scholarly journals Contribution of High Mechanical Fatigue to Gas Turbine Blade Lifetime during Steady-State Operation

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 229 ◽  
Author(s):  
Sung Chang ◽  
Ki-Yong Oh
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Low Cycle Fatigue ◽  
Thermomechanical Fatigue ◽  
Cycle Fatigue ◽  
Bond Coating ◽  
Barrier Coating ◽  
Steady State Operation ◽  
Coating Failure ◽  
Useful Lifetime

In this study, the contribution of high thermomechanical fatigue to the gas turbine lifetime during a steady-state operation is evaluated for the first time. An evolution of the roughness on the surface between the thermal barrier coating and bond coating is addressed to elucidate the correlation between operating conditions and the degradation of a gas turbine. Specifically, three factors affecting coating failure are characterized, namely isothermal operation, low-cycle fatigue, and high thermomechanical fatigue, using laboratory experiments and actual service-exposed blades in a power plant. The results indicate that, although isothermal heat exposure during a steady-state operation contributes to creep, it does not contribute to failure caused by coating fatigue. Low-cycle fatigue during a transient operation cannot fully describe the evolution of the roughness between the thermal barrier coating and the bond coating of the gas turbine. High thermomechanical fatigue during a steady-state operation plays a critical role in coating failure because the temperature of hot gas pass components fluctuates up to 140 °C at high operating temperatures. Hence, high thermomechanical fatigue must be accounted for to accurately predict the remaining useful lifetime of a gas turbine because the current method of predicting the remaining useful lifetime only accounts for creep during a steady-state operation and for low-cycle fatigue during a transient operation.

Research on Matching Characteristics of Ship-Engine-Propeller of COGAG

2021 ◽  
Author(s):  
Zhitao Wang ◽  
Jiayi Ma ◽  
Haichao Yu ◽  
Tielei Li
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Research Work ◽  
Simulation Models ◽  
Operating Characteristics ◽  
Modular Modeling ◽  
Steady State Operation ◽  
Pitch Ratio ◽  
Main Engine

Abstract The combined gas turbine and gas turbine power propulsion device (COGAG power propulsion device) is an advanced combined power system, which uses multiple gas turbines as the main engine to drive propellers to propel the ship. COGAG power propulsion device has high power density, excellent stability and maneuverability, it receives more and more attention in the field of ship power at home and abroad. This article takes the COGAG power propulsion device as the research object, uses simulation methods to study its steady-state operating characteristics, and conducts a ship-engine-propeller optimization matching analysis based on economy and maneuverability. The research work carried out in this article is as follows. Firstly, according to the structural relationship between the various components and the system thermal cycle mode of the COGAG power propulsion device, establish the controller, main engine, gear box, clutch, shafting, propeller, ship and other components and simulation models of the system with the modular modeling idea. Secondly, divide the gears according to ship speed. For the four working modes of single-gas turbine with load, dual-gas turbine with load, three-gas turbine with load, and four-gas turbine with load, analysis the ship-engine-propeller optimization matching of the COGAG power propulsion device based on economy and maneuverability, and calculate the best shaft speed and propeller pitch ratio in each gear, so as to obtain the steady-state operation characteristics of the COGAG power propulsion device based on the ship-engine-propeller matching, which provides a basis for determining the target parameters of the dynamic process.

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.

Life evaluation of a combustion chamber by thermomechanical fatigue panel tests based on a creep fatigue and ductile damage model

2019 ◽  
Vol 29 (2) ◽  
pp. 226-245 ◽  
Author(s):  
Tadashi Masuoka ◽  
Jörg R Riccius
Keyword(s):  
High Temperature ◽  
Combustion Chamber ◽  
Fatigue Test ◽  
Test Data ◽  
Low Cycle Fatigue ◽  
Thermomechanical Fatigue ◽  
High Load ◽  
Cycle Fatigue ◽  
Damage Propagation ◽  
Damage Models

The inner liner of a combustion chamber of a cryogenic liquid rocket engine is exposed to a high load induced by the high temperature of the hot gas and the low temperature of the coolant. The high load causes some inelastic strain that accumulates with each operational cycle until the fracture or rupture of the inner liner. A model that can reproduce the propagation of damage under a thermally cycled load is essential for precisely predicting the chamber life. However, the damage propagation phenomenon or the quantitative value of the damage was so far not fully discussed using the damage data obtained from basic testing of a rocket chamber material. The purpose of the present study was to investigate a precise prediction model based on damage mechanics for simulating the damage propagation of a rocket chamber material. In this study, low cycle fatigue test data at a high temperature (900 K) were analyzed, and damage models that could reproduce the damage propagation under cyclic load conditions were investigated. Then the parameters were identified to reproduce uniaxial test data. These damage models were also subject to a finite element method analysis of a thermomechanical fatigue panel test in order to quantitatively evaluate the deformation, damage propagation, and life of a chamber wall. The analysis of low cycle fatigue test data at 900 K suggested a specific model that could precisely reproduce the damage propagation phenomenon and the basic material test data. From the results, it was confirmed that the model could predict the location of crack initiation.

