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.

Unsteady 3D-Numerical Investigation of the Influence of the Blading Design on the Stator-Rotor Interaction in a 2-Stage Turbine

2005 ◽  
Author(s):  
Dieter E. Bohn ◽  
Jing Ren ◽  
Christian Tu¨mmers ◽  
Michael Sell
Keyword(s):  
Gas Turbines ◽  
Flow Characteristics ◽  
Computer Code ◽  
Experimental Investigations ◽  
Blade Design ◽  
Test Rig ◽  
3D Flow ◽  
Two Stage ◽  
Flow Phenomena ◽  
Flow Through

An important goal in the development of turbine bladings is improving their efficiency to achieve an optimized usage of energy resources. This requires a detailed insight into the complex 3D-flow phenomena in multi-stage turbines. In order to investigate the flow characteristics of modern highly loaded turbine profiles, a test rig with a two-stage axial turbine has been set up at the Institute of Steam and Gas Turbines, Aachen University. The test rig is especially designed to investigate different blading designs. In order to analyze the influence of the blade design on the unsteady blade row interaction, the 3D flow through the two-stage turbine is simulated numerically, using an unsteady Navier-Stokes computer code. The investigations include a comparison of two bladings with different design criteria. The reference blading is a commonly used cylindrical designed blading. This blade design will be compared with a bow-blading, which is designed to minimize the secondary flow phenomena near the endwall in order to achieve a balanced mass flow through nearly the whole passage height. The investigations will focus on the different loss behavior of the two bladings. Unsteady profile pressure distributions and radial efficiencies of the two blade designs will be discussed in detail. The flow conditions are taken from experimental investigations performed at the Institute of Steam and Gas Turbines. On the basis of the experiments a validation of the code will be performed by comparing the numerical results to the corresponding experimental data at the inlet and the outlet of the blading.

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.

scholarly journals Advanced Labyrinth Seal Design Performance for High Pressure Ratio Gas Turbines

1975 ◽  
Author(s):  
H. L. Stocker
Keyword(s):  
High Pressure ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Internal Cavity ◽  
Water Tunnel ◽  
High Pressure Ratio ◽  
Test And Evaluation ◽  
Seal Design ◽  
Dynamic Seal

Labyrinth seal air leakage performance in current and advanced high pressure ratio gas turbines is directly related to the limitations of current available sealing technology. Sea design technology has not kept pace with the gas turbine major component advances. Therefore, an investigation was undertaken to design, fabricate and test several unique labyrinth seal concepts intended to decrease leakage through higher efficiency. The approach used in the unique designs for improving the efficiency of labyrinth seals involved increasing the internal cavity turbulence of the seal. The program involved three test and evaluation phases: (a) water tunnel studies; (b) static air rig tests; and (c) dynamic air rig tests. The water tunnel rig provided an economical method of screening the unique candidate designs. The most promising configurations from the water rig were fabricated and tested in the static air rig. Those configurations demonstrating a significant reduction in seal leakage over current designs were tested dynamically up to 786 ft/sec in an air rig to assess the effects of rotation. The results of this program effort show that each of the unique seal designs achieved lower leakage rates than a standard baseline step seal. In addition the dynamic seal test results show minimal effect on leakage due to rotation up to 786 ft/sec.

3-D Numerical Simulation of the Flow Through a Turbine Blade Cascade With Cooling Injection at the Leading Edge

1996 ◽  
Author(s):  
Dieter Bohn ◽  
Karsten Kusterer ◽  
Harald Schönenborn
Keyword(s):  
Numerical Simulation ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Stokes Equations ◽  
Leading Edge ◽  
Body Region ◽  
Gas Temperature ◽  
Hot Gas ◽  
Blade Cascade ◽  
Flow Through

