, Сумский государственный университет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/62587.
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Жидкостно-кольцевая машина относится к объемным машинам с внутренним сжатием и принудительным осевым газораспределением через окна, поэтому формы окон во многом определяют ее характеристики. Объемная характеристики определяется правильной организацией процесса всасывания, для которого большое значение имеет форма внешней кромки всасывающего окна. С возрастанием отношения давлений коэффициент подачи машины быстро снижается. Наиболее заметно с возрастанием отношения давлений снижается коэффициент плотности, связанный с перетечками сжимаемого газа с нагнетания на всасывание через торцовые зазоры. На их величину влияет не только величина зазоров и разность давлений нагнетания и всасывания, но и размеры окон, с которыми связана площадь перетечек. Для уменьшения этих перетечек в торцовые зазоры машины подается рабочая жидкость, или торцы рабочего колеса частично закрывают дисками, концентричными его втулке, или на торцовых поверхностях втулки колеса и лопаток выполняют канавки в качестве лабиринтных уплотнений.
20
Jelínek, Tomáš. "Oprava turbínové skříně." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-320107.
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This diploma thesis deals with the repair of a steam backpressure single-stage turbine. This thesis is assigned to a specific Spilling turbine case. A revisional report of this turbine with repair or exchange suggestions of demaged turbine parts is processed. In addition, a simulation of the contact pressure is carried out on the split plane of the housing. Structural modifications are designed and simulated to increase the parting plane's tightness. Further, the calculation of the tightening torque of the split plane is performed and a control thermodynamic and strength calculation of the labyrinth seals is performed.
21
Vítek, Tomáš. "Parní kondenzační turbína malého výkonu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400497.
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The goal of this Master’s thesis is to create the design of a low power condensing steam turbine. The turbine has a Curtis control stage and a reaction blading. The work also contains the calculation of gland labyrinth seals and the balancing piston, specification of a forces and losses at bearings. Finally, the gearbox and generator are selected and the efficiency at generator’s clamps is specified. The Master’s thesis includes the design drawing of a longitudinal turbine view.
22
Phibel, Richard. "A numerical investigation of labyrinth seal flutter." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/59973.
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This thesis investigates numerically the phenomenon of flutter in labyrinth seals. Computational fluid dynamics (CFD) methods are used to predict the fluid forces produced in the labyrinth when one of the seal members is vibrating in its natural mode. The geometry of the seal, the vibrational characteristics and the flow characteristics are varied to determine their influence on the aeroelastic stability. The CFD results are used to develop a bulk-flow model for labyrinth seal flutter analysis. An aeroelastic design procedure for labyrinth seal is pro-posed.
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Xu, Jinming. "Effects of operating damage of labyrinth seal on seal leakage and wheelspace hot gas ingress." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5867.
Full textAbstract:
The labyrinth seal is widely used in turbomachinery to minimize or control
leakage between areas of different pressure. The present investigation numerically
explored the effect of damage and wear of the labyrinth seal on the turbomachinery
flow and temperature fields. Specifically, this work investigated: (1) the effect of rubgroove
downstream wall angle on seal leakage, (2) the effect of tooth bending damage
on the leakage, (3) the effect of tooth "ÃÂÃÂmushrooming"ÃÂÃÂ damage on seal leakage, and (4)
the effect of rub-groove axial position and wall angle on gas turbine ingress heating.
To facilitate grid generation, an unstructured grid generator named OpenCFD was
also developed. The grid generator is written in C++ and generates hybrid grids
consisting primarily of Cartesian cells.
This investigation of labyrinth seal damage and wear was conducted using the
Reynolds averaged Navier-Stokes equations (RANS) to simulate the flows. The high-
Reynolds k - Model and the standard wall function were used to model the turbulence.
STAR-CD was used to solve the equations, and the grids were generated using
the new code OpenCFD.
It was found that the damage and wear of the labyrinth seal have a significant
effect on the leakage and temperature field, as well as on the flow pattern. The
leakage increases significantly faster than the operating clearance increase from the
wear. Further, the specific seal configuration resulting from the damage and wear was found to be important. For example, for pure-bending cases, it was found that the
bending curvature and the percentage of tooth length that is bent are important, and
that the mushroom radius and tooth bending are important for the mushrooming
damage cases. When an abradable labyrinth seal was applied to a very large gas
turbine wheelspace cavity, it was found that the rub-groove axial position, and to
a smaller degree, rub-groove wall angle, alter the magnitude and distribution of the
fluid temperature.
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Gao, Rui. "Computational Fluid Dynamic and Rotordynamic Study on the Labyrinth Seal." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28134.
Full textAbstract:
The labyrinth seal is widely used in turbo machines to reduce leakage flow. The stability of the rotor is influenced by the labyrinth seal because of the driving forces generated in the seal. The working fluid usually has a circumferential velocity component before entering the seal; the ratio of circumferential velocity and shaft synchronous surface velocity is defined as pre-swirl rate. It has been observed that pre-swirl rate is an important factor affecting driving forces in the labyrinth seal thus affecting the stability of the rotor. Besides the pre-swirl, the eccentricity, the clearance, and the configuration of tooth locations are all factors affecting the rotordynamic properties of the labyrinth seal. So it is of interest to investigate the exact relationships between those factors and the sealâ s rotordynamic properties.
In this research, three types of labyrinth seals have been modeled: the straight eye seal, the stepped eye seal, and the balance drum seal. For the straight eye seal, a series of models were built to study the influence of eccentricity and clearance. The other two seals each have only one model. All models were built with Solid Works and meshed with ANSYS-ICEM. Flows in those models were simulated by numerically solving the Reynolds-Averaged Navier-Stokes (RANS) equations in the ANSYS-CFX and then rotordynamic coefficients for each seal were calculated based on the numerical results.
It had previously been very difficult to generate a pre-swirl rate higher than 60% in a numerical simulation. So three ways to create pre-swirl in ANSYS-CFX were studied and finally the method by specifying the inlet velocity ratio was employed. Numerical methods used in this research were introduced including the frame transfer, the k-ε turbulence model with curvature correction, and the scalable wall function. To obtain the optimal mesh and minimize the discretization error, a systematical grid study was conducted including grid independence studies and discretization error estimations. Some of the results were compared with previous bulk-flow or experimental results to validate the numerical model and method.
The fluid field in the labyrinth seal must be analyzed before conducting rotordynamic analysis. The predicted pressure distributions and leakages were compared with bulk-flow results. A second small vortex at the downstream edge of each tooth was found in the straight eye seal. This has never been reported before and the discovery of this small vortex will help to improve seal designs in the future. The detailed flows in discharged region and in chambers were also discussed.
