Leakage Flow and Heat Transfer Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
High Efficiency ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Sharp Drop ◽  
Leakage Flow Rate

Abstract In this paper a high efficiency labyrinth seal and the staggered labyrinth seal for shrouded blades was presented. The flows in the seal with single, double, and triple tip seals were simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the presently proposed staggered labyrinth seal is more efficient than the typical one and the leakage flow rate is dominated by the minimum flow area and the pressure difference. Comparing the performance with the typical labyrinth seal, the present staggered labyrinth seal model can average the total pressure drop among the seals, while the typical one induces a sharp drop across the first tooth. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, decreasing the wall temperature will result in an increase of leakage flow.

Leakage Flow Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Navier Stokes Equations ◽  
Leakage Flow Rate

In this paper the flows over shrouded turbine blades with single, double, and triple tip seals were simulated by using the two-dimensional Reynolds-averaged Navier-Stokes equations and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the flow in the seal channel is very complicated and the leakage flow rate is dominated by the minimum flow area and the pressure difference. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, it appears there is not a simple function between the leakage flow and the pressure difference.

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.

Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals—Part II: Effects of Partition Wall Type, Partition Wall Number, and Cavity Depth

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Cavity Depth ◽  
Partition Wall ◽  
Leakage Flow Rate ◽  
Direct Stiffness ◽  
Cfd Method ◽  
Positive Direct ◽  
Orbit Model

Effects of partition wall type, partition wall number and cavity depth on the leakage and rotordynamic characteristics of the pocket damper seal (PDS) were numerically investigated using a presented 3D transient computational fluid dynamics (CFD) method based on the multifrequency elliptical whirling orbit model. The accuracy and availability of this transient CFD method and the multifrequency elliptical whirling orbit model were demonstrated with the experimental data of the experimental eight-bladed fully partitioned pocket damper seal (FPDS). The leakage flow rates and frequency-dependent rotordynamic coefficients of PDS were computed for two types of partition wall (namely conventional PDS and fully partitioned PDS), four partition wall numbers including the labyrinth seal (no partition wall) and six cavity depths including the plain smooth seal (zero cavity depth) at operational conditions with or without inlet preswirl and 15,000 rpm rotational speed. The numerical results show that the FPDS has the similar leakage performance and more superior stability capacity than the conventional PDS. The FPDS possesses slightly larger leakage flow rate (∼2.6–4.0% larger) compared to the labyrinth seal. Eight is a preferable value for the partition wall number to gain the best leakage performance of the FPDS with the least manufacturing cost. The FPDS possesses significantly larger stiffness and damping than the labyrinth seal. Increasing partition wall number results in a significant increase in the direct stiffness but limited desirable effect on the effective damping. The FPDS possesses the lowest leakage flow rate when the cavity depth is about 2.0 mm. Compared to the plain smooth seal, the FPDS possesses larger positive direct stiffness and significantly less direct damping and effective damping. Increasing cavity depth results in a significant decrease in the stabilizing direct damping and the magnitude of the destabilizing cross-coupling stiffness. H= 3.175 mm is a preferable value of the cavity depth for which the effective damping of the FPDS is largest, especially for the concerned frequencies (80–120 Hz) where most multistage high-pressure centrifugal compressors have stability problem.

Study of Losses in a Leakage Flow Through the Passage of Shrouded Turbine Blades With Swirl Velocity

2001 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Major Effect ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Local Pressure ◽  
Leakage Flow Rate ◽  
Calculation Results

In this paper the study of the flows over shrouded turbine blades with staggered-seals is presented by computing the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations along with a compressible non-linear k-ε turbulence model. The swirl of the blade is coupled into the calculation. A multi-zone technique is used to generate the grids in the complex flow channel. The calculation results show that the leakage flow rate in the seal-channel is dominated by the pressure difference. It was also observed that the circumferential momentum transfer in the channel is very slow in the region in front of the seal tooth. The major effect of the rotating blade is the increase of local pressure distribution along the shrouded tip clearance path. However, the swirl motion of the blade tip does not significantly change the flow pattern in the axial-radial plane.

Development of a New Loss Model for Turbomachinery Labyrinth Seals

2021 ◽  
Author(s):  
Davendu Y. Kulkarni ◽  
Luca di Mare
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Stream Tube ◽  
Flow Area ◽  
Loss Model ◽  
Seal Design ◽  
Wide Range ◽  
Numerical Experimentation