Shear Strength of a Thermal Barrier Coating Parallel to the Bond Coat

1998 ◽  
Vol 120 (1) ◽  
pp. 26-32 ◽  
Author(s):  
T. A. Cruse ◽  
R. C. Dommarco ◽  
P. C. Basti´as
Keyword(s):  
Shear Strength ◽  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Test Method ◽  
Thermal Barrier ◽  
Cycle Fatigue ◽  
Air Plasma ◽  
Barrier Coating

The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard losipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material.

scholarly journals Design and Experimental Validation of a Supersonic Concentric Micro Gas Turbine

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Gabriel Vézina ◽  
Hugo Fortier-Topping ◽  
François Bolduc-Teasdale ◽  
David Rancourt ◽  
Mathieu Picard ◽  
...  
Keyword(s):  
Steady State ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Structural Model ◽  
Structural Integrity ◽  
Turbine Blades ◽  
External Diameter ◽  
Impulse Turbine ◽  
Micro Gas Turbine ◽  
Steady State Operation

This paper presents the design and experimental results of a new micro gas turbine architecture exploiting counterflow within a single supersonic rotor. This new architecture, called the supersonic rim-rotor gas turbine (SRGT), uses a single rotating assembly incorporating a central hub, a supersonic turbine rotor, a supersonic compressor rotor, and a rim-rotor. This SRGT architecture can potentially increase engine power density while significantly reducing manufacturing costs. The paper presents the preliminary design of a 5 kW SRGT prototype having an external diameter of 72.5 mm and rotational speed of 125,000 rpm. The proposed aerodynamic design comprises a single stage supersonic axial compressor, with a normal shock in the stator, and a supersonic impulse turbine. A pressure ratio of 2.75 with a mass flow rate of 130 g/s is predicted using a 1D aerodynamic model in steady state. The proposed combustion chamber uses an annular reverse-flow configuration, using hydrogen as fuel. The analytical design of the combustion chamber is based on a 0D model with three zones (primary, secondary, and dilution), and computational fluid dynamics (CFD) simulations are used to validate the analytical model. The proposed structural design incorporates a unidirectional carbon-fiber-reinforced polymer rim-rotor, and titanium alloy is used for the other rotating components. An analytical structural model and numerical validation predict structural integrity of the engine at steady-state operation up to 1000 K for the turbine blades. Experimentation has resulted in the overall engine performance evaluation. Experimentation also demonstrated a stable hydrogen flame in the combustion chamber and structural integrity of the engine for at least 30 s of steady-state operation at 1000 K.

Structural Integrity Assessment and Engine Test of an Additive Manufactured First Stage Ring Segment of a Siemens Large Gas Turbine

2019 ◽  
Author(s):  
Tobias T. Rühmer ◽  
Uwe Gampe ◽  
Kathrin A. Fischer ◽  
Thomas Wimmer ◽  
Christoph Haberland
Keyword(s):  
Gas Turbine ◽  
Structural Integrity ◽  
Low Cycle Fatigue ◽  
Creep Rupture ◽  
Measuring System ◽  
Dynamic Strain ◽  
Uniaxial Tensile ◽  
Cycle Fatigue ◽  
Integrity Assessment ◽  
Ring Segment

Abstract The first stage ring segment (RS) of a Siemens large gas turbine has been redesigned for Selective Laser Melting (SLM) in order to reduce the cooling air consumption and to increase the gas turbine efficiency. The material is IN939. Cylindrical specimen for uniaxial tensile, cyclic tests and creep rupture tests have been manufactured by SLM to characterize the material by derivation of stress strain and creep rupture curves. The ring segment has been tested in a real gas turbine. The loading conditions as well as measurement data from thermocouples and dynamic strain gages have been taken as input for numerical structural integrity assessment. Permissible service life of the ring segment was evaluated in respect of low cycle fatigue (LCF), high cycle fatigue (HCF) and creep. Results have been compared with the conventional design. Furthermore the hook lock up in the engine was evaluated. The manufacturing quality was ensured through several methods including an optical 3D measuring system and computer tomography, process specimen and flow tests. Post investigations such as cut ups and metallography have also been conducted. The results show that the additive manufactured RS meets the required service lifetime.

Sign in / Sign up

Export Citation Format

Share Document