Emergence of Kelvin-Helmholtz Instabilities in Gas Turbine Rim Cavities: A Parameter Study

2012 ◽  
Author(s):  
M. Rabs ◽  
F.-K. Benra ◽  
O. Schneider
Keyword(s):  
Gas Turbine ◽  
Linear Theory ◽  
Gas Turbines ◽  
Gas Flow ◽  
Splitter Plate ◽  
Parameter Study ◽  
Plate Model ◽  
Cavity Model ◽  
Hot Gas ◽  
Vortex Velocity

In an earlier paper of the authors, the occurrence of the so called Kelvin-Helmholtz instabilities (KHI) near the rim cavity of a 1.5 stage gas turbine has been examined by the use of CFD methods. It is shown that the KHI’s occur, when the swirl component of the hot gas flow is very strong. Due to the fact, that a high swirl is produced by the guide vanes of the first stage, this matter concerns most common gas turbines. A further paper validated the CFD methods used and derived KHI parameters (vortex appearance, vortex periodicity and vortex velocity) of a splitter plate model. In the current study, essential parameters revealed by the analysis of a gas turbine rim cavity model are compared to the parameters extracted from the investigation of the splitter plate model and the potential linear theory of Turner. The rim cavity model is derived from a test rig of a 1.5 stage gas turbine. The blades and vanes have been removed from the computations. As main flow boundary conditions, surface averaged parameters are used. It is shown that a description of KHI developing in a rim cavity model is partly possible using splitter plate KHI characteristics and the potential linear theory of Turner as well. A mathematical approach is formulated, which can predict the vortex velocity of KHI’s in turbine rim cavities.

Computational Study of Kelvin-Helmholtz Instability Created by Interaction of the Mainstream Flow and the Seal Flow in Gas Turbines

2011 ◽  
Author(s):  
M. Rabs ◽  
F.-K. Benra ◽  
C. Domnick ◽  
O. Schneider
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Gas Flow ◽  
Computational Study ◽  
Theoretical Background ◽  
Splitter Plate ◽  
Parameter Study ◽  
Test Rig ◽  
Hot Gas ◽  
Mainstream Flow

The present paper gives a contribution to a better understanding of the emergence of Kelvin-Helmholtz instabilities (KHI) in gas turbines. In an earlier paper of the authors, the occurrence of the KHI’s near the rim cavity of a 1.5 stage gas turbine has been examined by use of CFD methods. It is shown that the KHI’s occur, when the swirl component of the hot gas flow is very strong. Due to the fact, that a high swirl is produced by the guide vanes of the first stage, this matter concerns all common gas turbines. In order to get a basic theoretical background of the emergence of the KHI’s, 2D CFD investigations of the flow behind a splitter plate have been performed showing the development of KHI’s downstream of the splitter plate. To validate the numerical results a comparison to test rig data is used. This shows that the numerical method can simulate the characteristics of the KHI’s. Furthermore, a parameter study is conducted to extract parameters describing the appearance of KHI’s, the vortex periodicity and stability criteria. The main intention of this paper is to deliver “KHI parameters”, which are able to describe the development of the KHI in gas turbine rim cavities.

A Combustion Study of Gas Turbines Using Multi-Species/Reacting Computational Fluid Dynamic

2002 ◽  
Author(s):  
Sasan Armand ◽  
Mei Chen
Keyword(s):  
Carbon Monoxide ◽  
Gas Turbine ◽  
Environmental Contamination ◽  
Gas Turbines ◽  
Gas Flow ◽  
Fluid Dynamic ◽  
Combustion Products ◽  
Contamination Level ◽  
Short Term ◽  
Hot Gas

A multi-species/reacting combustion study was performed. The focus of the study was to quantify the effects of variation in air extraction and power rates on flame/outlet temperatures of a General Electric (GE), Frame 5 gas turbine. The environmental contamination level due to generation of carbon monoxide was also reported. GE, Frame 5 gas turbine has been widely used around the world for power generation, and as mechanical drives. The combustion products were examined throughout a range of air extraction rates, upon which it was determined that the combustion liners were susceptible to damage at air extraction rates above 10%, and the environmental contamination level due to carbon monoxide was increased. Furthermore, the gas flow exiting the combustion liner became non-homogeneous (i.e. a pocket of relatively hot gas formed in the middle of the flow path), which would cause damage to the downstream components. In conclusion, the short-term monetary gains from using compressed air from a gas turbine do not justify the costs of down time for repairs and the replacement of expensive hot-gas-path components.