High process efficiencies and high power-weight ratios are two major requirements for the economic operation of present day gas turbines. This development leads to extremely high turbine inlet temperatures and adjusted pressure ratios. The permissible hot gas temperature is limited by the material temperature of the blade. Intensive cooling is required to guarantee an economically acceptable life of the components which are in contact with the hot gas. Although film-cooling has been successfully in use for a couple of years along the suction side and pressure side, problems occur in the vicinity of the stagnation point due to high stagnation pressures and opposed momentum fluxes. In this area basic investigations are necessary to achieve a reliable design of the cooled blade. In the present calculations, a code for the coupled simulation of fluid flow and heat transfer in solid bodies is employed. The numerical scheme works on the basis of an implicit finite volume method combined with a multi-block technique. The full, compressible 3-D Navier-Stokes equations are solved within the fluid region and the Fourier equation for beat conduction is solved within the solid body region. An elliptic grid generator is used for the generation of the structured computational grid, which is a combination of various C-type and H-type grids. Results of a 3-D numerical simulation of the flow through a turbine blade cascade with and without cooling ejection at the leading edge through two slots are presented. The results are compared with 2-D numerical simulations and experimental results. It is shown that the distribution of the coolant on the blade surface is influenced by secondary flow phenomena which can not be taken into account by the 2-D simulations. Further coupled simulations with non-adiabatic walls in the leading edge region are performed with realistic temperature ratios and compared to the same case with adiabatic walls. It is shown that in the case of non-adiabatic walls the temperature on the blade wall is significantly lower than in the case of adiabatic walls.

Performance Evaluation of Gas Turbine Labyrinth Seals Using Computational Fluid Dynamics

2007 ◽  
Author(s):  
Bambang I. Soemarwoto ◽  
Johan C. Kok ◽  
Koen M. J. de Cock ◽  
Arjen B. Kloosterman ◽  
Gerrit A. Kool ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Real Life ◽  
Labyrinth Seal ◽  
Test Case ◽  
Analysis Tool ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Flow Through

The paper presents an investigation on the characteristics of flow through labyrinth seals. The focus of the paper lies in the application of the Computational Fluid Dynamics (CFD) methodology. The Reynolds-Averaged Navier-Stokes equations are employed as the flow governing equations. Turbulence is incorporated through a variant of the two-equation k-ω turbulence model. Three test cases are considered. The first test case concerns a labyrinth seal configuration with a honeycomb land. The computational results are compared to those obtained from seal test rig measurements. The second test case addresses the same labyrinth seal where the honeycomb land is replaced by a solid smooth land. The third test case addresses the flow through a labyrinth seal with canted knives. The CFD method is considered as an analysis tool complementary to rig-testing and enables investigating the effect of new seal design features. Additionally CFD is seen as a tool to support the correct representation of test-data in semiempirical engineering models for seal design. An industrial perspective is presented towards the exploitation of these modeling capabilities for real-life design of seals.

Development of Cavity Shapes of Labyrinth Seals Through CFD Analysis

2013 ◽  
Author(s):  
Mohana Rao Ramanadham ◽  
Balakrishna Gaja ◽  
Sravan Kumar Kanchanapally
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Axial Flow ◽  
Labyrinth Seal ◽  
Geometric Shape ◽  
Working Fluid ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Primary Flow ◽  
Flow Through

Axial flow compressors of Gas turbines use labyrinth seals to prevent the backflow of the working fluid. However some fluid will leak through the seals due to the clearance provided between the stationery and rotating components and due to the pressure difference across the seals, which affects the efficiency. The geometric shape of the seal plays an important role in influencing the fluid flow through the seals and the leakage rate. The flow through the seals consists of the primary flow and the secondary flow. The secondary flow is the flow through the cavity which is associated with vortex currents and tends to obstruct the primary flow. The geometric shape of the cavity is varied to study its effect on the vortex and resultant leakage flow through the seals. The curvatures of the seal and the distance of the seal tip to the end of the seal are the main parameters considered to arrive at the desired cavity which helps to create the required whirling action and to reduce the velocity of the leakage flow. Gambit software is used for modeling the geometry and Fluent software is used for the analysis. Axi-symmetric pressure based analysis is carried out using the standard κ-ε turbulence. The results of the standard cavity are compared with different variants. The flow velocity and mass flow is studied at different locations of the seal. The results indicate that by optimizing the shape of the seal cavity, the leakage through the labyrinth seal can be reduced.

