Thermal Modeling of an Intermediate Pressure Steam Turbine by Means of Conjugate Heat Transfer—Simulation and Validation

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Dominik Born ◽  
Peter Stein ◽  
Gabriel Marinescu ◽  
Stefan Koch ◽  
Daniel Schumacher
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Conjugate Heat Transfer ◽  
Thermal Stresses ◽  
Numerical Models ◽  
Thermal Modeling ◽  
Transfer Coefficients ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Product Costs

Today's power market asks for highly efficient turbines which can operate at a maximum flexibility, achieving a high lifetime and all of this on competitive product costs. In order to increase the plant cycle efficiency, during the past years, nominal steam temperatures and pressures have been continuously increased. To fulfill the lifetime requirements and still achieve the product cost requirements, accurate mechanical integrity based assessments on cyclic lifetime became more and more important. For this reason, precise boundary conditions in terms of local temperatures as well as heat transfer coefficients are essential. In order to gain such information and understand the flow physics behind them, more and more complex thermal modeling approaches are necessary, like computational fluid dynamics (CFD) or even conjugate heat transfer (CHT). A proper application of calculation rules and methods is crucial regarding the determination of thermal stresses, thermal expansion, lifetime, or creep. The aim is to exploit during turbine developments the limits of the designs with the selected materials. A huge effort especially in validation and understanding of those methodologies was done with detailed numerical investigations associated to extensive measurement studies at onsite turbines in operation. This paper focuses on the validation of numerical models based on CHT calculations against experimental data of a large intermediate pressure steam turbine module regarding the temperature distribution at the inner and outer casing for nominal load as well as transient shut-down.

Thermal Modelling of an Intermediate Pressure Steam Turbine by Means of Conjugate Heat Transfer: Simulation and Validation

2016 ◽  
Author(s):  
Dominik Born ◽  
Peter Stein ◽  
Gabriel Marinescu ◽  
Stefan Koch ◽  
Daniel Schumacher
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Conjugate Heat Transfer ◽  
Thermal Stresses ◽  
Numerical Models ◽  
Thermal Modelling ◽  
Transfer Coefficients ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Product Costs

Today’s power market asks for highly efficient turbines which can operate at a maximum flexibility, achieving a high lifetime and all of this on competitive product costs. In order to increase the plant cycle efficiency, during the past years, nominal steam temperatures and pressures have been continuously increased. To fulfill the lifetime requirements and still achieve the product cost requirements, accurate mechanical integrity based assessments on cyclic lifetime became more and more important. For this reason, precise boundary conditions in terms of local temperatures as well as heat transfer coefficients are essential. In order to gain such information and understand the flow physics behind them, more and more complex thermal modelling approaches are necessary, like Computational Fluid Dynamics (CFD) or even Conjugate Heat Transfer (CHT). A proper application of calculation rules and methods is crucial regarding the determination of thermal stresses, thermal expansion, lifetime or creep. The aim is to exploit during turbine developments the limits of the designs with the selected materials. A huge effort especially in validation and understanding of those methodologies was done with detailed numerical investigations associated to extensive measurement studies at onsite turbines in operation. This paper focuses on the validation of numerical models based on CHT calculations against experimental data of a large intermediate pressure steam turbine module regarding the temperature distribution at the inner and outer casing for nominal load as well as transient shut-down.

Numerical Investigation of the Heat Transfer and Flow Phenomena in an IP Steam Turbine in Warm-Keeping Operation With Hot Air

2017 ◽  
Author(s):  
Dennis Toebben ◽  
Piotr Łuczyński ◽  
Mathias Diefenthal ◽  
Manfred Wirsum ◽  
Stefan Reitschmidt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Steam Turbine ◽  
Flow Structure ◽  
Conjugate Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Hot Air ◽  
Start Up ◽  
Flow Phenomena

