Rotor Support Research Articles

Improvement of the information system of remote monitoring of the technical condition of gas turbine engines

The implementation in the information system for remote monitoring (ISRM) of the technical condition of gas turbine engines (GTE) of a new method (hereinafter referred to as the Method) for early detection of deterioration in the technical condition of the rotor supports of a power turbine (PT) GTE is considered. The method is based on an expert rule, which analyzes the parameters of the engine oil system. The distinctive advantages of the Method are the possibility of use when atmospheric conditions and engine operating modes change, as well as its versatility. Automatic monitoring of the technical condition of the GTE in real-time mode and automated analysis of changes in the historical values of its operating parameters depending on time, performed in the ISRM, make it possible to timely identify the deterioration of the technical condition of engine components and carry out their maintenance or repair. The structure and graphical user interface of the ISRM are considered. The algorithm that implements the Method is described in detail, the script in which this algorithm is programmed, and the graphical user interface created to display and analyze the results of applying the Method are described. The procedure for testing the ISRM functionality created for the application of the Method using the historical values of the GTE parameters is outlined. The implementation of the Method in ISRM showed its openness and versatility for the implementation of new methods for diagnosing equipment using algorithms for analytical processing of the values of its operating parameters. Keywords: remote monitoring of the technical condition; gas turbine engine; real-time mode; new method for assessing technical condition; implementation of the method; power turbine rotor support; early detection of faults; reduction of operating costs.

Intelligent Bearing Fault Diagnosis of Switched Reluctance Motor Using Hilbert-Huang Transformation and Region-Based Convolutional Neural Network

With the widespread trend of transportation electrification, much research has been focused on switched reluctance motor (SRM) because of its robustness and wide speed range. Though the SRM has a promising electric fault tolerance, the rotor support bearings subjected to mechanical friction are vulnerable to brinelling and corrosion. Furthermore, traditional bearing fault diagnosis approaches adopted for conventional motors are not well suited for SRM bearings because of its high torque ripples and noisy operation. Aiming at offering an efficient solution, this work proposes a novel technique by fusing the Hilbert-Huang transformation of vibration signal with region based Convolutional Neural Network. The core idea of the method is to decompose the vibration signal and employ a new kind of offline region generation algorithm for the detection of fault characteristics. The effectiveness of the designed model is tested and evaluated by a series of experiments. The results show that the proposed method achieved a remarkable diagnosis accuracy of 99.6%. Conclusively, a systematic comparison of the proposed model with the other state of the art models is carried out.

Vibration reduction of rotor systems using magneto-rheological elastomeric supports

Support characteristics (stiffness and dissipation) are well understood to influence the dynamic behaviour of rotors. Supports play an essential role in deciding the stability and response of the rotors. Therefore, frequency-dependent support characteristics are beneficial in determining the rotor response as the frequency of excitation keeps changing. An elegant choice of making rotor supports is by using magneto-rheological elastomeric (MRE) materials. The magnetic field application results in a change in the stiffness and dissipation behaviour of MREs and consequently influences the dynamics of the rotor–shaft system. An attempt is made in this work to conceptualize the MRE as viscoelastic sectors put between the outer race of a bearing and the bearing housing to make the rotor support. A rigorous analytical formulation is done to obtain the stiffness and dissipation of the support so formed in terms of a viscoelastic model of the material under the effect of dispersed magnetic material, the geometry of the sectors, the intensity of the magnetic field, and the frequency of forcing function the supports are subject to. The supports show promising results by reducing the vibrations at resonance by suitably applying the magnetic field. Therefore, MRE materials may be proposed as adaptive supports to both structures and rotors to induce intended dynamic behaviour.

Intelligent robust controllers for tribotronic conical fluid film bearings

The article presents the results of the development of means for intelligent robust control of the parameters of a tribotronic rotor-support system with a tapered bearing with a removable bush. The proposed controller is implemented on the basis of deep Q-network reinforcement learning (DQN) synthesized on the basis of a numerical model of a rotor support system. The control strategy involved simultaneous control of the shaft position and friction in the lubrication layer. Methods for control synthesis are presented for both a deterministic system and a system with stochastic parameters. In the latter case, a controller synthesis technique is proposed that takes into account uncertainties in the system at the training stage. Testing of the resulting controllers shows the better ability of a controller trained to take into account uncertainties to cope with variable loads, as well as predict possible changes in the system and proactively transfer the system to more advantageous states.

