Обзор и классификация пространственно-временных векторов дискретных состояний семифазного преобразователя

The subject of the research is the control algorithms for a seven-phase converter that implement space-vector voltage modulation of a seven-phase motor as an alternative to a three-phase engine in modern electric traction. The study used elements of set theory, combinatorics, Fourier series expansion and vector analysis. Checking research results was implemented on a special stand for experimental studies of spatial vector voltage modulation of a seven-phase motor.

Differentiated Integration: Project Competition and Contradictions of the EU Integration Process

Introduction. In 2017 the European Commission proposed five scenarios for the future of the EU, one of which was ‘those who want to do more do more’. However, it was not specific enough and ignored the variability of this way of integration. Methods and materials. Ignoring the characteristics of various types of differentiated integration is a common problem in scientific research, which leads to uncertainty and incorrect conclusions. This is largely due to the fact that researchers miss the analysis of interests and the negotiation process, focusing more on finding a common institutional design for all participants of integration. The intergovernmentalism that sees differentiated integration as a special institutional design that helps overcome the impasse in negotiations caused by the growing heterogeneity of member states is lacking. This approach has the potential for research and planning of integration processes in other regions, especially in the Post-Soviet space. Analysis. The article shows that differentiated integration has a long tradition in the EU, but that has little relation to the projects of the European future discussed in recent years (often with the same name). We have focused on the differences in the positions of European governments and groups of countries, trying to explain their motives and to answer the question of whether an intergovernmental approach is justified. The greatest attention is paid to French-German discussions, analysis of the UK’s role prior to EU secession, and the special stand of Scandinavian and Central-Eastern European countries. Results. The author concludes that the discussions on differentiated integration are not so much a search for unity in diversity, but are aimed at achieving ambitions, redistributing resources and fight against dirigisme. However, EU reform challenges integration leaders to choose between unprecedented concessions and the need to ignore the positions of many countries. In addition to EU heterogeneity, it also helps to exclude alternatives to differentiation in the future. Since the change of leadership in 2019, the EU has entered a new stage in its development, but there is nothing to suggest that its members are able to find common approaches. For the first time it is not possible to formulate a common compromise out of a wide variety of future options, and an attempt to avoid reform could aggravate the crisis of the integration process.

Experimental Studies of Liquid Holdup in the Impeller of Electric Submersible Pump

Artificial lift of oil by electric submersible pumps (ESP) is often complicated by free gas in production. Free gas content in production leads to ESP performance degradation in rate and head. Gas slip in the ESP impeller is one of the reasons of ESP performance degradation. Thus, the goal of the work is to determine the gas slip coefficient i.e. liquid holdup in the ESP impeller. It is known that a gas-liquid mixture (GLM) flow characterized by a slippage effect. Gas slippage relative to the liquid determines the GLM structure (bubble, dispersed-bubble, slug, stratified or annular), as well as the difference between the GLM densities calculated by liquid holdup or liquid volume content. Special stand was designed and created to determine the liquid holdup at the Department of Oil Fields Development and Operation of Gubkin University. Liquid holdup in the impeller of the ESP was measured by the method of cutting off the flow. This paper shows the results of experimental studies of liquid holdup and gas slip velocity in the ESP impeller (ESP5-50) at a rotational speed n = 2997 rpm, at an absolute intake pressure Pin = 0.4 MPa. The dependence of the liquid holdup on liquid volume content (i.e. the dependence of the gas void fraction on gas volume fraction) was determined for the model GLM "water-air", "water-surfactant-air" with different foaming capacity. The degradation of the ESP characteristics, boundaries of surging and gas locking limits are determined taking into account liquid holdup. The dependence of gas holdup was experimentally obtained over the entire range of ESP operation (from 0.5∙Qopt to Qmax). A comparison of the obtained correlation with existing models is presented too. A new correlation for predicting liquid holdup in the ESP impeller for the low-rate wells operation is obtained. A new approach to determining the liquid holdup and consequently gas slip velocity in the ESP impeller is proposed.

EXOSKELETON FOR LOWER JAW FRACTURES TREATMENT

The aim of this study was to study the possibility of the lower jaw exoskeleton as a means of treating its fractures. The analysis took into account the ability of the extrafocal osteosynthesis apparatus to maintain the spatial orientation of bone fragments under load. For this, the apparatus was analyzed by the finite element method on 3D models and a study was carried out in a special stand on the bones of the human lower jaw. As a result of the analysis, it was revealed that the lower jaw exoskeleton makes it possible to qualitatively fix the fragments of the lower jaw for the period of fracture healing.

