Fretting Fatigue Experiment and Finite Element Analysis for Dovetail Specimen at High Temperature

The dovetail attachment between the turbine blade and disk for an aero-engine operates under varying centrifugal load and vibration at elevated temperatures. The fretting fatigue is prone to occur at the contact surface of the dovetail attachment. This paper investigated the fretting fatigue behavior of the dovetail specimen at 630 °C through experiment and numerical simulation, in which the blade-like dovetail specimen is nickel-based single crystal superalloy DD10 while two fretting pads in contact with the dovetail specimen simulating the mortise of the disk are made of powder metallurgy FGH99. It is revealed from all the tests that the fracture induced by the fretting wear occurs at the upper edge area of the contact surface. The contact surface near the upper edge is more severely worn; hence, the phenomenon of partition on the worn contact surface can be observed, which is consistent with the fretting fatigue mechanism. Moreover, the calculated area of maximum contact pressure gradient through finite element method is in good agreement with the experimental position of the initial fretting fatigue cracks.

Pre-Deformation Method for Manufactured Compressor Blade Based on Load Incremental Approach

The blade deformation caused by aerodynamic and centrifugal loads during operating makes blade configurations different from their stationary shape. Based on the load incremental approach, a novel pre-deformation method for cold blade shape is provided in order to compensate blade deformation under running. Effect of nonlinear blade stiffness is considered by updating stiffness matrix in response to the variation of blade configuration when calculating deformations. The pre-deformation procedure is iterated till a converged cold blade shape is obtained. The proposed pre-deformation method is applied to a transonic compressor rotor. Effect of load conditions on blade pre-deformation is also analyzed. The results show that the pre-deformation method is easy to implement with fast convergence speed. Neither the aerodynamic load nor centrifugal load can be neglected in blade pre-deformation.

Dynamic Modelling of Deep-Water Riser With Slug Flow Based on ALE-ANCF

The internal flow in gas-liquid mixing riser often displays a flow pattern known as slug flow, in which gas and liquid are alternately distributed. Dynamic effects due to slug flow is normally most obvious in areas along the riser with high curvature, which is caused by the centrifugal load component. The global riser response to this excitation can be predicted by nonlinear time domain analysis using the load model as described for slug flow conditions. In this study, the riser with internal slug flow is modeled under the framework of Arbitrary-Lagrange-Euler (ALE) description by using the Absolute Node Coordinate Formula (ANCF). The riser is discretized into ANCF cable element based on the Euler-Bernoulli beam assumption, while one-dimensional moving medium modeling method with time-varying density is used to model slug element. Compared with other FEA models of riser subjected to internal flow, the ALE-ANCF model allow easily modeling of complex mass flow and has the advantages of high speed and high precision in handling large deformation of riser, especially for the compliant riser configurations. Numerical simulations of two simplified models are carried out to validate the developed model, then the dynamic response such as displacement, tension force and bending moment of the riser conveying slug flow are analyzed.

Geometry-Load Based Hybrid Correction Method for the Pre-Deformation Design of a Steam Turbine Blade

To solve the problem of the slow convergence of the geometry-based correction (GC) method in the design of a steam turbine blade, this paper proposes a geometry-load-based hybrid correction (GLHC) method. In this method, the deformation of the blade caused by the centrifugal load is still corrected by the GC method, while the deformation caused by the aerodynamic load is corrected by the load-based correction (LC) method instead of the GC method. The LC method updates the cold shape of the blade by reversely applying the aerodynamic load to the ideal shape according to the balance between the internal force generated by the deformation of the blade and the aerodynamic load acting on surface of the hot blade shape, thereby reducing the number of iterations by reducing the shape deviation in each step of the iteration. The GLHC method, which combines the GC and LC methods, is used to improve the design process. The efficiency of the GLHC and GC methods are compared with the maximum number of position deviations of the corresponding mesh nodes between the hot blade and ideal blade shapes, which acts as the criterion. The results show that the GLHC method reduces the number of iterations.

A Review of the High-speed Permanent Magnet Rotor Stress Analysis used for Automotive Air-handling Machines

Machines incorporating high-speed electrical machines (HSEM) are becoming increasingly common place in applications including air handling, energy storage and medical devices. They are of increasing interest within the automotive field for air handling applications. HSEM’s use surface-mounted permanent magnet (PM) rotors, manufactured from rare earth metals. However, these PM’s have low tensile strength and are susceptible to failure under the centrifugal load produced at high speed rotation. Retaining sleeves which are an interference fit around the magnets, provide compression and hence resistance to tensile stress. The ability to predict the stresses within the rotor assembly is essential for robust design. This review paper examines existing analytical calculations and finite element analysis (FEA) models. The analytical approaches include both plane stress and plane strain models and the limitations of these are discussed. For relatively long rotors, a generalised plane strain approach is suitable, however it is seldom used. In addition, this latter approach has not been extended to assemblies where the magnets are assembled onto a carrier or shaft. Optimisation of rotors has been addressed in a relatively small number of papers. However, further work is required in this area to ensure that the optimised rotors can be manufactured.

FEA Assisted Design and Structural Research on Vertical Axis Wind Turbine Rotor

The scope of the project is to perform finite element analysis of the Vertical axis wind turbine rotor assembly.Blade, arm, connectors and strings assembly of rotor are considered for analysis and to study the static behaviour at the different loading conditions. Total vertical load of 132 kg self-weight is acting downward direction to the structure. Considered that rotor will be rotating at maximum speed (RPM) aerodynamic load with self weight conditions. Due to higher angular velocity (154 RPM) blades will be subjected to great centrifugal force. Along with the centrifugal load rotor also will get subjected to fluctuating aero dynamic loads. In analysis it is considered as the rotor in stationary position and subjected to the maximum drag force at 52 (m/s) wind velocity at azimuth value of 90˚. SOLID92 is used for the 3-D modelling of solid structures. The maximum stress value obtained from the analysis is 183.1 N/mm2 for the loading and boundary conditions.

Untwist Creep Analysis of Gas Turbine First Stage Blade

During operation, turbine blades subjected to high temperatures will experience permanent geometric distortion due to creep. The principal form of this distortion is blade elongation due to the centrifugal load, but the blade can also straighten or ‘untwist’. The magnitude of the untwist can be used to track the accumulated creep strain damage in a blade, and so measurements of blade untwist over time are often recorded. If the relationship between untwist and creep strain damage can be expressed, then it will be possible to make more informed maintenance decisions. This study describes a finite element creep analysis of a first stage turbine blade using a calibrated creep material model, and compares the calculated untwist to records kept by the operator. The creep model used in this study is a physics based model using the microstructural properties of the blade alloy, and is calibrated using a single creep test at representative stress and temperature. An important objective of this study is to demonstrate that application of the creep model in a component with non-uniform stress and temperature will lead to representative results. The analysis was repeated with two materials that correspond to different blade versions. The material with superior high temperature properties exhibited less untwist, and the analysis of both variants were comparable to the recorded blade measurements.