Determination of the Area of Rational Use of Hybrid Bearings With Steel Rings and Ceramic Rolling Elements in High-Speed Aircraft Engines

The process of improving gas turbine engines is associated with increased thermodynamic parameters and rotor speed. In advanced aircraft engines the main rotor bearings will operate at speed index dmn > 3 · 106 mm · rpm, where dm is the bearing pitch diameter (mm), and n is the rotational speed (rpm). Under these conditions, significant heat is generated in the bearings, and the use of hybrid rolling bearings with steel rings and ceramic rolling elements looks more attractive due to the ceramic’s low density and low coefficient of thermal expansion. A computational method for predicting the thermal state of rolling bearings operating at high speed parameters has been developed based on comparative tests of steel and hybrid rolling bearings. Knowing the thermal state of the bearing allows the value of the operating clearance to be set in the bearing, which is important for determining the contact angle and load distribution over the rolling elements. A comparison with the results from tests of hybrid and steel bearings presented in the previous literature has shown that the calculated values correspond to the experimental data. Criteria for selecting steel or hybrid bearings are proposed, and areas of rational use for hybrid rolling bearings in aircraft engines are determined.

Quantification and Analysis of Uncertainties in Parameters of Rotors Supported by Bearings

Rotating unbalance is one of the most important critical parameters that causes operational failures of rotating machinery. The uneven distribution of mass on the structure of the rotors creates heavy spots, which must be eliminated to avoid generating excessive stress on the rotor bearings. The main objective of this work is to perform the uncertainty analysis on rotating machine systems supported with rolling bearings. A computational procedure is implemented to achieve this objective that can qualitatively represent the main behaviors and parameters of rotating machines. Further, methods of uncertainty quantification are applied to verify the behavior of the system given the probability density functions of the input parameters. One of the most commonly used methods is the Monte Carlo method, which requires thousands of simulations to produce accurate results. This method is used to obtain means and standard deviations of the system responses, given the means and standard deviations of the inputs. In our work, Monte Carlo simulation has been successfully used as a reference stochastic solver to evaluating the variability of the dynamic responses.

A New Artificial Neural Network Based Failure Determination System For Electric Motors

A new measurement system was developed for determination of failures and defining the level of failure that may occur in bearings and rotor bearings or in foot of motor in single phase capacitor start motor. In system, the vibratory operation of the motor is provided by connecting different screws on the motor’s rotor mounted flywheel or by gradually removing the nut bolts of motor foot. The VB3 vibration sensor outputs were recorded to the computer. The changing characteristics of sensor output for each experiment had more than one frequency component; therefore, FFT was performed for determining such components. It was observed that the frequency and amplitude values of first 5 harmonics could be used for determining the presence, type and level of failure but there was a nonlinear relation between each other. 2 different ANN customized separately were developed for determining the type and rate of the failure of motor. 80%, 10% and 10% of available data were reserved for training, testing and verification respectively and the ANN was trained. Accuracy degree for the ANN in the estimations following the training stage was calculated as R = 0.97-0.98. Furthermore, the results of ANN was compared with the results obtained using Sequential Minimal Optimization (SMO), Naive Bayes (NB) and J48 algorithms; and it was determined that the accuracy degree of ANN was higher.

Equipment Operational Reliability Evaluation Method Based on RVM and PCA-Fused Features

Reliability assessment is of great significance in ensuring the safety and reducing maintenance cost of equipment. The traditional statistical method is widely used to estimate the reliability of mass equipment; however, it cannot efficiently predict the overall reliability of single or small batch equipment due to lack of failure data. This paper introduced the operational reliability concept to describe the running condition of single or small batch equipment and proposed a method based on the combination of Relevance Vector Machines (RVMs) and Principal Component Analysis (PCA) to evaluate the operational reliability. Some representative characteristic indexes of operating equipment were firstly selected, and PCA was applied to obtain a hybrid index of the equipment’s running condition. Then, a RVM prediction model was trained to predict the development of the hybrid index and corresponding probability density function (PDF). Based on this, the operational reliability of the equipment was calculated by the interval integral defined by the failure threshold and the predicted value of the hybrid index. The approach was validated using the experimental test conducted on the aero-engine rotor bearings. The results show a good agreement in the evaluations of the failure time between the proposed method and the experimental test.

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.

PREVENTIVE MAINTENANCE STRATEGY FOR CRUSHING EQUIPMENT

The research was carried out in order to develop a mathematical model and a diagnostic complex to determine the residual life of the rotor bearings of hammer crushers. Residual life information is essential for proactive maintenance and to prevent equipment crashes. To achieve this goal, Kazan State Agrarian University (Republic of Tatarstan) carried out calibration studies of the dependence of the diagnostic parameters of vibration on the value of the radial clearances of the bearings. 3610 bearings with different radial clearances (0.02 mm, 0.08 mm, 0.13 mm, 0.2 mm, 0.27 mm) were alternately installed on the rotor of the KD-2 hammer mill, from the drive pulley side and from the fan side) and recorded the vibration parameters. The information was read using a piezoelectric sensor. Signal processing was performed using a VVM-201 vibrometer. The results of mathematical processing of these data are presented in earlier publications. To determine the change in the value of the radial clearance from the operating time in hours, retrospective studies were carried out directly in the agricultural enterprises of the Republic of Tatarstan: “Shaimurzinskoe agricultural enterprise named after A.Sh. Abdreev” of Drozhzhanovskiy region, JSC “Kiyatskoe”of Buinskiy region, the agricultural production complex “Ural”of Kukmorskiy region, etc. The average operating time of the bearings of the rotor of the hammer-type KD-2 forage grinder before the onset of a pre-failure state on the drive side was 1900 ... 2000 hours, on the fan side - 2000 ... 2100 h. Based on the results of the research, the values of the radial clearances and vibration parameters of the rolling bearings of the rotor of hammer crushers were experimentally established, the regularities of the change in the radial clearance of the rolling bearings of the rotor of hammer crushers were revealed depending on the operating time. The developed mathematical models for determining the radial clearance in the rotor bearings of the hammer crusher by vibration parameters and calculating the residual life are implemented in a diagnostic complex consisting of a commercially available VVM-201 vibrometer and a residual life attachment

The dynamic response of a rotor supported by two foil-air bearings with an enhanced model of foil structure

Foil-air bearings have presented their advantageous performance due to their different structures when compared to traditional air bearings. However, it is the nonlinear characteristic of this kind of bearing that has drawn studies on dynamic response of the rotor-bearing system, especially rotor stability. In this paper, an improved foil dynamic model with internal bending moment included has been proposed to determine the nominal stiffness of the foil structure. Based on that, the nominal stiffness of the foil structure has been investigated with different geometry parameters of the foil structure. By such means, the stability of the rotor-bearings system has been theoretically studied through an equation system in a common turbocharger structure. The results can be effectively used for designing and suitably selecting some geometry parameters of foil-air bearings to have a good rotor performance in this case.