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.

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.

Flow Interactions Between Shrouded Power Turbine and Nonaxisymmetric Exhaust Volute for Marine Gas Turbines

2017 ◽  
Author(s):  
Jie Gao ◽  
Feng Lin ◽  
Xiying Niu ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Rotor Blade ◽  
Exhaust System ◽  
Computational Domain ◽  
Local Flow ◽  
Power Turbine ◽  
Flow Interactions ◽  
Shrouded Rotor ◽  
Turbine Exhaust

The marine gas turbine exhaust volute is an important component that connects a power turbine and an exhaust system, and it is of great importance to the overall performance of the gas turbine. Gases exhausted from the power turbine are expanded and deflected 90 degrees in the exhaust volute, and then discharge radially into the exhaust system. The flows in the power turbine and the nonaxisymmetric exhaust volute are closely coupled and inherently unsteady. The flow interactions between the power turbine and the exhaust volute have a significant influence on the shrouded rotor blade aerodynamic forces. However, the interactions have not been taken into account properly in current power turbine design approaches. The present study aims to investigate the flow interactions between the last stage of a shrouded power turbine and the nonaxisymmetric exhaust volute with struts. Special attention is given to the coupled aerodynamics and pressure response studies. This work was carried out using coupled computational fluid dynamics (CFD) simulations with the computational domain including a stator vane, 76 shrouded rotor blades, 9 struts and an exhaust volute. Three-dimensional (3D) unsteady and steady Reynolds-averaged Navier-Stokes (RANS) solutions in conjunction with a Spalart-Allmaras turbulence model are utilized to investigate the aerodynamic characteristics of shrouded rotors and an exhaust volute using a commercial CFD software ANSYS Fluent 14.0. The asymmetric flow fields are analyzed in detail; as are the unsteady pressures on the shrouded rotor blade. In addition, the unsteady total pressures at the volute outlet is also analyzed without consideration of the upstream turbine effects. Results show that the flows in the nonaxisymmetric exhaust volute are inherently unsteady; for the studied turbine-exhaust configuration the nonaxisymmetric back-pressure induced by the downstream volute leads to the local flow varying for each shrouded blade and low frequency fluctuations in the blade force. Detailed results from this investigation are presented and discussed in this paper.

Flow Guiding and Distributing Devices on the Exhaust Side of Stationary Gas Turbines

1990 ◽  
Vol 112 (1) ◽  
pp. 80-85
Author(s):  
F. Fleischer ◽  
C. Koerner ◽  
J. Mann
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Gas Flow ◽  
Flow Simulation ◽  
Exhaust System ◽  
Flow Distribution ◽  
Scale Model ◽  
Gas Turbine Exhaust ◽  
First Time ◽  
Turbine Exhaust

Following repeated cases of damage caused to exhaust silencers located directly beyond gas turbine diffusers, this paper reports on investigations carried out to determine possible remedies. In all instances, an uneven exhaust gas flow distribution was found. The company’s innovative approach to the problem involved constructing a scale model of a complete gas turbine exhaust system and using it for flow simulation purposes. It was established for the first time that, subject to certain conditions, the results of tests conducted on a model can be applied to the actual turbine exhaust system. It is shown that when an unfavorable duct arrangement might produce an uneven exhaust flow, scale models are useful in the development of suitable flow-distributing devices.

The Reduction of Low Frequency Gas Turbine Exhaust Noise: A Case Study

1996 ◽  
Author(s):  
William C. Lucas ◽  
George F. Hessler
Keyword(s):  
Gas Turbines ◽  
Low Frequency ◽  
Development Program ◽  
Exhaust System ◽  
Field Testing ◽  
Frequency Noise ◽  
Airborne Noise ◽  
Exhaust Noise ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

A well reported, industry-wide problem with simple cycle peaking gas turbines installed near residences is excessive low frequency airborne noise, sometimes termed “infrasound.” If the noise level is high enough, it can cause perceptible vibration of windows and frame buildings, and provoke an adverse response from the community. Such a situation recently occurred after construction of a four unit GT 11N1 peaking station. A team of specialists and outside consultants was formed to investigate the problem, and a development program found that a thick absorber could be effective against infrasound. This led to the design of a thick panel absorber which was installed at the rear of a 90 degree turn in the exhaust system. Field testing verified that the low frequency noise from the turbine exhaust was reduced by 5.9 and 6.7 dB in the 31.5 and 63 Hz octave bands respectively, and by 5.5 dB(C) overall.

