RESONANT ELECTROMAGNETIC PROCESSES AT UNSTABLE OPERATION OF SLIDING CURRENT COLLECTOR UNITS OF TURBOGENERATOR

The article is devoted to study of the resonance electromagnetic oscillations arising during unstable operation of the sliding current collection unit of turbo-generators. Mathematical modeling of these processes is carried out. It has been established that it is these processes that are the main cause of increased sparking and “ring fire” or “breakdown of commutation” on contact rings

Dust Transportation and Settling within the Mine Ventilation Network

Dust is ubiquitous in underground mine activities. Continuous inhalation of dust could lead to irreversible occupational diseases. Dust particles of size lower than 75.0 µm, also known as float coal dust, can trigger a coal dust explosion following a methane ignition. Ventilation air carries the float coal dust from the point of production to some distance before it’s deposited on the surfaces of underground coal mine. Sources of dust are widely studied, but study of dust transportation has been mainly based on experimental data and simplified models. An understanding of dust transportation in the mine airways is instrumental in the implementation of local dust control strategies. This thesis presents techniques for sampling float coal dust, computational fluid dynamics (CFD) analysis, and mathematical modeling to estimate average dust deposition in an underground coal mine. Dust samples were taken from roof, ribs, and floor at multiple areas along single air splits from longwall and room and pillar mines. Thermogravimetric analysis of these samples showed no conclusive trends in float coal dust deposition rate with location and origin of dust source within the mine network. CFD models were developed using the Lagrangian particle tracking approach to model dust transportation in reduced scale model of mine. Three dimensional CFD analysis showed random deposition pattern of particle on the mine model floor. A pseudo 2D model was generated to approximate the distance dust particles travel when released from a 7 ft. high coal seam. The models showed that lighter particles released in a high airflow field travel farthest. NIOSH developed MFIRE software was adopted to simulate dust transportation in a mine airway analogous to fume migration. The simulations from MFIRE can be calibrated using the dust sampling results to estimate dust transportation in the ventilation network

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Improved transistor-controlled and commutated brushless DC motors for electric vehicle propulsion

The development, design, construction, and testing processes of two electronically (transistor) controlled and commutated permanent magnet brushless dc machine systems, for propulsion of electric vehicles are detailed. One machine system was designed and constructed using samarium cobalt for permanent magnets, which supply the rotor (field) excitation. Meanwhile, the other machine system was designed and constructed with strontium ferrite permanent magnets as the source of rotor (field) excitation. These machine systems were designed for continuous rated power output of 15 hp (11.2 kw), and a peak one minute rated power output of 35 hp (26.1 kw). Both power ratings are for a rated voltage of 115 volts dc, assuming a voltage drop in the source (battery) of about 5 volts. That is, an internal source voltage of 120 volts dc. Machine-power conditioner system computer-aided simulations were used extensively in the design process. These simulations relied heavily on the magnetic field analysis in these machines using the method of finite elements, as well as methods of modeling of the machine power conditioner system dynamic interaction. These simulation processes are detailed. Testing revealed that typical machine system efficiencies at 15 hp (11.2 kw) were about 88% and 84% for the samarium cobalt and strontium ferrite based machine systems, respectively. Both systems met the peak one minute rating of 35 hp

Summaries

Приведены рефераты статей данного номера на английском языке

Topical scientific researches into resource-saving technologies of mineral mining and processing

