Numerical Benchmark of Turbulence Modeling in Gas Turbine Rotor-Stator System

2010 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Luca Innocenti ◽  
Antonio Andreini ◽  
Se´bastien Poncet
Keyword(s):  
Gas Turbine ◽  
Boundary Layers ◽  
Correction Term ◽  
Computational Cost ◽  
Turbulence Models ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Curvature Effects ◽  
Low Reynolds ◽  
Secondary Air

Accurate design of the secondary air system is one of the main tasks for reliability and performance of gas turbine engines. The selection of a suitable turbulence model for the study of rotor-stator cavity flows, which remains an open issue in the literature, is here addressed for several operating conditions. A numerical benchmark of turbulence models is indeed proposed in the case of rotor-stator disk flows with and without superimposed throughflow. The predictions obtained by the means of several two equation turbulence models available within the CFD solver Ansys CFX 12.0 are compared with those previously evaluated by Poncet et al. (1; 2) through the Reynolds Stress Model (RSM) of Elena and Schiestel (3; 4) implemented in a proprietary finite volume code. The standard k-ε and k-ω SST models including high and low Reynolds approaches, have been used for all calculations presented here. Furthermore, some tests were performed using the innovative k-ω SST-CC and k-ω SST-RM models that take into account the curvature effects via the Spalart-Shur correction term (5) and the reattachement modification proposed by Menter (6) respectively. The numerical calculations have been compared to extensive velocity and pressure measurements performed on the test rig of the IRPHE’s laboratory in Marseilles (1; 2). Several configurations, covering a large range of real engine operating conditions, were considered. The influence of the typical non dimensional flow parameters (Reynolds number and flowrate coefficient) on the flow structure is studied in detail. In the case of an enclosed cavity, the flow exhibits a Batchelor-like structure with two turbulent boundary layers separated by a laminar rotating core. When an inward axial throughflow is superimposed, the flow remains of Batchelor type with a core rotating faster than the disk because of conservation of the angular momentum. In this case, turbulence intensities are mainly confined close to the stator. Turbulence models based on a low Reynolds approach provide better overall results for the mean and turbulent fields especially within the very thin boundary layers. The standard k-ω SST model offers the best trade-off between accuracy and computational cost for the parameters considered here. In the case of an outward throughflow, the k-ω SST in conjunction with a low Reynolds approach and RSM models provide similar results and predict quite well the transition from the Batchelor to the Stewartson structures.

Experience With Large Heavy-Duty Gas Turbine Rotors

1981 ◽  
Author(s):  
O. R. Schmoch ◽  
B. Deblon
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Rotor ◽  
Strength Properties ◽  
Operating Conditions ◽  
Material Strength ◽  
Heavy Duty ◽  
Turbine Rotors ◽  
Heavy Duty Gas Turbine ◽  
Response To Temperature

The peripheral speeds of the rotors of large heavy-duty gas turbines have reached levels which place extremely high demands on material strength properties. The particular requirements of gas turbine rotors, as a result of the cycle, operating conditions and the ensuing overall concepts, have led different gas turbine manufacturers to produce special structural designs to resolve these problems. In this connection, a report is given here on a gas turbine rotor consisting of separate discs which are held together by a center bolt and mutually centered by radial serrations in a manner permitting expansion and contraction in response to temperature changges. In particular, the experience gained in the manufacture, operation and servicing are discussed.

Principles of Imitation for the Loading of the Test Bench for Gas Turbines of Gas Pumping Units, Adequate to Real Conditions

2021 ◽  
Vol 13 (24) ◽  
pp. 13678
Author(s):  
Anton Petrochenkov ◽  
Aleksandr Romodin ◽  
Vladimir Kazantsev ◽  
Aleksey Sal’nikov ◽  
Sergey Bochkarev ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Simulation Models ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Automation System ◽  
Model Free ◽  
Gas Pumping ◽  
Pumping Units

The purpose of the study is to analyze the prospects for the development of loading methods for gas turbines as well as to develop a mathematical model that adequately describes the real operating conditions of the loading system at various loads and rotation speeds. A comparative analysis of the most common methods and technical means of loading the shafts of a free turbine at gas turbine plants intended for operation as part of gas pumping units is presented. Based on the results of the analysis, the expediency of using the loading model “Free Power Turbine Rotor–Hydraulic Brake” as a load simulation is shown. Recommendations for the creation of an automation system for the load testing of power plants have been developed. Mathematical models and Hardware-in-the-Loop simulation models of power plants have been developed and tested. One of the most important factors that predetermine the effectiveness of the loading principle is the possibility of software implementation of the loading means using software control systems that provide the specified loading parameters of the gas turbine.

Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart–Shur Correction Term

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Pavel E. Smirnov ◽  
Florian R. Menter
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Transport Model ◽  
Correction Term ◽  
Computational Cost ◽  
Turbulence Models ◽  
Reynolds Stress Transport Model ◽  
Wide Range ◽  
Sst Model ◽  
The One

A rotation-curvature correction suggested earlier by Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature,” Aerosp. Sci. Technol., 1(5), pp. 297–302) for the one-equation Spalart–Allmaras turbulence model is adapted to the shear stress transport model. This new version of the model (SST-CC) has been extensively tested on a wide range of both wall-bounded and free shear turbulent flows with system rotation and/or streamline curvature. Predictions of the SST-CC model are compared with available experimental and direct numerical simulations (DNS) data, on the one hand, and with the corresponding results of the original SST model and advanced Reynolds stress transport model (RSM), on the other hand. It is found that in terms of accuracy the proposed model significantly improves the original SST model and is quite competitive with the RSM, whereas its computational cost is significantly less than that of the RSM.

Analysis of Gas Turbine Rotating Cavities by an One-Dimensional Model

2009 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Luca Innocenti ◽  
Mirko Micio
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Design Tool ◽  
Operating Conditions ◽  
Outer Flow ◽  
One Dimensional ◽  
Wide Range ◽  
Air System ◽  
Secondary Air ◽  
Radial Outflow

Reliable design of secondary air system is one of the main tasks for the safety, unfailing and performance of gas turbine engines. To meet the increasing demands of gas turbines design, improved tools in prediction of the secondary air system behavior over a wide range of operating conditions are needed. A real gas turbine secondary air system includes several components, therefore its analysis is not carried out through a complete CFD approach. Usually, that predictions are performed using codes, based on simplified approach which allows to evaluate the flow characteristics in each branch of the air system requiring very poor computational resources and few calculation time. Generally the available simplified commercial packages allow to correctly solve only some of the components of a real air system and often the elements with a more complex flow structure cannot be studied; among such elements, the analysis of rotating cavities is very hard. This paper deals with a design-tool developed at the University of Florence for the simulation of rotating cavities. This simplified in-house code solves the governing equations for steady one-dimensional axysimmetric flow using experimental correlations both to incorporate flow phenomena caused by multidimensional effects, like heat transfer and flow field losses, and to evaluate the circumferential component of velocity. Although this calculation approach does not enable a correct modeling of the turbulent flow within a wheel space cavity, the authors tried to create an accurate model taking into account the effects of inner and outer flow extraction, rotor and stator drag, leakages, injection momentum and, finally, the shroud/rim seal effects on cavity ingestion. The simplified calculation tool was designed to simulate the flow in a rotating cavity with radial outflow both with a Batchelor and/or Stewartson flow structures. A primary 1D-code testing campaign is available in the literature [1]. In the present paper the authors develop, using CFD tools, reliable correlations for both stator and rotor friction coefficients and provide a full 1D-code validation comparing, due to lack of experimental data, the in house design-code predictions with those evaluated by CFD.

Aerodynamic Design and Numerical Investigation on Overall Performance of a Micro Radial Turbine With Millimeter-Scale

2009 ◽  
Author(s):  
Lei Fu ◽  
Yan Shi ◽  
Qinghua Deng ◽  
Zhenping Feng
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Micro Gas Turbine ◽  
Radial Turbine ◽  
Overall Performance ◽  
Low Reynolds ◽  
Exit Mach Number ◽  
Installation Technology

For millimeter-scale microturbines, the principal challenge is to achieve a design scheme to meet the aerothermodynamics, geometry restriction, structural strength and component functionality requirements while in consideration of the applicable materials, realizable manufacturing and installation technology. This paper mainly presents numerical investigations on the aerothermodynamic design, geometrical design and overall performance prediction of a millimeter-scale radial turbine with rotor diameter of 10mm. Four kinds of turbine rotor profiles were designed, and they were compared with one another in order to select the suitable profile for the micro radial turbine. The leaving velocity loss in micro gas turbines was found to be a large source of inefficiency. The approach of refining the geometric structure of rotor blades and the profile of diffuser were adopted to reduce the exit Mach number thus improving the total-static efficiency. Different from general gas turbines, micro gas turbines are operated in low Reynolds numbers, 104∼105, which has significant effect on flow separation, heat transfer and laminar to turbulent flow transition. Based on the selected rotor profile, several micro gas turbine configurations with different tip clearances of 0.1mm, 0.2mm and 0.3mm, respectively; two different isothermal wall conditions; and two laminar-turbulent transition models were investigated to understand the particular influence of low Reynolds number. These influences on the overall performance of the micro gas turbine were analyzed in details. The results indicate that these configurations should be included and emphasized during the design process of the millimeter-scale micro radial turbines.