Squeeze film dampers supporting high-speed rotors: Rotordynamics

2020 ◽  
pp. 135065012092208
Author(s):  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Gas Turbines ◽  
High Speed ◽  
Squeeze Film ◽  
Jet Engines ◽  
Transient Vibration ◽  
Element Analysis ◽  
Squeeze Film Damper ◽  
The Time Domain

This work develops a finite element based multi-mass flexible rotor model for theoretical investigation of the influence of the squeeze film damper lubricant inertia on the unbalance-induced steady-state and transient vibration amplitudes of high speed turbomachinery. The rotordynamic model is developed by applying the principles of finite element analysis to discretize the rotor components, including the rotor shaft and disk, into local elements with mass, stiffness, and gyroscopic matrices. Subsequently, the local matrices are assembled together to develop the global model of the rotordynamic system. The influence of squeeze film damper lubricant inertia is incorporated into the model by using short-length cavitated damper models with retaining springs executing circular-centered orbits. Additionally, the rotordynamic model incorporating the nonlinear squeeze film damper models is iteratively solved in the time domain by applying a predictor-corrector transient modal integration numerical method and the steady-state and transient motions of the rotor system are investigated under different rotor and squeeze film damper parameters. The results of the study verify the substantial influence of squeeze film damper lubricant inertia on attenuating the vibrations of high-speed turbomachinery. Furthermore, the developed rotordynamic model delivers an efficient and powerful platform for the analysis of high-speed turbomachinery, including jet engines and gas turbines.

Investigations of Influential Factors on the Aerodynamic Performance of a Steam Turbine Exhaust System

2010 ◽  
Author(s):  
Jing-Lun Fu ◽  
Jian-Jun Liu
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Full Scale ◽  
Small Scale ◽  
Flow Angle ◽  
Fluid Properties ◽  
Turbine Exhaust ◽  
Exhaust Systems

The purpose of this paper is to investigate the influences of different parameters on the three-dimensional flow fields in the low-pressure steam turbine exhaust hood of a typical power station. The complex flows in both small-scale and full-scale turbine exhaust systems under different inlet flow conditions were simulated. The effects of inlet Reynolds number, inlet Mach number and fluid properties on the aerodynamic performance and flow fields in the exhaust systems were analyzed. The influential rules of inlet tangential flow angle distributions in the radial direction for a low speed small-scale model and a full speed full-scale exhaust system were summarized and compared. It is found that the inlet tangential flow angle at different radial position has different effects on the aerodynamic performance for both small-scale and full-scale exhaust systems. The influences of inlet Reynolds number on the aerodynamic performance depend on the inflow swirl conditions. The changing of inlet Mach number leads to the flow pattern variations in the exhaust system. The influences of fluid properties on the exhaust system performance are small.

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.

scholarly journals Gas Turbine Exhaust Systems: Design Considerations

1987 ◽  
Author(s):  
Roy A. Morris
Keyword(s):  
Gas Turbine ◽  
Systems Design ◽  
Exhaust System ◽  
Cost Savings ◽  
Operating Life ◽  
Power Turbine ◽  
Additional Input ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

The users of Gas Turbine powered equipment are very careful to ensure that they achieve their objectives in terms of power output and overall efficiency, but other important aspects of the system may be underspecified, and cause the user serviceability and maintenance problems during the systems planned operating life. One important area, crucial to reliable operation of the Gas Turbine, is the power turbine exhaust system. If particular care is not taken on the part of the user in specifying this component, he is likely to be provided with the minimum standard of equipment from the supplier. This paper highlights some of the areas that should be considered during the preparation of specifications, and in the evaluation of proposals. Specific problems of exhaust design will be addressed to assist the user to identify and question possible problem areas. The paper concludes that for minimal additional input during the initial stages of a project, long term cost savings could be made and that the overall system would be more reliable.

Applying CAx Technology for the Design of a Gas Turbine Exhaust

2003 ◽  
Author(s):  
L. Itter ◽  
M. Cagna ◽  
A. Wiedermann ◽  
M. Boehle
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Complex Geometry ◽  
Exhaust System ◽  
Cad System ◽  
Leading Role ◽  
Market Requirements ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

Today’s market for gas turbines is getting bigger since there is a huge demand for power generation and mechanical drive applications. To meet the market requirements gas turbine components have to be very efficient to play a leading role. In order to accelerate component improvement the introduction of integrated CAx Technology is a key to achieve a less time-consuming and therefore cheaper design. This paper will describe a procedure which can be used to design an exhaust system for gas turbines with hot-end drive. It shows how to combine various technologies like CAD and CFD and make them work together rapidly. Firstly a 1D design is done and compared with a performance chart of conventional use. Then, a 2D parametric study of a 90 degree bend will be performed by the combination of a CAD-system and a CFD-solver. Thirdly a full 3D-simulation of the entire exhaust will be performed with a calibrated solver. Different complex geometry modifications are applied and their influence on the performance of the exhaust will be discussed.

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.

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