Experimental determination of damping coefficient of a support with elastic ring under harmonic loading

The article describes the possibility of determining the damping coefficient of a support with an elastic ring based on dry friction forces using a special test bench. The forced excitation force is set by the oscillations of a compact speaker installed on top of the oscillating mass through a U-shaped crossbar. The object of the study is a damper with an elastic ring, that is a thin-walled ring with evenly distributed bulges inside and outside, arranged in a checkerboard pattern. The damping coefficient is estimated using a device for simulating a rotor support, an acceleration sensor, an exciter speaker, a controller and a processing station. The amount of damping is estimated according to the width of the peak at the resonant frequency. A comparison is given of the magnitude of the damping coefficient obtained from the analysis of the resonance peak and from the decay rate during the impact experiment.

The Effect of Support Misalignment on Vibration Characteristics of Aero-Engine Rotor Systems under Ultra-High Operating Speeds

In order to ensure the vibration safety of rotor systems in the next generation of aero-engines and reduce the impact of misalignment faults, the effect of support misalignment on the vibration characteristics of rotor systems under ultra-high operating speeds is investigated in this paper. Firstly, an analytical excitation model of the rotor systems under ultra-high operating speeds is established, considering the impact of the support misalignment. Then, based on the model of the misaligned combined support system, the dynamic model of the flexible discontinuous rotor support system with the support misalignment is presented. Subsequently, based on the established model, the effects of support parameters and support misalignment amounts on the vibration characteristics of the rotor support system are analyzed. Finally, experimental validation of the research findings is conducted. The research result shows that the support misalignment increases the vibration response of the rotor, reduces the vibration reduction efficiency of the combined support system, and consequently decreases the vibration safety of the rotor support system.

Improving the technological process of balancing electric machine rotors on a balancing machine

The object of research is the process of dynamic balancing of rotors on a balancing machine in the process of restoring electric machines. The work is aimed at improving the quality of balancing rotors in the process of major repairs of traction electric motors for electric trains. The problem addressed was the quality of balancing the rotors of electric machines on stationary balancing machines. According to the conventional balancing technology, the rotor to be balanced is mounted on the supports of the balancing machine with support surfaces that usually have mechanical defects. These defects cannot be eliminated by machining due to the peculiarities of rotor repair technology. Theoretical and experimental studies of the effect of damage to the rotor support surfaces on the balancing parameters have been carried out. It has been proven that the properties of the bearing surfaces of the rotor during its balancing on a balancing machine significantly affect the results of determining the imbalance. At the same time, the difference in the mass values of balancing loads can reach 25 %. This is because damage to the bearing surfaces of the rotor generates false signals unrelated to the imbalance. In order to increase the accuracy of determining the mass of balancing loads during rotor balancing, it is proposed to improve the technological process of balancing. The improvement involves the inclusion of a frequency filter in the signal conversion chain of acceleration sensors. The filter is designed to separate signals with a frequency greater than the rotational frequency of the rotor. A condition for the practical application of the research results is the expediency of introducing a frequency filter of signals of acceleration sensors with a threshold frequency of filtering signals that exceeds the rotational frequency of the rotor into the schematic diagram of the balancing machine.

RTCA-Net: A New Framework for Monitoring the Wear Condition of Aero Bearing with a Residual Temporal Network under Special Working Conditions and Its Interpretability

The inter-shaft bearing is the core component of a high-pressure rotor support system of a high-thrust aero engine. One of the most challenging tasks for a PHM is monitoring its working condition. However, considering that in the bearing rotor system of a high-thrust aero engine bearings are prone to wear failure due to unbalanced or misaligned faults of the rotor system, especially in harsh environments, such as those at high operating loads and high rotation speeds, bearing wear can easily evolve into serious faults. Compared with aero engine fault diagnosis and RUL prediction, relatively little research has been conducted on bearing condition monitoring. In addition, considering how to evaluate future performance states with limited time series data is a key problem. At the same time, the current deep neural network model has the technical challenge of poor interpretability. In order to fill the above gaps, we developed a new framework of a residual space–time feature fusion focusing module named RTCA-Net, which focuses on solving the key problem. It is difficult to accurately monitor the wear state of aero engine inter-shaft bearings under special working conditions in practical engineering. Specifically, firstly, a residual space–time structure module was innovatively designed to capture the characteristic information of the metal dust signal effectively. Secondly, a feature-focusing module was designed. By adjusting the change in the weight coefficient during training, the RTCA-Net framework can select the more useful information for monitoring the wear condition of inter-shaft bearings. Finally, the experimental dataset of metal debris was verified and compared with seven other methods, such as the RTC-Net. The results showed that the proposed RTCA-Net framework has good generalization, superiority, and credibility.