Nowadays, steam turbines in conventional power plants deal with an increasing number of startups due to the high share of fluctuating power input of renewable generation. Thus, the development of new methods for flexibility improvements, such as reduction of the start-up time and its costs, have become more and more important. At the same time, fast start-up and flexible steam turbine operation increase the lifetime consumption and reduce the inspection intervals. One possible option to prevent these negative impacts of a flexible operation is to keep the steam turbine warm during a shut down and a startup. In order to do so, General Electric has developed a concept for warm-keeping respectively pre-warming of a high-pressure (HP) / intermediate-pressure (IP) steam turbine with hot air: After a certain cool-down phase, air is passed through the turbine while the turbine is rotated by the turning engine. The flow and the rotational direction can be inverted to optimize the warming operation. In order to fulfill the requirements of high flexibility in combination with reduced costs and thermal stresses during the start-up, a detailed investigation of the dominant heat transfer effects and the corresponding flow structure is necessary: Complex numerical approaches, such as Conjugate Heat Transfer (CHT), can provide this corresponding information and help to understand the physical impact of the flow phenomena. The aim of the present work is thus to understand the predominant heat transport phenomena in warm-keeping operation and to gain detailed heat transfer coefficients within the flow channel for blade, vane and shrouds. A multitude of steady-state simulations were performed to investigate the different warm-keeping operation points. Data from literature was recomputed in good agreement to qualitatively validate the numerical model in windage operation. Furthermore, the steady-state simulations were compared with transient Computational Fluid Dynamics (CFD) simulations to verify that the flow in warming operation can be simulated with a steady-state case. The transient calculations confirm the steady-state results. A variation of the mass flow rate and the rotational speed was conducted to calculate a characteristic map of heat transfer coefficients. The Conjugate Heat Transfer simulations provide an insight into the flow structure and offer a comparison with the flow phenomena in conventional operation. In addition, the impact of the flow phenomena on the local heat transfer was investigated.

Validation of Conjugate Heat Transfer Predictions on Labyrinth Seals and Novel Designs for Improved Component Lifetime

2011 ◽  
Author(s):  
Dominik Born ◽  
Kurt Heiniger ◽  
Giorgio Zanazzi ◽  
Thomas Mokulys ◽  
Patrick Grossmann ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Conjugate Heat Transfer ◽  
Labyrinth Seal ◽  
Turbine Rotor ◽  
Transfer Coefficients ◽  
Labyrinth Seals ◽  
Heat Transfer Coefficients ◽  
Low Pressure Turbine ◽  
Single Flow

Cyclic lifetime assessment of steam turbine components has become increasingly important for several reasons. In the last years and decades the nominal steam temperatures and pressures were further increased to improve cycle efficiency. In addition, the market constantly demands increased flexibility and reliability for given lifetime exploiting the limits of the existing materials. A number of components in a steam turbine are critical in the focus of lifetime predictions such as the rotor and front stage blades, the inner casing and the area of labyrinth seals connected to the life steam. For this reason, it becomes extremely important to rely on accurate predictions of local temperatures and heat-transfer-coefficients of components in the steam path. The content of this paper aims on the validation of the numerical tools based on CHT (conjugate heat transfer) approach against experimental data of a labyrinth seal regarding discharge coefficients and measured heat transfer coefficients. Furthermore, a real steam turbine application has been optimized in design and operation to improve lifetime. The improved prediction of temperature and heat transfer allowed novel designs of labyrinth seals of a single flow high-pressure turbine and a combined intermediate and low-pressure turbine, which helped to strongly increase the component lifetime of a steam turbine rotor by more than 100%.

Comparison of a Conventional Thermal Analysis of a Turbine Cascade to a Full Conjugate Heat Transfer Computation

2008 ◽  
Author(s):  
Christoph Starke ◽  
Erik Janke ◽  
Toma´sˇ Hofer ◽  
Davide Lengani
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Conjugate Heat Transfer ◽  
Complex Geometry ◽  
Thermal Analyses ◽  
Turbine Cascade ◽  
Transfer Coefficients ◽  
Commercial Code ◽  
Blade Tip ◽  
Transfer Method

Recent development in commercial CFD codes offers possibilities to include the solid body in order to perform conjugate heat transfer computations for complex geometries. The current paper aims to analyse the differences between a conjugate heat transfer computation and conventional uncoupled approaches where a heat transfer coefficient is first derived from a flow solution and then taken as boundary condition for a thermal conduction analysis of the solid part. Whereas the thermal analyses are done with a Rolls-Royce in-house finite element code, the CFD as well as the conjugate heat transfer computation are done using the new version 8 of the commercial code Fine Turbo from Numeca International. The analysed geometry is a turbine cascade that was tested by VKI in Brussels within the European FP6 project AITEB 2. First, the paper presents the aerodynamic results. The pure flow solutions are validated against pressure measurements of the cascade test. Then, the heat transfer from flow computations with wall temperature boundary conditions is compared to the measured heat transfer. Once validated, the heat transfer coefficients are used as boundary condition for three uncoupled thermal analyses of the blade to predict its surface temperatures in a steady state. The results are then compared to a conjugate heat transfer method. Therefore, a mesh of the solid blade was added to the validated flow computation. The paper will present and compare the results of conventional uncoupled thermal analyses with different strategies for the wall boundary condition to results of a conjugate heat transfer computation. As it turns out, the global results are similar but especially the over-tip region with its complex geometry and flow structure and where effective cooling is crucial shows remarkable differences because the conjugate heat transfer solution predicts lower blade tip temperatures. This will be explained by the missing coupling between the fluid and the solid domain.

