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1
Content available Evaluation of leakage through labyrinth seals with analytical models
Szymański Artur, Dykas Sławomir
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
|
2019
|
Vol. 23, No 1
61--79
EN
Secondary flows in turbomachinery highly affect the overall efficiency and rotorstability. A prime example of such a phenomenon are leakage flows. Despite their complexity, they can often be estimated with simple semi-empirical formulae, solved with hand calculations.Such an approach is much more cost and time effective during the design process. The formula econsists of a carry-over coefficient and a discharge coefficient elements. To evaluate the leakage properly, an adequate model of the carry-over coefficient has to be developed. This paper presents how the flow conditions and the cavity geometry changes in a straight through labyrinth sea laffect the amount of leakage. The effect of the number of teeth, the gap size, the Reynolds number and the pressure ratio are considered. The data to validate the results was obtained from an in-house experiment, where a vast number of cases was tested. Additionally, the study was supported by a two-dimensional steady-state CFD study. Eleven analytical models, including both very simple as well as more sophisticated methods, were solved according to the experimental case and compared. Six different seal configurations were examined. They included straight through seals with two and three straight knives for various gap sizes.The comparison highlighted differences in the results for models – a certain group presented underestimated results. However, another group of models – presented an excellent agreement with the experimental data. Based on this study, a group of models representing the results within the 10% uncertainty band was selected.
2
Content available Analiza krytyczna metod obliczania uszczelnień labiryntowych w maszynach cieplnych wirnikowych
Kaszowski Paweł, Dzida Marek
Journal of Polish CIMEEAC
|
2019
|
Vol. 14, no 1
97--110
PL
Uszczelnienia labiryntowe są ważnym elementem budowy maszyn cieplnych wirnikowych. Istnieje wiele metod obliczeniowych, pozwalających określić parametry termodynamicznych gazu na długości dławnicy labiryntowej. W niniejszej pracy przedstawiona zostanie krytyczna analiza metod obliczania uszczelnień labiryntowych dostępnych w literaturze oraz przykładowe wyniki obliczeń wykonanych metodą wyznaczania linii Fanno i zasady De Saint–Venanta.
3
Content available The effects of variable operational parameters on an aero engine labyrinth seals performance
Szymański A., Dykas S., Majkut M., Strozik M.
Transactions of the Institute of Fluid-Flow Machinery
|
2018
|
nr 140
83--104
EN
The paper presents the accurate assessment of the amount of gas flowing through three types of aero-engine expander sealing. Structures consisting of straight-through labyrinth seals – with one, two and three fins are considered. The study deploys two independent approaches. The first one focuses on the experimental research using high-precision test section with non-rotating labyrinth seals specimen connected to a high capacity vacuum installation. Experimentally tested seals are of actual size (model to engine scale is 1:1). High accuracy hot-wire anemometry probes, and orifice plate are deployed to evaluate the flow indicators accurately, allowing for comparison of different sealing structures. The second approach uses quasi-two-dimensional axissymmetric, steady-state Reynolds averaged Navier Stokes (RANS) computations to simulate the flow field. Various meshes and turbulence models were tested, presenting capabilities as well as limitations of specific computational approaches. The experimental and computational results were compared with literature data, showing a good agreement regarding overall trends, yet underlining some local discrepancies. This paper brings two significant findings. The 2D RANS methods tend to overestimate the leakage when compared with experimental results, and the difference is more significant for advanced arrangements. There is a notable difference between the performance of labyrinth seal with one fin and structure with two and three fins. In some operational areas, one-finned seal performs better than more advanced ones, reducing the leakage more effectively. This feature of one finned seal is not intuitive, as one would expect it to perform worse than a seal with two or three fins.
4
Content available Experimental research and CFD calculations based investigations into gas flow in a short segment of a heavily worn straight through labyrinth seal
Joachimiak D., Krzyślak P.
Polish Maritime Research
|
2017
|
nr 2
83--88
EN
Steam turbines are used as propulsion components in not only power plants but also on merchant and naval ships. The geometry of the steam turbine seals changes throughout the machine life cycle. The rate of deterioration of these seals, in turn, affects heavily the efficiency of the thermal machine. However, the literature overview does not provide any research reports on flow phenomena occurring in heavily deteriorated seals. The paper describes the course and results of investigations into a model straight through labyrinth seal composed of 4 discs, each with the slot height of 2 mm. The investigations have been conducted with air as the working medium. Changes of gas flow parameters due to wear were analysed. Based on the experimental data, more intensive leakage was observed as the result of the increased slot height. The static pressure distribution along the examined segment was measured. The experimentally recorded distribution differed remarkably from the theoretical assumptions. Another part of the experimental research focused on comparing the gas velocities at points situated upstream of the first and second seal disc. The velocity measurements were carried out using a constant temperature wire probe. This part of the investigations provided opportunities for analysing the influence of seal wear on gas flow conditions in the seal segment. The paper compares the results of the experimental research with those obtained using the CFX software. The presented results of velocity distributions provide a clear picture of the nature of the gas flow in the seal, which enables its analysis.