Design and Comparative Analysis of Rotating Cold Rotor Support Scheme for Superconducting Motor

Design and Comparative Analysis of Rotating Cold Rotor Support Scheme for Superconducting Motor

Towards an Integrated Design of Direct-Drive Wind Turbine Electrical Generator Supporting Structures

Rotor and stator support structures of significant size and mass are required to withstand the considerable loads that direct-drive wind turbine electrical generators face to maintain an air-gap clearance that is open and stable. With the increase of scale, reducing the weight and environmental impact of these support structures is believed to be one of the key components to unlocking the true potential of direct-drive generators. An investigation on the electrical generator rotor structure of the IEA 15 MW offshore reference wind turbine was conducted. An integrated approach that considered the environmental impact, including the manufacturing energy usage and CO2 footprint, as well as the financial repercussions of structural parameter modifications as they are optimised was followed, making use of distinct commercial pieces of software. The rotor structure was parametrically optimised, and its operating loading conditions were evaluated at various size scales. The study determined that the effect of thermal loading is significant, which forces the designer to augment the mass to comply with the imposed structural requirements. The ensuing life-cycle assessment showed an increase in the environmental impact due to the consideration of this particular load, whose effect in structural deflection and stress has been typically underestimated.

Investigation on the Rotordynamic Characteristics of Turbopumps with Angular Contact Ball Bearings

The support stiffness of the turbopump rotor system with angular contact ball bearing varies with the rotational speed, which leads to the inaccurate prediction of the dynamics of the turbopump rotor system. The model of the rotor bearing system was constructed based on the theoretical model of angular contact ball bearing stiffness, and the dynamics characteristics of the turbopump system were calculated. To verify the accuracy of the stiffness and the dynamics model, a test system of the turbopump rotor with angular contact ball bearings was designed. Since the bearing stiffness cannot be measured directly, a stiffness identification model was introduced, and an unbalanced response test was conducted to verify the dynamics model. It was found that the turbopump bearing stiffness increased dynamically with speed and reduced the unbalance response of the rotor. The results show that the angular contact ball bearing stiffness model and the dynamics model of the rotor support system are accurate and provide support for the dynamics design of the turbopump rotor system with angular contact ball bearings.

A 3-D finite element modeling method for time-varying rotor-support system based on rotating-fixed coordinates

The asymmetry of rotor systems is sometimes evident, such as keyed shafts, crack rotors, two-pole generator rotors and especially shaft-disk-blade systems. Meanwhile, the coupling vibration problem between rotor and support structure is becoming more and more prominent due to the light weight of aero-engines. The design and analysis method for the dynamic characteristics of time-varying rotor-support system with detailed structure is needed. Therefore, a modeling method is proposed by using 3-D finite element for time-varying rotor-support system based on rotating-fixed coordinates. The rotor is modeled in rotating coordinate system and the support structure is modeled in fixed coordinate system respectively. The force, energy and displacement between rotor and support structure are transmitted by bearing mechanical parameters. Thus, the time-varying characteristics of the system are expressed explicitly by bearing mechanical parameters, and the dynamic equation of time-varying rotor-support system can be obtained. Then, Floquet theory and Hill infinite determinant method are used to analyze quasi-mode frequency characteristics and stability of time-varying rotor-support system. The results of a typical asymmetric rotor-support system got by the proposed method were compared with existed methods, and more coupling vibration characteristics such as the coupling vibration of rotor axial motion and support plate bending, the coupling vibration of shaft bending and support plate torsion were obtained.

Characteristics of a tip-vortex generated by a single rotor used in agricultural spraying drone

A better understanding of downwash flow is required to increase the efficiency of unmanned aerial vehicle sprayers. The tip vortex rolled up by the rotor blade tip rotating at high speed produces a complex induced velocity field, which has an important impact on the downwash flow in the wake of the rotor. Usually, a symmetrical experimental setup with a central rotor support perpendicular to the rotation plane is used in studies on rotating blade wake and vortices, potentially leading to differences in observed wake and vortices in real situations. whereas in reality, the rotor is typically supported by a parallel arm extending below the rotor in the rotation plane. It is crucial to consider these differences for accurate results in analyzing blade rotation. The behavior of the tip vortices, dynamic characteristics, and velocity field of the rotor wake in agricultural drone single-rotor downwash flow was experimentally investigated using particle image velocimetry (PIV) combined with high-speed camera imaging. The dynamics of blade tip vortices at different wake ages and rotational speeds of the rotor, 1000–3000 rpm, were measured and analyzed. The results indicate that in the early stages of a vortex's life, tip vortices generated by rotors do not have an axisymmetric structure, and the swirl velocity in the core decreases logarithmically as the wake age increases. Vortex models were validated by examining the swirl velocity structure of the tip of the vortex. Vortices within the vortex core exhibit a comparable self-similar velocity profile to the Iverson model's laminar profile, despite the transition flow outside the vortex core. With these measurements, the behavior of vortices in the rotor’s wake could be described with generalized semi-empirical models.