SELF-CLEANING FILTER FOR CLOSED HYDROSYSTEMS OF AGRICULTURAL EQUIPMENT

The issue of increasing the reliability and durability of hydraulic units of closed hydraulic systems of agricultural equipment is considered, due to better cleaning of the working fluid by filtration units. The design of a self-cleaning filter with hydraulic automatic control of backwashing of slotted filtration elements with a counterflow of the working fluid is proposed. A special stand has been developed for simulating the operation of a self-cleaning filter of closed hydraulic systems of agricultural equipment. Experimental studies on a special stand confirmed the efficiency of the proposed design and made it possible to identify its main advantages in comparison with domestic and foreign counterparts. Based on the analysis of transient processes with increased pressure pulsation of agricultural equipment of a closed hydraulic drive, the actual pressure drop at which automatic flushing is triggered was established, compared with the calculated one, in which it was impossible to take into account such real factors as friction in the sealing units, the characteristics of the springs, distortions, tightness of valve pairs, fluctuations in dimensional chains. The most optimal operating mode of auto-washing equipment with a choke diameter of 1.0 mm has been determined. The auto-washing equipment was switched on at a pressure drop of 1.5 MPa (15 atm) and in an improved mode – pressure pulsations with an amplitude of 2 MPa (20 atm) when the auto-wash was turned off decreased in time to 0.12 s. It is noted that the developed self-cleaning filter for closed hydraulic systems of agricultural equipment will improve the reliability and increase the service life of the elements of hydraulic units and the machine itself as a whole.

Investigation of a Turbogenerator Based on the Vortex Expansion Machine with a Peripheral Side Channel

The creation of energy-saving turbogenerators is an essential component of the development of small energy systems. The gradual growth of interest in distributed electricity generation necessitates the constant improvement of these units. Moreover, they implement a more environmentally friendly generation method than when using microturbine units that use fuel to carry out the work process. Nowadays, turbogenerators are created based on different types of expansion machines, which have their advantages and disadvantages, given in this article. Compared to competitors, vortex expansion machines have good prospects and the necessary potential to expand their research and produce turbogenerators. An experimental vortex expansion machine with a peripheral-lateral channel and ability to change the geometric parameters of its flowing part was created to meet these needs. Experimental studies of the machine were performed on a special stand with air as a working fluid. As a result of the tests, the data were successfully obtained and processed. They are presented in the form of tables and graphical dependencies. The nature of the influence of thermodynamic parameters and geometric parameters of the flow part on the efficiency of the vortex expansion machine and turbogenerator based on it to further improve and create new turbogenerators is clarified.

Wear tests of modified powder coatings at low climatic temperatures

The results of comparative wear tests for sliding friction of modified powder coatings with metal counterbodies at room and low climatic temperatures are presented. For this, a special stand has been developed and manufactured for testing the wear of powder coatings in conditions of low climatic ambient temperatures. The temperature of the friction pairs "powder coating — metal counterbody" and the profiles of the friction surface of coatings and counterbodies were measured.

Influence of initial imperfections of thin-walled cylindrical shells with loose aggregate on their bending stability

Экспериментально и теоретически исследовано предельное состояние при изгибе тонкостенных цилиндрических оболочек, имеющих начальные несовершенства геометрии. Изготовлены качественные образцы глубокой вытяжкой в матрице из листа и из трубы точением на токарном станке, имеющие геометрические несовершенства (толщины, диаметров). Материал образцов: алюминиевые сплавы 3004 и Д16Т. Перед испытанием образцы тщательно измерялись и обследовались на наличие дефектов. Изготовлен специальный стенд, к которому жестко одним концом крепились образцы, другой конец был свободным. На свободный конец прикладывалась ступенями поперечная сила до потери устойчивости. Испытывались пустые и заполненные железным порошком образцы. Фиксировались нагрузка и прогиб свободного конца образца индикатором часового типа ИЧ-10. Получены линейные зависимости прогиба от нагрузки, устойчивость терялась в упругости. Численные расчеты выполнялись в программном комплексе «Динамика-3». Для расчетов принимались идеальные образцы. Сопоставив критические нагрузки, полученные экспериментами и численными расчетами, судили о влиянии начальных несовершенств на предельное состояние. Численно рассчитанная критическая сила была всегда больше экспериментального значения. Начальные несовершенства образцов снижали критическую силу от 2,3% до 32,5%. У образцов с небольшими вмятинами в зоне потери устойчивости критическая сила уменьшилась в 1...2 раза. У заполненных железным порошком образцов критическая сила была больше до 40,5%, чем у пустых. The limit state for bending thin-walled cylindrical shells with initial geometry imperfections has been studied experimentally and theoretically. High-quality samples are made by deep drawing in a matrix from a sheet and from a pipe by turning on a lathe, which have geometric imperfections (thickness, diameter). The material of the samples is aluminum alloys 3004 and D16T. Before testing, the samples were carefully measured and examined for defects. A special stand was made, to which samples were rigidly attached at one end, while the other end was free. A transverse force was applied to the free end in steps until it lost stability. Empty and iron-powder-filled samples were tested. The load and deflection of the free end of the sample were recorded by an ICH-10 clock type indicator. Linear dependences of the deflection on the load were obtained; stability was lost in elasticity. Numerical calculations were performed in the Dynamics-3 software package. Ideal samples were taken for calculations. Comparing the critical loads obtained by experiments and numerical calculations, we judged the effect of initial imperfections on the limit state. The numerically calculated critical force was always greater than the experimental value. Initial imperfections of the samples reduced the critical force from 2.3% to 32.5%. For samples with small dents in the zone of loss of stability, the critical force decreased by 1..2 times. In iron powder-filled samples, the critical force was greater by up to 40.5% than in empty samples.

