Numerical Investigations on the Leakage Flow Characteristics of Brush Seal Based on the Three-Dimensional Staggered Tube Bundle Model

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Dengqian Ma ◽  
Yuanqiao Zhang ◽  
Zhigang Li ◽  
Jun Li ◽  
Xin Yan
Keyword(s):  
Flow Rate ◽  
Tube Bundle ◽  
Aerodynamic Resistance ◽  
Three Dimensional ◽  
Leakage Flow ◽  
Mesh Motion ◽  
Brush Seal ◽  
Leakage Flow Rate ◽  
Structured Mesh ◽  
Brush Seals

Abstract To accurately predict the leakage flow and resistance characteristics of brush seals, the multiblock structured mesh and the mesh motion technique are applied to the three-dimensional (3D) staggered tube bundle model of brush seals. The multiblock structured mesh can easily add nodes and set boundary layers in the interbristle gap between adjacent bristles, which can ensure good mesh quality (orthogonal angle and expansion ratio). The mesh motion technique realizes the overall axial compactness of the bristle pack. The effects of pressure ratio Rp, sealing clearance c, and bristle pack compactness on the leakage flow and resistance characteristics are investigated. To analyze the aerodynamic resistance of the brush seals, Euler number (Eu) is applied in this study. The numerical results are in good agreement with the experimental data. Thus, the accuracy of the presented numerical method is validated. For the contacting brush seal, ΔSx, i has a significant effect on the leakage flow rate reduction. For the clearance brush seal, ΔSx, i has little effect on the leakage flow rate reduction. The leakage flow passing through the sealing clearance keeps almost constant. As for aerodynamic resistance, the presence of the sealing clearance can effectively convert the pressure energy of the leakage flow into the kinetic energy. As a result, the leakage flow velocity exiting the bristle pack of the clearance brush seal is 1.5 to 2.0 times larger than that of the contacting brush seal. Although the existence of the sealing clearance obviously increases the leakage flow rate, it effectively reduces the aerodynamic forces acting on the bristles. The developed numerical approach based on the three-dimensional staggered tube bundle model and multiblock structured mesh can serve as a technical method for analysis of the sealing mechanisms of brush seals.

Numerical Investigations on the Leakage Flow Characteristics of Brush Seal Based on the 3D Staggered Tube Bundle Model

2020 ◽  
Author(s):  
Dengqian Ma ◽  
Yuanqiao Zhang ◽  
Zhigang Li ◽  
Jun Li ◽  
Xin Yan
Keyword(s):  
Flow Rate ◽  
Tube Bundle ◽  
Pressure Ratio ◽  
Aerodynamic Resistance ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Rate Reduction ◽  
Brush Seal ◽  
Leakage Flow Rate ◽  
Rotational Components

Abstract Brush seals are widely applied in turbomachinery to control leakage flow between the stationary and rotational components due to the high sealing performance. In consideration of the axial compression of the bristle pack posing a challenge to accurately predict the leakage flow rate at the practical operating condition, the 3D staggered tube bundle model is established based on the multi-block structured mesh. The mesh motion technique is used to obtain the leakage flow pattern and aerodynamic resistance performance of the brush seal. The effects of pressure ratio Rp, sealing clearance c and axial pitch reduction ΔSx,i on leakage flow characteristics as well as Eu of the brush seal were investigated. The numerical results were in good agreement with the experimental data. Thus the accuracy of the presented numerical method was validated. For the contacting brush seal, ΔSx,i has a significant effect on the leakage flow rate reduction. As the ΔSx,i increases from 0 mm to 0.004 mm, the leakage flow rate is reduced by 39.63% when Rp equals to 1.5. For the clearance brush seal, ΔSx,i has little effect on the leakage flow rate reduction. As the ΔSx,i increases from 0 mm to 0.004 mm, the leakage flow rate is reduced by 3.44% when Rp equals to 1.5 and c equals to 0.2 mm. As for the aerodynamic resistance, the presence of the sealing clearance could effectively convert the pressure energy of the leakage flow into kinetic energy. This causes that the leakage flow velocity exiting the bristle pack of the clearance brush seal is 1.5 to 2.0 times than that of the contacting brush seal. Although the existence of the sealing clearance obviously increases the leakage flow rate, it effectively reduces the aerodynamic forces acting on the bristles. This research would provide technical support for the analysis of the leakage flow characteristics of the brush seal.

