Effect of Air-Curtains on Labyrinth Seal Performance

2016 ◽  
Author(s):  
Aakash C. Rai ◽  
Deoras Prabhudharwadkar ◽  
Sunil Murthy ◽  
Andrew Giametta ◽  
David Johns
Keyword(s):  
Gas Turbines ◽  
Cross Flow ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Air Curtain ◽  
Baseline Design ◽  
Leakage Flows ◽  
Seal Design ◽  
Parametric Studies ◽  
Secondary Air

Labyrinth seals are used in many key sealing locations in gas turbines to control various leakage flows, e.g., to control the secondary air-flow from the compressor (bypassing the combustor), the turbine inter-stage leakages and blade tip leakages. This study was performed to assess the improvement in the performance of a labyrinth seal by using an air-curtain (cross-flow jet(s)) from the stator. Detailed parametric studies were performed to study the effect of the air-curtain jet pressure, location, and the number of jets on the seal performance with respect to the leakage flow. The analysis was done using 2-dimensional axisymmetric CFD simulations. It was found that in the case of a labyrinth seal with a flat stator (without a honeycomb attached to the stator) the air-curtain design can reduce the seal leakage by about 30% over the baseline seal design without air-curtains. This reduction happened because the air-curtain jet deflected the main seal jet away from the seal clearance. A similar conclusion was also obtained in case of a labyrinth seal with a honeycombed stator. Furthermore, our parametric studies with different air-curtain designs parameters implemented over a honeycombed labyrinth seal showed that the air-curtain jet pressure, location, and the number of jets were crucial factors governing the seal leakage. Amongst the air-curtain designs studied, it was found that implementing three air-curtains in the 1st pocket gave the maximum leakage reduction (by about 50%) over the baseline design.

Experimental and Numerical Investigation on Leakage Characteristic of Stepped Labyrinth Seal

2016 ◽  
Author(s):  
Li Zhang ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Fei Tong
Keyword(s):  
Gas Turbines ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Scaling Effects ◽  
Labyrinth Seals ◽  
Maximal Deviation ◽  
Tooth Number ◽  
Leakage Coefficient ◽  
Secondary Air ◽  
Aero Engines

Labyrinth seals represent an important flow element in the secondary air system of aero engines. The influence of seal clearance and teeth parameters on the leakage characteristic of a real size stepped labyrinth seal was experimentally and numerically analyzed in a stationary state. Two kinds of labyrinth seals were studied in this investigation that are generally used in gas turbines, namely downward stepped labyrinth and upward stepped labyrinth. The differences of seal flow leakage mechanisms between the two types of the labyrinth were investigated. In order to eliminate the scaling effects on leakage losses in labyrinth seals, the experimental labyrinth seal model took the size of the real one in an aero engine. The experiments covered a range of pressure ratio from 1.1 to 3.5. The experimental and numerical results show that in the range of the studied parameters the main teeth parameters affecting leakage coefficient are seal clearance, tooth tip thickness, tooth number and tooth front inclination. The influence of tooth height, pith and rear inclination angle on leakage coefficient of downward stepped labyrinth seal can almost be neglected in this research. And when the step height is more than twice the width of seal clearance, its effect on seal performance can be ignored. An empirical formula express of leakage coefficient with pressure ratio, seal clearance and teeth parameters of downward stepped labyrinth seal was organized which fits the experimental data with a maximal deviation of 8%. With similar pressure ratios and seal clearances, the downward stepped labyrinth seal displays lower leakage rates and provides the best sealing efficiency.

Labyrinth-Seal Leakage Analysis

1959 ◽  
Vol 81 (3) ◽  
pp. 332-336 ◽  
Author(s):  
W. Zabriskie ◽  
B. Sternlicht
Keyword(s):  
Fluid Flow ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Steam Turbines ◽  
Labyrinth Seals ◽  
Gas Leakage ◽  
Leakage Flows ◽  
Seal Design ◽  
Flow Through ◽  
The Subject

The leakage flow through labyrinth seals in turbomachinery has been the subject of increasing concern as refinements and advances in design are made. Accurate knowledge of seal leakage is necessary in at least three areas of design: (a) Estimating the effect of seal leakage on performance; (b) regulating the leakage flow required for cooling purposes; (c) determining the thrust-bearing load which is a function of the pressure drop through the seal. This paper is concerned primarily with the fluid-flow aspect of gas leakage through labyrinth seals of the types commonly used in gas and steam turbines. This includes staggered and unstaggered seals of the axial type, which are most commonly used in turbomachinery. The attention to fluid-flow considerations does not imply that material compatibility and operating problems of expansion, deformation, and rub-in are unimportant. In fact, these mechanical considerations may overrule the fluid-flow considerations. For the foregoing reasons, it is desirable to be able to predict seal leakage flows, and thus this aspect of seal design has been singled out for consideration here.

