Probabilistic Life Assessment of Turbine Vanes

2011 ◽  
Author(s):  
Alexander N. Arkhipov ◽  
Yevgeny E. Krasnovskiy ◽  
Igor V. Putchkov
Keyword(s):  
Mechanical Properties ◽  
Gas Turbine ◽  
Material Properties ◽  
Field Data ◽  
Life Assessment ◽  
Creep Life ◽  
Thermal Boundary Conditions ◽  
Life Distributions ◽  
Manufacturing Tolerances ◽  
Life Analysis

Life of a gas turbine vane generally depends on different factors such as scatter of material properties, load variation and manufacturing tolerances. However, deterministic finite element (FE) life analysis gives just a discrete value typically based on the nominal or worst case conditions. It precludes considering sensitivity to the input parameters and obtaining the expected life range. To consider the possible variations of the input parameters from their nominal values, a probabilistic approach has been applied to compute the LCF (Low Cyclic Fatigue) and creep life distributions for the uncooled vane. The deterministic 3D FE life assessment of the gas turbine components is based on the input data such as physical and mechanical properties of the base material and coating at operating temperatures, nominal geometry of the component, thermal and mechanical loadings. Each of the above mentioned inputs has its own scatter band characterized either by average and minimum values of mechanical properties (tensile strength, LCF, creep) or by variations of manufacturing tolerances; thermal boundary conditions and gas pressure distribution. The probabilistic life analysis has been performed in order to assess individual impact of each input on vane’s life scatter. LCF and creep life distributions as well as variation of the base metal oxidation layer thickness have been obtained for each scatter factor and for their overall contribution. It is seen from results that LCF and creep lives of the analyzed vane have been influenced mainly by material properties and secondarily by OTDF (hot gas temperature variation in the circumferential direction) and uncertainties of thermal boundary conditions, which depended on the operation conditions of the engine. Manufacturing tolerances and alternation of ambient air temperature in the compressor intake have the lowest impact. The derived model is useful for the risk analysis or maintenance planning. For instance, it has been shown how probability of small fatigue crack indication in one vane can be extended onto the overall probability for the failure detection of n vanes at the stator stage during regular inspection. The probability of micro crack growth due to creep after the determined amount of operating hours for the single vane may be also redefined into the overall stage probability for the detection of n such vanes. To perform validation, normalized field data have been used for comparison with the analytical predictions. Good correlations between the field data and analytical predictions have been shown.

Life assessment of a high temperature probe designed for performance evaluation and health monitoring of an aero gas turbine engine

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Benny George ◽  
Nagalingam Muthuveerappan
Keyword(s):  
Performance Evaluation ◽  
Gas Turbine ◽  
Health Monitoring ◽  
Gas Turbine Engine ◽  
Life Assessment ◽  
Exhaust Gas ◽  
Cycle Fatigue ◽  
Creep Life ◽  
Turbine Engine ◽  
Engine Components

AbstractTemperature probes of different designs were widely used in aero gas turbine engines for measurement of air and gas temperatures at various locations starting from inlet of fan to exhaust gas from the nozzle. Exhaust Gas Temperature (EGT) downstream of low pressure turbine is one of the key parameters in performance evaluation and digital engine control. The paper presents a holistic approach towards life assessment of a high temperature probe housing thermocouple sensors designed to measure EGT in an aero gas turbine engine. Stress and vibration analysis were carried out from mechanical integrity point of view and the same was evaluated in rig and on the engine. Application of 500 g load concept to clear the probe design was evolved. The design showed strength margin of more than 20% in terms of stress and vibratory loads. Coffin Manson criteria, Larsen Miller Parameter (LMP) were used to assess the Low Cycle Fatigue (LCF) and creep life while Goodman criteria was used to assess High Cycle Fatigue (HCF) margin. LCF and HCF are fatigue related damage from high frequency vibrations of engine components and from ground-air-ground engine cycles (zero-max-zero) respectively and both are of critical importance for ensuring structural integrity of engine components. The life estimation showed LCF life of more than 4000 mission reference cycles, infinite HCF life and well above 2000 h of creep life. This work had become an integral part of the health monitoring, performance evaluation as well as control system of the aero gas turbine engine.

