Investigations on the Discharge and Total Temperature Increase Characteristics of the Labyrinth Seals With Honeycomb and Smooth Lands

2008 ◽  
Author(s):  
Xin Yan ◽  
Jun Li ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Temperature Increase ◽  
Numerical Approach ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
Total Temperature ◽  
Direct Loss ◽  
Sufficient Precision

The viscous work generated by the rotating components of the seal not only represents the direct loss of power, but also causes the increase in total temperature of fluid (windage effect). In order to study the discharge and total temperature increase characteristics of the stepped labyrinth seals with smooth and honeycomb lands, 3D RANS solutions from CFX is used in this work. At first, the influences of the inlet preswirl, leakage flow rate and rotational speed on the total temperature increase in the convergent and divergent stepped labyrinth seals with smooth and honeycomb lands are conducted. The obtained 3D numerical results are well in agreement with the referenced experimental data. It shows that the utilized numerical approach has sufficient precision to predict the total temperature increase in seals. Then, a range of pressure ratios and four sizes of sealing clearance are performed to investigate the effects of sealing clearances and pressure ratios impact on the discharge and total temperature increase of the stepped labyrinth seals with honeycomb and smooth liners.

Investigations on the Discharge and Total Temperature Increase Characteristics of the Labyrinth Seals With Honeycomb and Smooth Lands

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Xin Yan ◽  
Jun Li ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Temperature Increase ◽  
Pressure Ratio ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
Total Temperature ◽  
Direct Loss ◽  
Sufficient Precision

The viscous work generated by the rotating components of a seal not only represents a direct loss of power but also causes an increase in the total temperature of fluid (windage effect). In order to study the discharge and total temperature increase characteristics of the stepped labyrinth seals with smooth and honeycomb lands, 3D Reynolds-averaged Navier–Stokes solutions from CFX is used in this work. At first, the influences of the inlet preswirl, leakage flow rate, and rotational speed on the total temperature increase in the convergent and divergent stepped labyrinth seals with smooth and honeycomb lands are conducted. The obtained 3D numerical results are well in agreement with the referenced experimental data. It shows that the utilized numerical approach has sufficient precision to predict the total temperature increase in seals. Then, a range of pressure ratios and four sizes of sealing clearance are performed to investigate the effects of sealing clearances and pressure ratio impact on the discharge and total temperature increase of the stepped labyrinth seals with honeycomb and smooth liners.

Effects of Pressure Ratio and Fin Pitch on Leakage Flow Characteristics in High Rotating Labyrinth Seals

2006 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Zhenping Feng
Keyword(s):  
Flow Rate ◽  
Geometrical Structure ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Rotational Axis ◽  
Labyrinth Seals ◽  
Sealing Performance ◽  
Leakage Flow Rate

Labyrinth seals represent an important flow element in the sealing equipment of modern turbomachinery industries. The straight-through and stepped labyrinth seal are widely used in modern steam turbine due to their comparable simple structure and low manufactured costs. The influence of pressure ratio and fin pitch on the leakage flow characteristics of the straight-through and stepped labyrinth seals is numerically determined. The pressure ratio is defined as the outlet static pressure divided by the inlet total pressure. The fin pitch varied in the fixed axial distance of the labyrinth seal. The geometries investigated represent designs of the straight-through and stepped labyrinth seal typical for modern steam turbines. The leakage flow fields in the high rotating straight-through and stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT with the fixed seal clearance and fins geometrical structure. The effect of the rotational axis is also taken into account in numerical computations. Numerical simulations covered a range of pressure ratio and fin pitch for the straight-through and stepped labyrinth seals. Dimensionless discharge coefficients, describing the sealing performance, are calculated from the simulation results. The numerical results show that pressure ratio and fin pitch both affects the sealing performance with the fixed seal clearance and fin geometrical structure. The leakage flow rate decreases with the decreasing fin pitch for both the straight-through and stepped labyrinth seal at the fixed pressure ratio. Furthermore, the leakage flow rate decreases with the increasing pressure ratio at the fixed fin pitch for two kinds of labyrinth seals in the present study. This research provides technical support for improved design of labyrinth seals in turbomachinery.

