Rotordynamics

A mesoscale turbocompressor spinning above 500,000 RPM is evolutionary technology for micro turbochargers, turbo blowers, turbo compressors, micro-gas turbines, auxiliary power units, etc for automotive, aerospace, and fuel cell industries. Objectives of this work are: 1) ...

Turbogenerator as a set of turbines and electric generator presents a very complicated mechanical system. Its design must take into consideration the rotordynamics of rotor, which undergoes bending and torsional oscillation. The oscillation of the rotor depends upon its geometry and type of support. In this paper the dynamic models for the turbogenerator with three turbines and an electric generator supported in different types of bearings has been analysed. The mathematic model was extended with electromagnetic moment and the resistant moment of the working machine. The adopted models – mechanical and its mathematical - are a good base for dynamic analysis at the

Many rotating machines such as compressors, turbines, and pumps have long thin shafts with resulting vibration problems. They would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment, unlike conventional bearings. This paper describes an experimental test rig that was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82 percent, the disk location reduced it 75 percent, and the bearing location attained a 74 percent reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both th...

This research focuses on the structural analysis of aircraft electrical harnesses for the ± 270 VDC network. A combined experimental and simulation-based approach is used, where numerical models for the harnesses are developed and experimental data are acquired for basic test cases (steady load, pendulum test, etc.) as well as for different vibration load cases. Validation of the numerical models is done using the preliminary experimental data, resulting in a mature refined model in order to simulate complex scenarios. The goal of the project is thus to develop a suite of tools that allows detailed structural analysis of the aircraft harnesses, both stand alone as well as in combination with other systems.

Helicopter rotor track and balance (RTB) is the process of reducing to a minimum the rotor induced vibration present during helicopter flight. We propose here the use of an optimisation algorithm to reduce the number of dedicated flights required to perform RTB and return an aircraft to a serviceable state. The algorithm has recently been flight trialled by UK MoD on their Puma aircraft as part of a project to embody the algorithm on their existing RTB equipment. Both main and tail rotor applications were tested. Some of the results from that flight trial are shown here along with their effects on the development of the algorithm itself. The outcome indicates that there is significant potential cost saving and increased availability benefits to be made by using the algorithm across the fleet. Background The Minimum Flight Routine (MFR) algorithm was first conceived in early 2006, development then commenced in the summer of 2006 through a Knowledge Transfer Program (KTP) between Heli...

A machine-tool structure optimization is an important technique that improves the machining efficiency and saves materials and the energy resource. In this work, dynamic design optimization method for Machine-Motorized-Spindle (MMS) subjected to a number of rotating unbalanced forces effects is presented. Linear forced-Rotordynamic analysis with design explorer method has been used to simulate the output response. The Design Variables (DVs) and their limits were carefully chosen and applied to develop the Design-of-Experiment (DOE). The Box-Behnken Design (BBD) method, because of its good organization in providing much information in a minor number of required statistical experiments was used to generate the DOE. The influences of DVs on the dynamic of MMS and their levels optimization were evaluated by utilizing the Response-Surface (RS) method. The results showed that the spindle shaft inner diameter of the motor-rotor seat and its rotating unbalanced mass, and modulus of elastici...

Electromagnetic actuators that use a current-carrying coil (which is placed in a magnetic field) to generate mechanical force are conceptually attractive components for active control of rotating shafts. In one concept that is being tested in the laboratory, the control forces from such actuators are applied on the flexibly supported bearing housings of the rotor. Development of this concept into

DYNROT is a code based on the finite element method aimed to perform a complete study of the dynamic behaviour of rotors. Although initially designed to solve the basic linear rotordynamic problems (Campbell diagram for damped or undamped systems, unbalance response, critical speeds, static loading), it can be used for the study of nonstationary motions of nonlinear rotating systems and for the torsional analysis of rotors and reciprocating machines. 
One of the distinctive features of the code is the use of complex co-ordinates, both for isotropic and nonsymmetric systems. Extensive use of complex arithmetics is then made in all parts of the analysis. The modal approach is used in some of the solution routines to increase the efficiency of the computation or to compute an equivalent viscous damping in the cases where hysteretic damping cannot be entered directly into the model.