Radial and tangential forces on the rotor were solved based on the fluid field results. It is shown that the traditional first-order rotordynamic model works well for low pre-swirl cases but does not accurately reflect the characteristics for high pre-swirl cases. For example compressor eye seals usually have pre-swirl rates bigger than 70% and the second order model is required. Thus a second-order model including inertia terms was built and applied to the rotordynamic analysis in this research. The influence of pre-swirl, eccentricity and clearance were studied using the straight eye seal model. The rotordynamic characteristics of the stepped eye seal and the balance drum seal were studied considering high pre-swirl rates. Some relationships between influencing factors and the four rotordynamic coefficients were concluded. The results also showed that for all the three seals higher pre-swirl leads to higher cross-coupled stiffness which is one of the main factors causing rotor instability.
The rotor stability analysis was conducted to study the influence of drum balance seal on the stability. The rotor was designed with typical dimensions and natural frequencies for a centrifugal compressor rotor. The parameters for bearing and aerodynamic force were also set according to general case in compressors to minimize the effects from them. The result shows that the high pre-swirl rate in balance drum seal leads to rotor instability, which confirmed the significant effect of pre-swirl on the seal and the rotor system.Ph. D.
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Mehta, Rumeet Pradeep. "Labyrinth Seal Preprocessor and Post-Processor Design and Parametric Study." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32646.
Full textAbstract:
Vibrations caused due to aerodynamic excitation may cause severe limitation to the performance of turbomachines. The force resulting from the non-uniform pressure distribution within the labyrinth cavity is identified as a major source of this excitation. In order to perform rotor dynamic evaluation of rotor-bearing-seal system, accurate prediction of this force is essential.
A visual basic based front-end, for a labyrinth seal analysis program, has been designed herein. In order to accurately predict the excitation force, proper modeling of labyrinth leak path is important. Thus, the front-end developed herein incorporates a leak-path geometric diagram for visual analysis of labyrinth leak path and tooth location. Furthermore, to investigate influence of various operating conditions and gas properties on excitation force (effective cross-coupling stiffness), a parametric study is performed on both the eye seal and the balance piston labyrinth seal.
Master of Science
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Konicki, Joseph S. "Design of a two dimensional planer pressurized air labyrinth seal test rig." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277232.
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Williston, William C. "Rotordynamic effects driven by fluid forces from a geometrically imperfect labyrinth seal." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA276424.
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Al-Ghasem, Adnan Mahmoud. "Windback seal design for gas compressors: a numerical and experimental study." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5740.
Full textAbstract:
Seals are considered one of the important flow elements of a turbomachinery device.
Traditional labyrinth seals have proven their performance functionality by reducing leakage
rates. Significant improvements on labyrinth seal functionality were obtained through altering
the design geometry of labyrinth seals to prevent contamination across a seal and maintaining
small leakage flowrates. This results in a windback seal that has only one tooth which
continuously winds around the shaft like a screw thread. These seals are used in gas compressors
to isolate the gas face seal from bearing oil. A purge gas is passed through the seal into the
bearing housing. The helical design allows the seal to clear itself of any oil contamination.
Windback seal performance is controlled through changing the seal geometry. A 2D graphical
design tool for calculating the total and cavity leakage flowrates for windback seals is
introduced.
The effectiveness of the Fluent CFD (Computational Fluid Dynamics) commercial code
to accurately predict the leakage rate for windback seals was evaluated. The objective is to
determine if CFD simulations can be used along with a few experimental tests to study windback
seals of this design with air as the working fluid. Comparison of measurement and predictions
for a windback seal using the ú-õ turbulence model with enhanced wall treatment functions show
predictions and measurements comparing very well with a maximum difference of 5% for
leakage rate. Similarly, the leakage rate of the tested smooth seal compares favorably with two
dimensional CFD predictions, with a difference of 2%-11% and 8%-15% using laminar and ú-õ
turbulent flow models, respectively. The variation of leakage with shaft speed and pressure ratio
across the seals is accurately predicted by the CFD simulations. Increasing the rotor speed to
15000 rpm increases the measured leakage flowrate for the windback seal by 2% at high
differential pressure and 4.5% at low differential pressure, and decreases it by 10 % for the
smooth seal. The effects of seal clearance, tooth pitch, cavity depth and the tooth number of starts on
leakage flowrate, velocity and pressure distributions were studied numerically for three
differential pressures and four rotor speeds.
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Dairien, Alexa. "Stabilité des écoulements et interaction fluide structure dans les joints labyrinthe." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC038.
Full textAbstract:
Des joints labyrinthes sont utilisés dans les turbopompes spatiales pour limiter les fuites du gaz qui entraine la turbine dans l’interstice séparant le rotor du stator. Les tendances actuelles sont à la minimisation des jeux (pour optimiser le rendement) et à l’allègement du stator. Ces contraintes conduisent à l’apparition d’instabilités qualifiées d’aéroélastique qui peuvent mener à l’endommagement des structures internes de la turbine, notamment au niveau des partie statoriques selon des analyses post-mortem. Ces évolutions rendent nécessaires l’élaboration de modèles plus prédictifs au niveau de la prise en compte des fuites et de la souplesse du stator.L’objet de ce travail est de développer un modèle numérique avancé de joint labyrinthe prenant en compte un rotor non déformable et un stator flexible. La souplesse de la partie statorique induit des variations de pression et de vitesse au sein de l’écoulement. Le modèle peut comporter plusieurs cavités, le rotor peut être mis en rotation et les dents sont positionnées sur l’arbre.Le modèle d’écoulement développé est inspiré des travaux de Childs et utilise les équations simplifiées de Navier-Stokes. Le modèle de fluide est couplé à un modèle de dynamique des structures correspondant au stator (anneau ou cylindre). La structure peut être encastrée du côté des hautes pressions ou des basses pressions. La prise en considération de cette condition aux limites permet une confrontation précise des résultats avec les travaux d’Abbott. Le système fluide-structure obtenu comprend des équations non-linéaires aux dérivées partielles. Pour s’affranchir de ces non linéarités, une méthode de perturbation est utilisée. Pour résoudre ce problème à deux dimensions (en temps et en espace), une approche de Galerkin est utilisée.Ces développements prennent alors en considération un couplage fort entre le fluide et la structure, incluant les modes à diamètres et le comportement du joint labyrinthe. Les résultats obtenus apportent de nouvelles perspectives sur l’approche actuelle des instabilités aéroélastiquesAerospace turbopumps usually use labyrinth gas seals to prevent the gas driving the turbine to leak in the gap between the rotor and the stator parts. Current trends in turbopumps design focus on the minimization of the clearance, so as to optimise the efficiency, and on the reduction of the stator weight. However, these trends may lead to aeroelastic stability issues which can damage the structure, mainly static parts according to post-mortem observations.To tackle these new challenges, more predictive models must be devised in order to take the stator flexibility and the leakages into account. The purpose of this work is to carry out a numerical investigation on an advanced labyrinth gas seal model comprising a non-deformable rotor, and a flexible stator. The flexibility of the static part induces pressure and velocity fluctuations within the leakage flow. The model retains several cavities formed by the teeth located on the shaft. Eventually, a strong coupling between the fluid and the structure is assumed.The model governing the behaviour of the flow in a cavity is inspired by Childs analytical model and Navier-Stokes equations. The model of the flow is then coupled to a mechanical model corresponding to the stator. The structure can be supported on the low pressure side as well as on the high pressure side. Taking into account those boundary conditions allows a direct comparison with results given by Abbott.The coupled system obtained includes non linear differential equations. To overcome these non- linearities a perturbation method is used, as proposed by Childs. To solve this two-dimensional problem a Galerkin approach with a Fourier transform with respect to the space variables is used.This investigation takes into account a full coupling between the dynamics of the stator, including diameter modes, and the behavior of the labyrinth seal, providing new interesting insights on the dynamic of such system, especially in terms on aeroelastic stability
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Fleury, Marine. "Étude expérimentale d’instabilités aéroélastiques de joints labyrinthe." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEC037.