Life assessment of a high temperature probe designed for performance evaluation and health monitoring of an aero gas turbine engine

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Benny George ◽  
Nagalingam Muthuveerappan
Keyword(s):  
Performance Evaluation ◽  
Gas Turbine ◽  
Health Monitoring ◽  
Gas Turbine Engine ◽  
Life Assessment ◽  
Exhaust Gas ◽  
Cycle Fatigue ◽  
Creep Life ◽  
Turbine Engine ◽  
Engine Components

Abstract Temperature probes of different designs were widely used in aero gas turbine engines for measurement of air and gas temperatures at various locations starting from inlet of fan to exhaust gas from the nozzle. Exhaust Gas Temperature (EGT) downstream of low pressure turbine is one of the key parameters in performance evaluation and digital engine control. The paper presents a holistic approach towards life assessment of a high temperature probe housing thermocouple sensors designed to measure EGT in an aero gas turbine engine. Stress and vibration analysis were carried out from mechanical integrity point of view and the same was evaluated in rig and on the engine. Application of 500 g load concept to clear the probe design was evolved. The design showed strength margin of more than 20% in terms of stress and vibratory loads. Coffin Manson criteria, Larsen Miller Parameter (LMP) were used to assess the Low Cycle Fatigue (LCF) and creep life while Goodman criteria was used to assess High Cycle Fatigue (HCF) margin. LCF and HCF are fatigue related damage from high frequency vibrations of engine components and from ground-air-ground engine cycles (zero-max-zero) respectively and both are of critical importance for ensuring structural integrity of engine components. The life estimation showed LCF life of more than 4000 mission reference cycles, infinite HCF life and well above 2000 h of creep life. This work had become an integral part of the health monitoring, performance evaluation as well as control system of the aero gas turbine engine.

scholarly journals Influence of thermal-varying material properties on stress calculation for creep life assessment of seamless medium-carbon steel boiler tubes

2020 ◽  
Vol 844 ◽  
pp. 012029
Author(s):  
L M Castellanos-González ◽  
H Hernández Herrera ◽  
R Goytisolo Espinosa ◽  
L M Castellanos Molina ◽  
E E Vergara Verbel ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Material Properties ◽  
Medium Carbon Steel ◽  
Life Assessment ◽  
Creep Life ◽  
Medium Carbon ◽  
Stress Calculation ◽  
Boiler Tubes ◽  
Creep Life Assessment ◽  
Steel Boiler

Life Assessment of Gas Turbine Blades Under Creep Failure Mechanism Considering Humidity

2018 ◽  
Author(s):  
Bita Soltan Mohammad Lou ◽  
Mohammad Pourgol-Mohammad ◽  
Mojtaba Yazdani
Keyword(s):  
Gas Turbine ◽  
Failure Mechanism ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Prediction Models ◽  
Turbine Blades ◽  
Life Assessment ◽  
Creep Life ◽  
Creep Failure ◽  
Design Assessment

Gas turbines are the most important components in thermal power plants, and these components such as turbine has been studied carefully. Gas turbine components operate predominantly under elevated temperature and high stress, and consequently gradual deformation becomes temporally inevitable. In turbine blades, creep is common failure mechanism, and it is an important factor for design assessment. The gas turbine blade is a component operating at high elevated temperatures, requiring a cooling systems to reduce the temperature. Common power enhancement approach is to spray water into compressor, and it is how humidity becomes an important factor in creep failure mechanism. The humidity variability results in temperature level change during the turbine operation, potentially affecting the blades creep life. In this paper, first different creep life prediction models were classified, and then a new model is proposed for creep life considering humidity based on Arrhenius equation. In our study, failure criterion is rupture. As a case study, the creep life of Nimonic-90 alloy turbine blade was predicted using proposed method and compared with FEA results which collected by literature surveys. Proposed model is capable of predicting creep life with only knowing dry temperature (WAR = 0), and there is no need to measure blade temperature variation during operation. The influence of humidity (%WAR) were studied on turbine blades creep life, and results show that creep life of turbine blade increase with increasing humidity percentage.