Coupled Simulation of the Secondary Air Flow, Heat Transfer, and Structural Deflection of a Gas Turbine Engine

2012 ◽  
Author(s):  
Guilherme Tondello ◽  
Wolodymir Boruszewski ◽  
Fernando Mengele ◽  
Marcelo Assato ◽  
Silvio Shimizu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Model ◽  
Air Flow ◽  
Labyrinth Seal ◽  
Simulation Software ◽  
Thermal Loads ◽  
Labyrinth Seals ◽  
Secondary Air

In secondary air flow in gas turbines, labyrinth seals are used to control the flow to and from each cavity and to the rotor blades for cooling purposes. Those components and the final flow rate are very sensitive to gap clearance and displacement due to structural and thermal loads during operation, therefore designing those seals and knowing the resultant flow rates in each part of the circuit during the design phase is not an easy task, and tuning those gap values may bring significant increase in turbine efficiency. This paper describes the application of coupled commercial codes for secondary air flow and structural simulation for better evaluating temperature profiles and labyrinth seal behavior during operation. Flowmaster V7 was used for building a one dimensional model of the complete secondary air flow path including swirl effects and heat transfer phenomena, and ANSYS was used for building a structural model, taking into account both rotational and thermal loads. The labyrinth seals clearances, and thermal interactions between solid and fluid were coupled bi-directionally between the two simulation software. This simulation focused in the system, including the effects of each region, passage, seal and cavity in the calculations. The turbine model simulated was a VSE’s gas turbine under development, having a nominal rotation of 22600 rpm. This paper presents the numerical characteristics of each model, the details about the 1D fluid and 3D structural coupling, and the results obtained.

Parametric Studies on Gas Turbine Labyrinth Seal for the Secondary Air Flow Optimization at Static and Rotating Conditions

2019 ◽  
Author(s):  
Karthick Raja Kaliraj ◽  
Giridhara Babu Yepuri ◽  
Jayakumar Janardanan Sarasamma ◽  
Kishor Kumar ◽  
Felix Jesuraj
Keyword(s):  
Experimental Data ◽  
Numerical Data ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Stationary Condition ◽  
Cfd Analysis ◽  
Labyrinth Seals ◽  
Sst Turbulence Model ◽  
Parametric Studies ◽  
Secondary Air

Abstract Various studies have been carried out related to the labyrinth seals and reported in the open literature using the different seal arrangements at the stator-rotor seal cavity region. In the present study, numerical analysis has been carried out for the static and rotational effects of labyrinth seals at various flow and geometrical, parametric conditions for the optimized leak flow using straight and steeped seal configurations. And, an experimental data has been generated for the straight through seals, and the numerical data of the same case is validated with the experimental data. The k-omega SST turbulence model is considered with 5% turbulence intensity for the CFD analysis. At a particular seal clearance, as the number of teeth increases the leakage flow is found to be decreased. The leak flow is found to be lower with the stepped labyrinth seals in comparison to the straight through seals. The leak flow amount is found to be lower at a rotational condition in comparison to the stationary condition. From the overall results, it is observed that the stepped seal with a lower clearance at a compressor bleed air temperature and rotational conditions have shown better performance with the lower leak air mass flow.

scholarly journals Investigation of Flow through a Labyrinth Seal

2021 ◽  
Vol 13 (2) ◽  
pp. 51-58
Author(s):  
Marius ENACHE ◽  
Razvan CARLANESCU ◽  
Andreea MANGRA ◽  
Florin FLOREAN ◽  
Radu KUNCSER
Keyword(s):  
Gas Turbines ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Cfd Modeling ◽  
Gas Temperature ◽  
Continuous Increase ◽  
Seal Design ◽  
Air Temperatures ◽  
Flow Through ◽  
Gas Leaks

Growing performance requirements for gas turbines have led to a continuous increase in gas temperature and pressure ratios. Together with the resulting increase in cooling flows, this requires more and more minimization and control of internal gas leaks. To meet future performance goals, the application of a new seal design and an improved understanding of leakage flow characteristics are of particular importance. The air mass flow through a labyrinth seal designed for a low-pressure turbine has been determined both through analytical calculus and CFD modeling. Different radial clearances and different air temperatures have been considered. In the next stage, the results will be validated through experiments.

