Development of methodology and measures to ensure the reliability of energy systems equipment

THE PURPOSE: The article presents the results of the development of a methodology for the design calculation of reliability and changes in the level of reliability of energy systems, taking into account the influence of control actions based on statistical methods of collection, analysis and models of experimental data processing.METHODS: The system analysis and generalization of experimental data on technological failures of the main equipment of thermal power plants were used in the calculation assessment.RESULTS: The objective function of controlling the reliability parameters of the thermal power plant power equipment is proposed. The approbation of the presented objective control function was performed, which showed the adequacy of the results obtained to assess the reliability of the main nodes and elements of the TPP power equipment.CONCLUSION: The results of the conducted studies show that when determining reliability indicators, it is necessary to take into account the actual technical condition of individual elements and resource-determining functional units of thermal power plant power equipment. The results obtained can be used to develop a methodology for evaluating control actions for calculating the output control parameters and a mathematical model for changing the output characteristics of TPP steam turbines in terms of heat and electric energy generation, as well as at the stage of developing design documentation for the creation of structural elements and practical recommendations in order to extend the service life of power equipment generating systems based on digital technologies.

Automatic quality detection system for structural objects using dynamic output method: Case study Vilnius bridges

Paper provides an attempt to create a methodology for automated structure health monitoring procedures using vibration spectrum analysis. There is an option to use autoregressive (AR) spectral analysis to extract information from frequency spectra when conventional Fast Fourier transformation (FFT) analysis cannot give relevant information. An autoregressive spectrum analysis is widely used in optics and medicine; however, it can be applied for different purposes, such as spectra analysis in electronics or mechanical vibration. This paper presents an automated structural health monitoring approach based on the algorithm-driven definition of the first resonant frequency value from a noisy signal, acquired from traffic-created bridge vibrations. We implemented the AR procedure and developed a peak detection algorithm for experimental data processing. The functionality of the proposed methodology was evaluated by performing research on six bridges in Vilnius (Lithuania). We compared three methods of data processing: FFT, filtered FFT and AR. Bridges vibrations under different excitation conditions (wind, impulse and traffic) in normal direction were measured using accelerometers. AR provided one peak representing the lowest resonant frequency in all cases, while FFT and filtered FFT provided up to 12 peaks with similar frequency values. Such results allow implementing our method for remote automated structures health monitoring and ensure structures safety using a convenient and straightforward diagnostic method.

Comparative research of electrical energy transformation processes in locomotive traction drives with asynchronous motors and series-wound brushed DC motors

An estimate of the Russian railways expenses level for the purchase of fuel and energy resources is given. It is shown the costs for the purchase of electric energy for train traction account for more than half of the total costs. In this regard, the problem of increasing the traction rolling stock energy efficiency seems certainly relevant. The diagram of voltage and current measurements at the primary winding of the AC cargo electric locomotive transformer is given. The experimental data processing algorithm is proposed. A comparative analysis of the results obtained for electric locomotives with series-wound brushed DC motors (throughout what follows will be denoted as BTMs) and asynchronous traction motors (will be denoted as ATMs) showed that the power factor of the asynchronous drive is higher: 0.99, compared to 0.65 for the drive with BTMs; and the coefficient of nonlinear current distortions is only 0.15, compared to 0.53 for the BTMs. The conclusion is made about higher efficiency of electric energy conversion process in asynchronous traction drive in trust mode.

Studies of Dynamic Processes

The traditional approach to experimental data processing is based on the estimation of the averaged characteristics of the process, such as mean, variance, and range. However, a deeper processing with the identification of the features of the non-wicked dynamic behavior of the process allows us to see those features that are very important for a more complete understanding of its essence. The article provides examples of identifying the features of the dynamic behavior of processes in the atmosphere, studying the dynamics of heat and mass transfer when air moves in the upper respiratory tract of a person, and acoustic vibrations excited by a flame in the environment. Using the example of processing the time series of fluctuations in atmospheric air temperature, it is shown what unexpected information can be hidden in dynamic changes.

Automated system for identification of data distribution laws by analysis of histogram proximity with sample reduction

The error in the identification of the distribution law entails an incorrect assessment of other characteristics (standard deviation, kurtosis, antikurtosis, etc.). The article is devoted to the development of accessible and simple software products for solving problems of identifying distribution laws and determining the optimal size of a data sample. The paper describes a modified method for identifying the law of data distribution by visual analysis of the proximity of histograms with a reduction in the sample size with software implementation. The method allows choosing the most probable distribution law from a wide base of the set. The essence of the method consists in calculating the entropy coefficient and absolute entropy error for the initial and half data sample, determining the optimal method for processing the histogram using visual analysis of the proximity of histograms, and identifying the data distribution law. The experimental data processing model makes it possible to take into account the statistical properties of real data and can be applied to various arrays, and allows to reduce the sample size required for analysis. An automated system for identifying the laws of data distribution with a simple and intuitive interface has been developed. The results of the study on real data indicate an increase in the reliability of the identification of the data distribution law.

