Rotordynamic Coefficients of Labseals for Turbines: Comparing CFD Results With Experimental Data on a Comb-Grooved Labyrinth

2005 ◽  
Author(s):  
Joachim Schettel ◽  
Martin Deckner ◽  
Klaus Kwanka ◽  
Bernd Lu¨neburg ◽  
Rainer Nordmann
Keyword(s):  
Stokes Equations ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Test Rig ◽  
Navier Stokes Equations ◽  
Detailed Model ◽  
Identification Methods ◽  
Rotating Speed ◽  
Flow Models ◽  
Rotordynamic Coefficients

The main goal of this paper is to improve identification methods for rotordynamic coefficients of labseals for turbines. This aim was achieved in joint effort of the Technische Universita¨t Mu¨nchen, working on experimental identification methods for rotordynamic coefficients, the University of Technology, Darmstadt, working on prediction methods, and Siemens AG, realizing the results. The paper focuses on a short comb-grooved labyrinth seal. Short labseals, amongst others the above mentioned comb-grooved labyrinth, were examined. by means of a very accurately measuring test rig. The rotor was brought into statically eccentric positions relative to the stator, in order to measure the circumferential pressure distribution as a function of pressure, rotating speed and entrance swirl. The data collected were used to validate results obtained with a numerical method. The theoretical approach is based on a commercial CFD tool, which solves the Navier Stokes equations using numerical methods. As a result, a detailed model of the flow within the test rig is produced. The efforts of computation here are greater than when compared with the likewise wide-spread Bulk flow models, however improved accuracy and flexibility is expected. As the validation of the model is successful, it could then be used to gain further insight in the flow within the seal, and to understand the results better. This showed that rotordynamic coefficients of labseals gained from different test rigs are not necessarily comparable.

Dynamic Coefficients of Labyrinth Gas Seals: A Comparison of Experimental Results and Numerical Calculations

2000 ◽  
Author(s):  
K. Kwanka ◽  
J. Sobotzik ◽  
R. Nordmann
Keyword(s):  
Stokes Equations ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Labyrinth Seals ◽  
Navier Stokes Equations ◽  
Rotating Speed ◽  
Dynamic Coefficients ◽  
Flow Through ◽  
Gas Seals ◽  
Good Agreement

Non-contacting labyrinth seals are still the most common constructive elements used to minimize leakage losses in turbomachinery between areas with high pressure and areas with low pressure. Unfortunately, the leakage flow through the labyrinth seal generates forces which can have a great impact on the dynamics of the turborotor. Particularly in cases of instability, the turbomachinery is restricted in its power or rotating speed because of violent self-excited vibrations of the rotor. The occurrence of self-excited rotor vibrations due to lateral forces must definitely be excluded. To consider the labyrinth forces in Finite-Element prediction, a set of preferably exact dynamic coefficients is required. Numerical approaches used to calculate the coefficients are based on Navier-Stokes equations. A comparison with experimental data is essential for a validation of the calculation. The experimental identification is difficult, because of the littleness of the forces to be measured in gas seals. Especially the non-conservative coefficients, cross-coupled stiffness and direct damping, show a good agreement in both magnitude and trend depending on the entry swirl of the seal.

scholarly journals Calculating Rotordynamic Coefficients of Seals by Finite-Difference Techniques

1987 ◽  
Vol 109 (3) ◽  
pp. 388-394 ◽  
Author(s):  
F. J. Dietzen ◽  
R. Nordmann
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Flow Field ◽  
Pressure Distribution ◽  
Difference Method ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Rotordynamic Coefficients ◽  
Finite Difference Techniques

For modelling the turbulent flow in a seal the Navier-Stokes equations in connection with a turbulence model (k-ε-model) are solved by a finite-difference method. A motion of the shaft around the centered position is assumed. After calculating the corresponding flow field and the pressure distribution, the rotordynamic coefficients of the seal can be determined. These coefficients are compared with results obtained by using the bulk flow theory of Childs [1] and with experimental results.