Table of contents Preface . 5 Malanchuk Z.R., Soroka V.S., Lahodniuk O.A., Marchuk M.M. Physical-mechanical and technological features of amber extraction in the Rivne-Volyn region of Ukraine . 6 Moshynskyi, V.S., Korniyenko V.Ya., Khrystyuk A.O., Solvar L.M. Research of energy effective parameters of the process of hydro mechanical extraction of amber from sandy deposits . 24 Mohamed Tafsir Diallo, Mamadou Oury Fatoumata Diallo Tidal Park – Modeling and Control Strategy . 38 Savina N.B., Malanchuk L.O., Ignatiuk I.Z., Moshchych S.Z. Institutional basis and trends of management of the use of the subsoil in Ukraine . 51 Dedelyanova Kr.Y. Column flotation machine – innovative aeration, vibra-tory – acoustic and technological researches . 60 Makarenko V.D., Manhura A.M., Lartseva I.I., Manhura S.I. Magnetic field on asphalt, resin, paraffin and salt deposits 79 Krzysztof Tomiczek The problem of beds stability in the conditions of undermining higher deposited beds in the context of selected analytical solutions . 95 Safonyk A.P., Koziar M.M., Martyniuk P.M., Fylypchuk V.L. Management of pollution - purification system for mining plants . 117 Marinela Panayotova, Vladko Panayotov Recent developments in the flotation of sulfide ores of base metals - bioflotation . 130 Remez N., Dychko A., Bronytskyi V., Kraychuk S. Simulation of shock waves from explosion of mixture explosive charges . 149 Melodi M.M. Akande V.O. Analysis of productivity and technical efficiency in granite aggregate production in selected quarries in south-western, Nigeria . 166 Doroshenko Ya.V., Karpash O.M., Rybitskyi I.V. Investigation of dispersed contaminates influence on the hydraulic energy consumption of elements of gas pipeline systems with complex geometry . 182 Skipochka S.I., Krukovskyi O.P., Krukovska V.V., Palamarchuk T.A. Features of methane emission in coal mines at high speed longwall face advance 208 Daouda Keita, Valery Pozdnyakov Statistical analysis of experimental data on the indices of operation of the loading units of the bauxite compa-ny of Guinea (CBG) . 226 Yevhenii Malanchuk, Sergiy Stets, Ruslan Zhomyruk, Andriy Stets Modeling of the process of mining of zeolite-smectite tuffs by hydro-well method . 244 Samusia V. I., Kyrychenko Y. О., Cheberiachko I. M., Trofymova, O. P. Development of experimental methods to study heterogenic flows in the context of hydraulic hoisting design . 260 Makarenko V.D., Kharchenko M.O., Manhura A.M., Petrash O.V. Magnetic treatment of production fluid with high content of asphalt-resin-paraffin deposits . 268 Kovshun N.E., Ignatiuk I.Z., Moshchych S.Z. Malanchuk L.O. Innovative model of development of fuel and energy complex of Ukraine 279 Bondarenko А.O., Ostapchuk O.V. Design and implementation of a jet pump dredge . 296 Sotskov V.O., Dereviahina N.I. Research of dependencies of stope stress-strain state change under various conditions of partial stowing of developed space . 305 Sakhno S., Liulchenko Y., Chyrva T., Pischikova O. Determination of bear-ing capacity and calculation of the gain of the damaged span of a railway overpass by the finite element method . 326 Melodi М.М., Ojulari M.K. Oluwafemi V.I. Economic and environmental impacts of artisanal gold mining on near-by community of Sauka-Kahuta, Nigeria . 340 Kruchkov A.I., Besarabets Y.J., Yevtieieva L.I. Energy saving modes of excavators type power shovel . 353 Hryhorash M.V., Kuzminskyi V.P., Ovchinnikova O.V., Kukhar V.Yu. Energy saving through quality of technical water: new types of mechanical screen filters for various links of water treatment . 369 Didenko M. The modeling of the interaction of rock mass and compliant lining while it is expanded . 394 Makarenko V.D., Liashenko A.V. Complex approach to research and selection of hydrocarbon solvents for asphaltene-resin-paraffin-hydrate deposits control . 408 Mykhailovska O.V., Zotsenko M.L. Investigation of the oscillations amplitudes bases and foundations of the forming machine . 417 Inkin O.V., Puhach A.M., Dereviahina N.I. Physical-chemical and technological parameters of improving profitability of underground coal burning . 42