Full textAbstract:
Dans les machines tournantes, les joints labyrinthes sont utilisés à plusieurs niveaux (turbine, compresseur) pour limiter les fuites et les phénomènes de recirculation entre les zones hautes pressions et les zones basses pressions. Ces composants sont donc critiques pour les performances du moteur. Ils opèrent sans contact, par perte de charge, en minimisant les jeux radiaux entre parties fixes et parties tournantes de la machine. De plus, l’épaisseur du stator est réduite pour obtenir des géométries légères. Ces contraintes de conception mènent à l’apparition d’instabilités aéroélastiques qui constituent un risque pour l’intégrité des parties internes du moteur (fissuration, rupture). Pour éviter ces problématiques, il est nécessaire de disposer de modèles prédictifs. Si des critères existent, peu de données expérimentales permettent de valider et recaler ceux-ci aujourd’hui. L’objet de ce travail est double : il s’agit d’abord de mettre en place un dispositif expérimental spécifique à l’étude d’instabilités aéroélastiques de joints labyrinthe et de réaliser des essais de stabilité pour constituer une base de données expérimentale suffisamment fournie. D’autre part, le développement d’un nouveau modèle numérique est proposé. Des premiers éléments de comparaison calculs-essais sont présentés avec les résultats des simulations. Le banc d’essais mis en place est une reconception d’un premier dispositif expérimental dédié aux instabilités de joints labyrinthe. Le retour d’expérience, les analyses et optimisations réalisées, les solutions technologiques choisies ont permis de concevoir et fabriquer un banc d’essais modulaire et opérationnel pour l’observation et la caractérisation du phénomène. Les forts niveaux vibratoires relevés pendant les essais ont pu être associés à des instabilités aéroélastiques. Les analyses des campagnes d’essais ont permis de mettre en évidence deux paramètres d’influence : le débit massique et l’amortissement structural du stator. Le modèle d’écoulement est basé sur les équations de Navier-Stokes et prend en compte les variations de température au sein du joint labyrinthe. La cinématique du stator est décrite par une théorie de coque cylindrique. Le système global fluide-structure obtenu est développé et linéarisé par la méthode de perturbation. La résolution du problème bidimensionnel (temps et espace) se fait par une approche de Galerkin. Les résultats des simulations, confrontés aux résultats expérimentaux issus des campagnes d’essais, fournissent de nouvelles perspectives pour l’amélioration et le recalage du modèle et pour des campagnes d’essais futuresExperimental study of labyrinth seal aeroelastic instabilities Abstract In turbomachinery, labyrinth seals are used to control the leakage between high-pressure and low-pressure regions. Therefore, labyrinth seals are key components to reach high performance of the engine. These non-contact systems generate pressure drops, minimizing radial clearances between rotating and stationary parts of the structure. Moreover, manufacturers of sealing systems tend to reduce the thickness of structural parts to get lighter designs. These new designs could lead to aeroelastic instability issues, which entails fatigue cracks. To prevent such instability problems, an accurate prediction of the aeroelastic effective damping is necessary. Stability criteria used in the industry are mainly based on empirical observations and show limitations ; moreover, the lack of experimental data can’t allow to validate existing models. This work has a dual objective : firstly, the design and manufacturing of a specific experimental rig to study labyrinth seal aeroelastic instabilities and carry out test campaigns to provide a substantial database. The development of a new analytical model is also proposed. Comparison between numerical and experimental results are presented in the analyses of the simulations. The developed test rig is a redesign of a first experimental device dedicated to labyrinth seal instabilities study. The feedback, analyses and optimisations carried out, the technological solutions set up allowed to design and manufacture an operational and modular test rig for the observation and characterisation of the phenomenon. High vibration levels recorded were associated to aeroelastic instabilities. Test campaigns analyses allowed to highlight two parameters of influence : the mass flow rate and the mechanical damping of stator part. Fluid behavior is described by Navier-Stokes equations, using a one control-volume bulk flow model, and assuming temperature fluctuations. Stator dynamics equation is written using cylindrical shell theory. The resulting fluid-structure system is developped and linearized by a perturbation method. The problem resolution is carried out using a Galerkin approach. Simulations results, compared to experimental results obtained from test campaigns provide numerous perspectives to get better fidelity models and to perform new test campaigns
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Delebarre, Corentin. "Etude expérimentale des systèmes d'étanchéité de type labyrinthe pour turbomachine par l'étude du contact grande vitesse." Thesis, Toulouse, INPT, 2015. http://www.theses.fr/2015INPT0130.
