Effects of Pressure Ratio and Rotational Speed on Leakage Flow and Cavity Pressure in the Staggered Labyrinth Seal

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Xin Yan ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Rotational Speed ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Flow Coefficient ◽  
Leakage Flow ◽  
Cavity Pressure ◽  
Cavity Structure

Effects of pressure ratio and rotational speed on the leakage flow and cavity pressure characteristics of the rotating staggered labyrinth seal were investigated by means of experimental measurements and numerical simulations. The rotating seal test rig with turbine flowmeter and pressure measuring instruments was utilized to investigate the leakage flow of the staggered labyrinth seal at eight pressure ratios and five rotational speeds. The repeatability of the experimental data was demonstrated by three times measurements at different pressure ratios and fixed rotational speed. The three-dimensional Reynolds-averaged Navier–Stokes equations and standard k-ε turbulent model were also applied to study the leakage flow characteristics of the staggered labyrinth seal at the experimental conditions. The validation of the numerical approach was verified through comparison of the experimental data. The detailed flow field in the staggered labyrinth seal was illustrated according to the numerical simulations. The experimental and numerical results show that the leakage flow coefficient increases with increasing pressure ratio at the fixed rotational speed and is more sensitive to the smaller pressure ratio. The influence of rotational speed on the leakage flow coefficient is not obvious in the present rotational speed limitations. The cavity pressure coefficient in the staggered labyrinth seal decreases and is significantly influenced by the cavity structure along the flow direction.

Numerical Investigations on the Leakage Flow Characteristics of Pocket Damper Seals

2011 ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng ◽  
Jiandao Yang ◽  
Rui Yang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Leakage Rate ◽  
Numerical Results ◽  
Flow Coefficient ◽  
Leakage Flow ◽  
Leakage Flow Rate

The effects of pressure ratios, rotational speeds and sealing clearances on the leakage flow characteristics of pocket damper seals (PDS) were numerically investigated using Reynolds-Averaged Navier-Stokes (RANS) solutions. The leakage flow rate of the experimental PDS with the eight-bladed and eight-pocket was conducted at three different pressure drops and three different rotational speeds. The numerical results were in agreement with the experimental data. Six pressure ratios, four rotational speeds and four sealing clearances were utilized to study the effects of theses factors on the leakage flow characteristics of the PDS. Numerical results show that the leakage rate of the PDS increases with decreased pressure ratio. The leakage rate decreases with the increasing rotational speed, and this phenomenon is more pronounced at higher rotational speed. At the highest rotational speed 20200rpm, the flow coefficient is up to 4.4% less than that of the non-rotating case. The leakage rate increases linearly with sealing clearance increasing. The comparison of the leakage flow rate shows that the PDS leaks slightly less than that of the labyrinth seal at the same pressure ratio, rotational speed and sealing clearance, especially at the higher rotational speed case. Furthermore, the circumferential partition wall can significantly decrease the circumferential flow in the PDS cavity. At the highest rotational speed with 20200rpm, the swirl ratio in the active and inactive cavity of the PDS is reduced by 94.5% and 46% compared to the labyrinth seal, respectively.

Investigation on the Leakage Flow, Windage Heating and Swirl Development of Rotating Labyrinth Seal in a Compressor Stator Well

2016 ◽  
Author(s):  
Xiaozhi Kong ◽  
Gaowen Liu ◽  
Yuxin Liu ◽  
Qing Feng
Keyword(s):  
Mass Flow ◽  
Rotational Speed ◽  
Heat Dissipation ◽  
Pressure Ratio ◽  
Great Influence ◽  
Labyrinth Seal ◽  
Swirl Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Rotating Disc