scholarly journals Experimental Assessment of Fiber Reinforced Ceramics for Combustor Walls

1997 ◽  
Author(s):  
D. Filsinger ◽  
S. Münz ◽  
A. Schulz ◽  
S. Wittig ◽  
G. Andrees
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Gas Flow ◽  
Ceramic Materials ◽  
Inlet Temperature ◽  
Test Duration ◽  
Fiber Reinforced ◽  
Hot Gas ◽  
Sic Composites

Experimental and theoretical work concerning the application of ceramic components in small high temperature gas turbines has been performed for several years. The significance of some non-oxide ceramic materials for gas turbines in particular is based on their excellent high temperature properties. The application of ceramic materials allows an increase of the turbine inlet temperature resulting in higher efficiencies and a reduction of pollution emissions. The inherent brittleness of monolithic ceramic materials can be virtually reduced by reinforcement with ceramic fibers leading to a quasi-ductile behavior. Unfortunately, some problems arise due to oxidation of these composite materials in the presence of hot gas flow containing oxygen. At the Motoren- und Turbinen Union, München GmbH, comprehensive investigations including strength, oxidation, and thermal shock tests of several materials that seemed to be appropriate for combustor liner applications were undertaken. As a result, C/C, SiC/SiC, and two C/SiC-composites coated with SiC, as oxidation protection, were chosen for examination in a gas turbine combustion chamber. To prove the suitability of these materials under real engine conditions, the fiber reinforced flame tubes were installed in a small gas turbine operating under varying conditions. The loading of the flame tubes was characterized by wall temperature measurements. The materials showed different oxidation behavior when exposed to the hot gas flow. Inspection of the C/SiC-composites revealed debonding of the coatings. The C/C- and the SiC/SiC-materials withstood the tests with a maximum cumulated test duration of 90 hours without damage.

A Combustion Study of Gas Turbines Using Multi-Species/Reacting Computational Fluid Dynamic

2002 ◽  
Author(s):  
Sasan Armand ◽  
Mei Chen
Keyword(s):  
Carbon Monoxide ◽  
Gas Turbine ◽  
Environmental Contamination ◽  
Gas Turbines ◽  
Gas Flow ◽  
Fluid Dynamic ◽  
Combustion Products ◽  
Contamination Level ◽  
Short Term ◽  
Hot Gas

A multi-species/reacting combustion study was performed. The focus of the study was to quantify the effects of variation in air extraction and power rates on flame/outlet temperatures of a General Electric (GE), Frame 5 gas turbine. The environmental contamination level due to generation of carbon monoxide was also reported. GE, Frame 5 gas turbine has been widely used around the world for power generation, and as mechanical drives. The combustion products were examined throughout a range of air extraction rates, upon which it was determined that the combustion liners were susceptible to damage at air extraction rates above 10%, and the environmental contamination level due to carbon monoxide was increased. Furthermore, the gas flow exiting the combustion liner became non-homogeneous (i.e. a pocket of relatively hot gas formed in the middle of the flow path), which would cause damage to the downstream components. In conclusion, the short-term monetary gains from using compressed air from a gas turbine do not justify the costs of down time for repairs and the replacement of expensive hot-gas-path components.

Numerical Investigations of Flow Pattern and Heat Transfer in a Rotating Cavity Between Two Discs of the Compressor of a Siemens KWU V84.3 Gas Turbine

1995 ◽  
Author(s):  
Dieter Bohn ◽  
Uwe Krüger ◽  
Klaus Nitsche
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
Gas Flow ◽  
Complex Flow ◽  
Numerical Investigations ◽  
Hot Gas ◽  
Start Up ◽  
First Results