5
Content available remote Description of a test stand and measurement equipment for labyrinth seal testing
Joachimiak D., Krzyślak P.
Journal of Mechanical and Transport Engineering
|
2017
|
Vol. 69, No. 3
21--35
EN
The paper presents a test stand for testing segments of single sided and double-sided labyrinth seals. The geometry of the test stand has been designed and constructed by the authors of the paper. The elements and the design of the test stand allow investigations of the seal for a variety of initial pressures with the measurement of the mass flow in the inlet and outlet channels. The design of the test stand enables testing seal segments with a turbulent flow. The geometry of the mating pairs of single and double-sided seals allows a measurement of the pressure in selected chambers of the seal chambers.
PL
W artykule przedstawiono stanowisko do badań segmentów uszczelnień labiryntowych jednostronnych i dwustronnych. Geometria stanowiska została zaprojektowana i wykonana przez autorów. Elementy i konstrukcja stanowiska umożliwiają przeprowadzenie badań uszczelnienia z uwzględnieniem różnych zakresów ciśnienia początkowego z pomiarem strumienia masy w kanale dopływowym i kanałach wypływowych. Konstrukcja stanowiska umożliwia badanie segmentów uszczelnień z zaburzonym przepływem. Geometria korpusu i wsadu uszczelnień jednostronnego i dwustronnego umożliwia pomiar ciśnienia w wybranych komorach uszczelnienia.
6
Content available The assessment of the calculation method for determining characteristics of one straight fin labyrinth sea
Szymański A., Dykas S., Majkut M., Strozik M.
Transactions of the Institute of Fluid-Flow Machinery
|
2016
|
nr 134
89--107
EN
The method for the selection of a calculation scheme for the evaluation of the flow behaviour of labyrinth seal with one straight fin, against smooth wall, was presented. Experimental results were obtained from measurement data carried out on the in house, vacuum test section. The advantage of the test rig is a circular shape of the labyrinth specimen, providing similar shape to configuration operated in practise. In computational fluid dynamics study different types of mesh resolution were tested, with variable volume discretization in the area of a labyrinth fin tip. Moreover, a wide range of turbulence models basing on k-ε and k-ω, exploiting the (Reynolds Average Navier Stokes) scheme, for the flow pattern evaluation, were examined. All obtained results were compared with literature data, covering research conducted on similar configurations. The presented study shows challenges as well as the possibilities of calculation simplification and compares results obtained by means of simulations and experiment. The proposed method is characterised by excellent agreement of computational results with experiment data.
7
Content available Analysis of the impact of mass flow extraction on the change of parameters in a labytinth seal using the Stodola method
Kaszowski P., Dzida M.
Journal of Polish CIMEEAC
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2016
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Vol. 11, no 1
55--67
EN
Labyrinth seals are an important element of a steam turbine set design. The use of diagnostic extraction makes it possible to control the operation of a seal by providing information on the thermodynamic parameters along the length of the seal. Diagnostic extraction has a considerable impact on the change of the parameters, the amount of the extracted mass. This article describes the dependence of pressure in the clearance downstream of the extraction and in the chamber in which the extraction point is located, on the amount of the extracted steam. Relation between pressure and nominal seal clearance is discussed, which enables the control of the seal operation. The calculations of the seal operation parameters were performed using a method proposed by Stodola.
8
Content available CFD analysis of fluid flow through the labyrinth seal
Kaszowski P., Dzida M.
Transactions of the Institute of Fluid-Flow Machinery
|
2015
|
nr 130
57--69
EN
Steam and gas turbines are essential to produce electricity. Since the launch of the first turbine in the world, there become a tendency to constantly achieve higher efficiency. There are many solutions to overcome losses in the working steam turbine. One of such methods is the use of seals. To determine thermodynamic parameters of steam, which prevail in the seal, we could use experimental methods or numerical calculations. Experimental researchs are too expensive and time consuming. Therefore, computational fluid dynamics (CFD) is increasingly used in the analysis of fluid flow through the labyrinth seal. The paper describes the results using CFD simulation software with the help of contained a computational k-ε model.
