Low-Cycle Fatigue Lifetime Estimation and Predictive Maintenance for a Gas Turbine Compressor Vane Carrier under Varying Operating Conditions

2021 ◽  
pp. 1-47
Author(s):  
Zixi Han ◽  
Zixian Jiang ◽  
Sophie Ehrt ◽  
Mian Li
Keyword(s):  
Gas Turbine ◽  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Predictive Maintenance ◽  
Cycle Fatigue ◽  
Operating Cycle ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Gas Turbine Compressor ◽  
Operational Data

Abstract In the age of Industry 4.0, the capability of health management is critical to the design and maintenance of gas turbines. This work presents a probabilistic method to estimate the low-cycle fatigue (LCF) life of a gas turbine compressor vane carrier (CVC) under varying operating conditions. Sensitivity analysis based on finite element analysis (FEA) indicates that an operating cycle can be characterized by three predominant contributors to the LCF damage of the CVC among multiple parameters of an operating cycle. Two surrogate models mapping these three features to equivalent stresses are then built for fast computation of the LCF damage. Miner's rule is applied in a probabilistic way to calculate the distribution of accumulated LCF damage over varying operating cycles. Finally, the probabilistic LCF life of the CVC is assessed using real operational data. The proposed approach includes two novel solutions: 1) a new data processing technique inspired by the cumulative sum (CUSUM) control chart to identify the first ramp-up period as well as the shutdown period of each cycle from noisy operational data; 2) the sequential convolution strategy adapted from Miner's rule to compute the probability distribution of accumulated LCF damage (and hence LCF life) from the single-cycle damage distribution, and an approximative quick estimation method to reduce computational expense. Both the offline application for design and online implementation for predictive maintenance show that the expected LCF life at a critical location of the CVC is significantly longer than the deterministically assessed life.

Quantification of Low-Cycle Fatigue Life for a Gas Turbine Compressor Vane Carrier Under Varying Operating Conditions

2020 ◽  
Author(s):  
Zixi Han ◽  
Zixian Jiang ◽  
Sophie Ehrt ◽  
Mian Li
Keyword(s):  
Low Cycle Fatigue ◽  
Computational Cost ◽  
Mass Function ◽  
Operating Conditions ◽  
Probability Mass Function ◽  
Assessment Approach ◽  
Probability Mass ◽  
Gas Turbine Compressor ◽  
Operating Cycles ◽  
Operational Data

Abstract The design of a gas turbine compressor vane carrier (CVC) should meet mechanical integrity requirements on, among others, low-cycle fatigue (LCF). The number of cycles to the LCF failure is the result of cyclic mechanical and thermal strain effects caused by operating conditions on the components. The conventional LCF assessment is usually based on the assumption on standard operating cycles — supplemented by the consideration of predefined extreme operations and safety factors to compensate a potential underestimate on the LCF damage caused by multiple reasons such as non-standard operating cycles. However, real operating cycles can vary significantly from those standard ones considered in the conventional methods. The conventional prediction of LCF life can be very different from real cases, due to the included safety margins. This work presents a probabilistic method to estimate the distributions of the LCF life under varying operating conditions using operational fleet data. Finite element analysis (FEA) results indicate that the first ramp-up loading in each cycle and the turning time before hot-restart cycles are two predominant contributors to the LCF damage. A surrogate model of LCF damage has been built with regard to these two features to reduce the computational cost of FEA. Miner’s rule is applied to calculate the accumulated LCF damage on the component and then obtain the LCF life. The proposed LCF assessment approach has two special points. First, a new data processing technique inspired by the cumulative sum (CUSUM) control chart is proposed to identify the first ramp-up period of each cycle from noised operational data. Second, the probability mass function of the LCF life for a CVC is estimated using the sequential convolution of the single-cycle damage distribution obtained from operational data. The result from the proposed method shows that the mean value of the LCF life at a critical location of the CVC is significantly larger than the calculated result from the deterministic assessment, and the LCF lives for different gas turbines of the same class are also very different. Finally, to avoid high computational cost of sequential convolution, a quick approximation approach for the probability mass function of the LCF life is given. With the capability of dealing with varying operating conditions and noises in the operational data, the enhanced LCF assessment approach proposed in this work provides a probabilistic reference both for reliability analysis in CVC design, and for predictive maintenance in after-sales service.

