Vol 10, No 3 (2024): 20.11.2024
- Year: 2024
- Published: 20.11.2024
- Articles: 11
- URL: https://dynvibro.ru/dynvibro/issue/view/678
Full Issue
Articles
Application of the equivalent source method for numerical simulation of hydrodynamic noise of elastic bodies
Abstract
The paper presents a novel approach to predicting the emission characteristics of hydrodynamic edge noise, which occurs when elastic bodies move in turbulent flow. The solution is based on the decomposition of the computational domain and replacing it with a set of segments. Each such subdomain determines the corresponding energy contribution of hydrodynamic noise sources to the total sound field of a streamlined body. The statistical independence of the processes of the selected regions allows us to give a simplified representation of the radiation flowing around the body in the form of a sound propagation process from a finite number of point sources. The purpose of the report is to cross-verify the method on the model problem of profile flow by a liquid flow. The average error of the method relative to the associated calculation "hydrodynamics-acoustics" is no more than 3dB in the range up to 1500 Hz.
7-18
Self-excitation of non-synchronous rotation of closely spaced unbalanced rotors
Abstract
The results of experimental studies of the process of self-excitation of rotation with close coaxial arrangement of thin-walled disks, as well as rigidly and movably installed screens coaxially located with them, are considered and analyzed. Self-excitation of rotation was observed only when one dynamically unbalanced rotor (disk) rotated with a frequency of more than 50...150 Hz and when circular vibration of an initially non-rotating second rotor (disk or screen) was excited, located coaxially at a distance of 1...4 mm from it on a common rigid base. The self-excitation of the rotation of the rotor installed on an electric motor not connected to the network was not synchronous with the rotation speed of the dynamically unbalanced rotor rotated by the electric motor. With a rotor (disk) weight of 0.5 N and an initial distance from the screen of 3...3.5 mm, the force causing repulsion of the movable screen from the rotor was about 2.5...2.7 N, and the torque was about 0. 01 Nm. When the distance between the surfaces of the coaxially located dynamically unbalanced rotating rotor and the initially stationary disk or screen was more than 5...6 mm, the process of repulsion and self-excitation of rotation of the screen or rotor was not observed. The rotation of a well-balanced rotor in the absence of circular vibration of the second rotor or screen, even with a distance between them of 1...1.5 mm, other things being equal, also did not lead to their forceful interaction and self-excitation of rotation.
19-28
Asymptotic analysis of monotonic stability of the amplitude of pendulum oscillations with small nonlinear damping
Abstract
An ordinary differential equation of the second order describing free oscillations of a pendulum with small damping in the form of a third-degree polynomial is considered. The aim of the work is to analyze the monotonic stability of the amplitude of free oscillations of the pendulum with small damping, having one degree of freedom. The equation of the pendulum oscillations is written as a system of amplitude-phase equations. Then, the equation for the oscillation amplitude is averaged over the fast phase. By analyzing the expressions for the first- and second-order derivatives for the averaged amplitude, the monotonic stability of the pendulum oscillations is analyzed. The following main results are obtained in the work: the conditions of the monotonic stability of the pendulum oscillation amplitude are formulated, the region of monotonic stability is described, the number of qualitatively different cases of monotonic stability is determined, the condition for the attainability of a stable equilibrium position by the pendulum is considered. Verification of the results of the work confirmed their correctness. At the same time, they have both theoretical and applied significance. For example, they can be used in studying the stability of self-oscillations of the pendulum systems.
29-38
Complex analysis of the vessel's shaft
Abstract
The article considers the impact of operating loads on a ship's shaft. Preliminary static, dynamic, modal and harmonic calculations were performed in the finite element modeling environment. Data on the shaft's natural vibration frequencies, as well as load values in a given frequency range and structure deformations in the operating mode were obtained. A complex analysis of the ship's shaft has been carried out. Data on the frequencies of natural vibrations of the shaft, the values of loads in a given frequency range and deformation of the structure in the operating mode were obtained. According to the data obtained, it is possible to judge the change in the state of the structure during operation.
39-49
Development of a data exchange service between software systems
Abstract
This article presents the development of a service information model for data exchange between ERP and MES systems used for planning and control of production processes. The purpose of the service is the efficient transfer and structuring of information between databases in the production process, as well as control of operations through the user interface. This approach allows for the integration of various external software systems, which is an urgent task in the field of automation and control of production processes. The service was implemented in Python using SQLAlchemy to work with PostgreSQL databases. The graphical interface of the service allows you to edit the required JSON template, used for working with databases. Testing was carried out on two databases for a system for monitoring the movement of parts during the production process, confirming the functionality and reliability of the service.
50-57
Application of a high-speed balancing facility digital model to prepare and conduct trials for aircraft engine rotors
Abstract
The paper presents digital model of vacuum high-speed balancing facility MAI. Russian and foreign experience of usage of vacuum chambers for rotor balancing and research purposes was reviewed. Example of usage of the proposed high-speed balancing facility digital model for development of the layout scheme of the high-pressure rotor of aviation engine with low-bypass ratio inside the facility prior its testing was observed. Example of usage of finite element model of vacuum chamber for identification of resonant modes related to coupled modes of the struts-facility dynamic system was shown. The issues of damping consideration during preparation of vacuum facility computational models were observed. Dynamic model of vacuum balancing facility built in DYNAMICS R4 software for further usage in simulations related to rotordynamics was proposed. The issues of computational rotor models preparation on example of verification of high-pressure rotor model based on results of virtual modal tests, performed for its main load frame structure on the base of its solid finite element model, were observed. Principle of model creation for rotor-bearings-tooling-struts-balancing facility dynamic system was described. Example of usage of vacuum facility dynamic model for planning of dynamic tests of high-pressure rotor related to investigation of constructive measures related to its assembling on vibration activity of the rotor in operating range was shown. The case of usage of the vacuum facility dynamic model to prepare for the experiments related to rotor dampers operation check during rotor tests at high-speed balancing facility was observed.