The rotor of modern gas turbines often consists of single discs forming air-filled rotating cavities. During stationary operation each disc in the compressor section is of nearly uniform temperature. This results from the radial heat conduction in the disc material and from the negligible axial temperature gradients between surface and air in the adjacent cavities. The situation changes rapidly during cold start-ups of the engine. The disc rims respond quickly to the temperature of the mainstream (500 to 600 K), whereas the average temperature of the massive hub section follows with some delay thus forming a radial thermal gradient. This induces a buoyancy-driven flow inside the cavity, which is superimposed by a controlled hot gas ingress. A defined amount of hot air flows radially inwards through the Hirth-type serration at the head of the discs, causes increased convection within the cavity and speeds up the thermal equilibration process in the discs. Numerical investigations of the very complex flow situation have been carried out to get a better knowledge of both the flow-physics and the heat transfer from the hot fluid to the cold rotating wall. A modern numerical Finite-Volume-Code with multiblock and body-fitted grid-options has been used to calculate three different cases: one cavity without hot gas ingress and two cases with two different mass flow parameters. The boundary conditions have been chosen in such a way that they cover real gas turbine conditions at the very beginning of the start-up. The most stringent case has been investigated, i. e. the head of the discs and the hot gas mass flow having the mainstream temperature while the discs in the hub region remain at ambient temperature. It has been found that in the case without throughflow the core-region rotates approximately with the speed of a solid body. In the case of superimposed hot gas flow directed radially inwards, the flow has the character of a potential-vortex-flow, with exception of the regions near the wall. The hot gas is transported to the hub-region so that the heat transfer in this region is very large in the first period of the start-up-procedure. Some aspects are presented which should be investigated in more detail in future work, especially the 3-D effects and the conjugate heat transfer. First results of a 3-D calculation are shown.

Experimental Assessment of Fiber-Reinforced Ceramics for Combustor Walls

1997 ◽  
Vol 123 (2) ◽  
pp. 271-276 ◽  
Author(s):  
D. Filsinger ◽  
S. Mu¨nz ◽  
A. Schulz ◽  
S. Wittig ◽  
G. Andrees
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Gas Flow ◽  
Ceramic Materials ◽  
Inlet Temperature ◽  
Test Duration ◽  
Fiber Reinforced ◽  
Hot Gas ◽  
Sic Composites

Experimental and theoretical work concerning the application of ceramic components in small high-temperature gas turbines has been performed for several years. The significance of some nonoxide ceramic materials for gas turbines in particular is based on their excellent high-temperature properties. The application of ceramic materials allows an increase of the turbine inlet temperature resulting in higher efficiencies and a reduction of pollution emissions. The inherent brittleness of monolithic ceramic materials can be virtually reduced by reinforcement with ceramic fibers leading to a quasiductile behavior. Unfortunately, some problems arise due to oxidation of these composite materials in the presence of hot gas flow containing oxygen. At the Motoren und Turbinen Union, Mu¨nchen GmbH, comprehensive investigations including strength, oxidation, and thermal shock tests of several materials that seemed to be appropriate for combustor liner applications were undertaken. As a result, C/C, SiC/SiC, and two C/SiC composites coated with SiC, as oxidation protection, were chosen for examination in a gas turbine combustion chamber. To prove the suitability of these materials under real engine conditions, the fiber-reinforced flame tubes were installed in a small gas turbine operating under varying conditions. The loading of the flame tubes was characterized by wall temperature measurements. The materials showed different oxidation behavior when exposed to the hot gas flow. Inspection of the C/SiC composites revealed debonding of the coatings. The C/C and SiC/SiC materials withstood the tests with a maximum cumulated test duration of 90 h without damage.

Coal-Water Slurry Testing of an Industrial Gas Turbine

1992 ◽  
Author(s):  
R. A. Wenglarz ◽  
C. Wilkes ◽  
R. C. Bourke ◽  
H. C. Mongia
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Water Injection ◽  
Department Of Energy ◽  
Combustion System ◽  
Hot Gas ◽  
Water Slurry ◽  
Coal Water Slurry ◽  
Burning Coal ◽  
Industrial Gas Turbine

This paper describes the first test of an industrial gas turbine and low emissions combustion system on coal-water-slurry fuel. The engine and combustion system have been developed over the past five years as part of the Heat Engines program sponsored by the Morgantown Energy Technology Center of the U.S. Department of Energy (DOE). The engine is a modified Allison 501-K industrial gas turbine designed to produce 3.5 MW of electrical power when burning natural gas or distillate fuel. Full load power output increases to approximately 4.9 MW when burning coal-water slurry as a result of additional turbine mass flow rate. The engine has been modified to accept an external staged combustion system developed specifically for burning coal and low quality ash-bearing fuels. Combustion staging permits the control of NOx from fuel-bound nitrogen while simultaneously controlling CO emissions. Water injection freezes molten ash in the quench zone located between the rich and lean zones. The dry ash is removed from the hot gas stream by two parallel cyclone separators. This paper describes the engine and combustor system modifications required for running on coal and presents the emissions and turbine performance data from the coal-water slurry testing. Included is a discussion of hot gas path ash deposition and planned future work that will support the commercialization of coal-fired gas turbines.