Thermal Analysis of Cooling System in a Gas Turbine Transition Piece

2011 ◽  
Author(s):  
Jun Su Park ◽  
Namgeon Yun ◽  
Hokyu Moon ◽  
Kyung Min Kim ◽  
Sin-Ho Kang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Cooling System ◽  
Structural Information ◽  
Thermal Analyses ◽  
Thermal Design ◽  
Transfer Coefficients ◽  
Transition Piece ◽  
Inlet Conditions

This paper presents thermal analyses of the cooling system of a transition piece, which is one of the primary hot components in a gas turbine engine. The thermal analyses include heat transfer distributions induced by heat and fluid flow, temperature, and thermal stresses. The purpose of this study is to provide basic thermal and structural information on transition piece, to facilitate their maintenance and repair. The study is carried out primarily by numerical methods, using the commercial software, Fluent and ANSYS. First, the combustion field in a combustion liner with nine fuel nozzles is analyzed to determine the inlet conditions of a transition piece. Using the results of this analysis, pressure distributions inside a transition piece are calculated. The outside of the transition piece in a dump diffuser system is also analyzed. Information on the pressure differences is then used to obtain data on cooling channel flow (one of the methods for cooling a transition piece). The cooling channels have exit holes that function as film-cooling holes. Thermal and flow analyses are carried out on the inside of a film-cooled transition piece. The results are used to investigate the adjacent temperatures and wall heat transfer coefficients inside the transition piece. Overall temperature and thermal stress distributions of the transition piece are obtained. These results will provide a direction to improve thermal design of transition piece.

Analysis of Heat Transfer through PVC Window Profile Reinforced with Ti6Al4V Alloy

2016 ◽  
Vol 687 ◽  
pp. 236-242 ◽  
Author(s):  
Piotr Lacki ◽  
Judyta Różycka ◽  
Marcin Rogoziński
Keyword(s):  
Heat Transfer ◽  
Titanium Alloy ◽  
Thermal Insulation ◽  
Numerical Models ◽  
Characteristic Temperature ◽  
Permanent Deformation ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Ti6al4v Titanium Alloy ◽  
Characteristic Points

This requires the use of additional reinforcement in order to prevent excessive or permanent deformation of PVC windows. In the paper particular attention was devoted to space located in a corrosive environment exposed to chemical agents. For this purpose, proposed to change the previously used steel profiles reinforcements made of Ti6Al4V titanium alloy corrosion-resistant in the air, at sea and many types of industrial atmosphere. Analysis of the thermal insulation properties of PVC windows with additional reinforcement of profile Ti6Al4V titanium alloy was performed. PVC window set in a layer of thermal insulation was analyzed. Research was conducted using Finite Element Analysis. Numerical models and thermal calculations were made in the program ADINA, assuming appropriate material parameters. The constant internal temperature of 20 ̊ and an outer-20 ̊ was assumed. The course of temperature distribution in baffle in time 24 hours and graphs of characteristic points was obtained. The time of in which followed the steady flow of heat, as well as the course of isotherm of characteristic temperature in the baffle was determined. On the basis of numerical analysis obtained vector distribution of heat flux q [W/m2] and was determined heat transfer coefficients U [W/m2K] for the whole window with titanium reinforcement . All results were compared with the model of PVC windows reinforced with steel profile.

Simulation of Unsteady Flows in Intermediate Pressure Steam Turbine with Cutback Stator Blade Row

2020 ◽  
Vol 2020 (0) ◽  
pp. J05102
Author(s):  
Hironori MIYAZAWA ◽  
Akihiro UEMURA ◽  
Takashi FURUSAWA ◽  
Satoru YAMAMOTO ◽  
Shuichi UMEZAWA ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Unsteady Flows ◽  
Intermediate Pressure ◽  
Blade Row ◽  
Pressure Steam ◽  
Stator Blade

Degradation of Aerodynamic Performance of an Intermediate-Pressure Steam Turbine Due to Erosion of Nozzle Guide Vanes and Rotor Blades

