Experimental and Numerical Investigations on the Leakage Flow Characteristics of the Labyrinth Brush Seal

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Jun Li ◽  
Bo Qiu ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Leakage Rate ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Blow Down ◽  
Pressure Distributions ◽  
Brush Seal ◽  
Brush Seals

The leakage rate of the labyrinth brush seal was experimentally measured and numerically investigated in this paper. Four different rotational speeds of 0, 1500, 2400 and 3000 rpm were utilized to investigate the effects on the leakage rate of the labyrinth brush seal. In addition, five different pressure ratios and two initial clearances were also adopted to study the influences of pressure ratio and clearance size on the leakage rate of the labyrinth brush seal. The leakage rates of the experimental labyrinth brush seal at different rotational speeds, pressure ratios, and initial clearances were also predicted using Reynolds-averaged Navier-Stokes (RANS) solutions coupling with a non-Darcian porous medium model. The rotor centrifugal growth and bristle blow-down effects were considered in the present numerical research. The rotor centrifugal growth at different rotational speeds was calculated using the finite element method (FEM). The variation of the sealing clearance size with rotor centrifugal growth and bristle blow-down was analyzed. The numerical leakage rate was in good agreement with the experimental data. The effects of rotational speeds, pressure ratios, and clearance sizes on the leakage flow characteristics of brush seals were also investigated based on the experimental data and numerical results. The detailed leakage flow fields and pressure distributions of the brush seals were also presented.

Experimental and Numerical Investigations on the Leakage Flow Characteristics of the Labyrinth Brush Seal

2012 ◽  
Author(s):  
Jun Li ◽  
Bo Qiu ◽  
Shengke Jiang ◽  
Xianglin Kong ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Leakage Rate ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Blow Down ◽  
Pressure Distributions ◽  
Brush Seal ◽  
Brush Seals

The leakage rate of the labyrinth brush seal was experimentally measured and numerically investigated in this paper. Four different rotational speeds with 0, 1500, 2400 and 3000 rpm were utilized to investigate the effects on the leakage rate of the labyrinth brush seal. In addition, five different pressure ratios and two initial clearances were also adopted to study the influences of pressure ratio and clearance size on the leakage rate of the labyrinth brush seal. The leakage rate of experimental labyrinth brush seal at different rotational speeds, pressure ratios and initial clearances were also predicted using Reynolds-Averaged Navier-Stokes (RANS) solution coupling with non-Darcian porous medium model. The rotor centrifugal growth and bristle blow-down effects were considered in the present numerical research. The rotor centrifugal growth at different rotational speeds was calculated using Finite Element Method (FEM). The variation of sealing clearance size with rotor centrifugal growth and bristle blow-down was analyzed. The numerical leakage rate was in good agreement with the experimental data. The effects of rotational speeds, pressure ratios and clearance sizes on the leakage flow characteristics of brush seals were also investigated based on the experimental data and numerical results. The detailed leakage flow fields and pressure distributions of brush seals were also presented.

Experimental and Numerical Investigations on Leakage Flow Characteristics of Two Kinds of Brush Seals

2018 ◽  
Author(s):  
Yuanqiao Zhang ◽  
Jun Li ◽  
Xin Yan ◽  
Zhigang Li
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Blow Down ◽  
Brush Seal ◽  
Leakage Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Brush Seals ◽  
Deflector Plate ◽  
Hysteresis Characteristics

The leakage characteristics of interference and clearance brush seals were experimentally measured and numerically simulated in this paper. The leakage coefficients of the brush seals without a deflector plate at different pressure differentials were firstly measured. The effect of deflector plate and clearance on seal performance and the detailed flow field of the brush seal were numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions coupled with a Non-Darcian Porous Medium model. In addition, this study experimentally investigated the hysteresis characteristic of interference and clearance brush seals without deflector plates, and presented detailed investigations on the blow down effect of clearance brush seal using Computational Fluid Dynamics (CFD) as mentioned above and Finite Element Method (FEM) approaches. The obtained results show that the leakage coefficient and blow-down effect of the brush seal with a deflector plate is lower than that of the brush seal without a deflector plate at the same pressure difference and the clearance between the bristle pack and shaft will increase the leakage coefficient significantly. The different hysteresis characteristics of interference and clearance brush seals are illustrated and discussed.

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.

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.