Advanced Models for Fatigue Life Estimation of Combustor Components for Gas Turbine Application

2019 ◽  
Author(s):  
Dileep Sivarama Iyer ◽  
Nikhil Chandran Pillai
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Multiaxial Fatigue ◽  
Universal Method ◽  
Cycle Fatigue ◽  
Operating Cycle ◽  
Experimental Values

Abstract Modern day combustors operate at very high temperatures which are close to combustor material softening temperatures. At the same time, to meet stringent emission legislations there is a strong drive to improve upon the rich burn combustor technology or shift to advanced lean burn combustor technologies. One of the key driver to improve emission is to save the cooling air budget and use the saved air for primary combustion but this approach would require more advanced and efficient cooling techniques. Fan shaped effusion cooling technology is a very promising technique as it offers high film cooling effectiveness. However, complex cooling features associated with this technology can lead to higher stress concertation and localized triaxial stress state. This stressstrain field in combination with a typical gas turbine engine operating cycle makes such effusion holes highly vulnerable to the thermo-mechanical fatigue failure. Hence to ensure the safety and reliability of combustor liners with such innovative features, it is essential to have thorough understanding of the stress-strain field in the vicinity and accurate prediction of life to first crack. The biggest challenge the designers and engineers face while predicting the initiation life of a structure is selecting the appropriate fatigue damage model for an application. This is due to following reasons: (a) The scatter in fatigue life predicted using different models and experimental values are very huge (b) There is no general universal method which can predict the multiaxial fatigue life accurately for all the materials and loading conditions (c) No general consensus exits among the researchers on which model have to be used for a particular application, material, loading and geometry (d) Application level studies are seldom available on this subject, most of the studies are restricted to laboratory level specimens with very limited implications to industry. Ideally, the fatigue damage model which has to be used for a particular application has to be validated through experiments. To meet this objective, several test specimens featuring novel fan shaped hole geometries were mass-produced using state of the art laser drilling technology. All these specimens were subjected to strain controlled isothermal low cycle fatigue test and the cycles to crack initiation was monitored using potential drop method. Six different multiaxial fatigue damage models (which can be used in low cycle fatigue regime) viz. Walker model, Smith Watson and Topper model (SWT), Fatemi Socie model (FS), Wang and Brown model (WB), Shang model (SW) and Xu model were selected and the life estimated by these models were compared with the experimental values. From the study it is observed that Xu model in which the damage parameter is built using the concept of shear strain energy looks most promising for this application.

Correlations among growth law of small cracks, low-cycle fatigue law and applicability of miner's rule

1983 ◽  
Vol 18 (5) ◽  
pp. 909-924 ◽  
Author(s):  
Y. Murakami ◽  
S. Harada ◽  
T. Endo ◽  
H. Tani-Ishi ◽  
Y. Fukushima
Keyword(s):  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Miner’S Rule ◽  
Small Cracks ◽  
Miner's Rule

Design of Heat Shield for Compressor Case of Industrial Gas Turbine to Meet Clearance Requirement

2020 ◽  
Author(s):  
Prashant Malavade ◽  
Santhana G. Babu ◽  
Luca Frosini ◽  
Simone Marchetti
Keyword(s):  
Gas Turbine ◽  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Heat Shield ◽  
Design Parameters ◽  
Cycle Fatigue ◽  
Excessive Heat ◽  
The Impact ◽  
Shield Design ◽  
Aerodynamic Losses

Abstract In Gas Turbine design key important role was to establish proper clearance between rotating and statoric parts during operating conditions which controls the performance, cooling flow requirements, part performance etc., These clearances must be optimized to meet product requirements. Too tight clearance at assembly condition causes excessive rubbing during starting or shutdown of gas turbine which could cause excessive heat generation and damage rotating and statoric parts. In some case, rubbing can cause tip liberations and damages to flow path causing aero dynamic losses. Similarly, if clearance is large at assembly condition causes aerodynamic losses. In this paper describes the experience of Baker Hughes, in design of compressor case wherein different design options in casing design with and without considering external features / components are considered to have adequate clearance between rotating and statoric parts. It also describes the Heat shield design iterations which was provided on a compressor case to establish proper thermal response during transient operating conditions. This helps in providing adequate clearance without causing excessive rubs or too large clearance avoiding aerodynamic losses. During development of heat shield design, challenges encountered considering clearance, manufacturing aspects, assembly feasibility and part life capabilities like low cycle fatigue, high cycle fatigue requirements are discussed in the paper. Also heat shield was subjected to high thermal gradient due to temperature difference, this makes heat shield to have constrained growth. This restriction in growth provides huge stresses beyond the material limit causing it to fail before product requirement time period. To avoid constrained growth, this paper describes how the heat shield was connected to casing by different means are mentioned. It also describes the impact on frequency margin if there is not adequate fixity in heat shield design. Some of the design parameters like circumferential & axial ribs and intermittent stiffeners and its influence on stress by comparing against yield and on frequency margin with reference to potential driver are also discussed in this paper. It also incorporates the methods to control intersegment leakages and design features to avoid interface interference. Feasibility study of heat shield design was done using finite element modeling techniques using ANSYS tool and its best practices would also be dealt in this paper.