Influence of Rub-Grooves on Labyrinth Seal Leakage

2003 ◽  
Vol 125 (2) ◽  
pp. 387-393 ◽  
Author(s):  
J. Denecke ◽  
V. Schramm ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Gas Turbines ◽  
Water Channel ◽  
Large Data ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Data Set ◽  
Engine Efficiency ◽  
Discharge Coefficients ◽  
Flow Mechanisms ◽  
Insight Into

An experimental investigation on the influence of stator rub-grooves on labyrinth seal leakage is presented in the present paper. In current labyrinth seal designs, abradable lands allow the rotor labyrinth teeth to rub grooves into the stator. These rub-grooves have a large influence on the seal leakage characteristic and impair the overall engine efficiency. To improve the understanding of rub-groove effects, discharge coefficients were determined using a plain nonrotating labyrinth seal model of scale 4:1 considering a wide variation of rub-groove geometries at different seal clearances. Three labyrinth seal types were covered in this investigation that are generally used in gas turbines, namely 1) straight-through labyrinth seals, 2) stepped labyrinth seals with forward facing steps, and 3) stepped labyrinth seals with backward facing steps. To attain a deeper insight into the flow mechanisms, water-channel visualizations were performed. The large data set generated in this study, provides the basis to analyze and quantify the influence of rub-grooves on the seal leakage for the three aforementioned labyrinth seal types. Current results were in agreement with previous studies on worn labyrinth seals for several seal geometries.

Design approach for maximising contacting filament seal performance retention

2014 ◽  
Vol 229 (5) ◽  
pp. 926-942 ◽  
Author(s):  
Ingo HJ Jahn
Keyword(s):  
Gas Turbines ◽  
Labyrinth Seal ◽  
Generic Properties ◽  
Labyrinth Seals ◽  
Blow Down ◽  
Operating Cycle ◽  
And Performance ◽  
Gas Turbine Cycle ◽  
Operating Cycles ◽  
The Ideal

Good sealing is a key requirement for modern efficient turbomachinery such as steam and gas turbines. A class of seals that promise better performance, compared to conventional labyrinth seals, are contacting filament seals such as brush, leaf, or finger seal. When new, these filament seals offer better performance; however, if poorly designed they wear excessively, resulting in leakages higher than a comparable labyrinth seal. This paper outlines a design methodology for selecting ideal contacting filament seal properties for a given operating cycle or set of operating cycles. Following this approach ensures the seal performs well, the seal retains its performance, and performance is retained if the operating cycle is altered. In the approach, the seals are described by four generic properties (stiffness, blow-down, cross-coupling, and build clearance), which are then used for a performance evaluation based on a number of test cycles. Once the ideal seal properties for a given operating cycle have been identified, a seal to match these can be designed. The approach is evaluated with a generic gas turbine cycle and recommendations for ideal contacting filament seal properties for this cycle are made.

Labyrinth Seal Leakage Tests: Tooth Profile, Tooth Thickness, and Eccentricity Effects

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Ahmed J. M. Gamal ◽  
John M. Vance
Keyword(s):  
Labyrinth Seal ◽  
Design Parameters ◽  
Working Fluid ◽  
Test Results ◽  
Blade Profile ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Blade Thickness ◽  
Center Position ◽  
Blade Tip