A Case Study on the Effect of Peaked Pipe Welds on Piping Life Expectancy

2010 ◽  
Author(s):  
Warren Brown ◽  
Martin Prager ◽  
Sarah Wrobel
Keyword(s):  
Material Properties ◽  
Life Assessment ◽  
Piping System ◽  
Creep Life ◽  
Element Analysis ◽  
Omega Method ◽  
Detailed Assessment ◽  
Creep Life Assessment ◽  
Pipe Geometry

This paper details a case study on the effect of weld peak geometry on the expected creep life of a piping system operating in a refining environment. Inspection of the 1-1/4 Cr piping system revealed significant peaked geometry at the longitudinal weld locations. A Finite Element Analysis (FEA) assessment of the remaining life was made using the Omega method of creep life assessment. The sensitivity of the results to modeled pipe geometry and assumed material properties was assessed. The variability of life prediction that was obtained indicated a necessity to perform further more detailed assessment of the pipe geometry and material properties by the removal of samples at the weld locations. The improvement obtained in the assessment accuracy and final life predictions from the sample analysis is presented in the paper and practical implications on the operation of the piping system are detailed. Suggestions and cautions for the practical assessment of similar peaked pipe problems are also discussed.

Residual Life Assessment of In-Service High Temperature Components by Small Punch Creep Test

2007 ◽  
Author(s):  
Jianhua Shan ◽  
Xiang Ling ◽  
Zhenmai Qian
Keyword(s):  
High Temperature ◽  
Residual Life ◽  
Assessment Method ◽  
Life Assessment ◽  
Analysis Method ◽  
Creep Life ◽  
Uniaxial Creep ◽  
Life Analysis ◽  
High Temperature Components ◽  
Residual Life Assessment

The knowledge of mechanical long term behaviour under static loading for high temperature components requires methodologies for residual life assessment in order to employ the full potential of materials, particularly in non-destructive methods. In this paper, in order to apply small punch creep (SPC) test to the residual creep life assessment of in-service high temperature components, a variety of SPC tests for Cr5Mo steel in a protective Argon atmosphere were carried out, which used disc test specimens of 10mm in diameter and 0.5mm in thickness extracted both new material and in-service high temperature components. The relationship of the creep deflection curve, the test load, rupture time and ductility of miniature specimens were investigated. Based on SPC test and finite element numerical analysis methods, a novel residual life assessment method was proposed to substitute conventional uniaxial creep life analysis method by introducing an initial creep damage parameter. Moreover, the fractographic observation and the structural damage detection analysis were examined. Finally, the results using conventional uniaxial creep life analysis method were studied to validate the reliability of SPC life assessment method.

The Influence of Humidity on the Creep Life of a High Pressure Gas Turbine Blade: Part II—Case Study

2012 ◽  
Author(s):  
S. Eshati ◽  
P. Laskaridis ◽  
A. Haslam ◽  
P. Pilidis
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Life Assessment ◽  
Coolant Temperature ◽  
Creep Life

The determination of the rate of heat transfer from the turbine blade in a cross flow is important in hot section gas turbine life assessment. For design purposes, the rate of heat transfer is normally fixed by semi-empirical correlations. These correlations require knowledge of fluid properties which depend on temperature. For gases these properties are normally available only for the dry state, thus the possible effect of the water vapour content has been overlooked. Many gas turbines operate in environments in which air humidity is very low and therefore has little influence on gas turbine performance. However humidity becomes more important in hot, humid climates where there are large variations in ambient absolute humidity, especially in hot and humid climates. The aim of this paper is to investigate and present the effect of humidity at different operating conditions on the turbine blade coolant heat transfer and blade creep life. The effect of humidity was considered only on the air coolant side. he The heat transfer coefficient on the hot side was calculated for dry hot gas. This avoided the balancing effect of each other (heat transfer coefficient coolant side and hot side). The WAR at each operating point is quantified based on the ambient temperature and the relative humidity (0%–100%). Results showed that with increasing WAR the blade inlet coolant temperature reduced along the blade span. The blade metal temperature at each section was reduced as WAR increased, which in turn increased the blade creep life. The increase in WAR increased the specific heat of the coolant and increased the heat transfer capacity of the coolant air flow. Different operating points were also evaluated at different WAR and Tamb to identify the effect of WAR on the creep life. The results showed that an increase in WAR increased the blade creep life. The creep life of the blade at each section of interest was obtained as a function of the blade section stress and the blade metal section temperature using the LMP approach.

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