What make the labyrinth seal in a compressor stator well different from the normal labyrinth seal are the inlet and outlet rotor-stator disc cavities. Due to the presence of rotating disc cavities, the windage heating and the swirl development are remarkable, which can have a great influence on the leakage characteristic. Besides, when compressor operates at different speeds, the rotor and stator grow differently owing to centrifugal expansion and thermal expansion. Hence the tip clearance which determines the leakage mass flow changes with the varying of rotational speed and temperature in the stator well. A rotating test rig with rotational speed 8100rpm and pressure ratio range 1.05∼1.3 was designed for the test of labyrinth seal in a compressor stator well. A cantilevered structure was used to entirely collect the mass flow for an accurate measurement. To know the working tip clearance precisely, the set up tip clearance was measured with plug gauges, while the radial displacements of rotating disc and stationary casing were measured separately with two high precision laser distance sensors. The total temperatures of airflow in the stator well were measured with thermocouples to analyze the proportion of windage heating among the inlet rotating disc cavity, outlet rotating disc cavity, and labyrinth seal segment. The disc and stator casing were manufactured with non-metallic materials to reduce heat dissipation. Furthermore, the circumferential velocity of the leakage flow was measured using probes to reveal the swirl development. Two-dimensional, axisymmetric swirl flow numerical simulations were carried out to provide insight into the flow field details, total temperature variation and swirl flow development in the stator well. The numerical results of discharge coefficient, windage heating and swirl ratio were compared with the experimental data. Of particular note is, the tip clearance of numerical model at a specific rotating speed was set to be the same with the actual working clearance which was measured in the experiment. The inlet and outlet parameters corresponded with the experimental conditions also.

Rounded Fin Edge and Step Position Effects on Discharge Coefficient in Rotating Labyrinth Seals

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Andrea Rapisarda ◽  
Alessio Desando ◽  
Elena Campagnoli ◽  
Roberto Taurino
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Leading Edge ◽  
Experimental Tests ◽  
Velocity Profiles ◽  
Pollutant Emission ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Position Effects ◽  
Impact Reduction

The design of modern aircrafts propulsion systems is strongly influenced by the important objective of environmental impact reduction. Through a great number of researches carried out in the last decades, significant improvements have been obtained in terms of lower fuel consumption and pollutant emission. Experimental tests are a necessary step to achieve new solutions that are more efficient than the current designs, even if during the preliminary design phase, a valid alternative to expensive experimental tests is the implementation of numerical models. The processing power of modern computers allows indeed the simulation of more complex and detailed phenomena than the past years. The present work focuses on the implementation of a numerical model for rotating stepped labyrinth seals installed in low-pressure turbines. These components are widely employed in sealing turbomachinery to reduce the leakage flow between rotating components. The numerical simulations were performed by using computational fluid dynamics (CFD) methodology, focusing on the leakage performances at different rotating speeds and inlet preswirl ratios. Investigations on velocity profiles into seal cavities were also carried out. To begin with, a smooth labyrinth seal model was validated by using the experimental data found in the literature. The numerical simulations were extended to the honeycomb labyrinth seals, with the validation performed on the velocity profiles. Then, the effects of two geometrical parameters, the rounded fin tip leading edge, and the step position were numerically investigated for both smooth and honeycomb labyrinth seals. The obtained results are generally in good agreement with the experimental data. The main effect found when the fin tip leading edge was rounded was a large increase in leakage flow, while the step position contribution to the flow path behavior is nonmonotone.

Rotordynamic Characteristics of the Straight-Through Labyrinth Seal Based On the Applicability Analysis of Leakage Models Using Bulk-Flow Method

2021 ◽  
Author(s):  
Tianhao Wang ◽  
Zhigang Li ◽  
Jun Li
Keyword(s):  
Rotational Speed ◽  
Control Volume ◽  
Labyrinth Seal ◽  
Bulk Flow ◽  
Inlet Pressure ◽  
Leakage Flow ◽  
Flow Method ◽  
Leakage Model ◽  
Outlet Pressure ◽  
Prediction Approach