The effects of two seal design parameters, namely blade (tooth) thickness and blade profile, on labyrinth seal leakage, as well as the effect of operating a seal in an off-center position, were examined through a series of nonrotating tests. Two reconfigurable seal designs were used, which enabled testing of two-, four-, and six-bladed see-through labyrinth seals with different geometries using the same sets of seal blades. Leakage and cavity pressure measurements were made on each of 23 seal configurations with a in.(101.6mm) diameter journal. Tests were carried out with air as the working fluid at supply pressures of up to 100psia (6.89bar). Experimental results showed that doubling the thickness of the labyrinth blades significantly influenced leakage, reducing the flow rate through the seals by up to 20%. Tests to determine the effect of blade-tip profile produced more equivocal results, with the results of experiments using each of the two test seal designs contradicting each other. Tests on one set of hardware indicated that beveling blades on the downstream side was most effective in limiting leakage, whereas tests on newer hardware with tighter clearances indicated that seals with flat-tipped blades were superior. The test results illustrated that both blade profile and blade thickness could be manipulated so as to reduce seal leakage. However, an examination of the effects of both factors together indicated that the influence of one of these parameters can, to some extent, negate the influence of the other (especially in cases with tighter clearances). finally, for all configurations tested, results showed that leakage through a seal increases with increased eccentricity and that this phenomenon was considerably more pronounced at lower supply pressures.

Comparison of Discharge Coefficient Measurements and Correlations for Several Orifice Designs With Cross-Flow and Rotation Around Several Axes

2008 ◽  
Author(s):  
M. Hu¨ning
Keyword(s):  
Gas Turbines ◽  
Computer Network ◽  
Cross Flow ◽  
Angular Speed ◽  
Jet Engines ◽  
Component Design ◽  
Engine Design ◽  
Contour Plots ◽  
Secondary Air ◽  
Temperature Levels

Gas turbines and jet engines consist of a network of connected cavities beside the main gas path, called secondary air system. These cavities, which are often surrounded by stationary and high angular speed rotating walls are exposed to varying pressure and temperature levels of air or oil contaminated air and are connected to each other by orifices or restrictors. It is vital to control the secondary flow, to enable a reliable and efficient engine design, which meets component durability with a minimum of parasitic air consumption. It is essential to understand the flow physics as well as network inter-dependency in order to minimise the flow consumption and yet, meeting engine operating requirements, as well as practical parts component design or manufacturing needs. In this connexion computer network codes containing model conceptions, which can accurately predict orifice flows, are essential. In an effort to provide usable further insight into flows across restrictors such as orifices this publication compares test results, CFD calculations and orifice loss calculation models from the open literature with the aid of transformation laws and contour plots. The influence of different geometric features is incorporated into a model for the calculation of discharge coefficients.

Performance evaluation of the inter-stage labyrinth seal for different tooth positions in an axial compressor

2017 ◽  
Vol 232 (6) ◽  
pp. 579-592 ◽  
Author(s):  
Xiaozhi Kong ◽  
Gaowen Liu ◽  
Yuxin Liu ◽  
Zhao Lei ◽  
Longxi Zheng
Keyword(s):  
Axial Compressor ◽  
Labyrinth Seal ◽  
Tip Clearance ◽  
Test Facility ◽  
Leakage Flow ◽  
Rotating Disc ◽  
Labyrinth Seals ◽  
Leakage Flows ◽  
Sealing Performance ◽  
Set Up

Labyrinth seals are normally used to control the leakage flow in the compressor stator well. The upstream and downstream rotor-stator cavities of the labyrinth seal can cause complex reverse leakage flows. Remarkable temperature increases and high swirl velocities are observed in this region. In addition, another characteristic of inter-stage labyrinth seal is that large expansions of rotor and stator may easily lead to severely rubbing between the teeth and shrouds, which can shorten the lifetime of the compressor obviously. Experiments were conducted at a rotating compressor inter-stage seal test facility. Different labyrinth rings were tested to compare the performances of inter-stage labyrinth seals with different tooth positions. Leakage flow rates, windage heating and swirl ratios in the outlet cavity were measured at different rotating speeds and pressure ratios. In order to get the working tip clearance accurately, 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. Numerical simulations were carried out to present the important flow physics responsible for the effects of different tooth positions. In this article, performances of different cases for single, double and triple teeth were investigated and the experimental data provide a new way for the design of inter-stage seals. This method can reduce the leakage flow and avoid severely rubbing at the same time by changing axial positions of teeth in the stator well. When teeth are placed downstream of the model and the tooth pitch is larger, the inter-stage seal would have better sealing performance. For triple teeth cases, N = 3-Case1 has the lowest discharge coefficients, 15% less than that of N = 3-Baseline.

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