Full textAbstract:
Une des solutions envisagées par les motoristes pour améliorer le rendement des turbomoteurs consiste à réduire le jeu en fonctionnement dans les deux systèmes d’air des turbomachines. Plus particulièrement dans le système d’étanchéité d’air secondaire, la réduction du jeu entre les parties fixes et tournantes améliore le contrôle des étanchéités du moteur et les niveaux de refroidissement entre les différents modules des turbomoteurs, mais entraînent des interactions indésirables entre les différents composants. Les systèmes d’étanchéité dynamiques sont composés de joints labyrinthes couplés à un revêtement abradable sacrificiel en vis-à-vis, qui offre la particularité de s’user préférentiellement en préservant la majeure partie du système d’étanchéité en évitant une usure de la partie tournante. L’objectif de cette thèse est de reproduire et d’étudier, par l’intermédiaire d’un banc technologique haute vitesse spécialement conçu pour l’étude, les interactions labyrinthe-abradable appliquées au couple acier inoxydable/Al-Si 6%, dans des conditions de fonctionnement d’un turbomoteur. Une instrumentation spécifique est développée sur le banc et apporte à l’étude les données expérimentales manquantes visant à la caractérisation des interactions labyrinthe-abradable. Une analyse tribologique, basée sur le concept de troisième corps, est menée afin d’identifier les différents débits de matière puis de décrire les étapes successives des mécanismes d’usure (circuit tribologique) du revêtement Al-Si 6%. L’influence des paramètres de pilotage de l’interaction et de la géométrie du joint a été étudiée. Enfin, une étude statistique basée sur l’iconographie des corrélations, permet de modéliser le comportement global du système labyrinthe-abradable, d’identifier les paramètres influents du système et d’apporter des critères pour une potentielle surveillance des interactions. Ces travaux de thèse ont été réalisés dans le cadre d’une collaboration entre TURBOMECA Bordes (groupe SAFRAN), et le Laboratoire Génie Production (LGP) de TarbesS of turbomachinery. Especially in the secondary air sealing system, the tight clearance between the stationary and rotating parts improves control of engine seals and cooling levels between the different modules of the engines but may cause undesirable interactions between the static and rotating components. Dynamic sealing systems are composed of labyrinth seals coupled to a sacrificial abradable coating, which can accommodate interactions to preserve the global geometrical seal integrity. The objective of this thesis is to study and reproduce, through a technological high speed test rig specifically designed for the study, the labyrinth-abradable interactions applied to stainless steel/Al-Si 6% couple, under similar turbo-engine operating conditions. A suitable instrumentation is developed on the test ring to complete missing experimental data to characterize abradable labyrinth interactions. A tribological study, based on the third body concept, is proposed to identify wear mechanisms process of the Al-Si 6% coating. The influence of interaction control parameters and the seal geometry was investigated. Finally, a statistical study, based on the iconography of the correlation, is proposed to model the overall labyrinth-abradable system behavior and to identify influential parameters of the system and provide suitable criteria to monitor labyrinth seal interactions. This work was achieved within the framework of cooperation between TURBOMECA Bordes (SAFRAN Group), and the Laboratoire Génie de Production (LGP) de Tarbes
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Millsaps, Knox Taylor. "The impact of unsteady swirling flow in a single gland labyrinth seal on rotordynamic stability : theory and experiment." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/43281.
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Šnajdárek, Ladislav. "Přestup tepla v kanálech malých průřezů s rotující stěnou." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-403860.
Full textAbstract:
This work deals with the determination of the heat transfer coefficient in small channels with a rotating wall. The research part of the thesis is focused on specific geometry, namely labyrinth seals used in rotary machines. Existing criteria equations determining heat transfer coefficients and other parameters in these specific geometries are described. The central part describes the built experimental device for the determination of values of heat flows and heat transfer coefficients on both stator and rotor for given airflow and rotor speed. The following section is devoted to presenting the results of the performed experiments with the corresponding criteria equations. The next part describes the basic mathematical models of inverse heat conduction problems. Calculations of heat flux using these inverse methods are performed and compared with reference heat flux sensors.
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Thevenot, Mael. "Contact à grande vitesse en zone labyrinthe, identification des phénomènes mécaniques et thermiques et du comportement des matériaux." Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0010.
Full textAbstract:
La maitrise de l'étanchéité des systèmes d'air dans les turboréacteurs est améliorée en minimisant le jeu entre les pièces tournantes et le carter qui les entoure, garantissant un meilleur rendement du moteur. La réduction de ce jeu permet de diminuer les fuites aérodynamiques à travers le moteur, mais cela peut occasionner des contacts indésirables entre les pièces en rotation à haute vitesse et les pièces fixes en vis-à-vis. Les joints labyrinthes sont des systèmes d'étanchéité dont la partie fixe est revêtue d'un matériau abradable sacrificiel afin de limiter l'endommagement de la partie rotor du joint. Ces interactions labyrinthe-abradable peuvent être critiques pour le bon fonctionnement du joint. L'objectif de cette thèse est d'identifier expérimentalement l'influence des conditions de contact sur les mécanismes d'interaction en jeu. Un banc de contact haute vitesse développé pour l'étude permet de reproduire des conditions de contacts proches de celles survenant sur turboréacteur. Deux configurations de contact qui se produisent dans différents endroits du moteur sont étudiées, avec trois revêtements massifs et trois revêtements alvéolés, aux matériaux et à la géométrie distinctes. La caractérisation thermomécanique des interactions est réalisée avec une instrumentation spécifiquement développée sur le banc. A l'analyse expérimentale est couplée une méthode d'analyse tribologique, basée sur le concept du troisième corps. À travers cette approche les débits de matière engendrées par les interactions sont identifiés et permettent de décrire l'évolution du comportement du contact (circuit tribologique). Ces travaux de thèse ont été réalisés dans le cadre d'une collaboration entre Safran Tech Saclay (groupe SAFRAN), Safran Aircraft Engines Villaroche (groupe SAFRAN) et le Laboratoire Génie de Production (LGP) de TarbesImproving the control over sealing of secondary air systems of aircraft engines require a minimum gap clearance between rotating parts and the surrounding casing, which guarantees higher engine efficiency. The tight clearance allows to reduce leakage flows but may leads to undesirable interactions between the static and rotating parts. Labyrinth seals are dynamic sealing systems for which an abradable coating is deposited on the stationary part of the seal to limit the damage of the rotating shaft. Depending on contact conditions, labyrinth-abradable interactions are potentially critical for the seal. This study aims to identify experimentally the material behaviour during these contact conditions. A high-speed contact test rig was developed to recreate contact conditions occurring in an aircraft engine. Two contact configurations involved in different locations of the engine were explored, with three thermally sprayed coatings and three honeycomb coatings, presenting different materials and surface areas. Thermomechanical characterisation is achieved with a specific instrumentation designed for the study. A tribological analysis based on the third body concept is coupled to the experimental analysis. This approach allows to identify wear mechanisms and material flows through the contact (tribological circuit), which determine the thermomechanical constraints in the high-speed contact. This work was achieved within the framework of cooperation between Safran Tech Saclay (SAFRAN group), Safran Aircraft Engines Villaroche (SAFRAN group) and the Laboratoire Génie de Production (LGP) de Tarbes
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Бага, Вадим Миколайович, Вадим Николаевич Бага, and Vadym Mykolaiovych Baha. "Совершенствование методов расчета и проектирования лабиринтных уплотнений валов пневмоагрегатов на основе моделирования рабочего процесса." Thesis, Изд-во СумГУ, 2015. http://essuir.sumdu.edu.ua/handle/123456789/40851.