9
Content available Comparison of results of experimental research with numerical calculations of a model one-sided seal
Joachimiak D., Krzyślak P.
Archives of Thermodynamics
|
2015
|
Vol. 36, no. 2
61--74
EN
Paper presents the results of experimental and numerical research of a model segment of a labyrinth seal for a different wear level. The analysis covers the extent of leakage and distribution of static pressure in the seal chambers and the planes upstream and downstream of the segment. The measurement data have been compared with the results of numerical calculations obtained using commercial software. Based on the flow conditions occurring in the area subjected to calculations, the size of the mesh defined by parameter y+ has been analyzed and the selection of the turbulence model has been described. The numerical calculations were based on the measurable thermodynamic parameters in the seal segments of steam turbines. The work contains a comparison of the mass flow and distribution of static pressure in the seal chambers obtained during the measurement and calculated numerically in a model segment of the seal of different level of wear.
10
Content available remote Analiza rozkładu prędkości w komorze uszczelnienia labiryntowego na podstawie badań eksperymentalnych i obliczeń numerycznych
Joachimiak D., Krzyślak P.
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika
|
2014
|
z. 86 [290], nr 2
215--224
PL
W pracy przedstawiono wyniki badań eksperymentalnych i numerycznych badania rozkładu prędkości w dziesiątej komorze modelowego segmentu uszczelnienia labiryntowego składającego się z dwudziestu tarcz. Pomiar ciśnienia dynamicznego wykonano sondą Pito i sondą ciśnienia statycznego. Badania eksperymentalne przeprowadzono w trzech płaszczyznach komory. W obliczeniach numerycznych założono warunki termodynamiczne i przepływowe występujące w warunkach pomiaru. Praca zawiera porównanie prędkości osiowych powietrza w wymienionych płaszczyznach uzyskanych z eksperymentu i obliczeń.
EN
The paper presents the results of the experimental and numerical studies of the velocity distribution in the tenth chamber of labyrinth seal of model segment consisting of twenty discs. The measurement of the dynamic pressure was carried out by using both Pito and static pressure probes. Experimental tests were carried out at three planes of the chamber. In numerical calculations thermodynamic and flow conditions occurring during the measurement were assumed. The work includes a comparison between the experimental and calculated values of axial air velocities at above mentioned planes.
11
Content available Comparative analysis of the results of gas flow in a labyrinth seal for a numerical and theoretical model
Kaszowski P., Dzida M.
Journal of Polish CIMAC
|
2014
|
Vol. 9, no 2
117--125
EN
Labyrinth seals are an important component of gas and steam turbines design. Many calculation models are available in order to determine the thermodynamic parameters of gas along the seal length: starting with models based on an analytical solution to the problem of gas flow through a seal to numerical models resulting in numerical data and visualizations of conditions inside the seal. In this article the results of calculations made using the Fanno model and the Saint-Venant's Principle with the k-epsilon model in Ansys Fluent are compared.
12
Content available Calculations of labyrinth seals with and without diagnostic extraction in fluid-flow machines
Kaszowski P., Dzida M., Krzyślak P.
Polish Maritime Research
|
2013
|
nr 4
34--38
EN
Labyrinth seals are essential components of steam turbine unit constructions. Two types of labyrinth seals can be named, the first of which is the seal without diagnostic steam extraction, and the second – with extraction. The distribution of flow parameters along the packing is affected remarkably by the average seal clearance. The presence of diagnostic extraction leads to the equation system which is determinable and can be inversed to calculate the average seal clearance Si. Analysing the obtained results leads to the conclusion that the information about this parameter provides opportunities to monitor the current state of the packing in real time. The applied calculation procedure bases on the de Saint - Venant equation. The article also includes a brief description of both types of seals.
13
Content available The analysis of the calculation process related to labyrinth sealing with extraction
Joachimiak D., Joachimiak M., Krzyślak P.
International Journal of Applied Mechanics and Engineering
|
2013
|
Vol. 18, no. 4
1057--1066
EN
The work presents a calculation process enabling one-dimensional numerical calculations of labyrinth sealing. A DSV program determines the thermodynamic parameters of gas in the sealing chambers with extraction. The influence of the sealing length upon the stability of a matrix solution of the system of equations with the use of Cond(C) parameter is analysed. Next, the operation of the software extended with a module that enables determination of the initial pressure p0, to which the assumed mass flow for a set geometry and sealing length would correspond is discussed. The work analyzes Cond(C) and initial pressure values for various sealing lengths with an assumed leak value. The work also compares the values of static pressures on the extraction plane, as obtained from the measurements, to theoretically calculated values. The calculations and comparisons were made for various heights of incomplete sealing fissures.
