Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part II — Power Turbine Exhaust System

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Don Shaffer ◽  
Graeme Short
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Strain Gauge ◽  
Gas Turbines ◽  
Life Prediction ◽  
Exhaust System ◽  
Back Pressure ◽  
Full Scale ◽  
Power Turbine ◽  
Turbine Exhaust

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to losses from the downstream balance-of-plant systems. Also, gas turbines for mechanical drive application have a wide operating envelope which leads to a fluctuating back pressure that varies with change in exhaust flows. This increased back pressure on the power turbine results in increased exhaust gas temperatures and aerodynamic loading that can influence the mechanical integrity and life of Power Turbine Exhaust System. This Paper discusses the Impact to Fatigue and Creep life of free power turbine exhaust system subjected to high back pressure applications using Siemens Energy approach. Steady state and transient temperature fields were predicted using finite element method. These predictions were validated using full-scale engine test and are found to correlate well with the test results. Full Scale strain gauge survey of the exhaust hood was undertaken at ambient conditions at various pressure levels to validate the structural boundary conditions of lifing models. Strain Predictions were found in good agreement with measured strain gauge data. Steady State and Transient stress fields have been estimated using validated structural and thermal finite element models. Walker Strain Initiation model [1] is utilized to predict Low Cycle Fatigue Life and Larson Miller Parameter Creep Model has been used to estimate creep damage to the exhaust system. The Life Prediction Study shows that the exhaust system design for high back pressure applications meets the product design standards.

Impact of High Exhaust Back Pressure on Power Turbine Secondary Flows and Disc Thermals

2015 ◽  
Author(s):  
Deepak Thirumurthy
Keyword(s):  
Gas Turbines ◽  
Thermal Characteristics ◽  
Cavity Flow ◽  
Back Pressure ◽  
Secondary Flows ◽  
Flow Dynamics ◽  
Test Results ◽  
Power Turbine ◽  
Turbine Disc ◽  
The Impact

Industrial and aeroderivative gas turbines use exhaust systems for flow diffusion and pressure recovery. The downstream balance-of-plant systems such as heat recovery steam generators or selective catalytic systems require, in general, a steady, uniform flow out of the exhaust system. One detrimental effect of having these downstream systems is the increased back pressure. These combined-cycle systems increase the back pressure on the free power turbine which results in decreased power output and efficiency. Aeroderivative gas turbines for mechanical drive application have a wide operational envelope. In general, at baseload, the exhaust back pressure ranges from 1.5 to 2.5 kPa above ambient pressure. Increased exhaust back pressure results in changes to power turbine secondary flows by changing the cavity flow dynamics, sealing flows, and rim seal ingestion. This impacts the thermal characteristics of turbine rotor discs and their lives. The primary motivation for this research and development work was to develop solution for secondary air system and investigate the impact of high exhaust back pressure on power turbine disc thermals. At first, 1-D system-level power turbine secondary flow analyses were carried out with normal back pressure (3.0 kPa) and with high back pressure (11.37 kPa). In addition, 3-D computational fluid dynamic simulations were performed to understand the cavity flow dynamics and disc heat transfer coefficient variations. These results were used in a high-fidelity 2-D thermal modeling of the power turbine to study the impact of back pressure on turbine disc thermal characteristics and their lives. The fluid and thermal predictions were validated using normal back pressure full-scale full-load test results. Cooling mass flow rate, static pressure, air temperature, and metal temperature predictions are compared with test results over a wide operating range. The numerical predictions are in good agreement with test results.

scholarly journals Comparison between 1-D and grey-box models of a SOFC

2019 ◽  
Vol 128 ◽  
pp. 01007
Author(s):  
Ramin Moradi ◽  
Andrea Di Carlo ◽  
Federico Testa ◽  
Luca Del Zotto ◽  
Enrico Bocci ◽  
...  
Keyword(s):  
Power Systems ◽  
Solid Electrolyte ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Box Model ◽  
System Level ◽  
Internal Temperature ◽  
Box Models ◽  
The Impact ◽  
D Model

Solid Oxide Fuel Cells (SOFCs) have shown unique performance in terms of greater electrical efficiency and thermochemical integrity with the power systems compared to gas turbines and internal combustion engines. Nonetheless, simple and reliable models still must be defined. In this paper, a comparisonbetween a grey-box model and a 1-D model of a SOFC is performed to understand the impact of the heat transfer inside the cell on the internal temperature distribution of the solid electrolyte. Hence, a significant internal temperature peak of the solid electrolyte is observed for a known difference between anode and cathode inlet temperatures. Indeed, it highlights the difference between the 1-D model andthe grey-box model regarding the thermal conditioning of the SOFC. Therefore, the results of this study can be used to investigate the reliability of the thermal results of box models in system-level simulations.