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У дисертаційній роботі виконано уточнення робочого процесу та методики розрахунку лабіринтних ущільнень, що дає можливість підвищити їх ефективність, надійність, економічність та термін служби.
Одержані візуалізації течії, запропонований поелементний підхід до опису робочого процесу в ущільненні, що полягає в його розгляді як суми отворів з індивідуальними характеристиками. Цей підхід дав змогу встановити наявність аномальних явищ у проточній частині багатощілинного лабіринтного ущільнення у вигляді флуктуацій параметрів течії – одночасно існуючих зон із різними режимами вихрової течії. Отримані графічні та аналітичні залежності впливу різних параметрів на характеристики ущільнення, уточнені існуючі методики розрахунку з урахуванням факторів, раніше не врахованих, розраховані коефіцієнти окремих видів втрат методом ідентифікації математичної моделі ущільнення. Проведений порівняльний аналіз щодо впливу властивостей газів. Отриманий ряд нових й
уточнені відомі дані щодо вибору геометрії лабіринтних ущільнень, запропоновано збільшення геометричного об’єму розширювальних камер за ходом течії.В диссертационной работе выполнено уточнение рабочего процесса и методики расчета лабиринтных уплотнений, что дает возможность повысить их эффективность работы, надежность, экономичность и срок службы. Получены визуализации течения в проточной части лабиринтного уплотнения c использованием программного комплекса Flow Vision в виде векторов, заливок, изолиний и вспышек. Показана корректность применения данного программного комплекса для исследования расходных характеристик лабиринтных уплотнений. Предложен поэлементный подход к описанию рабочего процесса в уплотнении, заключающийся в его рассмотрении как суммы отверстий с индивидуальными характеристиками, который позволил установить наличие аномальных явлений в проточной части многощелевого лабиринтного уплотнения в виде флуктуаций параметров потока – одновременно существующих зон с различными режимами вихревого течения, что нашло отражение в значениях локальных коэффициентов расхода. Получены графические и аналитические зависимости влияния режимных и геометрических параметров на характеристики лабиринтного уплотнения с гладким валом. Уточнены существующие методики расчета характеристик уплотнений с учетом факторов, ранее не учитываемых, а именно: кольцевая форма зазора, влияние вращения вала, эксцентриситета, масштабного фактора, критериев подобия и др. Рассчитаны коэффициенты отдельных видов потерь методом идентификации математической модели уплотнения. Проведен сравнительный анализ относительно влияния физических свойств различных газов при модельных и натурных условиях численным методом и с использованием экспериментальных данных, полученных на водяном паре и воздухе при сопоставимых условиях. Получен ряд новых и уточнены известные данные по выбору геометрии проточной части лабиринтных уплотнений, предложено увеличение геометрического обьема расширительных камер уплотнения по ходу течения газа. Показано, что при заданной длине уплотнения лучше выполнить большее количество гребней при меньших значениях шага t.
The thesis offers improved view on workflow and methods of the design of labyrinth seals that increase their performance, reliability, profitability and service life. The visualizations of workflow were obtained. The element approach to description of workflow in labyrinth seal was developed. It considers the seal as composition of holes with individual characteristics. This approach allowed determination of existence of abnormal phenomena in flow section of multislot labyrinth seal in the form of fluctuations of parameters of a stream. These are zones with various regimes of a vortex-type flow. Graphical relationships and equations for description of influence of various factors on characteristics of the seal are determined. The equations take into account some factors which were negligible earlier. The correction coefficients for separate types of losses are calculated by method of identification of seal mathematical model. The comparative analysis on influence of properties of gases was performed. A set new and improved data about choice of geometry of labyrinth seals are represented in the thesis. The increase in geometrical volume of broad cameras of the seal in the direction of gas flow is offered.
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Belko, Milan. "Součinitele přestupu tepla na parou obtékaných plochách parních turbín." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230763.
Full textAbstract:
This thesis in introductory part aims to analyze the available literature on the heat transfer coefficient in labyrinth seals and rotating discs of steam turbines. The available experiment studies were processed to summarize heat transfer coefficients on the rotating parts of the turbine. Then, this thesis specifies a design calculation to determine the heat transfer coefficient in selected parts of the turbine, exercisable for specific geometric and operating parameters. The outcome of this work is simulation of rotor dilation of operating steam turbine in the program Ansys during cold start of turbine.
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Skoupý, Pavel. "Parní turbina." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228802.
Full textAbstract:
The master´s thesis concentrates on a project of steam turbine with controlled extraction points destined for a communal waste incineration plant. First, there the history of devices using steam as a moving medium is introduced and than follows the description of computing program, where the calculation was running. The master´s thesis subject consists in the thermodynamic project of turbine vaning, in basic project of gearbox including the check calculations and in technical economic comparison of single shaft and twin shaft constructional design. The design documentation is worked up according to the calculated outcomes and contains longitudinal section of turbine and dispositional turbine and gearbox settlement.
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Беллауар, Абдеррахман. "Підвищення ефективності експлуатації компресорних станцій шляхом вдосконалення конструктивних елементів газоперекачувальних агрегатів." Thesis, Івано-Франківський національний технічний університет нафти і газу, 2010. http://elar.nung.edu.ua/handle/123456789/1968.
Full textAbstract:
Робота присвячена питанням удосконалення конструкцій елементів газоперекачувальних агрегатів (ГПА) з відцентровим нагнітачем (ЦБН)
компресорних станцій. Проаналізовані надійність ГПА, спосіб її підвищення і її зв'язок із залишковим ресурсом, а також вплив вібрації на технічний стан ГПА і можливості використання її для проведення діагностування і віброконтролю ГПА.