Abstract Labyrinth seals are widely applied in the turbomachinery to control the leakage flow through the clearance between the stationary and rotating components. The fluid excitation induced by the labyrinth seal would deteriorate the stability of turbomachinery shaft. Developing an accurate and rapid prediction approach is crucial for the analysis of the fluid excitation rotordynamics of the labyrinth seal. The objective of this study is to analyze the applicability of leakage models using Bulk-Flow method and investigate the factors affecting the rotordynamic characteristics of the labyrinth seal. An elliptical orbit for rotor whirling was assumed in the one-control-volume Bulk-Flow model considering an isentropic process to predict the frequency-dependent rotordynamic coefficients of the labyrinth seal. The optimal leakage model was determined by comprehensively analyzing the applicability of 72 leakage models. Employing the optimal leakage model in the Bulk-Flow method, the effects of sealing clearance, pressure ratio, preswirl ratio and rotational speed on the rotordynamic characteristics of the labyrinth seal were investigated. The conclusions show that the Bulk-Flow method has an average prediction error of around 10% for the leakage flow rate, cross-coupled stiffness and direct damping when equipped with the optimal leakage model. Increasing preswirl ratio has a significantly destabilizing effect on the rotor stability, while the influence of increasing rotational speed is strongly related to preswirl direction. The effective damping of the labyrinth seal is sensitive to the inlet pressure, but insensitive to the outlet pressure and sealing clearance. The crossover frequency is almost impervious to the inlet pressure, outlet pressure and sealing clearance.

scholarly journals Leakage Characteristic Identification of Labyrinth Seals on Reciprocating Piston through Transient Simulations

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Lingzi Wang ◽  
Jianmei Feng ◽  
Mingfeng Wang ◽  
Zenghui Ma ◽  
Xueyuan Peng
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Piston Compressor ◽  
Pressure Change ◽  
Labyrinth Seal ◽  
Relative Molecular Mass ◽  
Geometrical Parameters ◽  
Leakage Flow ◽  
Reciprocating Motion ◽  
Leakage Flow Rate

In the reciprocating labyrinth piston compressor, the characteristic of the internal leakage is crucial for the leakage management and performance improvement of the compressor. However, most of the published studies investigated the rotor-stator system, and those who study the reciprocating piston-cylinder system basically focus on the effects of the geometrical parameters. These conclusions could not directly be applied to predict the real-time leakage flow rate through the labyrinth seal because of the fast reciprocating motion of the piston, which will cause continually pressure change in two compression chambers, and then the pressure fluctuation will affect the flow through the labyrinth seal. A transient simulation model employing the multiscale dynamic mesh, which considers the effect of the reciprocating motion of the piston in the cylinder, is established to identify the characteristics of the internal leakage. This model was verified by a specially designed compressor, and the influence of various parameters was analyzed in detail. The sealing performance decreased linearly with the increase in the pressure ratio, and higher pressure inlet leads to higher leakage flow under the same pressure ratio. The labyrinth seal performance positively correlated to the increase of the rotational speed. Leakage characteristics of five working mediums were carried out, and the results indicated that the relative leakage decreased with an increase in the relative molecular mass. From this study, the realistic internal leakage flow rate under different operating parameters in the reciprocating labyrinth piston compressor could be predicated.

Simulation of the Interaction of Labyrinth Seal Leakage Flow and Main Flow in an Axial Turbine

2002 ◽  
Author(s):  
Jan E. Anker ◽  
Ju¨rgen F. Mayer
Keyword(s):  
Experimental Data ◽  
Labyrinth Seal ◽  
Main Flow ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Test Case ◽  
Leakage Flow ◽  
Computational Results ◽  
Axial Turbine ◽  
The Impact

This paper presents the simulation of the flow in a 1.5 stage low-speed axial turbine with shrouded rotor blades and focuses on the interaction of the labyrinth seal leakage flow with the main flow. The presented results were obtained using the Navier-Stokes code ITSM3D developed at University of Stuttgart. A comparison of the computational results with experimental data of this test case gained at Ruhr-Universita¨t Bochum verifies that the flow solver is capable of reproducing the leakage flow effects to a sufficient extent. The computational results are used to examine the influence of the leakage flow on the flow field of the turbine. By varying the clearance height of the labyrinth in the simulations, the impact of the re-entering leakage flow on the main flow is studied. As demonstrated in this paper, leakage flow not only introduces mixing losses but can also dominate the secondary flow and induce severe losses. In agreement with the experimental data the computational results show that at realistic clearance heights the leakage flow gives rise to negative incidence over a considerable part of the downstream stator which causes the flow to separate.