Introduction of the Taurus™ 65 Industrial Gas Turbine for Power Generation

2008 ◽  
Author(s):  
George Rocha ◽  
Simon Reynolds ◽  
Theresa Brown
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Electrical Power ◽  
Field Evaluation ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Liquid Fuels ◽  
Operating Cycle ◽  
Product Experience ◽  
Exhaust Heat

Solar Turbines Incorporated has combined proven technology and product experience to develop the new Taurus 65 gas turbine for industrial power generation applications. The single-shaft engine is designed to produce 6.3 megawatts of electrical power with a 33% thermal efficiency at ISO operating conditions. Selection of the final engine operating cycle was based on extensive aerodynamic-cycle studies to achieve optimum output performance with increased exhaust heat capacity for combined heat and power installations. The basic engine configuration features an enhanced version of the robust Centaur®50 air compressor coupled to a newly designed three-stage turbine similar to the Taurus 70 turbine design. Advanced cooling technology and materials are used in the dry, lean-premix annular combustor, consistent with Solar’s proven SoLoNOx™ combustion technology, capable of reducing pollutant emissions while operating on standard natural gas or diesel liquid fuels. Like the Titan™ 130 and Taurus 70 products, a traditional design philosophy has been applied in development of the Taurus 65 gas turbine by utilizing existing components, common technology and product experience to minimize risk, lower cost and maximize durability. A comprehensive factory test plan and extended field evaluation program was used to validate the design integrity and demonstrate product durability prior to full market introduction.

A Life Prediction Model for Single-Crystal Nickel-Base Alloys Under Low-Cycle Fatigue

2020 ◽  
Author(s):  
Firat Irmak ◽  
Navindra Wijeyeratne ◽  
Taejun Yun ◽  
Ali Gordon
Keyword(s):  
Single Crystal ◽  
Gas Turbine ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Deformation Model ◽  
Cycle Fatigue ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
Prediction Approach

Abstract In the development and assessment of critical gas turbine components, simulations have a crucial role. An accurate life prediction approach is needed to estimate lifespan of these components. Nickel base superalloys remain the material of choice for gas turbine blades in the energy industry. These blades are required to withstand both fatigue and creep at extreme temperatures during their usage time. Nickel-base superalloys present an excellent heat resistance at high temperatures. Presence of chromium in the chemical composition makes these alloys highly resistant to corrosion, which is critical for turbine blades. This study presents a flexible approach to combine creep and fatigue damages for a single crystal Nickel-base superalloy. Stress and strain states are used to compute life calculations, which makes this approach applicable for component level. The cumulative damage approach is utilized in this study, where dominant damage modes are capturing primary microstructural mechanism associated with failure. The total damage is divided into two distinctive modules: fatigue and creep. Flexibility is imparted to the model through its ability to emphasize the dominant damage mechanism which may vary among alloys. Fatigue module is governed by a modified version of Coffin-Manson and Basquin model, which captures the orientation dependence of the candidate material. Additionally, Robinson’s creep rupture model is applied to predict creep damage in this study. A novel crystal visco-plasticity (CVP) model is used to simulate deformation of the alloy under several different types of loading. This model has capability to illustrate the temperature-, rate-, orientation-, and history-dependence of the material. A user defined material (usermat) is created to be used in ANSYS APDL 19.0, where the CVP model is applied by User Programmable Feature (UPF). This deformation model is constructed of a flow rule and internal state variables, where the kinematic hardening phenomena is captured by back stress. Octahedral, cubic and cross slip systems are included to perform simulations in different orientations. An implicit integration process that uses Newton-Raphson iteration scheme is utilized to calculate the desired solutions. Several tensile, low-cycle fatigue (LCF) and creep experiments were conducted to inform modeling parameters for the life prediction and the CVP models.

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