CALCULATION OF FLOOR BEARING WITH FERROMAGNETIC LIQUID OF TURBOGENERATORS OF POWER DISTRIBUTION SYSTEMS

The article discusses ways to solve the problem of wear of the rotor bearings of turbine units at the moments of start–up and shutdown. The concept of a new type of elastic–damping combined sliding bearings, which combines the use of ferromagnetic fluids in the design of multi–blade bearings, is proposed. On the basis of this, a design of a petal bearing with an electromagnetic effect on elastic elements and a ferromagnetic lubricant has been proposed. The properties and features of the use of ferromagnetic fluids in precision engineering as a lubricant are described. A mathematical model of an electromagnetic petal bearing with a ferromagnetic fluid is proposed on the basis of the Reynolds equation from the course of magnetohydrodynamics, Maxwell's equations for a magnetic field, a system of equations in displacements based on the theory of cylindrical shells. An algorithm for the operation of the rotor support during start–up, shutdown, as well as when the power supply of the electromagnets is turned off.

Prediction of the thermal bow of rotor based on the measured displacement and temperature

The thermal bow of the rotor occurs in the cooling process after the shutdown of the aeroengine. The deflection of the bowed rotor is the primary concern of the research on this problem. The objective of this work is to propose a method to predict the bow shape of the rotor with the measured temperature and displacement in a rotor thermal bow experiment. The experiment was introduced and the variations of the measured temperature and displacement were analyzed. A series of polynomial function was proposed to model the bowed shape of the rotor. The measured temperature and displacement were taken into considered in the constraint equations, with which the coefficients in the polynomial function were obtained. The bow shapes of the rotor at different time in the experiments were analyzed. Results showed that the maximum deflection of the rotor was much greater than the measured displacement at the sections near the rotor support. The forced cooling could reduce the thermal deflection of the rotor quickly. The analysis of the different cases of experiment indicated that the proposed method could predict the bow shape of the rotor with the measured temperature and displacement.

Analysis of Instantaneous Vibrational Energy Flow for an Aero-Engine Dual-Rotor–Support–Casing Coupling System

The aero-engine casing is a key component for carrying loads. With the purpose of improving the thrust-weight ratio of the aero-engine, the casing is required to be designed to be as thin as possible. Therefore, the vibration of aero-engine's rotor, support, and casing will be easily coupled causing the whole engine's vibration to be more serious. Considering the structural vibration propagation is essentially the vibration energy transmission, the structural intensity (SI) method is popular and widely used to investigate the transmission phenomena of vibration energy in vibrating structures. This method combines forces with velocities to quantify the vibrational energy flow (VEF) transmitted in the structures by its directions and magnitude. Therefore, the SI fields are quantified by the developed computation system which combines the finite element design language and the in-house code. And a model of dual-rotor–support–casing coupling system subjected to the unbalanced forces of the rotors is established in this paper. The scalar and vector diagrams of instantaneous SI fields are visualized to show the main vibration energy transmission paths among these three parts. Moreover, the relationship between the SI and the mechanical energy is derived from the kinetic equation. According to this relationship, the phenomenon that the vibration energy and the strain energy are always converted to each other in the middle part of the rotor shaft with the first-order bending mode is discussed, which reveals the cause of the first-order bending mode of the rotor from a microscopic point of view.

Simulation, Test, and Mitigation of ½× Forward Whirl Following Rotor Drop Onto Auxiliary Bearings

1/2× forward whirl repeatedly occurred after a test rotor spinning at 5800 rpm was dropped onto ball bearing type auxiliary bearings (AB), utilized as a backup for magnetic bearings (MB). The measured contact forces that occurred between the rotor and the AB during the ½× subsynchronous vibration were about thirteen times larger than the static reaction force. The vibration frequency coincided with the rotor-support system natural frequency with the rotor at rest on the AB, an occurred at ½ of the rotor spin speed when dropped. The test rig provided measurements of rotor-bearing contact force, rotor orbit (vibrations), and rotational speed during rotor drop events. A simulation model was also developed and demonstrated that parametric excitation in the form of a Mathieu Hill model replicated the measured ½× forward whirl vibrations. The simulation model included a nonlinear, elastic-thermal coupled, ball bearing type AB model. The transient model successfully predicted the ½× vibration when the rotor was passing 5800 RPM as well, and the simulation results quantitatively agreed well with the test results in the frequency domain. Several approaches for mitigating the 1/2× forward whirl were presented such as adding an elastomer O-ring or waviness spring in the AB support system. Measurements confirmed that adding AB dampers effectively mitigated the ½ subsynchronous forward whirl and significantly reduced the contact forces.

CLUSTER ANALYSIS FOR DETECTING GROUPS OF DEFECTS ROTARY SUPPORT SYSTEM

Cluster analysis is widely used in the machine diagnostic and monitoring field. This article discusses the issue of recognizing the states of rotary-support systems with fluid-friction bearings. An experiment was carried out to investigate the effect of tightening the bolts that connect rotor-support unit body to the frame; to investigate the effect of tightening the bolts that connect electric motor to the frame; to investigate the rotor imbalance, as well as a combination of these factors. Cluster analysis based on the K-means method was applied. The readings of the eddy- current transducer were used as an input data for training. Analysis of the results revealed two groups of defects. During testing, the accuracy of group identification was 100%.

Performance Simulation for the Supporting Structure of Aero-Engine Rotor in Wide Frequency Domain

The inertia load of aero-engine indeterminate rotor support is calculated by the finite element method coupled with plane stress element and Fourier ring element. Without considering the dynamic characteristics of rotor’s supporting structure, the test results are error-prone and inefficient. A new method for testing the supporting structure performance of aero-engine rotor in wide frequency domain is proposed. On this basis, the structural model of the casing-support and the structural model of aero-engine rotor are constructed by substructure modelling method. Combining the two sub-models, the semi-physical simulation model of the vibration of the engine rotor’s supporting structure is obtained. By superimposing the additional dynamic stiffness matrix of the casing-supporting structure at the designated DOF position in the overall stiffness matrix of the finite element model of the rotor structure, the overall stiffness matrix of the aero-engine rotor supporting structure is obtained. The effective stiffness matrix can be used to calculate the structural dynamic characteristics of aero-engine rotor supporting structure. Experiments show that the average error of the proposed method is 0.0023 and the number of units is 7.98 e4. The calculation time and storage space are reduced by 310 minutes and 166 GB respectively compared with the performance test method of rotor support based on finite element analysis, which shows that the proposed method is more efficient and accurate.