Effects of Pressure Ratio and Sealing Clearance on Leakage Flow Characteristics in the Rotating Honeycomb Labyrinth Seal

2007 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Flow Losses ◽  
Leakage Flow Rate ◽  
Swirl Velocity

Honeycomb stepped labyrinth seals in turbomachinery enhance aerodynamic efficiency by reducing leakage flow losses through the clearance between rotating and stationary components. The influence of pressure ratio and sealing clearance on the leakage flow characteristics in the honeycomb stepped labyrinth seal is numerically determined. The geometries investigated represent designs of the honeycomb labyrinth seal typical for modern turbomachinery. The leakage flow fields in the honeycomb and smooth stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT. Numerical simulations covered a range of pressure ratio and three sizes of sealing clearance for the honeycomb and smooth stepped labyrinth seals. The numerical discharge coefficients of the non-rotating honeycomb and smooth stepped labyrinth seals are in good agreement with previous experimental data. In addition rotational effects are also taken into account in numerical computations. The numerical results show that the leakage flow rate increases with the increasing pressure ratio at the fixed sealing clearance for the rotating and non-rotating honeycomb labyrinth seal. The influence of the sealing clearance on the leakage flow pattern for the rotating and non-rotating honeycomb labyrinth seal are observed. Moreover, the similar leakage flow rates are obtained at the same flow condition between the rotating and non-rotating honeycomb labyrinth seal due to the honeycomb acts to kill swirl velocity development for the rotating honeycomb labyrinth seal.

Effects of Clearances on the Leakage Flow Characteristics of Two Kinds of Brush Seals and Referenced Labyrinth Seal

2010 ◽  
Author(s):  
Jun Li ◽  
Yangzi Huang ◽  
Zhigang Li ◽  
Zhenping Feng ◽  
Hong Yang ◽  
...  
Keyword(s):  
Porous Medium ◽  
Flow Characteristics ◽  
Numerical Approach ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Medium Model ◽  
Multi Stage ◽  
Brush Seal ◽  
Brush Seals ◽  
Porous Medium Model

Numerical investigations of leakage flow fields of two kinds of brush seals with four sealing clearances were conducted in this paper. The Reynolds-Averaged Navier-Stokes (RANS) and non-Darcian porous medium model solutions were applied as the numerical approach to analyze the flow characteristics of brush seal. The reliability and accuracy of the RANS and non-Darcian porous medium model for leakage flow in brush seals were established by comparison with the experimental data. The referenced labyrinth seal was changed into a multi-stage brush seal which has two configurations. One configuration had a traditional geometrical structure. The other had a shim structure installed between the front plate and brush bristle pack. The leakage flow rates of the brush seal with two different configurations were calculated for four bristle pack tip clearances (0mm, 0.1mm, 0.3mm, 0.5mm) which were compared with the results for the referenced labyrinth seal. The numerical results show that the leakage flow rate increases rapidly with the increasing of clearance between the bristle pack tip and the rotor surface for two kinds of brush seals. The sealing performance of the brush seal with shim structure is similar to that of the traditional design with the same sealing clearance and flow conditions. In addition, as compared with the traditional brush seal, the brush seal with shim structure can reduce the pressure difference between the bristle free and fence height at 0.3mm and 0.5mm sealing clearance. The leakage flow patterns in brush seals with two different configurations were also illustrated.

Improved Understanding of Blow-Down in Filament Seals

2008 ◽  
Author(s):  
Gervas Franceschini ◽  
Terry V. Jones ◽  
David R. H. Gillespie
Keyword(s):  
Gas Turbines ◽  
Flow Resistance ◽  
Large Scale ◽  
Scale Model ◽  
Blow Down ◽  
Pressure Distributions ◽  
Brush Seal ◽  
Large Scale Model ◽  
Rotor Surface ◽  
Brush Seals

Brush seals are used to provide flow resistance between rotating and stationary components in gas turbines. Compliant filament seals such as brush seals exhibit a phenomenon called blow-down where the filaments deflect towards the rotor surface when a differential pressure is applied across the seal. This phenomenon is desirable as it enables seal contact to be maintained during rotor contractions and eccentric excursions. This paper describes an aerodynamic mechanism which can cause the blow-down of bristles. Importantly it shows that distortion of the bristle pack is not necessary to achieve blow-down. Experimental and computational investigations of a large scale model representative of a section of a brush seal are also reported. The measured and predicted detailed pressure distributions thus obtained are used to validate the model of blow-down presented.

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.

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.

Improved Understanding of Blow-Down in Filament Seals

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Gervas Franceschini ◽  
Terry V. Jones ◽  
David R. H. Gillespie
Keyword(s):  
Gas Turbines ◽  
Flow Resistance ◽  
Large Scale ◽  
Scale Model ◽  
Blow Down ◽  
Pressure Distributions ◽  
Brush Seal ◽  
Large Scale Model ◽  
Rotor Surface ◽  
Brush Seals

Brush seals are used to provide flow resistance between rotating and stationary components in gas turbines. Compliant filament seals, such as brush seals, exhibit a phenomenon called blow-down, where the filaments deflect toward the rotor surface when a differential pressure is applied across the seal. This phenomenon is desirable as it enables seal contact to be maintained during rotor contractions and eccentric excursions. This paper describes an aerodynamic mechanism, which can cause the blow-down of bristles. Importantly it shows that distortion of the bristle pack is not necessary to achieve blow-down. Experimental and computational investigations of a large scale model representative of a section of a brush seal are also reported. The measured and predicted detailed pressure distributions thus obtained are used to validate the model of blow-down presented.

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