Виявлено інформаційні показники, за якими можна визначити технічний стан ГПА; розроблено метод самоорганізації моделей і отримано рівняння регресії; створено тривимірну параметричну комп'ютерну модель ЛУ; складено програму управління геометричними параметрами ЛУ; оптимізовано конструкцію
лабіринтного ущільнення ГПА з ВН за критерієм мінімального тиску в останньому зазорі ЛУ; проаналізовано дані по відмовах ГПА; побудовано графік залежності кількості нарядів на ремонт від часу, витраченого на ремонт (крива АВС); уточнено періодичність технічного обслуговування ГПА за їх поточним технічним станом на основі аналізу АВС і з використанням комп'ютерних баз даних.The present thesis is devoted to the problems of improving the design elements of the gas-pumping units (GPU) with centrifugal compressor (CC) of compressor stations. The reliability of GPU, methods of its improvement and its connection with residual life, as well as influence of vibration on technical state of GPU and potential for its use aiming at GPU diagnosis and vibration-based diagnostics are analyzed. Information indexes to determine technical state of GPU are exposed; method of selforganization of models and regression equation are obtained; three-dimensional parametric computer model labyrinth seal is created; the program to manage geometries of labyrinth seal is made; construction of GPU with CC labyrinth seal on the criterion of the least pressure in the last gap is optimized; information on the malfunctions of GPU is analyzed; dependence of the repair work orders amount on the time expanded on the repair (ABC curve) is diagrammed; periodicity of maintenance of GPU on their current technical state based on the analysis of ABC and with a use of computer databases is specified.
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Рапута, М. В. "Чисельне та експериментальне дослідження впливу шорсткості поверхні на характеристики лабіринтних ущільнень." Master's thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/72180.
Full textAbstract:
У роботі виконано чисельне та експериментальне дослідження впливу шорсткості поверхні на характеристики лабіринтних ущільненьВ работе выполнено численное и экспериментальное исследование влияния шероховатости поверхности на характеристики лабиринтных уплотнений.
A numerical and experimental study of the effect of surface roughness on the characteristics of labyrinth seals was performed.
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Nayak, Kali Charan. "Flow and Windage Heating in Labyrinth Seals." Thesis, 2014. http://etd.iisc.ac.in/handle/2005/2800.
Full textAbstract:
The ability to quantify leakage flow and windage heating for labyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predicting its component lifes. Variety of labyrinth seal configurations (number of teeth, stepped or straight, honeycomb cell size) are in use in gas turbines, and for each configuration, there are many additional geometric factors that can impact a seal’s leakage and windage characteristics. To achieve high performance in modern gas turbine engines, the labyrinth seals operate at low clearances and high rotational speed which are generally deployed with honeycomb lands on the stator. During the transient operation of aircraft engines, the stator and rotor mechanical and thermal growths differ from one another and can often result in the rotor’s incursion into the stator honeycomb structure. The incursions create rub-grooves in the honeycomb lands that can subsequently enlarge as the engine undergoes various manoeuvres. However, the effects of different honeycomb cell size, rotation and presence of rub-groove have not been thoroughly investigated in previously published work. The objective of the present research is to numerically investigate the influence of the above three factors on seal leakage and windage heating.
The present work focuses the development of a numerical methodology aimed at studying above effects. Specifically, a three-dimensional CFD model is developed utilizing commercial finite volume-based software incorporating the RNG k-ε turbulence model. Detail validation of the numerical model is performed by comparing the leakage and windage heating measurements of several rig tests. The turbulent Schmidt number is found to be an important parameter governing the leakage prediction. It depends on honeycomb cell size and clearance for honeycomb seals, and Reynolds number in the presence smooth lands. The present numerical
model with the modified RNG k- turbulence model predicts seal leakage and windage heating within 3-10% with available experimental data.
Using the validated numerical model, a broad parametric study is conducted by varying honeycomb cell size, radial clearance, pressure ratio and rotational speed for a four-tooth straight-through labyrinth seal with and without rub-grooves. They further indicate that presence of rub-grooves increases seal leakage and reduce windage heating, specifically at smaller clearance and for larger honeycomb cell size. Rotation significantly reduces leakage with smooth stator land and smaller honeycomb cells whereas the effect is minimal for larger (3.2mm) honeycomb cells. However, at very high rotational speed seal flow reduces in all seal configurations due to high temperature rise and Rayleigh line effects. At no rub condition and lower clearance, the larger honeycomb cells leak more flow due to high bypass flow through the honeycomb cells. This results into lower pocket swirl and higher windage. When the seal clearance increases the larger honeycomb cells offers more drag to the seal flow, therefore they leak less. At higher clearances the flow travels like a strong wall jet and isolates the pocket air from honeycomb cells. Hence, at open clearances labyrinth seals with any honeycomb cell size essentially produce the same pocket swirl and windage heating.
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Nayak, Kali Charan. "Flow and Windage Heating in Labyrinth Seals." Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2800.
Full textAbstract:
The ability to quantify leakage flow and windage heating for labyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predicting its component lifes. Variety of labyrinth seal configurations (number of teeth, stepped or straight, honeycomb cell size) are in use in gas turbines, and for each configuration, there are many additional geometric factors that can impact a seal’s leakage and windage characteristics. To achieve high performance in modern gas turbine engines, the labyrinth seals operate at low clearances and high rotational speed which are generally deployed with honeycomb lands on the stator. During the transient operation of aircraft engines, the stator and rotor mechanical and thermal growths differ from one another and can often result in the rotor’s incursion into the stator honeycomb structure. The incursions create rub-grooves in the honeycomb lands that can subsequently enlarge as the engine undergoes various manoeuvres. However, the effects of different honeycomb cell size, rotation and presence of rub-groove have not been thoroughly investigated in previously published work. The objective of the present research is to numerically investigate the influence of the above three factors on seal leakage and windage heating.
The present work focuses the development of a numerical methodology aimed at studying above effects. Specifically, a three-dimensional CFD model is developed utilizing commercial finite volume-based software incorporating the RNG k-ε turbulence model. Detail validation of the numerical model is performed by comparing the leakage and windage heating measurements of several rig tests. The turbulent Schmidt number is found to be an important parameter governing the leakage prediction. It depends on honeycomb cell size and clearance for honeycomb seals, and Reynolds number in the presence smooth lands. The present numerical
model with the modified RNG k- turbulence model predicts seal leakage and windage heating within 3-10% with available experimental data.