Англійська мова для студентів електромеханічних спеціальностей

Навчальний посібник розрахований на студентів напряму підготовки 6.050702 Електромеханіка. Містить уроки, що структуровані за тематичними розділами, граматичний коментар, короткі англо-український і українсько- англійський словники та додатки, які спрямовані на закріплення загальних навичок володіння англійською мовою. Акцентований на ɨсобливості термінології, що застосовується у науково-технічній галузі, зокрема, в електромеханіці та виконання запропонованих завдань, що буде сприяти формуванню навичок перекладу з англійської та української мов, сприйняттю письмової та усної англійської мови, вмінню письмового викладення англійською мовою науково-технічних та інших текстів під час професійної діяльності, спілкуванню з професійних та загальних питань тощо

Investigation of micro gas turbine system configurations for compact lightweight applications based on reversible bladeless Tesla machinery

Globally, the demand for low-emission, cost-effective, low-noise, lightweight and compact devices is rapidly increasing. In order to meet such market demands on a small scale, microgas turbines (MGTs) could play a crucial role. However, there are many challenges with MGT compatibility with internal combustion engines (e.g., low efficiency, fuel flexibility, light weight-compactness). As part of this study, the focus is on the component basis, where the study examines the Tesla or bladeless turbomachinery in both a compressor and expander configuration. Since little data is available on Tesla compressors/pumps, this study focuses primarily on the bladeless compressor, which is also analyzed as an expander due to its reversibility. The activity started from a 3-kW air Tesla expander prototype available at the University of Genoa. It is examined in compressor mode using a 3D CFD approach and its results are compared to experimental results. The CFD and experiments show good agreement for the pressure, with an error of less than 3% at zero flow condition. Despite the CFD analysis predicting a static efficiency of around 42% (without losses), the experiment did not meet that prediction due to significant leakage flows and other losses. Moreover, using LMS Test Lab software, the acoustic behavior of the Tesla compressor has been analyzed at different speeds and distances, and several aspects are compared with conventional or bladed technologies (same tip speed, same mass flow rate, and same pressure). It has been demonstrated that Tesla technologies are substantially quieter than bladed technologies. To improve Tesla compressor performance, a 3D numerical analysis has been carried out for the rotor only and coupled rotor-stator and volute configurations. The disk gap is optimized by relying on Ekman and Reynolds numbers. Based on the numerical analysis, the disk gap should be 3 times the thickness of the boundary layer with the best Reynolds number 9-11 and Ekman number 1.5-1.65. Moreover, numerical analysis has been performed for 2, 2.5, 3 and 4 diameter ratios in order to optimize the rotor diameter ratio. Higher diameter ratios indicate better performance than lower diameter ratios. Based on a CFD analysis, it has been predicted that at low mass flow rates, greater than 95 % efficiency can be achieved with the optimal disk gap and diameter ratio. In this case, the outlet flow angle would be around 89.9 degree, however, in practice, maintaining almost a tangential flow angle is difficult. In order to improve the performance of Tesla compressors, several stators have been studied. The stator outlet and inlet ratio between 2 and 4 is optimal for stator/diffuser performance. With an optimal rotor and eight stators, CFD analysis predicts a total stator efficiency of >53%; however, with a low number of stators, this efficiency will be somewhat improved. As part of an effort to enhance the performance of the Tesla compressor, a (stator-less) volute design has also been numerically analyzed, which shows better performance in terms of pressure ratio and efficiency than the stator configuration. Compared to a stator configuration, the total to static efficiency is estimated to increase by 3 to 5%. A new reversible Tesla prototype model has been developed using an optimized rotor (optimal disk gap and diameter ratio) and volute configuration for 22 krpm. CFD predicted total to static efficiency of 58% in compressor mode and 66% in expander mode without consideration of system losses. For this new reversible machine, leakage and end wall losses are also analyzed under a variety of conditions, including different end wall gaps and different exit radial clearances (with and without sealing systems). The implementation of the sealing system has resulted in a reduction in leakage, but the amount varies in accordance with the clearance of the radial exit. The end wall power loss varies with end wall gap, but usually ranges between 50 W-60 W for 22 krpm design speed, while power is around 600 W. During this dissertation writing, experimental work on a reversible bladeless machine is in progress. Preliminary results show the pressure ratio is 1.24 and the isentropic efficiency is 31%. Comparing these results with CFD simulations at closed valve conditions shows good agreement in terms of pressure ratio with < 3% error. It is observed that leakage occurs during the first test which passes through the narrow radial clearance of 0.3 mm. As a result of this preliminary investigation, some modifications have been made to the test-rig in order to ensure that good results are achieved with the least amount of leakage. An in-depth study of the reversible Tesla machine (compressor and expander) has shown that such technologies possess several attractive features (reversibility, low noise level, cost effective and operate with any kind of fluid), but are difficult to implement as Tesla envisioned (higher efficiency). Under ideal design conditions, however, such technologies could potentially achieve > 50% efficiency. The use of such technologies can be beneficial in areas where conventional technologies are not practical or less efficient