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Koichi Yonezawa ◽  
Tomoki Kagayama ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Steam Turbine ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Flow Angle ◽  
Guide Vanes ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Deteriorations of nozzle guide vanes (NGVs) and rotor blades of a steam turbine through a long-time operation usually decrease a thermal efficiency and a power output of the turbine. In this study, influences of blade deformations due to erosion are discussed. Experiments were carried out in order to validate numerical simulations using a commercial software ANSYS-cfx. The numerical results showed acceptable agreements with experimental results. Variation of flow characteristics in the first stage of the intermediate pressure steam turbine is examined using numerical simulations. Geometries of the NGVs and the rotor blades are measured using a 3D scanner during an overhaul. The old NGVs and the rotor blades, which were used in operation, were eroded through the operation. The erosion of the NGVs leaded to increase of the throat area of the nozzle. The numerical results showed that rotor inlet velocity through the old NGVs became smaller and the flow angle of attack to the rotor blade leading edge became smaller. Consequently, the rotor power decreased significantly. Influences of the flow angle of at the rotor inlet were examined by parametric calculations and results showed that the angle of attack was an important parameter to determine the rotor performance. In addition, the influence of the deformation of the rotor blade was examined. The results showed that the degradation of the rotor performance decreased in accordance with the decrease of blade surface area.

Full 3D Conjugate Heat Transfer Simulation and Heat Transfer Coefficient Prediction for the Effusion-Cooled Wall of a Gas Turbine Combustor

2008 ◽  
Author(s):  
Andreas Jeromin ◽  
Christian Eichler ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Gas Turbine ◽  
Conjugate Heat Transfer ◽  
Solid Wall ◽  
Heat Fluxes ◽  
Computational Domain ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Numerical Predictions

Numerical predictions of conjugate heat transfer on an effusion cooled flat plate were performed and compared to detailed experimental data. The commercial package CFX® is used as flow solver. The effusion holes in the referenced experiment had an inclination angle of 17 degrees and were distributed in a staggered array of 7 rows. The geometry and boundary conditions in the experiments were derived from modern gas turbine combustors. The computational domain contains a plenum chamber for coolant supply, a solid wall and the main flow duct. Conjugate heat transfer conditions are applied in order to couple the heat fluxes between the fluid region and the solid wall. The fluid domain contains 2.4 million nodes, the solid domain 300,000 nodes. Turbulence modeling is provided by the SST turbulence model which allows the resolution of the laminar sublayer without wall functions. The numerical predictions of velocity and temperature distributions at certain locations show significant differences to the experimental data in velocity and temperature profiles. It is assumed that this behavior is due to inappropriate modeling of turbulence especially in the effusion hole. Nonetheless, the numerically predicted heat transfer coefficients are in good agreement with the experimental data at low blowing ratios.

Calculation of Disk Temperatures in Gas Turbine Rotor-Stator Cavities Using Conjugate Heat Transfer

2010 ◽  
Author(s):  
Aneesh Sridhar Vadvadgi ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Conjugate Heat Transfer ◽  
Computational Cost ◽  
Disk Surface ◽  
Turbine Rotor ◽  
Transfer Coefficients ◽  
Constant Wall Temperature ◽  
Heat Transfer Coefficients ◽  
Variable Surface

The present study deals with the numerical modeling of the turbulent flow in a rotor-stator cavity with or without imposed through flow with heat transfer. The commercial finite volume based solver, ANSYS/FLUENT is used to numerically simulate the problem. A conjugate heat transfer approach is used. The study specifically deals with the calculation of the heat transfer coefficients and the temperatures at the disk surfaces. Results are compared with data where available. Conventional approaches which use boundary conditions such as constant wall temperature or constant heat flux in order to calculate the heat transfer coefficients which later are used to calculate disk temperatures can introduce significant errors in the results. The conjugate heat transfer approach can resolve this to a good extent. It includes the effect of variable surface temperature on heat transfer coefficients. Further it is easier to specify more realistic boundary conditions in a conjugate approach since solid and the flow heat transfer problems are solved simultaneously. However this approach incurs a higher computational cost. In this study, the configuration chosen is a simple rotor and stator system with a stationary and heated stator and a rotor. The aspect ratio is kept small (around 0.1). The flow and heat transfer characteristics are obtained for a rotational Reynolds number of around 106. The simulation is performed using the Reynolds Stress Model (RSM). The computational model is first validated against experimental data available in the literature. Studies have been carried out to calculate the disk temperatures using conventional non-conjugate and full conjugate approaches. It has been found that the difference between the disk temperatures for conjugate and non-conjugate computations is 5 K for the low temperature and 30 K for the high temperature boundary conditions. These represent differences of 1% and 2% from the respective stator surface temperatures. Even at low temperatures, the Nusselt numbers at the disk surface show a difference of 5% between the conjugate and non-conjugate computations, and far higher at higher temperatures.

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