Non-Local Cyclic Life Prediction for Gas Turbine Components With Sharply Notched Geometries

2007 ◽  
Author(s):  
Roland Mu¨cke ◽  
Holger Kiewel
Keyword(s):  
Test Data ◽  
Gas Turbines ◽  
Life Prediction ◽  
Stress And Strain ◽  
Rotor Steel ◽  
Cyclic Life ◽  
Stress Strain ◽  
Efficient Operation ◽  
Strain Gradients ◽  
Non Local

The safe and efficient operation of modern heavy duty gas turbines requires a reliable prediction of fatigue behaviour of turbine components. Fatigue damage is located in areas where cyclic stress and strain amplitudes are highest. Thus, geometrical notches associated with stress/strain concentrations and stress/strain gradients appear to be the most important sites for fatigue crack initiation. The paper addresses a non-local concept for fatigue life prediction of notched components. In contrary to various local approaches in the field, the proposed method explicitly accounts for stress and strain gradients associated with notches, cooling holes, fillets and other design features with stress raising effect. As a result, empirical analytical expressions for considering either strain or stress gradients on cyclic life prediction are obtained. The method has been developed from cyclic test data on smooth and notched specimens made of a ferritic 1.5CrNiMo rotor steel. The obtained analytical formulations have then been applied to test data on the Nickel base superalloy MAR-M247 CC showing a good agreement between prediction and measurement. Moreover, the proposed non-local lifing concept has been validated by component tests on turbine blade firtrees. The predicted cycles to failure correlates well to the experimental results showing the applicability of the proposed method to complex engineering designs.

scholarly journals VATEMP: The Variable Area Turbine Engine Matching Program

1990 ◽  
Author(s):  
J. E. A. Roy-Aikins ◽  
J. R. Palmer
Keyword(s):  
Steady State ◽  
Gas Turbines ◽  
Variable Geometry ◽  
Aircraft Engines ◽  
Flow Temperature ◽  
Turbine Engine ◽  
Path Component ◽  
The Impact ◽  
Engine Cycle ◽  
Steady State Performance

Variable geometry in key gas turbine components offers the advantage of either improving the internal performance of a component or of re-matching the engine cycle to alter the flow-temperature-pressure relationships. Future gas turbines are expected to use variable geometry components extensively if they are to overcome some of the problems encountered by present day engines at off-design conditions in order to give much more advanced performance. Greater attention is also being paid to the impact of installation losses on the performance of aircraft engines. A computer program called VATEMP, herein described, has been developed capable of simulating the steady-state performance of arbitrary gas turbines with or without variable geometry in almost any gas path component. Results obtained from the program led to the conclusion that variable geometry components have the potential to improve significantly the off-design performance of gas turbines.

Thermo-Fluid Modelling for Gas Turbines—Part I: Theoretical Foundation and Uncertainty Analysis

2009 ◽  
Author(s):  
Konstantinos G. Kyprianidis ◽  
Vishal Sethi ◽  
Stephen O. T. Ogaji ◽  
Pericles Pilidis ◽  
Riti Singh ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Simulation Software ◽  
System Level ◽  
Fluid Models ◽  
Performance Simulation ◽  
Turbine Performance ◽  
Aircraft System ◽  
The Impact ◽  
Made In

In this two-part publication, various aspects of thermo-fluid modelling for gas turbines are described and their impact on performance calculations and emissions predictions at aircraft system level is assessed. Accurate and reliable fluid modelling is essential for any gas turbine performance simulation software as it provides a robust foundation for building advanced multi-disciplinary modelling capabilities. Caloric properties for generic and semi-generic gas turbine performance simulation codes can be calculated at various levels of fidelity; selection of the fidelity level is dependent upon the objectives of the simulation and execution time constraints. However, rigorous fluid modelling may not necessarily improve performance simulation accuracy unless all modelling assumptions and sources of uncertainty are aligned to the same level. Certain modelling aspects such as the introduction of chemical kinetics, and dissociation effects, may reduce computational speed and this is of significant importance for radical space exploration and novel propulsion cycle assessment. This paper describes and compares fluid models, based on different levels of fidelity, which have been developed for an industry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles. The latter comprises the following modules: engine performance, aircraft performance, emissions prediction, and environmental impact. The work presented aims to fill the current literature gap by: (i) investigating the common assumptions made in thermo-fluid modelling for gas turbines and their effect on caloric properties and (ii) assessing the impact of uncertainties on performance calculations and emissions predictions at aircraft system level. In Part I of this two-part publication, a comprehensive analysis of thermo-fluid modelling for gas turbines is presented and the fluid models developed are discussed in detail. Common technical models, used for calculating caloric properties, are compared while typical assumptions made in fluid modelling, and the uncertainties induced, are examined. Several analyses, which demonstrate the effects of composition, temperature and pressure on caloric properties of working mediums for gas turbines, are presented. The working mediums examined include dry air and combustion products for various fuels and H/C ratios. The errors induced by ignoring dissociation effects are also discussed.