FEATURES OF THE STAND AND METHODS FOR EXPERIMENTAL STUDIES OF PUMP-DOSING PUMPS OF HYDRAULIC STEERING SYSTEMS OF SELF-PROPELLED VEHICLES UNDER THE ASSOCIATED LOAD

The article discusses a special stand for experimental research of dosing pumps of hydrostatic steering systems of self-propelled machines, which makes it possible to analyze the quality of the dosing pump under conditions that correspond to different control actions and loads that arise during the operation of the steering system. An electro-hydraulic scheme of the stand has been developed to determine the characteristics of a dosing pump under the action of a associated load. The characteristics of control and measuring devices for determining parameters that are controlled both in statics and in dynamics are presented. To record changes in signals over time, a recording system has been developed that realizes the recording of signals on a computer and their processing using the «PowerGraph» program. A feature of this stand is that the load for the dosing pump is formed in the form of a pressure drop in its outlet channels. This makes it possible to evaluate the performance of these products regardless of their working volume and facilitates the experimental study of the behavior of the system when reproducing certain modes of its operation over a period of time that is not limited to the stroke of the executive hydraulic cylinder of the steering system. The stand implements an original technique for reproducing the associated load in the outgoing channels of the dosing pump, for which an additional pump driven by a hydraulic motor is installed in the outgoing channels of the metering pump. Regulation of the speed of rotation of the drive motor makes it possible to set the required value of the associated load. The method for determining the quality indicator of the dosing pump operation under the action of a associated load is briefly described In this case, the indicator of relative flow rates in the outgoing channels of the metering pump is determined, which shows how many times the actual flow rate of the working fluid increases in comparison with the nominal one, which is determined for the dosing pump with a certain working volume by the speed of rotation of the input shaft.

АВТОМАТИЗИРОВАННАЯ ОЦЕНКА ПОВЕРХНОСТНОЙ ПОРИСТОСТИ БЕТОННЫХ ИЗДЕЛИЙ

Currently in the territory of the Republic of Belarus the normative document is used in order to evaluate the surface of concrete and reinforced concrete products and constructions [1]. According to this normative document concrete surfaces of the constructions are divided into 7 categories from A1 to A7. The author suggests that the methods for evaluation of the surface quality, specified in [1], are not sufficient. Wherefore, the article reflects the works performed on development of the installation, methods and program to determine the surface porosity of concrete products. It describes the method to determine a particular and integral surface porosity through receipt and processing of the digital image with the developed program. It allows to automate the evaluation process of the surface and significantly speed up it (especially, in case of a great number of pores on the studied surface). The installation for receipt of the sample contrast images was developed, the modes for images photographic recording were selected. This installation for photographic recording used CANON EOS 1100D camera, on a special stand, used to maintain a constancy of focal length and distance to the registered object. VBA based program was developed, it allows to determine the pores size and their distribution, calculate their number and evaluate the form, and also allows to determine particular porosity for concrete diameters and integral porosity. The obtained value of the integral porosity can be used for a clarified calculation of the relative and absolute adhesion value when developing compositions of the release agents. Based on the obtained calculation results it is possible to plot a graph of the pores distribution that formalise and simplifies the aim of the surface quality evaluation. В настоящее время на территории Республики Беларусь при оценке поверхности бетонных и железобетонных изделий и конструкций пользуются нормативным документом [1]. Согласно данному нормативному документу бетонные поверхности конструкций разделены на 7 категорий от А1 до А7. Автором высказано мнение о недостаточности методов оценки качества поверхности, изложенных в [1], в связи с чем в статье отражены выполненные работы по разработке установки, методики и программы для определения поверхностной пористости бетонных изделий. Приведена методика определения частной и интегральной поверхностной пористости посредством получения и обработки цифрового изображения разработанной программой. Она позволяет автоматизировать процесс оценки поверхности и значительно ускорить процесс оценки (особенно в случае большого количества пор на исследуемой поверхности). Разработана установка для получения контрастных изображений образцов, подобраны режимы фоторегистрации изображений. В данной установке для фоторегистрации использовался фотоаппарат CANON EOS 1100D, на специальной стойке, служащей для обеспечения постоянства фокусного расстояния и расстояния до регистрируемого объекта. Разработана программа на основе VBA, позволяющая вычислять: размеры пор, их распределение, подсчитать их количество и оценить форму, также позволяет вычислить частную пористость для конкретных диаметров и интегральную пористость. Полученное значение интегральной пористости может быть использовано для уточненного вычисления величины относительной и абсолютной адгезии при разработке составов разделительных смазок. На основе получаемых результатов вычислений возможно построение графиков распределения пор, что формализует и упрощает задачу оценки качества поверхности.