The present study analyzes the effect of pressure dam depth and relief track depth on the performance of three-lobe pressure dam bearing. Different values of dam depth and relief track depth are taken in nondimensional form in order to analyze their effect. Results are plotted for different parameters against eccentricity ratios and it is shown that the effect of pressure dam depth and relief track depth has great significance on stability and other performance parameters. Study of stability and performance characteristics is undertaken simultaneously.

This paper deals with loss analysis, structural, thermal-fluid and rotordynamics (critical speed and unbalance) which need in developing the motor-generator. This machine has designed of a generator of 800 W, 400 krpm and a starter of 400 W, 200 krpm. The generated losses of motor-generator are derived by magnetic analysis. Thermal-fluid analysis is performed using loss analysis result. The critical speed is extracted by Campbell diagram. Unbalance vibration response analysis enable to predict the expected vibration amplitude by unbalance. The motor-generator is well-developed using the applied several techniques of analysis.

The spatial structure of the dynamics of a rotating nonlinear shaft is identified by processing its finite element dynamics by the method of Proper Orthogonal Decompositions. The Proper Orthogonal modes furnish characteristic signatures for the rigid body and the whirling modes of a motion. The pattern of energy distribution over the components of a mode reveals the strength of coupling between rigid body rotations and coupled vibrations. These modes are used to derive a two-degree-of freedom reduced model for the whirling motion of the rotating shaft.

Since the centrifugal compressors have a wide range of applications, the reliability of impellers as the vital components should be ensured. Due to the complicated operating conditions and various Gas compositions and its corrosive and non-corrosive nature, it is important to do Finite Element Analysis (FEA) on Impeller with alternate material for its feasibility. During the operation of centrifugal compressor, failure easily occurs in the presence of stresses, cyclic loads, vibrations, corrosion. The failure process characterizes with strong nonlinearity and hence it is difficult to be described by conventional methods. On this background aim of this research was to manufacture a new Aluminium alloy Impeller in order to improve the life of an impeller. In this project, Al25Zn new aluminium material developed and found its mechanical properties. The Al25Zn has higher yield strength among its binary composition. The hardness is also higher. The addition of zinc to aluminium increases the hardness and yield strength. The new developed material properties used in stress and deformation analysis. The analysis results show that new material exhibit good properties for yield strength, stress which are less compared to steel material. This is because the stresses built are function of centrifugal forces which is mass dependent. New material has less mass compared to steel impeller as there is density variation. Identification of new material for impeller application is studied and it is observed that Standard Elastic Analysis (SEA) at initial stages helps in determining use of new material in impeller design.

Accurate prediction of the dynamic behavior of coupled shafts in a fluid medium is crucial to accurately estimate equipment life and enable safe operation. However, this task is far from trivial due to the vibrations induced by the highly nonlinear nature of the machine system. This paper presents an experimental analysis of a cardan shaft under the influence of viscous hydrodynamic forces. An experimental setup was created using a cardan shaft rig installed in a plexiglas tank, with a self-aligned crack simulator supporting the driveshaft for crack extraction. Adequate instrumentation was used to measure the rotor’s fluctuation under industrial viscous fluid at various motor speeds. By analyzing the changes of unwanted high vibration, the obtained results demonstrated that the characteristics of the cracks in the fluid medium can be efficiently extracted from multiple tests using the wavelet synchrosqueezing transform and energy spectrum. This latter aspect, in particular, implies ...

As API mandates to conduct mechanical run tests (MRT) of all centrifugal compressors of similar deign and geometry, it takes a considerable amount of time to conduct these tests on original equipment manufacturer (OEM) test bed particularly if numbers of compressors are large. The test results are often found to be monotonously similar This paper proposes to conduct only one Full load Full speed (FLFS) test as mechanical run test at vendor works among the full lot of similar model and design. The primary intention of the paper is to classify the criticality of compressors and then deliberate on the extent / type of tests taking account of OEM test bed capability and schedule of delivery of machines and then optimize the test agenda .To supplement the FLFS test, the paper proposes to undertake extensive design audit activities in terms of rotor-dynamics, aerodynamics taking account of case histories of past failures which can raise the confidence level of the end user. The MRT does n...