Numerical Comparison of Leakage Flow and Rotordynamic Characteristics for Two Types of Labyrinth Seals With Baffles

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Yuanqiao Zhang ◽  
Jun Li ◽  
Zhigang Li ◽  
Xin Yan
Keyword(s):  
Rotational Speed ◽  
Flow Resistance ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Numerical Comparison ◽  
Vibration Frequencies ◽  
Labyrinth Seals ◽  
Rotordynamic Coefficients ◽  
Brush Seal ◽  
Swirl Intensity

Abstract Cavity separation baffles can decrease the circumferential swirl intensity of labyrinth seals and increase the seals' rotordynamic characteristics. Compared with conventional baffles, the bristle packs of brush seal baffles can contact the rotor directly, thereby further reducing the swirl intensity of the seal cavity. This paper, using the numerical model combining a multifrequency elliptical whirling orbit model, a porous medium model, and transient Reynolds-averaged Navier–Stokes (RANS) solutions, compares the leakage flow and rotordynamic characteristics of a labyrinth seal with brush-seal baffles (LSBSB) and a labyrinth seal with conventional baffles (LSCB). Ideal air flows into the seal at an inlet preswirl velocity of 0 m/s (or 60 m/s or 100 m/s), total pressure of 690 kPa, and temperature of 14 °C. The outlet static pressure is 100 kPa and the rotational speed is 7500 r/min (surface speed of 66.8 m/s) or 15,000 r/min (surface speed of 133.5 m/s). Numerical results show that the LSBSB possesses the slightly less leakage flow rate than the LSCB due to the flow resistance of the bristle pack to the fluid. Compared with the LSCB, the LSBSB shows a higher positive effective stiffness (Keff) at all considered vibration frequencies and a higher effective damping (Ceff) for most vibration frequencies. What is more, the crossover frequency (fc0) of the LSBSB is significantly lower than that of the LSCB, which means that the LSBSB has a wider frequency range offering positive effective damping. The increasing inlet preswirl velocity and rotational speed only slightly affect the Keff for both seals. The Ceff of two seals decreases as the inlet preswirl velocity rises, especially for the LSCB. The Ceff of the LSCB slightly decreases because of the increasing rotational speed. In contrast, the Ceff of the LSBSB is not sensitive to the changes in rotational speed. In a word, the LSBSB possesses superior rotordynamic performance to the LSCB. Note that this work also investigates the leakage flow and rotordynamic characteristics a labyrinth seal with inclined baffles (LSIB) under the condition of u0 = 60 m/s and n = 15,000 r/min. The inclined baffles of the LSIB are same as the backing plates of LSBSB baffles. The LSIB has rotordynamic coefficients almost equal to the LSCB. Hence, the reason why the LSBSB possesses better rotordynamic performance than that of the LSCB is the flow resistance of bristle packs of brush seal baffles, not the inclination direction variation of baffles.

Evaluation of Blade Passage Analysis Using Coarse Grids

2000 ◽  
Vol 122 (2) ◽  
pp. 345-348 ◽  
Author(s):  
Steven M. Miner
Keyword(s):  
Rotational Speed ◽  
Stokes Equations ◽  
Axial Flow ◽  
Measured Data ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Mixed Flow ◽  
Specific Speed ◽  
Coarse Grids ◽  
Flow Pump