Heavy Duty Gas Turbine Simulation: Global Performances Estimation and Secondary Air System Modifications

2006 ◽  
Author(s):  
Carlo Carcasci ◽  
Bruno Facchini ◽  
Stefano Gori ◽  
Luca Bozzi ◽  
Stefano Traverso
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Energy System ◽  
Operating Conditions ◽  
Coupled Analysis ◽  
Ambient Conditions ◽  
Air System ◽  
Secondary Air ◽  
And Performance

This paper reviews a modular-structured program ESMS (Energy System Modular Simulation) for the simulation of air-cooled gas turbines cycles, including the calculation of the secondary air system. The program has been tested for the Ansaldo Energia gas turbine V94.3A, which is one of the more advanced models in the family Vx4.3A with a rated power of 270 MW. V94.3A cooling system has been modeled with SASAC (Secondary Air System Ansaldo Code), the Ansaldo code used to predict the structure of the flow through the internal air system. The objective of the work was to investigate the tuning of the analytical program on the basis of the data from design and performance codes in use at Ansaldo Energy Gas Turbine Department. The results, both at base load over different ambient conditions and in critical off-design operating points (full-speed-no-load and minimum-load), have been compared with APC (Ansaldo Performance Code) and confirmed by field data. The coupled analysis of cycle and cooling network shows interesting evaluations for components life estimation and reliability during off-design operating conditions.

Boundary Layer Calculation Including the Prediction of Transition and Curvature Effects

1989 ◽  
Author(s):  
B. Guyon ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Layers ◽  
Convex Surface ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Detailed Knowledge ◽  
Flat Plates ◽  
Transfer Rates ◽  
Curvature Effects

The calculation of surface temperature on gas turbine blades in severe operating conditions requires a detailed knowledge of boundary layers behaviour. The prediction of laminar to turbulent transition as to existence and location, as well as the evaluation of heat transfer rates are major concerns. The program developed by SNECMA for this purpose is presented, in which models are introduced to take into account the main effects occuring on blades without film-cooling. The algorithm and discretisation scheme for boundary layer equations is Patankar and Spalding’s, with profiles initialization by Pohlhausen’s method. The turbulence and transition model, after Mc Donald and Fish, was improved in search for more stability and to have a better detection of the beginning of the transition. Adams and Johnston’s model for curvature, including propagation effects, was adapted to a transitional boundary layer. The validation tests of this program are described, which are based on numerous experimental data taken from a bibliography of tests over flat plates and blades. Other tests use heat transfer rate measurements conducted by SNECMA, together with VKI, on vanes and blades in non-rotating grids. The calculation results are further compared to the STAN5 program results; they show a superiority in predicting the transfer rates on a convex surface and for transitional boundary layers.

Calibration of a Computational Model to Predict Mist/Steam Impinging Jets Cooling With an Application to Gas Turbine Blades

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Ting Wang ◽  
T. S. Dhanasekaran
Keyword(s):  
Gas Turbine ◽  
Working Condition ◽  
Turbulence Models ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Operating Conditions ◽  
Experimental Results ◽  
Cfd Model ◽  
Cooling Enhancement ◽  
Mist Cooling

In heavy-frame advanced turbine systems, steam is used as a coolant for turbine blade cooling. The concept of injecting mist into the impinging jets of steam was experimentally proved as an effective way of significantly enhancing the cooling effectiveness in the laboratory under low pressure and temperature conditions. However, whether or not mist/steam cooling is applicable under actual gas turbine operating conditions is still subject to further verification. Recognizing the difficulties of conducting experiments in an actual high-pressure, high-temperature working gas turbine, a simulation using a computational fluid dynamic (CFD) model calibrated with laboratory data would be an opted approach. To this end, the present study conducts a CFD model calibration against the database of two experimental cases including a slot impinging jet and three rows of staggered impinging jets. The calibrated CFD model was then used to predict the mist cooling enhancement at the elevated gas turbine working condition. Using the experimental results, the CFD model has been tuned by employing different turbulence models, computational cells, and wall y+ values. In addition, the effects of different forces (e.g., drag, thermophoretic, Brownian, and Saffman’s lift force) are also studied. None of the models is a good predictor for all the flow regions from near the stagnation region to far-field downstream of the jets. Overall speaking, both standard k-ε and Reynolds stress model (RSM) turbulence models perform better than other models. The RSM model has produced the closest results to the experimental data due to its capability of modeling the nonisotropic turbulence shear stresses in the 3D impinging jet fields. The simulated results show that the calibrated CFD model can predict the heat transfer coefficient of steam-only case within 2–5% deviations from the experimental results for all the cases. When mist is employed, the prediction of wall temperatures is within 5% for a slot jet and within 10% for three-row jets. The predicted results with 1.5% mist at the gas turbine working condition show the mist cooling enhancement of 20%, whereas in the laboratory condition, the enhancement is predicted as 80%. Increasing mist ratio to 5% increased the cooling enhancement to about 100% at the gas turbine working condition.