Using the validated numerical model, a broad parametric study is conducted by varying honeycomb cell size, radial clearance, pressure ratio and rotational speed for a four-tooth straight-through labyrinth seal with and without rub-grooves. They further indicate that presence of rub-grooves increases seal leakage and reduce windage heating, specifically at smaller clearance and for larger honeycomb cell size. Rotation significantly reduces leakage with smooth stator land and smaller honeycomb cells whereas the effect is minimal for larger (3.2mm) honeycomb cells. However, at very high rotational speed seal flow reduces in all seal configurations due to high temperature rise and Rayleigh line effects. At no rub condition and lower clearance, the larger honeycomb cells leak more flow due to high bypass flow through the honeycomb cells. This results into lower pocket swirl and higher windage. When the seal clearance increases the larger honeycomb cells offers more drag to the seal flow, therefore they leak less. At higher clearances the flow travels like a strong wall jet and isolates the pocket air from honeycomb cells. Hence, at open clearances labyrinth seals with any honeycomb cell size essentially produce the same pocket swirl and windage heating.
42
Yeh, Chun-Ting, and 葉俊廷. "Parameter Modification for Liquid Plain Seals and Gas Labyrinth Seals." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/22167781576962912314.
Full textAbstract:
碩士元智大學
機械工程學系
96
The empirical parameters, (m, n), in the Childs’ equations for the dynamic coefficients of liquid plain seals and gas labyrinth seals, based on bulk flow theory, are modified in this paper. Instead of treating the parameters (m, n) as constant values, optimal functions of pressure difference for the parameters (m, n) are obtained by least square error fitting to approach the target values computed from Fluent. The accuracy of the dynamic coefficients of seals is improved and closer to the results of Fluent, which help the user saving computational time and fast implementation in applications.
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Panicker, Sunil M. "Leakage Prediction of Labyrinth Seals Having Advanced Cavity Shapes." 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-7775.
Full textAbstract:
Labyrinth seals are widely used in various turbo machines including turbines, compressors and pumps. Their purpose is to prevent the backflow of the working fluid. This backflow is due to the leakage of the seal. This loss affects the efficiency of the turbo machine, so it becomes critically important to assess the leakage of the seals under the given operating conditions. The accuracy of prediction of leakage is also important for performing rotodynamic analysis. The geometric shape of the seal plays an important role in influencing the fluid flowing through the seals and the leakage rate. Many empirical seal leakage prediction models, useful from a design/analysis point of view, have been developed.
Saikishan Suryanarayanan and Gerald. L .Morrison studied the influence of various geometric and flow parameters on the leakage of labyrinth seals with rectangular cavities. They proposed a leakage equation based on their Computational Fluid Dynamics (CFD) simulations using software FLUENT.
However, many real world labyrinth seals do not have simple rectangular cavities. In particular, this thesis focuses on seals with Isosceles triangle shaped teeth, right triangle shaped teeth, and a NASA seal. In the present work, CFD simulations of labyrinth seals with advanced cavity shapes are performed and the results are compared with the predictions of the rectangular seal model. The results show that the advanced cavities like, Isosceles shaped seal were more efficient as compared to rectangular seals. The pressure drop, which was taken as one of the key parameters to adjudge the efficiency of seals showed negative behavior in some of the advanced cavity shaped seal. The advanced cavity shaped seals are used in various turbo machinery equipments like steam and gas turbines. This study shows that Isosceles cavity shaped seals are the most efficient among all the advanced cavity shapes used in the present study.
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Yucel, Ugur. "Effects of labyrinth seals on the stability of rotors /." Diss., 2000. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9982879.
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Ashton, Zachary. "High Temperature Leakage Performance of a Hybrid Brush Seal Compared to a Standard Brush Seal and a Labyrinth Seal." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-7003.
Full textAbstract:
Adequate sealing in turbomachinery reduces secondary leakage and results in more efficient and stable systems. Labyrinth seals are most common, although brush seals are popular in specialized applications. The Hybrid Brush Seal (HBS) is a novel design that adds to the bristle brush matrix a number of cantilever pads that rest on the rotor surface. Upon shaft rotation the pads lift due to the generation of a hydrodynamic gas film while the brushes effectively seal an upstream pressure. Hence the HBS has no wear and no local thermal distortion effects.
Measurements of leakage versus pressure differential are obtained in a three-teeth labyrinth, a conventional brush seal, and a hybrid brush seal for operation at high temperature (300ºC), with shaft surface speeds to 27 m/s, and at supply pressures to 3.5 bar. Flow measurements are presented in terms of a flow factor to remove dependency on the air temperature and supply pressure. The measurements demonstrate the HBS leaks less (~61%) than a standard brush seal and is significantly better (~38%) than a similarly sized labyrinth seal. Predictions of flow through a labyrinth seal predict well at supply pressures under 1.7 bar but overpredict by as much as 25% at high supply pressures. A porous medium fluid flow model predicts the flow through the HBS and brush seal. The model for the HBS and brush seal underpredicts the flow rate at low supply pressures but match well at high supply pressures.
Measurements of the drag torque of the test seals show the HBS has a larger torque when pressurized compared to the brush seal and labyrinth seal. This indicates that the HBS experiences a larger degree of blow-down due to the pads decreasing the clearance.
The mechanical parameters of the brush seal and HBS are found based upon the flexibility function from impact load tests. A combined structural and dry friction damping model represent well the measured flexibility. An equivalent damping is found based upon the energy dissipation. Based upon the damping ratio, the HBS has twice of the viscous damping as the brush seal at a supply pressure of 2.0 bar.
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Yamsani, Vamshi Krishna. "Numerical Study of Geometry and Rotation Dependence on the Flow in Labyrinth Seals." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9728.
Full textAbstract:
A computational study was conducted on the flow, both compressible and incompressible, in a labyrinth seal at various geometries and rotation rates. The computations were performed using the commercial software Fluent® which solves the k-ε model to predict the flow field in the seal. Various clearance-pitch ratios were used to study the effect of clearance on the flow. The aspect ratio, which is defined as the pitch-height ratio was varied to study the influence of the depth of the cavity on the flow as a whole. These studies span a range of Taylor's number that is defined accordingly, while fixing the Reynolds number at 1000.
The effects of clearance, aspect ratio and rotational rates are studied using carry-over coefficient and discharge coefficient. It is observed that a secondary recirculation zone (SRZ) occurs inside a seal cavity at above certain Taylor's number. This significantly changes the flow field in the seal and the cavity which results an increases in pressure drop across the seal for a given flow boundary condition. This formation of SRZ's is more evident in incompressible flow and occur at prohibitively high rotational speeds in case of air (compressible flow). It is also observed that flow with teeth on rotor are characterized by SRZ's while it's not case with teeth on stator. A flow map which shows the onset and presence of SRZ's is shown.
The ratio of tangential velocity of the shaft to the average of the swirl velocity in a cavity at various geometries of the cavities are presented. They seem to be decreasing with decreasing depth and follow a linear pattern with the aspect ratios of the cavity.