This paper presents the results of a study using coarse grids to analyze the flow in the impellers of an axial flow pump and a mixed flow pump. A commercial CFD code (FLOTRAN) is used to solve the 3-D Reynolds Averaged Navier Stokes equations in a rotating cylindrical coordinate system. The standard k−ε turbulence model is used. The meshes for this study use 22,000 nodes and 40,000 nodes for the axial flow impeller, and 26,000 nodes for the mixed flow impeller. Both models are run on a SPARCstation 20. This is in contrast to typical analyses using in excess of 100,000 nodes. The smaller mesh size has advantages in the design environment. Stage design parameters for the axial flow impeller are, rotational speed 870 rpm, flow coefficient ϕ=0.13, head coefficient ψ=0.06, and specific speed 2.97 (8101 US). For the mixed flow impeller the parameters are, rotational speed 890 rpm, flow coefficient ϕ=0.116, head coefficient ψ=0.094, and specific speed 2.01 (5475 US). Evaluation of the models is based on a comparison of circumferentially averaged results to measured data for the same impeller. Comparisons to measured data include axial and tangential velocities, static pressure, and total pressure. A comparison between the coarse and fine meshes for the axial flow impeller is included. Results of this study show that the computational results closely match the shapes and magnitudes of the measured profiles, indicating that coarse CFD models can be used to accurately predict performance. [S0098-2202(00)02202-1]

Numerical Simulations of Regular and Irregular Wave Forces on a Horizontal Semi-Submerged Cylinder

2017 ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai ◽  
Sopheak Seng
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Simulations ◽  
Stokes Equations ◽  
Wave Length ◽  
Wave Structure ◽  
Numerical Results ◽  
Irregular Waves ◽  
Wave Forces ◽  
Submerged Cylinder

Two-dimensional (2D) numerical simulations have been performed using OpenFOAM (an open source CFD software package [1]) and waves2Foam (an OpenFOAM based add-on library for wave generations and absorption [2]) to investigate free surface waves past one fixed horizontally semi-submerged cylinder. The 2-D simulations are carried out by solving Navier-Stokes equations which are discretized based on finite volume method (FVM). Volume of Fluid (VOF) method is employed to capture the free surface in the numerical wave tank. Validation studies have been performed by comparing the numerical results of Stokes first-order wave past a semi-submerged circular cylinder with the published experimental data at different incident wave properties. The numerical results are in good agreement with the experimental data. Subsequently, regular and irregular waves past semi-submerged cylinder at different wave heights and the wave lengths are computed numerically to investigate the effect of the wave height and wave length on wave-structure interaction. The numerical results for irregular waves are compared with those induced by regular waves.

Experimental and Numerical Investigations on the Leakage Flow Characteristics of Helical-Labyrinth-Brush Seals

2020 ◽  
Author(s):  
Yuanqiao Zhang ◽  
Jun Li ◽  
Dengqian Ma ◽  
Yuan He ◽  
Jingjin Ji ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Rotational Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Absolute Value ◽  
Numerical Investigations ◽  
Brush Seal ◽  
Speed Up

Abstract This paper numerically investigates the leakage flow characteristics of two types of HLBSs (bristle pack installed upstream or downstream of helical-labyrinth tooth named as HLBS-U and HLBS-D, respectively) at various pressure ratios (1-1.3) and rotational speeds (0-10000r/min). In parallel, the leakage flow characteristics of the HLBS-D with the constant cb of 1.0 mm are experimentally measured at the pressure ratio up to 1.3 and rotational speed up to 2000 r/min. The effective clearance of the HLBS-U is smaller than that of the HLBS-D in the case of cb=0.5mm and rotational speed n<10000r/min, and the case of cb=1.0mm. However, for the case of cb=0.5mm and n=10000r/min, and the case of cb=0.1mm, the situation is opposite. The brush seal sections of the HLBS-U and the HLBS-D offer over 55% and 65% total static pressure drop in the case of cb=1.0 mm, respectively; The brush seal sections of two HLBSs bear almost the same static pressure drop of the over 97% total static pressure drop as cb equals to 0.1 mm. The HLBS-U has lower turbulent kinetic energy upstream of the bristle pack than the HLBS-D does, which means that intensity of bristles flutter of the HLBS-U is lower. The HLBS-U possesses significantly lower absolute value of aerodynamic forces than the HLBS-D does as cb=1.0 mm.

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