Rotor Lifecycle Management Program

2014 ◽  
Author(s):  
Michal Wrobel ◽  
Mark Richter ◽  
Rene Zimmermann ◽  
Holger Kiewel ◽  
Andreas Ullrich
Keyword(s):  
Gas Turbine ◽  
Individual Component ◽  
Operating Regime ◽  
Turbine Rotor ◽  
Management Program ◽  
Operating Conditions ◽  
Actual Condition ◽  
Standard Type ◽  
The Individual ◽  
Lifecycle Management

Minimizing the maintenance costs has become an ever growing topic in the power generation industry. Consequently, OEM’s constantly increase their efforts to exploit the full lifetime potential of capital intensive components, as for instance gas turbine rotors. More than ever, it is essential to have a closed loop from the design knowledge to solid facts about the actual condition of a gas turbine rotor in the field, in order to optimize the utilization and therefore to reduce total lifecycle costs. During initial design an iterative component design process is applied, comprising of analytical calculations and component and engine tests, to design a reliable, robust and maintenance friendly component. Individual component risk profiles (i.e. failure probability and consequences) have to be taken into account during the design phase to cover uncertainties regarding the operating regime, operating conditions and environment, resulting in the minimum expected lifetime. The lifetime of gas turbine components is limited and primarily depends on factors like the operating regime, dictating the mechanical and thermal loads, actual material properties, environmental conditions and the level of maintenance. Those parameters have a scatter and also interact with each other. As a consequence the progress of component degradation varies and the individual component lifetime isn’t known in detail at the time of the design. The purpose of a Rotor Lifecycle Management Program is to detect individual component degradation early in the lifecycle, in order to exploit the maximum rotor lifetime while ensuring safe operation. Periodic monitoring and condition assessment of the individual rotor is the first step, performed during standard type C inspections and comprising of visual inspection, dimensional and advanced non-destructive measurements. Typically the monitoring schedule is based on the operating regime and the operating history of the specific rotor. The combination of the monitoring results with validated analytical design models, extensive material data and the overall gas turbine rotor fleet experience of the OEM, allows proper planning of lifetime extension measures, such as repair and reconditioning activities. Specific repair solutions for both on-site and shop applications have been developed. A rotor lifecycle management program is a „living” program. The monitoring scope and schedule as well as the repair solutions portfolio are continuously optimized and adapted as a result of detailed analysis of operating data and inspection results of the whole global fleet.

Numerical and Experimental Investigation of Secondary Flows and Influence of Air System Design on Heavy-Duty Gas Turbine Performance

2012 ◽  
Author(s):  
Luca Bozzi ◽  
Enrico D’angelo
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Engine Performance ◽  
Combined Cycle ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Heavy Duty ◽  
Turbine Performance ◽  
Air System ◽  
Secondary Air

High turn-down operating of heavy-duty gas turbines in modern Combined Cycle Plants requires a highly efficient secondary air system to ensure the proper supply of cooling and sealing air. Thus, accurate performance prediction of secondary flows in the complete range of operating conditions is crucial. The paper gives an overview of the secondary air system of Ansaldo F-class AEx4.3A gas turbines. Focus of the work is a procedure to calculate the cooling flows, which allows investigating both the interaction between cooled rows and additional secondary flows (sealing and leakage air) and the influence on gas turbine performance. The procedure is based on a fluid-network solver modelling the engine secondary air system. Parametric curves implemented into the network model give the consumption of cooling air of blades and vanes. Performances of blade cooling systems based on different cooling technology are presented. Variations of secondary air flows in function of load and/or ambient conditions are discussed and justified. The effect of secondary air reduction is investigated in details showing the relationship between the position, along the gas path, of the upgrade and the increasing of engine performance. In particular, a section of the paper describes the application of a consistent and straightforward technique, based on an exergy analysis, to estimate the effect of major modifications to the air system on overall engine performance. A set of models for the different factors of cooling loss is presented and sample calculations are used to illustrate the splitting and magnitude of losses. Field data, referred to AE64.3A gas turbine, are used to calibrate the correlation method and to enhance the structure of the lumped-parameters network models.

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