Stress Redistribution for Increased Creep Life in the GE MS6001 B Second-Stage Blade

2004 ◽  
Vol 126 (1) ◽  
pp. 127-130 ◽  
Author(s):  
P. E. DiCristoforo ◽  
M. Elledge
Keyword(s):  
Gas Turbine ◽  
Stress Level ◽  
Low Cycle Fatigue ◽  
Failure Criteria ◽  
Bulk Temperature ◽  
Cycle Fatigue ◽  
Second Stage ◽  
Industrial Gas Turbine ◽  
Deflection Rate ◽  
Lower Stress Level

When a hot end blade for a gas turbine is designed, several failure criteria must be considered to insure reliability. The criteria include (but are not limited to) creep rupture, low-cycle fatigue, high-cycle fatigue, and creep deflection. This paper will focus on the second-stage turbine blade for the GE MS6001 industrial gas turbine. BP Amoco has experienced failure of this blade due to excessive creep deflection. Creep deflection rate is a function of stress level and metal temperature. A typical approach to reducing creep deflection is to reduce the bulk temperature in the blade. In this paper a design is reviewed that has had the stress redistributed, so that the high-temperature regions of the airfoil are at a lower stress level, thereby reducing the creep rate to an acceptable level.

Stress Redistribution for Increased Creep Life in the GE MS6001 B Second Stage Blade

2001 ◽  
Author(s):  
Paul E. DiCristoforo ◽  
Mark Elledge
Keyword(s):  
Gas Turbine ◽  
Stress Level ◽  
Low Cycle Fatigue ◽  
Failure Criteria ◽  
Bulk Temperature ◽  
Cycle Fatigue ◽  
Second Stage ◽  
Industrial Gas Turbine ◽  
Deflection Rate ◽  
Lower Stress Level

When a hot end blade for a gas turbine is designed, several failure criteria must be considered to insure reliability. The criteria include (but are not limited to) creep rupture, low cycle fatigue, high cycle fatigue and creep deflection. This paper will focus on the second stage turbine blade for the GE MS6001 industrial gas turbine. BP Amoco has experienced failure of this blade due to excessive creep deflection. Creep deflection rate is a function of stress level and metal temperature. A typical approach to reducing creep deflection is to reduce the bulk temperature in the blade. In this paper a design is reviewed that has had the stress redistributed, so that the high temperature regions of the airfoil are at a lower stress level, thereby reducing the creep rate to an acceptable level.

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.

Design Modification of a Heavy Duty Industrial Gas Turbine Blade for Life Improvement

2012 ◽  
Author(s):  
Chris Hutchison ◽  
Anthony Chan ◽  
Dan Stankiewicz
Keyword(s):  
Crack Initiation ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Low Cycle Fatigue ◽  
Inlet Temperature ◽  
Gas Turbine Blade ◽  
Heavy Duty ◽  
Trailing Edge ◽  
Design Modification ◽  
Industrial Gas Turbine

Cracking at the trailing edge of a heavy duty industrial gas turbine blade has been observed on a number of serviced parts. The cracking usually occurs within 1.0″ of the platform. The trailing edge (TE) cracks have been found to propagate through the airfoil, leading to airfoil separation and severe engine damage. Liburdi Turbine Services has undertaken an independent metallurgical and stress analysis of the blade to determine the cause of the cracking. This paper covers the stress and low cycle fatigue (LCF) analysis of a platform undercut modification designed to mitigate crack initiation and thus increase part life. A finite element model of the blade was developed. Thermal loading was applied from a conjugate heat and mass transfer analysis between the blade, gas path flow and internal cooling flow. Base load conditions were used at turbine inlet temperature 2482°F. Results showed that the peak stress was present in the TE cooling slot corner, and was large enough to cause local yielding and LCF. The geometry of the modification was shown to strongly influence stress in the TE airfoil region and in the undercut region. Thus a balance was found to provide sufficiently low stresses in both regions and still be practical for machining. The modification was found to decrease stress in the TE cooling slot by a factor of 0.71 relative to that of the current OEM design, and increase life by 1.79 times. A viable modification has been demonstrated to extend blade life by reducing local stress and thus mitigating crack initiation at the airfoil TE.

The Two-Shaft Industrial Gas Turbine Goes to Sea — Again

1971 ◽  
Author(s):  
Arne Loft
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
State Control ◽  
Flexible Control ◽  
Second Stage ◽  
Sequential Systems ◽  
Industrial Gas Turbines ◽  
Heavy Duty Gas Turbine ◽  
Basic Characteristics ◽  
Industrial Gas Turbine

This paper gives a brief summary of the experience of the first industrial gas turbine ship, the John Sergeant, then enumerates the basic characteristics of the heavy duty gas turbine and the philosophy employed in the design. The unique features of the second-stage variable area turbine nozzle, its effects on performance, and particularly the flexible control it affords in conjunction with the controllable and reversible pitch propeller, are discussed. The philosophy of design of the solid state control, protection and sequential systems are outlined, as are the experiences to date with a number of industrial gas turbines of the two-shaft, off-shore and heavy fuel varieties. It concludes by discussing some of the considerations for burning residual fuel and boil-off from liquefied natural gas.

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.

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