Abstract The preliminary design of labyrinth seals requires a fast and accurate estimate of the leakage flow. While the conventional bulk flow models can quickly predict labyrinth seal discharge characteristics, they lack the accuracy and pragmatism of modern CFD technique and vice-a-versa. This paper presents a new 1D loss model for straight-through gas labyrinth seals that can provide quick seal leakage flow predictions with CFD-equivalent accuracy. The present seal loss model is developed using numerical experimentation technique. Multiple CFD computations are conducted on straight-through labyrinth seal geometries for a range of pressure ratios. A distinct post-processing methodology is developed to extract the through-flow stream tube in seal. Total pressure losses and flow area variations experienced by the flow in seal stream-tube are systematically accounted for based on the well-known knife-to-knife (K2K) methodology. Regression analyses are conducted on the trends of variations of loss and area coefficients to derive the independent pressure loss and flow area correlations. These novel correlations can predict the bulk leakage flow rate, windage flow rate and inter-knife static pressures over a wide range of variation of flow and geometry parameters. Validation study shows that the leakage mass flow rate predicted by this model is accurate within ±8% of measured test data. This fast and accurate model can be employed for various applications such as, in seal design-analysis workflows, for secondary air system (SAS) performance analysis and for the rotor-dynamic and aeroelastic assessments of seals.

scholarly journals Optimizing the Geometric Parameters of a Straight-Through Labyrinth Seal to Minimize the Leakage Flow Rate and the Discharge Coefficient

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 705
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Flow Rate ◽  
Axial Length ◽  
Discharge Coefficient ◽  
Labyrinth Seal ◽  
Geometric Parameters ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Tooth Width ◽  
Cavity Width

A straight-through labyrinth seal is one of the most popular non-contacting annular seals through which energy dissipation by turbulence viscosity interaction is achieved with a series of teeth and cavities. The geometric parameters of the straight-through labyrinth seal, such as clearance, tooth width, tooth height, cavity width, and tooth inclination angle, affect its performance. The space for installing a labyrinth seal in turbomachinery is limited, and so it is important to optimize its geometry for a fixed axial length in order to minimize the leakage flow rate and the discharge coefficient. The objective of the current study is to understand the effects of changing the geometric parameters of the seal on the leakage flow rate and the discharge coefficient, and to determine the optimized geometry for a fixed axial length. When the whole axial length is fixed, the most effective way to decrease the discharge coefficient is to reduce the cavity width by increasing the number of cavities. However, if the number of cavities is too high, the beneficial effect of more cavities can be reversed. The results of this study will help turbomachinery manufacturers to design a more efficient labyrinth seal. Numerical simulations of leakage flow for the straight-through labyrinth seal were carried out using Reynolds-Averaged Navier–Stokes (RANS) models, and the results for their discharge coefficients and pressure distributions were compared to previously published experimental data.

Performance Analysis of a Rotating Labyrinth Seal With Radial Growth

2013 ◽  
Author(s):  
Sivakumar Subramanian ◽  
A. S. Sekhar ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Flow Rate ◽  
Radial Growth ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Wide Range ◽  
Structural Deformations ◽  
Angular Velocities ◽  
Computational Methodology ◽  
Initial Clearance

A computational methodology is proposed to predict the running clearance of a six-tooth straight-through rotating labyrinth seal numerically by taking into account both the centrifugal and thermal growths. Four different angular velocities ranging from 0 to 3000 rad/s are chosen to study the influence of rotation on the leakage flow rate. The detailed leakage flow fields and the structural deformations are presented. Further, different pressure ratios in the range of 1.1 to 2.5 have been investigated for a wide range of initial clearances. The methodology is validated against the available data in the literature. It is found out that there is a significant reduction in leakage flow rate by incorporating the radial growth for a particular operating condition. However, for a given initial clearance, the rotation has negligible effect on the reduction in the leakage flow rate, except at pressure ratios lower than 1.7. Further; the rotation has more prominent effect for smaller clearance values.

scholarly journals A Study on the Leakage Characteristics of a Stepped Labyrinth Seal with a Ribbed Casing

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3719
Author(s):  
Min-Seok Hur ◽  
Seong-Won Moon ◽  
Tong-Seop Kim
Keyword(s):  
Turbine Blades ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Flow Function ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
New Type ◽  
Computational Fluid Dynamics Cfd ◽  
Leakage Characteristics ◽  
Wide Operating

A new type of stepped seal with a ribbed casing is proposed to efficiently reduce the leakage at the tips of turbine blades. The leakage characteristics of two different types of labyrinth seals (conventional seal vs. ribbed seal) were compared and analyzed through computational fluid dynamics (CFD) in a wide operating range of pressure ratios and clearances. The analysis showed that the ribbed seal has superior leakage performance to the conventional seal at all clearance sizes. With the same clearance size (S/H = 1.0), the flow function of the ribbed seal was approximately 21.5–42.6% less than that of the conventional seal. Also, different trends of variation in the flow function according to the increase of the clearance were found between the conventional and ribbed seals. The leakage flow inside the labyrinth seal was analyzed to explain the cause of this difference in tendency, and it was confirmed that the added ribs cause collision between the leakage flow and the tooth wall, even with the increase of the clearance. Also, the ribbed seal enables operation at a larger clearance with the same leakage performance when comparing the absolute leakage flow rate of the two seals. In addition, a parametric study on the influence of the rib height and rib inclination angle revealed that the flow function generally decreases as both parameters increase.

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.

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