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.

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.

scholarly journals Effect of hydraulic and geometric factors upon leakage flow rate in pressurized pipes

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Mayara Francisca da Silva ◽  
Fábio Veríssimo Gonçalves ◽  
Johannes Gérson Janzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Leakage Flow ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Leakage Flow Rate ◽  
Geometric Factors ◽  
Leakage Area ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a leakage in a pressurized pipe were undertaken to determine the empirical effects of hydraulic and geometric factors on the leakage flow rate. The results showed that pressure, leakage area and leakage form, influenced the leakage flow rate significantly, while pipe thickness and mean velocity did not influence the leakage flow rate. With relation to the interactions, the effect of pressure upon leakage flow rate depends on leakage area, being stronger for great leakage areas; the effects of leakage area and pressure on leakage flow rate is more pronounced for longitudinal leakages than for circular leakages. Finally, our results suggest that the equations that predict leakage flow rate in pressurized pipes may need a revision.

Theoretical leakage equations towards liquid-phase flow in the straight-through labyrinth seal

2021 ◽  
pp. 1-44
Author(s):  
Lingsheng Han ◽  
Yongqing Wang ◽  
Kuo Liu ◽  
Ziyou Ban ◽  
Bo Qin ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Numerical Approach ◽  
Labyrinth Seal ◽  
Resistance Coefficient ◽  
Cryogenic Cooling ◽  
Geometrical Parameters ◽  
Phase Flow ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
Empirical Coefficients

Abstract Labyrinth seals are widely applied in turbomachinery for gas and liquid sealing. A series of labyrinth seal leakage equations so far have been proposed for compressible gas, but few equations for incompressible liquid. Based on the flow conserving governing equations, this paper originally presents semi-empirical analytic equations of the leakage flow rate and tooth-clearance pressure for liquid-phase flow in the straight-through labyrinth seal. The equations indicate that the leakage and pressure are closely related to the inlet pressure, outlet pressure, seal geometrical parameters and four empirical coefficients, whilst no relation to the temperature and compressibility effects compared to the common gas equations. The empirical coefficients include the velocity compensation coefficient, friction coefficient, jet contraction coefficient and resistance coefficient. Particularly, the velocity compensation coefficient is determined through an optimization by the genetic algorithm, while others are referred from previous research. Ultimately, taking the sealing of deeply subcooled liquid nitrogen within the spindle of the cryogenic cooling machine tool as a case, the accuracy of proposed equations is evaluated under various pressure ratios and geometry conditions using the numerical approach, whose numerical model has been validated by the experimental data in the literature. The results show that errors between calculation and simulation are generally within the limit of ±5%, except for the pressure values at the first two teeth. This work provides a theoretical basis for further studies on the liquid leakage equations in other labyrinth seal types.

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.

Analysis on the Side Leakage Amount of the Friction between Piston and Cylinder Block in Axial Piston Pump

2014 ◽  
Vol 635-637 ◽  
pp. 341-345 ◽  
Author(s):  
Wei Wang
Keyword(s):  
Flow Rate ◽  
Piston Pump ◽  
Cylinder Block ◽  
Correction Coefficient ◽  
Leakage Flow ◽  
Fluid Viscosity ◽  
Axial Piston Pump ◽  
Viscosity Change ◽  
Leakage Flow Rate ◽  
Axial Piston

The spherical distribution pairs of the plunger and the cylinder friction, has an important influence on the performance of spherical port plate axial piston pump. Based on the analysis of fluid viscosity change with pressure and temperature, considering friction differential pressure flow and shear flow, establishes the mathematics model of the friction pair of leakage. The simulation analysis using MATLAB software, the leakage flow rate is not proportional to pressure, but with the increase of pressure leakage flow was increased, and with the increase of pressure viscosity coefficient and temperature coefficient of viscosity, the leakage flow rate correction coefficient increases obviously, so in the choice of the hydraulic oil cylinder hole, should choose a relatively moving average leakage rate had no effect the piston ring slot.

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