Numerical studies on small rotor configurations with validation using acoustic wind tunnel data

This paper addresses the acoustic and aerodynamic characteristics of small rotor configurations, including the influence of the rotor–rotor interactions. For this purpose, a Rotor/Rotor/Pylon configuration is chosen for both the test and numerical simulations. The wind tunnel experiments on various rotor configuration were performed in DLR’s Acoustic Wind Tunnel Braunschweig (AWB). The experiments involve isolated rotors, and rotors in tandem and coaxial configuration in hover and forward flight. For numerical simulations, an unsteady free wake 3D panel method (UPM) is used to account for aerodynamic non-linear effects associated with the mutual interference among the Rotor/Rotor/Pylon configurations. The effect of the pylon is simulated using potential theory in form of a panelized body. Finally, the sound propagation into the far field is calculated with DLR’s FW–H code APSIM, using UPM blade surface pressure as input. The validation effort is supported by CFD TAU steady simulations on selected hover test cases. The experiments and numerical results indicate that the noise at the blade passing frequency (BPF) and its higher harmonics is the dominant source of the noise for the present rotor selection. The extra subharmonics between two BPFs appearing in the results are caused by the small geometric discrepancy between the blades as well as the motor noise. Broadband noise is also observed in the experiment, but its contribution to the overall sound pressure is very small and can be neglected. The simulation of the acoustic scattering from the rotor support system for the isolated rotor cases indicated an influence about 1–3 dB on the overall sound pressure of the polar microphones. In both the coaxial and the tandem configuration, the acoustic interferences are particularly well visible in the numerical simulations and cause a more complex noise directivity. There is almost no change in time-averaged inflow by applying phase angles. In the coaxial condition, in hover, the phase delay between rotors does not change the maximum noise level. In forward flight, the phase delay can influence the maximum level of the noise radiation. In both coaxial and tandem configuration, the position of the downstream rotor is key for the noise radiation, and therefore, avoiding the interaction with upstream wake can reduce the noise radiation.

ANALYSIS OF NONLINEAR RIGIDITY CHARACTERISTICS OF AIR BLOWER COMPRESSOR ELASTIC SUPPORTS

Vibrations of rotor systems are largely determined by elastic characteristics of supports. In the general case, the dependence of displacements on force for such supports is nonlinear. This applies to bearing supports of various types. In addition to bearings, elastic elements are also used in supports of rotor systems. They are designed to change the overall stiffness of the supports. The paper analyzes the radial stiffness of flexible ring dampers used in rotor supports. For this, two main approaches are proposed. The first is a conventional simulation of this problem of contact mechanics using the finite element method. The second is an analytical method that can be used as an alternative to expensive numerical calculations. This method is based on the principle of minimum additional energy. A special closed-form variational formulation is developed using the Euler-Bernoulli beam approximation for an elastic ring and a simplified model of normal contact on the ring flanges. It was shown that the surface tolerances of parts have a significant effect on the radial response of a flexible ring, which can become nonlinear. Tight fit of the ring on both sides makes it much stiffer, and non-tight fit leads to free movement of the rotor and much weaker damping of its movement. Both methods gave results that are consistent for the considered cases. By varying their design parameters, it is possible to adjust the rotor systems from critical modes of operation. Keywords: rotor system, elastic support, rigidity, finite element analysis, stress-strain state, contact interaction, principle of minimum additional energy

Optimization of Control Parameters of Magnetorheological Squeeze Film Dampers to Minimize the Vibration Amplitude of Rotors Passing the Critical Speed

Rotors are often coupled with a stationary part by rolling element bearings. To suppress their excessive vibration, the bearings are inserted in squeeze film dampers. The control of damping in the support elements offers the possibility to minimize the oscillation amplitude of accelerating or decelerating rotors, passing the regions of critical speeds. The controllable damping effect can be achieved if the squeeze film dampers are lubricated with magnetorheological oil. The change in the applied current feeding the electric coil changes magnetic induction in the damper gap, which changes the oil damping properties. The minimum vibration amplitude of the rotor running up or down through the resonance area is accomplished if the current increase or decrease is not sudden, but if it is distributed in some time interval. This article concentrates on determination of the optimum parameters of this manipulation. The developed procedure leads to solving an unconstrained optimization problem with the implicit objective function. The evolution method was used for its solving. In the investigated case, the proposed procedure made it possible to reduce maximum vibration amplitude by about 40% compared with the uncontrolled current decrease. The main contribution of the conducted research work is presentation of a new and original procedure for controlling the damping effect in the rotor supports. It provides a new idea to the designers and engineers regarding how to minimize amplitude of the rotor vibration when passing the critical speed. In addition, the article points to a new area of utilization of controllable magnetorheological squeeze film dampers.