58-80
Optimization of probabilistic operational characteristics of a neural network algorithm for predictive diagnostics of industrial equipment failures through automated processing of a training sample
Abstract
The paper considers the optimization of probabilistic operational characteristics of a neural network algorithm for predictive diagnostics of industrial equipment malfunctions. The probability of a false alarm and the probability of detecting a malfunction are accepted as optimized parameters, which are generally accepted metrics for the effectiveness of situation analysis and decision-making systems. The task of optimizing operational characteristics is decomposed to the level of influencing technical parameters of the system and reduced to finding the optimal values of the base calculation time of the derivatives of the measured technological parameters and the time of fault development. Automated processing of the training sample allows you to reduce the time spent on creating a system for predictive diagnostics of industrial equipment failures. The result of optimization of the probabilistic operational characteristics of the neural network algorithm is presented and optimal values of the variable parameters are obtained, as well as a result of training and testing on real telemetry data of the electric power pump of the turbine unit of the CHP, optimal values of the optimized parameters are obtained, according to which conclusions are drawn and further actions are proposed to improve the result.
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81-92
Teeth matching frequency in vibration diagnostics of technical condition of aviation gas turbine engine gearboxes
Abstract
The performance of an aviation gas turbine engine with gearbox is largely determined by the technical condition of this unit. Vibroacoustic diagnostics is the most effective method for identifying defects in rotary machines. It is generally recognized that the most informative diagnostic signs of gearing defects are the intensity of tooth harmonic and its multiples. However, in this case it is necessary to carry out vibration measurements in a wide frequency range. On the example of defects of the NK-12 engine gearbox we have shown that the use of the parameters of teeth matching frequency can reduce the frequency range under study by more than two orders of magnitude and improve efficiency of diagnostics of such defects as teeth wear and backlash.
93-98
Optoelectronic discrete-phase converter for automated control systems of geometric parameters of the surface of gas turbine engine blades
Abstract
Gas turbine engine blades are products with a complex spatial configuration that requires high manufacturing precision, which in turn is determined by the complex overall balance between aerodynamic, strength characteristics and production and technological requirements. During the production of blades, the surface profile in various sections of the blade airfoil is subject to control, among others. Deviations in the shape of the theoretical section and the installation angle of the profile lead in practice to a deviation of the natural vibration frequency of the blades from the calculated values. Increasing the accuracy of geometry control in the technological process of manufacturing gas turbine engine blades is in demand and important.
A measuring device developed by Samara University is briefly described: an optoelectronic discrete-phase converter (OEDPC), which is designed for non-contact determination of geometric parameters – the profile and curvature of gas turbine engine blades. The implementation of the OEDPC is based on a method for determining the parameters of the surface geometry of a gas turbine engine blade, which consists in measuring the deviations in time of the position of the maximum information signal from the reference one and makes it possible to increase the accuracy of determining the profile and curvature of the blade airfoil while maintaining performance at the level of the best examples of optoelectronic converters of a complex-profile surfaces.
99-110
Improving the quality of testing of hydralic equipment on a specialized measuring stand
Abstract
Improving the quality of testing of electro-hydraulic equipment is associated with the development of measures to reduce the levels of the stands own noise, increasing the stability of the operation of hydraulic systems by increasing the degree of test automation and maintaining the stability of the operating parameters of the test bench’s hydraulic systems.
Stands for control of noise and vibration of electro-hydraulic equipment are quite complex engineering structures which include pumps, control valves and the pipelines themselves with fittings. To be able to obtain reliable data during bench testing, it is necessary to take all possible measures to reduce the levels of acoustic interference from operating bench mechanisms to values much lower than the levels of acoustic disturbance created by a working controlled hydraulic device.
The comprehensive automation system for testing processes is designed to automate the installation and maintenance of modes, measurement processes and processing of the results obtained. It includes a system of setting and maintaining modes, as well as a vibration measuring complex.
The system for setting and maintaining modes allows you to remotely control the following processes from control panels installed at the measuring sections included in the bench installations:
- automated installation of parameters flow of working fluid and pressure in the lines of the stand;
- turning on and off pumping units;
- changing the rotation speed of electric drives of pumping units;
- operation of shut-off and control valves.
In the process of improving the stand, an original method of programmatic control of setting and maintaining the parameters of the working environment was developed and implemented. The use of this method makes it possible to minimize vibration and noise levels from the equipment and regulatory bodies of the stand by optimizing the combination of their operating parameters.
111-120
Determination of the elastic-damping characteristics of the vent-relief valve
Abstract
Valve devices are the main elements determining the reliability of pneumatic and gas systems. One of the main disadvantages of valve devices is their operation in an oscillatory mode, which occurs due to the instability of the system with the valve. To evaluate stability, linearized mathematical models with constant coefficients are used. In this paper, it is shown that for a relief valve maintaining pressure in the tank, the values of these coefficients are not constant and depend on the operating mode of the valve - the height of its lift. For these purposes, a mathematical model in lumped parameters of the "valve - tank" system is developed. The model takes into account that when leaving through the valve shatter, part of the gas follows the poppet. Mathematical modeling shows that such hydrodynamic interaction of the valve shatter and gas flow leads to additional negative components of general damping and elasticity in the equilibrium equation of the poppet, the values of which are proportional to the valve lift. This indicates that the coefficients of the poppet equilibrium equation during valve lift can become negative when the valve moves away from the sealing element, which ensures its instability and operation in an oscillatory mode. The obtained dependencies for the elastic-damping properties of the valve are confirmed experimentally.
121-137