Calculation of Rotordynamic Coefficients and Leakage for Annular Gas Seals by Means of Finite Difference Techniques

1989 ◽  
Vol 111 (3) ◽  
pp. 545-552 ◽  
Author(s):  
R. Nordmann ◽  
F. J. Dietzen ◽  
H. P. Weiser
Keyword(s):  
Finite Difference ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Zeroth Order ◽  
Navier Stokes Equations ◽  
First Order ◽  
Fluid Forces ◽  
Rotordynamic Coefficients ◽  
Gas Seals ◽  
Finite Difference Techniques

The compressible flow in a seal can be described by the Navier-Stokes equations in connection with a turbulence model (k–ε model) and an energy equation. By introducing a perturbation analysis in these differential equations we obtain zeroth order equations for the centered position and first order equations for small motions of the shaft about the centered position. These equations are solved by a finite difference technique. The zeroth order equations describe the leakage flow. Integrating the pressure solution of the first order equations yields the fluid forces and the rotordynamic coefficients, respectively.

Numerical Solutions of the Navier-Stokes Equations for Axisymmetric Flows

1968 ◽  
Vol 10 (5) ◽  
pp. 389-401 ◽  
Author(s):  
D. R. Strawbridge ◽  
G. T. J. Hooper
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Axisymmetric Flow ◽  
Labyrinth Seal ◽  
Taylor Vortex ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Taylor Vortex Flow ◽  
Concentric Cylinders ◽  
Flow Through

A numerical method is presented for the solution of the time dependent Navier-Stokes equations for the axisymmetric flow of an incompressible viscous fluid. The method is applied to the problems of Taylor-vortex flow about an enclosed rotating cylinder and between infinite concentric cylinders, and to the analysis of the flow through a labyrinth seal. The torque calculations, which show favourable agreement with experiment, and the resulting flow patterns are presented graphically.

Rotordynamic Coefficients of Circumferentially-Grooved Liquid Seals Using the Averaged Navier-Stokes Equations

1997 ◽  
Vol 119 (3) ◽  
pp. 556-567 ◽  
Author(s):  
Mihai Arghir ◽  
Jean Freˆne
Keyword(s):  
Coordinate Transformation ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
First Order ◽  
Rotordynamic Coefficients ◽  
High Reynolds ◽  
Good Agreement

The paper presents a method to calculate the rotordynamic coefficients of circumferentially-grooved liquid seals operating in centered position and turbulent flow regimes. The method is based on the integration of the averaged Navier-Stokes equations and uses a coordinate transformation proposed by Dietzen and Nordmann (1987). The effect of the coordinate transformation on the components of the stress tensor is included in the first order transport equations. To ensure grid independent solutions, numerical boundary conditions for the first-order velocities were formulated using the logarithmic law. The perturbation of the turbulent viscosity was also considered. A pressure recovery effect at the exit section was included in the first order mathematical model. The method is validated by calculations for straight and circumferentially-grooved seals. Comparisons with experimental and theoretical results show a good agreement for straight seals and for seals with few grooves, and a reasonable agreement for severe industrial cases (high Reynolds numbers and large number of grooves).

scholarly journals On baer-nunziato multiphase flow models

2019 ◽  
Vol 66 ◽  
pp. 61-83
Author(s):  
M. Hillairet
Keyword(s):  
Multiphase Flow ◽  
Stokes Equations ◽  
Analytical Tool ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Models ◽  
Flow Systems

In these notes, we present an analytical tool for the derivation of Baer-Nunziato multiphase flow systems with one velocity. We explain the method in the case of the isentropic Navier Stokes equations. We then apply this method to models with temperature and show the main computations which are necessary to the derivation.

Theory Versus Experiment for the Effects of Pressure Ratio on the Performance of an Orifice-Compensated Hybrid Bearing

1995 ◽  
Author(s):  
Phillip Mosher ◽  
Dara W. Childs
Keyword(s):  
Stokes Equations ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Pressure Ratio ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Rotordynamic Coefficients ◽  
Wide Range ◽  
Bearing Load ◽  
Hybrid Bearing

Abstract This research investigates the effect of varying the concentric recess pressure ratio of hybrid (combination hydrostatic and hydrodynamic) bearings to be used in highspeed, high-pressure applications. Bearing flowrate, load capacity, torque, rotordynamic coefficients, and whirl frequency ratio are examined to determine the concentric, recess-pressure ratio which yields optimum bearing load capacity and dynamic stiffness. An analytical model, using two-dimensional bulk-flow Navier-Stokes equations and anchored by experimental test results, is used to examine bearing performance over a wide range of concentric recess pressure ratios. Typically, a concentric recess pressure ratio of 0.50 is used to obtain maximum bearing load capacity. This analysis reveals that theoretical optimum bearing performance occurs for a pressure ratio near 0.40, while experimental results indicate the optimum value to be somewhat higher than 0.45. This research demonstrates the ability to analytically investigate hybrid bearings and shows the need for more hybrid-bearing experimental data.