Crack FEA of the First Stage Blade of Gas Turbines

2010 ◽  
Vol 450 ◽  
pp. 429-432
Author(s):  
Ping Zhao ◽  
Wei Li ◽  
Qing Hua He
Keyword(s):  
Gas Turbines ◽  
Life Prediction ◽  
Crack Nucleation ◽  
Creep Damage ◽  
Nucleation And Growth ◽  
Prediction System ◽  
Edge Region ◽  
Element Analysis ◽  
Fatigue Crack Nucleation ◽  
Crack Nucleation And Growth

To investigate the physical cause of premature blade cracking during the acceleration mission test (AMT) in a test cell environment, an in-depth finite element analysis (FEA) of the blade was conducted using a life prediction system. The results obtained showed that the blades had suffered excessive airfoil creep damage, leading to excessive blade lengthening and airfoil untwisting particularly in the trailing edge region. It is predicted that the uneven rubbing action might have contributed to the fatigue crack nucleation and growth process just below the platform in the shank region of the blade under AMT fatigue cycling conditions, and the excessive creep deformation made a significant effect on the overall crack nucleation process.

Nonlocal Cyclic Life Prediction for Gas Turbine Components With Sharply Notched Geometries

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Roland Mücke ◽  
Holger Kiewel
Keyword(s):  
Test Data ◽  
Gas Turbines ◽  
Life Prediction ◽  
Fatigue Crack Initiation ◽  
Stress And Strain ◽  
Rotor Steel ◽  
Cyclic Life ◽  
Stress Strain ◽  
Efficient Operation ◽  
Strain Gradients

The safe and efficient operation of modern heavy duty gas turbines requires a reliable prediction of fatigue behavior of turbine components. Fatigue damage is located in areas where cyclic stress and strain amplitudes are highest. Thus, geometrical notches associated with stress/strain concentrations and stress/strain gradients appear to be the most important sites for fatigue crack initiation. The paper addresses a nonlocal concept for cyclic life prediction of notched components. Contrary to various local approaches in the field, the proposed method explicitly accounts for stress and strain gradients associated with notches arising from grooves, cooling holes, fillets, and other design features with stress raising effect. As a result, empirical analytical expressions for considering either strain or stress gradients for cyclic life prediction are obtained. The method has been developed from cyclic test data on smooth and notched specimens made of a ferritic 1.5CrNiMo rotor steel. The analytical formulations obtained have then been applied to test data on the nickel base superalloy MAR-M247 CC showing a good agreement between prediction and measurement. Moreover, the proposed nonlocal lifing concept has been validated by component tests on turbine blade firtrees. The predicted number of cycles to failure correlates well with the experimental results showing the applicability of the proposed method to complex engineering designs.

Performance of a Turboshaft Engine for Helicopter Applications Operating at Variable Shaft Speed

2012 ◽  
Author(s):  
Gianluigi Alberto Misté ◽  
Ernesto Benini
Keyword(s):  
Steady State ◽  
Engine Performance ◽  
Engine Fuel ◽  
Main Rotor ◽  
Steady State Condition ◽  
Power Turbine ◽  
Steady State Model ◽  
Optimization Routine ◽  
Turboshaft Engine ◽  
The Impact

An off-design steady state model of a generic turboshaft engine has been implemented to assess the influence of variable free power turbine (FPT) rotational speed on overall engine performance, with particular emphasis on helicopter applications. To this purpose, three off-design flight conditions were simulated and engine performance obtained with different FTP rotational speeds were compared. In this way, the impact on engine performance of a particular speed requested from the main helicopter rotor could be evaluated. Furthermore, an optimization routine was developed to find the optimal FPT speed which minimizes the engine specific fuel consumption (SFC) for each off-design steady state condition. The usual running line obtained with constant design FPT speed is compared with the optimized one. The results of the simulations are presented and discussed in detail. As a final simulation, the main rotor speed Ω required to minimize the engine fuel mass flow was estimated taking into account the different requirements of the main rotor and the turboshaft engine.

Operational Mode Monitoring of Gas Turbines in an Offshore Gas-Gathering Application

1984 ◽  
Vol 106 (4) ◽  
pp. 940-945
Author(s):  
D. F. Toler ◽  
R. N. Yorio
Keyword(s):  
Gas Turbines ◽  
Life Prediction ◽  
Computer Assisted ◽  
Operational Mode ◽  
Structural Components ◽  
Power Turbine ◽  
Operating Load ◽  
Testing Techniques ◽  
Prediction Techniques ◽  
Life Predictions

A computer-assisted monitoring system has been implemented on GT-61 Gas Turbines employed in offshore gas gathering. Operating load data are continuously recorded at the site and evaluated at the turbine manufacturer’s plant on a mainframe computer, where existing analysis and testing techniques are utilized to predict the service fatigue lives of the power turbine structural components. The data acquisition hardware, the data reduction software, and the life prediction techniques are each described. The data collected indicate that offshore gas gathering equipment will experience many more operating load cycles than comparable equipment in pipeline service. The fatigue life predictions reaffirm the suitability of the GT-61 for this more severe service.

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