A Three-Dimensional Tube Bundle Model Analysis for Leakage Flow Characteristics of Variable Bristle Diameter Brush Seals With Bristle Pack Stratification

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Dengqian Ma ◽  
Zhigang Li ◽  
Jun Li
Keyword(s):  
Tube Bundle ◽  
Pressure Ratio ◽  
Large Diameter ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Sealing Performance ◽  
Leakage Flow Rate ◽  
Brush Seals ◽  
Resistance Coefficients

Abstract The leakage flow characteristics of the variable bristle diameter (VBD) brush seals are numerically investigated using the three-dimensional (3D) tube bundle model with consideration of bristle pack stratification. The discretization of the computational domain applies the multiblock structured mesh, which ensures that there is no need to set interfaces between the fluid domains of the bristle pack and the cavities to eliminate interpolation errors. The bristle pack stratification is achieved by using mesh motion technique from the point of cause-effect. The effects of pressure ratio (Rp=1.5, 2.5, 3.5), axial rows of bristles (Nx=9–21), sealing clearance (c=0, 0.1 mm), bristle pack arrangements, and bristles gapping (gi=0, 0.005, 0.010, 0.015 mm) on the leakage flow characteristics and aerodynamic forces are conducted. The recorded leakage flow of the 3D tube bundle model is multiplied by circumferential loop number (Ncl) to determine total leakage flow rate of the brush seal. The numerical results agreed well with the experimental data, which verifies the reliability of the numerical method. The numerical results indicate that the leakage flow rate increases linearly with the pressure ratio. The increase of Nx has a distinctly different effect on the relative rate of leakage flow for the contacting and clearance brush seals. The use of large diameter bristles weakens the sealing performance of the brush seals, particularly in the rear region. Bristle pack stratification can improve the sealing performance of the brush seals. The large diameter bristles increase the porosity and reduce the flow resistance coefficients. On the contrary, the bristle pack stratification decreases the porosity and rises the flow resistance coefficients in the rear region. The results of this article indicate when designing VBD brush seals, the effects of bristle diameter and bristle density on the sealing performance and pressure loading capacity of the brush seals should be fully considered.

Application of blade tip shroud brush seal to improve the aerodynamic performance of turbine stage

2019 ◽  
Vol 234 (6) ◽  
pp. 777-794
Author(s):  
Dengqian Ma ◽  
Jun Li ◽  
Yuanqiao Zhang ◽  
Zhigang Li ◽  
Xin Yan ◽  
...  
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Turbine Stage ◽  
Brush Seal ◽  
Leakage Flow Rate ◽  
Blade Tip ◽  
Brush Seals ◽  
Tip Shroud

The blade tip shroud brush seal is applied to replace the labyrinth seal for the aerodynamic performance improvement of turbine stage. The leakage flow characteristics of the brush seal are numerically predicted by using the Reynolds-Averaged Navier–Stokes equations and non-linear Darcian porous medium model. The numerical leakage flow rate of the brush seal is in well agreement with the experimental data. The last and first long teeth of the labyrinth seal were designed to bristle pack named as the postposed and preposed brush seals based on the 1.5 turbine stage. The leakage flow rate and aerodynamic performance of the turbine stage with blade tip shroud labyrinth seal and brush seal are numerically investigated. The effect of the sealing clearance between bristle pack and tip shroud on the aerodynamic performance of turbine stage is conducted which ranged from 0 mm to 0.4 mm. The axial deflection of the bristle pack is analyzed with consideration of the aerodynamic forces and contact frictional force. The obtained results show that the leakage flow rate of the tip shroud brush seals with bristle tip 0.4 mm clearance which decreases by up to 18% in comparison with the labyrinth seal, and the aerodynamic efficiency increases by 0.6%. Compared to the tip labyrinth seal, tip shroud brush seals can decrease the relative deflection angle of exit flow. This flow behavior results in reducing the mixing loss between the tip leakage flow and mainstream. The similar axial deflection of the bristle pack for two kinds of brush seals is observed at the same sealing clearance. The deflection of the bristle pack under the function of the aerodynamic forces is protected by the backing plate. This work provides the theoretical basis and technical support for the brush seal application in the turbine industries.

On the Behavior of Misaligned Journal Bearings Based on Mass-Conservative Thermohydrodynamic Analysis

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
J. Y. Jang ◽  
M. M. Khonsari
Keyword(s):  
Flow Rate ◽  
Thermal Field ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Comprehensive Analysis ◽  
Leakage Flow ◽  
Performance Parameters ◽  
Film Rupture ◽  
Leakage Flow Rate

Misalignment affects nearly all the bearing performance parameters including the cavitation, thermal field, leakage flow-rate, and moments. The present paper provides a comprehensive analysis of misaligned journal bearings based on a three-dimensional mass-conservative thermohydrodynamic model that appropriately takes into account the film rupture and reformation. An extensive set of numerical solutions are presented to closely examine the effects of misalignment in journal bearings.