14
Porównanie jednowymiarowych modeli obliczeniowych przepływu ściśliwego i nieściśliwego płynu w dławicy labiryntowej
Joachimiak D., Krzyślak P.
Zeszyty Naukowe Politechniki Poznańskiej. Maszyny Robocze i Transport
|
2011
|
Nr 64
51-67
PL
W artykule przedstawiono istotę działania uszczelnień labiryntowych oraz niektóre aspekty stosowania różnych wariantów ich konstrukcji. Publikacja zawiera opis modeli obliczeniowych, w których zakłożono przepływ izentalpowy. Pierwszy model uwzględnia przepływ ściśliwy, a drugi nieściśliwy. Dla założonego rodzaju gazu, jego parametrów termodynamicznych, zdefiniowanej geometrii i typu uszczelnienia za pomocą modeli wyznacza się początkowo rozkład liniowy spadku ciśnienia, a następnie rzeczywisty rozkład ciśnienia i wartości pozostałych parametrów termodynamicznych gazu. Określa się również prędkość i liczbę Macha w poszczególnych przewężeniach. W obliczeniach nie uwzględnia się lepkości płynu, pomijana jest również wymiana ciepła pomiędzy gazem a ściankami uszczelnienia.
EN
In the results of calculations of compressible model in article were compared was and incompressible for flow by labirynth seals. Near put the same the value of pressures before and for clearence seal: the course of fall of pressure, speed on length the seal as well as value of leakage differ considerably. Summing up it is possible to show apication considered computational models calculation. Incompressible model has first of all use in seal which liquid swims. From simplifying it can be applied to labirynth gas seals analysis near low differences of pressures. It is possible one dimensional compressible model apply to all labirynt seals in which it swims gauzes and we have the large differences of pressures. Introduced models make possible determination parameters thermodynamic flows through for defined seal geometry. The practically introduced computational tools will to be of service to designing to the stand project for the research of labirynth seals, as well as the foreseeing of measured thermodynamical values in definite points the designed seals on measuring position.
15
Content available remote Calculation of labyrinth seals with extraction
Joachimiak D., Krzyślak P.
International Journal of Applied Mechanics and Engineering
|
2011
|
Vol. 16, no 1
5-14
EN
The paper presents a method for calculation of labyrinth seals with extraction. It involves a disorder of movement by interfering with the flow and bringing some irrelevant value of the mass stream out of a specific point of the labyrinth packing and outside the seal. It is described how to detect changes in the seal geometry by introducing a diagnostic parameter. The results of calculations are determined by an algorithm based on linearizations of de Saint - Venant equations.
16
Content available remote The influence of labyrinth seals on the dynamic state of large power engineering objects
Prońska A.
Transactions of the Institute of Fluid-Flow Machinery
|
2003
|
nr 114
91-98
EN
In the research conducted has been an assesement on the influence of the labyrinth seals in the 13K215 turboset on the dynamic properties of the machine working under stable conditions, as well as when there was a reduction in the systems stability margin. The existing complex and nonlinear model of the 13K215 turboset and the application software for the model's dynamic investigation were used, coupling with two models of the seals. One - a very simplified model, the so-called bearings model, where the barriers in the form of labyrinth plates are neglected allowed the use of a code for the analysis of the static and dynamic properties of the slide bearings. The second one - much more complicated, the so-called fluid-flow model, allowed the incorporation of the disturbance of flow, caused by the labyrinth plates. Applying computer analysis, utilising a methodology appropriate to model based diagnostics, the process of the system's instability was traced accounting for the forces generated in the seals obtained from the two models, above mentiond as well as in their absence. A comparison of these processes underlies the conclusions about the influence of labyrinth seals on the dynamic state of the investigated object and the comparison of the proposed models of the labyrinth seals.
17
Content available remote On the influence of labyrinth seals on the dynamic behaviour of rotors
D'Agostino V., Guida D.
International Journal of Applied Mechanics and Engineering
|
2001
|
Vol. 6, no 4
1089-1098
EN
The influence of the labyrinth seals on the dynamic behaviour of a flexible rotor in journal bearings is investigated. In particular a code which makes possible the determination of the stiffness and damping coefficients and the calculus of the stability threshold in the absence of unbalance is discussed. The pressure field in journal bearings and in the labyrinth seal is determined using Warner's hypothesis and the bulk-flow model with two-control-volume, respectively.
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