Hafif elektrikli araç için FDAM tasarım ve uygulaması

The popularity of electrical vehicles is increasing rapidly in recent years due to energy generation/consumption ratio, transportation costs, decrease in fossil fuel reserves with increasing population as well as the environmental damage caused by fossil fuels. Therefore, Brushless Direct Current (BLDC) Motor design was actualized in the present study for use in electrical vehicles expected to replace the transportation vehicles of today. Firstly, analytical design of the targeted motor was completed after which the Finite Elements Method was used for modelling. Ansys Maxwell Program is one of the package programs used in FEM. This study was carried out with Ansys Maxwell Electromagnetic Suite version 17.2 . The prototype motor was manufactured after reaching the desired results with Finite Elements Method and experimental studies commenced with the experiment setup prepared in the laboratory environment. Experimental results were compared with electromagnetic results. Finally, the prototype motor was mounted on the ElektroGOP vehicle and it was observed to work without problem at the expected performance during the test drives.Son yıllarda artan nüfusla birlikte enerji üretim/tüketim oranı, ulaşım giderleri, fosil yakıt rezervlerinin azalması ve fosil yakıtların çevreye verdikleri zararlar gibi başlıca etkenler sebebiyle elektrikli araçların popülaritesi hızlı bir şekilde artmaktadır. Dolasıyla elektrikli araç ve ekipmanları üzerine yapılan çalışmalar da artmaktadır. Bu çalışmada günümüz ulaşım araçlarının yerini alan elektrikli araçlarda kullanılması hedeflenen Fırçasız Doğru Akım Motor (FDAM) tasarımı gerçekleştirilmiştir. Öncelikle hedeflenen motorun analitik tasarımı yapılarak Sonlu Elemanlar Yöntemi (SEY) ile modellemesi yapılmıştır. Ansys Maxwell Programı SEY'de kullanılan paket programlardan biridir. Bu çalışma Ansys Maxwell Elektromanyetik Suite 17.2 versiyonu ile gerçekleştirilmiştir. SEY ile hedeflenen sonuçlara ulaşıldıktan sonra motorun protorip üretimi gerçekleştirilmiş ve prototip motorun, laboratuvar ortamında hazırlanan deney düzeneği ile deneysel çalışmaları yapılmıştır. Deneysel sonuçlar elektromanyetik sonuçlarla karşılaştırılmıştır. Son olarak prototip motor ElektroGOP aracına monte edilmiş ve sürüş denemelerinde motorun hedeflenen performansta ve sorunsuz şekilde çalıştığı görülmüştür

Asset Management Framework for the United States Army Corps of Engineers Lock and Dam Electrical Equipment

The focus of this thesis is to design an efficient and effective preventative maintenance program for the electrical equipment that the United States Army Corps of Engineers (USACE) operates at the locks and dams. This thesis presents the concept of asset management and designs a framework to manage the electrical assets at USACE. The methodology was tested, and the results validated the framework proposed in this thesis. The framework was tested on two separate projects and the results were the same optimized strategies, which shows that the framework is robust and can be implemented into each project and can give an effective preventive maintenance program for the electrical components. The significance of this work is to perform asset management on the electrical equipment on the lock and dams USACE operates and owns, which has not been implemented before. While corrective and preventative maintenance programs have been compared previously for electrical equipment, most analyses have been conducted on production plants. The result of conducting this study is a recommended framework for conducting asset management at USACE locks and dams