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Ayyalasomayajula, Sricharan Kishore. "A numerical study of curved labyrinth seals for steam turbines." 2005. http://etd.utk.edu/2005/AyyalsomayajulaSricharan.pdf.
Full textAbstract:
Thesis (M.S.) -- University of Tennessee, Knoxville, 2005.Title from title page screen (viewed on January 30, 2006). Thesis advisor: Ahmad D. Vakili. Document formatted into pages (xiii, 99 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 68-72).
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Bob, In-Cheng, and 鮑盈丞. "Leakage Flow Analysis of Labyrinth Seals on a Hydraulic Cylinder." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/q45f7b.
Full textAbstract:
碩士逢甲大學
機械工程學所
90
Leakage plays an important role on the performance evaluation of hydraulic components. Leakage flow will induce adverse influence on many practical industrial applications. Therefore, most of the hydraulic components install some kind of sealing device to avoid or to reduce the leakage. This research is to investigate the leakage flow of labyrinth seals on a high speed hydraulic cylinder by using numerical analysis method. The parameters investigated in this study are linear velocity, groove type, groove number, groove depth, groove width, groove distance, clearance, and Reynolds number. In accordance with practical industrial problem, the rectangular type and triangular type grooves are both considered. It is shown that groove width is about 20~30 times of clearance, groove depth is about 3~5 times of clearance, and groove distance is greater than 50 times of clearance; the groove depth to width ratio is about 0.15~0.25 and the groove distance to width ratio is greater than 2.5 have better effect on preventing leakage. The results of this research will supply valuable design reference data for the hydraulic component designer and manufacturer.
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Woo, Jeng Won. "Analysis of Compressible and Incompressible Flows Through See-through Labyrinth Seals." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9264.
Full textAbstract:
The labyrinth seal is a non-contact annular type sealing device used to reduce the internal leakage of the working fluid which is caused by the pressure difference between each stage in a turbomachine. Reducing the leakage mass flow rate of the working fluid through the labyrinth seal is desirable because it improves the efficiency of the turbomachine.
The carry-over coefficient, based on the divergence angle of the jet, changed with flow parameters with fixed seal geometry while earlier models expressed the carry-over coefficient solely as a function of seal geometry. For both compressible and incompressible flows, the Reynolds number based on clearance was the only flow parameter which could influence the carry-over coefficient. In the case of incompressible flow based on the simulations for various seal geometries and operating conditions, for a given Reynolds number, the carry-over coefficient strongly depended on radial clearance to tooth width ratio. Moreover, in general, the lower the Reynolds number, the larger is the divergence angle of the jet and this results in a smaller carry-over coefficient at lower Reynolds numbers. However, during transition from laminar to turbulent, the carry-over coefficient reduced initially and once the Reynolds number attained a critical value, the carry-over coefficient increased again. In the case of compressible flow, the carry-over coefficient had been slightly increased if radial clearance to tooth width ratio and radial clearance to tooth pitch ratio were increased. Further, the carry-over coefficient did not considerably change if only radial clearance to tooth width ratio was decreased. The discharge coefficient for compressible and incompressible flows depended only on the Reynolds number based on clearance.
The discharge coefficient of the tooth in a single cavity labyrinth seal was equivalent to that in a multiple tooth labyrinth seal indicating that flow downstream had negligible effect on the discharge coefficient. In particular, for compressible fluid under certain flow and seal geometric conditions, the discharge coefficient did not increase with an increase in the Reynolds number. It was correlated to the pressure ratio, Pr. Moreover, it was also related to the fact that the flow of the fluid through the constriction became compressible and the flow eventually became choked.
At low pressure ratios (less than 0.7), Saikishan’s incompressible model deviated from CFD simulation results. Hence, the effects of compressibility became significant and both the carry-over coefficient compressibility factor and the discharge coefficient compressibility factor needed to be considered and included into the leakage model.
The carry-over coefficient compressibility factor, phi, had two linear relationships with positive and negative slopes regarding the pressure ratios. This result was not associated with the seal geometry because the seal geometry ratios for each instance were located within the nearly same ranges. Further, the phi-Pr relationship was independent of the number of teeth regardless of single and multiple cavity labyrinth seals.
The discharge coefficient compressibility factor, psi, was a linear relationship with pressure ratios across the tooth as Saikishan predicted. However, in certain flow and seal geometric conditions, Saikishan’s model needed to be modified for the deviation appearing when the pressure ratios were decreased. Hence, a modified psi-Pr relationship including Saikishan’s model was presented in order to compensate for the deviation between the simulations and his model.
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Lim, Chae H. "A NUMERICAL AND EXPERIMENTAL STUDY OF WINDBACK SEALS." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-506.
Full textAbstract:
Windback seals work similarly to labyrinth seals except for the effect of helical
groove. These seals are essentially a tooth on stator or tooth on rotor labyrinth seal
where the grooves are a continuous helical cut like a thread. Windback seals are used in
centrifugal gas compressor to keep oil out of the gas face seal area. These face seals
cannot be contaminated by oil. A purge gas is applied to the seal to help force the oil
back into the bearing area.
The windback seal should be designed to prevent any oil contamination into the
supply plenum and to reduce purge gas leakage. The CFD simulations have been
performed with the effect of clearance, tooth width, cavity shape, shaft rotation,
eccentricity, and tooth location on the seal leakage performance and the flow field inside
the seal. The leakage flow rate increases with increasing the pressure differential, rotor
speed, radial clearance, cavity size, and shaft diameter and with decreasing the tooth
width. The eccentricity has a minimal effect for the windback seal. From oil simulations,
the windback seal with 25% rotor eccentricity has some of the journal bearing action and
drives back flow into the gas plenum. However the windback seal can be used to force the oil back into the bearing side before starting the compressor by applying a purge gas
flow since the positive axial velocity inside the cavity is larger than the negative axial
velocity. m A Rw cav & / ? is constant for varying shaft rotation since the leakage flow rate
for the windback seal increases linearly as the the rotor speed increases. The leakage
flow rate for the windback seal increases as the groove size increases due to the pumping
action of the windback seal. A windback seal design based upon the numerical
simulations that minimize gas leakage and help prevent gas face seal oil contamination
was optimized.
The windback seal has two leakage flow paths. Since the leakage flow rate under
teeth of windback seals is the same as for a similar geometry labyrinth seal, the flow
under the teeth can be predicted by two-dimensional labyrinth seal analysis. An
empirical model for the leakage rate through the cavity has been developed which fits
the data with a standard deviation of 0.12.