Effects of Number of Porous Insert, Spindle Speed and Gap Thickness on Characteristics of a Partially Porous Aerostatic Journal Bearing

2015 ◽  
Vol 649 ◽  
pp. 30-37 ◽  
Author(s):  
Te Yen Huang ◽  
Shao Yu Hsu ◽  
Song Chiang Shen ◽  
Sheam Chyun Lin ◽  
Ta Hsin Chou
Keyword(s):  
Carrying Capacity ◽  
Journal Bearing ◽  
Stokes Equations ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Load Carrying Capacity ◽  
Navier Stokes Equations ◽  
Rotating Speed ◽  
Load Carrying

The effects of the rotating speed of the spindle, the number of the porous medium inserted into the partially porous aerostatic journal bearing and the thickness of the bearing gap on the characteristics of the bearing such as the pressure distribution, the load carrying capacity and the stiffness of the bearing were studied. Based on the finite volume method and the pressure-velocity coupling scheme of the SIMPLE algorithm with the standard k-ε turbulent model, the CFD software was used to solve the Navier-Stokes equations to calculate the pressure field in the bearing gap. The computed results revealed the faster the spindle rotated, the higher the gap pressure. As the gap thickness increased, the gap pressure, the load carrying capacity and the stiffness of the bearing decreased. The more the porous inserts, the higher the gap pressure and the load carrying capacity, but the less the bearing stiffness would be.

Investigation of the Flow in Centrifugal Compressor Volute

2008 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Static Pressure ◽  
Stokes Equations ◽  
Single Stage ◽  
Navier Stokes ◽  
Performance Tests ◽  
Test Rig ◽  
Peak Efficiency ◽  
Navier Stokes Equations ◽  
Flow Simulations ◽  
Compressor Efficiency

Volute is used to collect and transport swirling gas produced by impeller or diffuser. Design of the volute not only impacts compressor efficiency but also influences the operating ranges of the compressor. In this study, Navier-Stokes equations combined with an algebra turbulence model were used to simulate flows inside a single stage compressor. Detailed flow simulations for a large cut back tongue volute are presented and discussed. A rounded tongue volute was tested in a single stage test rig. The compressor stage performance tests were conducted in the test lab and static pressure taps were used to measure static pressures at volute internal walls at locations of θ = 240° and 360°. Thermal couples and other static pressure probes were instrumented at inlet and outlet of the compressor for performance tests. The numerical results were compared with experiments and good agreements are found. Studies showed that a large cut back rounded tongue volute provided good operating range without dramatically dropping compressor peak efficiency.

Influence of the Spacing of the Partially Porous Aerostatic Journal Bearings and the Rotating Speed on Performance of the Spindle

2017 ◽  
Vol 739 ◽  
pp. 7-11
Author(s):  
Te Yen Huang ◽  
Shi Jie Weng ◽  
Yu Kun Lin ◽  
Yu Chieh Kuo
Keyword(s):  
Stokes Equations ◽  
Simple Algorithm ◽  
Journal Bearings ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Navier Stokes Equations ◽  
Rotating Speed ◽  
Load Carrying ◽  
Net Pressure ◽  
Volume Method

The influence of the spacing of the partially porous aerostatic journal bearings and the rotating speed of the spindle on the pressure distribution in the bearing gap and the housing gap were studied. Based on the finite volume method and the pressure-velocity coupling scheme of the SIMPLE algorithm with the standard k-ε turbulent model, A CFD software was used to solve the Navier-Stokes equations to figure out the pressure in the bearing gap and the housing gap. The computed results indicated that when the spacing of the bearings between air outlets was increased, the pressure got higher not only in the bearing gap, but also in the housing gap. The load carrying capacity of the bearings and the stiffness of the spindle could be improved. If the spacing of bearings was reduced by adding one more bearing to the location between the original bearings, the pressure in the narrower housing gap would decrease, while that in the wider housing gap would increase. Though the extra bearing could not help increase the net pressure exerted on the spindle effectively, it did help redistribute the housing gap pressure so that the pressure difference in the air gap could be reduced and the spindle was able to rotate stably.

Sign in / Sign up

Export Citation Format

Share Document