Numerical Investigations on Leakage Performance of the Rotating Labyrinth Honeycomb Seal

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Jun Li ◽  
Shengru Kong ◽  
Xin Yan ◽  
Shinnosuke Obi ◽  
Zhengping Feng
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Cell Diameter ◽  
Leakage Flow ◽  
Steam Turbines ◽  
Honeycomb Seal ◽  
Leakage Flow Rate ◽  
Honeycomb Cell

Three-dimensional Reynolds-averaged Navier–Stokes (RANS) solutions from CFX were utilized to investigate the leakage flow characteristics in the labyrinth honeycomb seal of steam turbines. At first, the accuracy and reliability of the utilized RANS approach was demonstrated using the published experimental data of the honeycomb seal. It showed that the utilized numerical method has sufficient precision to predict the leakage performance in seals. Then a range of sealing clearances, cell diameters, cell depths, rotation speeds, and pressure ratios were investigated to determine how these factors affect the leakage flow rate of the labyrinth honeycomb seal. The computed leakage flow rate increased with increasing sealing clearance and pressure ratios. Furthermore, the results show that the studied labyrinth honeycomb seal has the optimum sealing performance in the case of honeycomb cell diameter equals labyrinth step width, and the ratio of the honeycomb cell depth to honeycomb cell diameter is 0.93 under the designed condition. The flow pattern of each case is also illustrated to describe the leakage flow characteristics in labyrinth honeycomb seals.

scholarly journals Impact of Orifice-to-Pipe Diameter Ratio on Leakage Flow: An Experimental Study

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2189
Author(s):  
Tingchao Yu ◽  
Xiangqiu Zhang ◽  
Iran E. Lima Neto ◽  
Tuqiao Zhang ◽  
Yu Shao ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Pipe Wall ◽  
Pressure Head ◽  
Diameter Ratio ◽  
Pipe Diameter ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Different Shapes ◽  
Real Scale

The traditional orifice discharge formula used to estimate the flow rate through a leak opening at a pipe wall often produces inaccurate results. This paper reports an original experimental study in which the influence of orifice-to-pipe diameter ratio on leakage flow rate was investigated for several internal/external flow conditions and orifice holes with different shapes. The results revealed that orifice-to-pipe diameter ratio (or pipe wall curvature) indeed influenced the leakage flow, with the discharge coefficient ( C d ) presenting a wide variation (0.60–0.85). As the orifice-to-pipe diameter ratio decreased, the values of C d systematically decreased from about 12% to 3%. Overall, the values of C d also decreased with β (ratio of pressure head differential at the orifice to wall thickness), as observed in previous studies. On the other hand, orifice shape, main pipe flow velocity, and external medium (water or air) all had a secondary effect on C d . The results obtained in the present study not only demonstrated that orifice-to-pipe diameter ratio affects the outflow, but also that real scale pipes may exhibit a relevant deviation of C d from the classical range (0.61–0.67) reported in the literature.

Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect

2016 ◽  
Author(s):  
Yang Chen ◽  
Jun Li ◽  
Chaoyang Tian ◽  
Gangyun Zhong ◽  
Xiaoping Fan ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Leakage Flows ◽  
Wheel Disk

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk. The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.

scholarly journals Theoretical Analysis of Brush Seals Leakage Using Local Computational Fluid Dynamics Estimated Permeability Laws

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Lilas Deville ◽  
Mihai Arghir
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Principal Direction ◽  
Experimental Results ◽  
Leakage Flow ◽  
Cfd Analysis ◽  
Brush Seal ◽  
Brush Seals ◽  
Local Reynolds Number

Brush seals are a mature technology that has generated extensive experimental and theoretical work. Theoretical models range from simple correlations with experimental results to advanced numerical approaches coupling the bristles deformation with the flow in the brush. The present work follows this latter path. The bristles of the brush are deformed by the pressure applied by the flow, by the interference with the rotor and with the back plate. The bristles are modeled as linear beams but a nonlinear numerical algorithm deals with the interferences. The brush with its deformed bristles is then considered as an anisotropic porous medium for the leakage flow. Taking into account, the variation of the permeability with the local geometric and flow conditions represents the originality of the present work. The permeability following the principal directions of the bristles is estimated from computational fluid dynamics (CFD) calculations. A representative number of bristles are selected for each principal direction and the CFD analysis domain is delimited by periodicity and symmetry boundary conditions. The parameters of the CFD analysis are the local Reynolds number and the local porosity estimated from the distance between the bristles. The variations of the permeability are thus deduced for each principal direction and for Reynolds numbers and porosities characteristic for brush seal. The leakage flow rates predicted by the present approach are compared with experimental results from the literature. The results depict also the variations of the pressures, of the local Reynolds number, of the permeability, and of the porosity through the entire brush seal.

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