Dynamic Susceptibility of Ferrofluids: The Numerical Algorithm for the Inverse Problem of Magnetic Granulometry

The size-dependent properties of magnetic nanoparticles (MNP) are the major characteristics, determining MNP application in modern technologies and bio-medical techniques. Direct measurements of the nanosized particles, involved in intensive Brownian motion, are very complicated; so the correct mathematical methods for the experimental data processing enable to successfully predict the properties of MNP suspensions. In the present paper, we describe the fast numerical algorithm allowing to get the distribution over the relaxation time of MNP magnetic moments in ferrofluids. The algorithm is based on numerical fitting of the experimentally measured frequency spectra of the initial dynamic magnetic susceptibility. The efficiency of the algorithm in the solution of the inverse problem of magnetic granulometry is substantiated by the computer experiments for mono- and bi-fractional ferrofluids.

Properties of nickel-based superalloys of equiaxial crystallization

Purpose. The aim of the work is to obtain predictive regression models, with the help of which, it is possible to adequately calculate the mechanical properties of nickel-based superalloys of equiaxial crystallization, without carrying out preliminary experiments. Research methods. To find regularities and calculate the latest CALPHAD method was chosen, and modeling of thermodynamic processes of phase crystallization was performed. Results. As a result of experimental data processing, the ratio of alloying elements Kg¢ was proposed for the first time, which can be used to assess the mechanical properties, taking into account the complex effect of the main alloy components. The regularities of the influence of the composition on the properties of heat-resistant nickel alloys of equiaxial crystallization are established. The analysis of the received dependences in comparison with practical results is carried out. The relations well correlated with heat resistance, mismatch and strength of alloys are obtained. Scientific novelty. It is shown that for multicomponent nickel systems it is possible with a high probability to predict a mismatch, which significantly affects the strength characteristics of alloys of this class. The regularities of the influence of the chemical composition on the structure and properties of alloys are established. A promising and effective direction in solving the problem of predicting the main characteristics of heat-resistant materials based on nickel is shown Practical value. On the basis of an integrated approach for multicomponent heat-resistant nickel-based alloys, new regression models have been obtained that make it possible to adequately predict the properties of the chemical composition of the alloy, which made it possible to solve the problem of computational prediction of properties from the chemical composition of the alloy. This allows not only to design new nickel-based alloys, but also to optimize the composition of existing brands.

INFLUENCE OF TOOLING SYSTEM ACCURACY ON DYNAMIC CHARACTERISTICS OF MULTI-PURPOSE MACHINE

Рассмотрена характерная для современного машиностроения тенденция по увеличению концентрации технологических операций на многоцелевых станках и интенсификации режимов резания. Приведен анализ станочных парков различных металлообрабатывающих предприятий, который показал преобладание станков фрезерно-расточной группы. Проанализированы причины широкой номенклатуры инструментальной системы станков фрезерно-расточной группы и рассмотрено влияние многообразия инструментальной системы на динамические характеристики многоцелевых станков. Рассмотрен пример характерной для станков фрезерно-расточной группы среднего типоразмера инструментальной системы, которая включает в себя цанговый патрон, цангу и фрезу. Приведены расчеты точности и жесткости для различных вариантов инструментальной системы. С целью подтверждения полученных теоретических расчетов были проведены экспериментальные исследования в условиях реального производства при обработке серийно изготавливаемой детали типа «Корпус» на фрезерном многоцелевом станке модели VMC-600. Результаты обработки экспериментальных данных показали, что точность инструментальной системы значительно влияет на геометрическую точность обработанной детали, виброустойчивость инструментальной системы и ее жесткость. Низкая точность инструментальной системы приводит к значительному отжиму режущего инструмента на рекомендуемых режимах резания, который может превысить величину допуска на обработку, что должно быть учтено на этапе проектирования технологического процесса путем занижения режимов резания The article discusses the characteristic tendency of modern mechanical engineering to increase the concentration of technological operations on multi-purpose machine tools and intensify cutting modes. We give the analysis of machine parks of various metalworking enterprises, which showed the prevalence of milling and boring machines. This article analyzes the reasons for a wide range of tool systems for milling-boring machines and considers the influence of the diversity of the tool system on the dynamic characteristics of multi-purpose machines. We considered an example of a medium-sized tool system typical for milling and boring machines, which includes a collet chuck, a collet and a milling cutter. We give calculations of accuracy and stiffness for various versions of the instrumental system. In order to confirm the obtained theoretical calculations, we carried out experimental studies in real production conditions when processing a serially manufactured part on a VMC-600 multi-purpose milling machine. The results of experimental data processing showed that the accuracy of the tool system significantly affects the geometric accuracy of the machined part, vibration resistance of the tool system and its rigidity. The low accuracy of the tool system leads to a significant squeezing out of the cutting tool at the recommended cutting conditions, which can exceed the machining tolerance, which should be taken into account at the design stage of the technological process by understating the cutting conditions