Health monitoring of the shaft bearings in a micro turbojet based on vibration analysis

In a recently implemented aerial target, the propulsion system consists of two JetCat micro turbojet engines. Due to the limited durability of the rotor support bearings, the engine operation time has been limited to two hours or two flights. In addition, after each flight, an engine bench test with vibration measurement is required. The adopted maintenance system is also labor-intensive and costly due to obligatory shaft bearing inspections performed frequently in the repair shop. These problems result from the limitations of the available high-speed bearing technology and the high rotor loads related to aircraft maneuvers in the air. The goal of the work is to develop a method for assessing the health of the main shaft bearings in the micro turbojet based on vibration signals. Methods known from full-scale jet engines were adapted for monitoring the health of the main shaft bearings. An accelerometer and rotational speed sensor were mounted on the engine. Vibration and other parameters of the engine were measured and analyzed, and then symptoms of damage were sought. The vibrations of seven JetCat engines were analyzed, selecting the one for further destructive testing. In all three axes X, Y and Z, the vibration components related to the rotational frequency and its orders are dominant, especially EO2 and EO3 related to rotor dynamics. Continuous engine vibration monitoring is a promising way of extending engine life and avoiding the deficiencies of microturbines related to their size and low-cost technology. The obtained results indicate that the tested JetCat engines have a life reserve, which has so far been used to a small extent.

Metrological support for the determination of akhial loads acting on the rotor supports of gas turbine engines

Based on the results of the analysis of the method of measuring axial forces acting on the structure of a ball bearing mounted in the rotor support of a gas turbine aircraft engine, a method for estimating the relative error of the measuring system using dynamometric rings is proposed. Keywords: tests, measurement of forces, measurement error. super-krisya12@yandex.ru

Influence of brush seal hysteresis effect on the nonlinear characteristics of rotor system

The hysteresis effect of brush seal is a key factor affecting the sealing performance of the rotor system, so it is particularly important to study the nonlinear behaviors of the rotor-bearing-brush seal system under the hysteresis effect. First, the entire circle of bristle pack is classified according to the position angle and contact condition of single bristle, and the rotor support force, the interaction force between the bristles, the air pressure and the friction of back plate are considered. It is proposed to use the loss rate to calculate the uniform load of the back plate, according to the linear beam theory, the bending force model of bristle under different rotor eccentricity is established. Second, the hysteresis angle is proposed to represent the degree of hysteresis effect of the whole circle of bristle pack, and the seal force model under hysteresis effect is established. Third, considering the interaction of seal force and oil-film force, the dynamic model of Jeffcott rotor-bearing-brush seal system is established. The influence of hysteresis effect on the dynamic characteristics of rotor system is studied by using bifurcation diagram, axis orbit, Poincaré map, spectrum diagram and time history. It is found that the hysteresis effect has different degrees of influence on the nonlinear dynamic characteristics of the rotor system in different rotational velocity intervals. In addition, the influence of seal interference on the motion state of rotor system cannot be ignored.

Способ оценки адекватности результатов численного моделирования поля параметров неравномерного потока на входе в вентилятор ТРДД экспериментальным данным

The article substantiates the need to intensify the process of oil cooling in the oil systems of aircraft turbojet engines. Currently, an increase in the thrust of turbojet engines is achieved by increasing the air pressure ratio in the compressor and the gastemperature in front of the turbine. However, an increase in thevalues of theseparameters leads to an increase inthe thermal loadof theengine elements,including rotor supports, which causes an increase in oil temperature. The oil systems of modern turbojet engines still use the same oils as several decades ago.Therefore, the intensification of the oil cooling process, which allows reducing its temperature, is the main way to preserve the lubricating properties.It is proposed to intensify the oilcooling process in the oil system of the bypass turbojet engine byinstalling an air-oil heat exchanger in the bypass duct.A thermal calculation of fuel-oil and air-oil heat exchangers has been carried out, the results of which show large values of the heat transfer coefficient when the oil is cooled by the bypass duct air