Advanced Hydraulic Seal Design for High Temperature Environments

2006 ◽  
Author(s):  
J. Denecke ◽  
V. Schramm ◽  
K. Dullenkopf ◽  
H.-J. Bauer ◽  
M. Klingsporn ◽  
...  
Keyword(s):  
Hot Spots ◽  
Analytical Calculation ◽  
Flow Characteristics ◽  
Reliable Operation ◽  
Seal Design ◽  
Air Temperatures ◽  
Recirculation Zones ◽  
Turbine Shaft ◽  
Set Up ◽  
Good Agreement

Hydraulic seals are successfully used to seal gas turbine shaft and bearing chambers because of their main advantages: reliable operation with zero leakage. However, due to the temperature limitations of the lubrication oil their application has been limited to relatively cold areas in the engine (e.g. front bearing chamber). To employ hydraulic seals in hotter areas, particularly at the rear bearing chamber with elevated wall and air temperatures, oil degradation and coking must be taken into account. Therefore, recirculation zones which lead to hot spots must be avoided and the oil residence time must be reduced. A new seal design that enforces a defined flow pattern through the seal (Bo¨ck, U.S. Patent No. 6,568,688B1) claims to keep oil temperature below degradation limits even in hotter operational environments. However, the circumferential velocities and oil levels in the seal are altered, which must be considered in the design process. This paper compares the flow characteristics of the classic and advanced seal design. Analytical calculation approaches for both seal designs are presented. The commercial software FLUENT was used for numerical simulations, applying the ‘Volume of Fluid’ (VoF) method. To validate the numerical and analytical results, a configuration was tested experimentally in a two shaft co-rotating set-up, which was especially designed for hydraulic seals. Good agreement could be achieved in a comparison of the monitored oil levels in the seal for different engine relevant shaft speeds and pressures.

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.

Prediction of Low Temperature Hot Corrosion Rate in Film Cooled Coal Fired Gas Turbines

2003 ◽  
Author(s):  
Vaidyanathan Krishnan ◽  
Sanjeev Bharani ◽  
J. S. Kapat ◽  
Y. H. Sohn ◽  
V. H. Desai
Keyword(s):  
Corrosion Rate ◽  
Hot Corrosion ◽  
Film Cooling ◽  
Gas Turbines ◽  
Power Plants ◽  
Gas Temperature ◽  
Air Temperatures ◽  
Operational Life ◽  
Cooling Hole ◽  
Cooling Air

The concept of coal based gas turbine power plants has drawn considerable interest in recent years. Coal or syngas based power plants like IGCC have shown significant potential for meeting the ever-increasing power demands as well as stricter environmental regulations. The trouble free operational life of such power plants is limited by a major factor namely hot corrosion of the turbine components. Hitherto, the mechanism of hot corrosion has been investigated in a simpler context, which is not directly applicable to gas turbines in the presence of film cooling techniques. The present paper is an attempt to model hot corrosion in the presence of film cooling relevant to gas turbines, using a simple resistance model and the inherent analogy between heat and mass transfer. This paper considers film cooling air temperatures in the range of 450°C to 550°C, and a free stream gas temperature of 1425°C, with 0.5% sulfur in the fuel. For lower cooling air temperatures (less than 500°C), film cooling air suppresses corrosion, whereas for higher cooling air temperature corrosion rate is more in the presence of film cooling. With film cooling, there is a sharp peak in corrosion rate close to the cooling hole (within 10 slot widths). Due to the possibility that the base superalloy may be exposed in this region, designers should consider the high corrosion rate seriously. However, the present model is limited in its prediction because of its simplicity. Further improvement of the model is essential for optimization purposes.

Numerical investigation of non-uniform flow in twin-silo combustors and impact on axial turbine stage performance

2021 ◽  
pp. 095765092199394
Author(s):  
Hafiz M Hassan ◽  
Adeel Javed ◽  
Asif H Khoja ◽  
Majid Ali ◽  
Muhammad B Sajid
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Flow ◽  
Large Temperature ◽  
Clear Understanding ◽  
Gas Temperature ◽  
Turbine Stage ◽  
Flow Angle ◽  
Axial Turbine ◽  
Stage Performance

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective.

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