Coupled Thermo-Mechanical Fatigue Tests for Simulating Load Conditions in Cooled Turbine Parts

2011 ◽  
Author(s):  
Roland Mu¨cke ◽  
Klaus Rau
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Mechanical Load ◽  
Fatigue Tests ◽  
Temperature Fields ◽  
Hot Gas ◽  
Mechanical Fatigue ◽  
Numerical Predictions ◽  
Temperature Capability ◽  
Load Conditions

Modern heavy-duty gas turbines operate under hot gas temperatures that are much higher than the temperature capability of nickel superalloys. For that reason, advanced cooling technology is applied for reducing the metal temperature to an acceptable level. Highly cooled components, however, are characterised by large thermal gradients resulting in inhomogeneous temperature fields and complex thermo-mechanical load conditions. In particular, the different rates of stress relaxation due to the different metal temperatures on hot gas and cooling air exposed surfaces lead to load redistributions in cooled structures, which have to be considered in the lifetime prediction methodology. In this context, the paper describes Coupled Thermo-Mechanical Fatigue (CTMF) tests for simultaneously simulating load conditions on hot and cold surfaces of cooled turbine parts, Refs [1, 2]. In contrary to standard Thermo-Mechanical Fatigue (TMF) testing methods, CTMF tests involve the interaction between hot and cold regions of the parts and thus more closely simulates the material behaviour in cooled gas turbine structures. The paper describes the methodology of CTMF tests and their application to typical load conditions in cooled gas turbine parts. Experimental results are compared with numerical predictions showing the advantages of the proposed testing method.

Investigation of Flow Instabilities Near the Rim Cavity of a 1.5 Stage Gas Turbine

2009 ◽  
Author(s):  
M. Rabs ◽  
F.-K. Benra ◽  
H. J. Dohmen ◽  
O. Schneider
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
Flow Instabilities ◽  
Navier Stokes ◽  
Flow Rates ◽  
Air Mass ◽  
Hot Gas ◽  
Path Modelling ◽  
Mass Flow Rates

The present paper gives a contribution to a better understanding of the flow at the rim and in the wheel space of gas turbines. Steady state and time-accurate numerical simulations with a commercial Navier-Stokes solver for a 1.5 stage turbine similar to the model treated in the European Research Project ICAS-GT were conducted. In the framework of a numerical analysis, a validation with experimental results of the test rig at the Technical University of Aachen will be given. In preceding numerical investigations of realistic gas turbine rim cavities with a simplified treatment of the hot gas path (modelling of the main flow path without blades and vanes), so called Kelvin-Helmholtz vortices were found in the area of the gap when using appropriate boundary conditions. The present work shows that these flow instabilities also occur in a 1.5 stage gas turbine model with consideration of the blades and vanes. Therefore, several simulations with different sealing air mass flow rates (CW 7000, 20000, 30000) have been conducted. The results show, that for high sealing air mass flow rates Kelvin-Helmholtz Instabilities are developing. These vortices significantly coin the flow at the rim.

Repair of Advanced Gas Turbine Blades

2005 ◽  
Author(s):  
Julie McGraw ◽  
Reiner Anton ◽  
Christian Ba¨hr ◽  
Mary Chiozza
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
High Reliability ◽  
Turbine Blades ◽  
Base Material ◽  
Operating Experience ◽  
Cost Effective ◽  
Directionally Solidified ◽  
Hot Gas

In order to promote high efficiency combined with high power output, reliability, and availability, Siemens advanced gas turbines are equipped with state-of-the-art turbine blades and hot gas path parts. These parts embody the latest developments in base materials (single crystal and directionally solidified), as well as complex cooling arrangements (round and shaped holes) and coating systems. A modern gas turbine blade (or other hot gas path part) is a duplex component consisting of base material and coating system. Planned recoating and repair intervals are established as part of the blade design. Advanced repair technologies are essential to allow cost-effective refurbishing while maintaining high reliability. This paper gives an overview of the operating experience and key technologies used to repair these parts.

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