Design of an optical-access expansion chamber for two-phase expansion

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Mathematical modelling of rolling element bearings fault for the diagnosis in the gearbox-induction machine

Inner race fault in bearing suspension is relatively the common fault in induction motors coupled with a gearbox, their detection is feasible by vibration monitoring of characteristic bearing frequencies. However, vibration signals have numerous drawbacks like signal background noise due to external excitation motion, sensitivity due to the installation position and their invasive measurement nature. For this reason, it is necessary to apply an extremely efficient method known as stator current signal analysis which offers significant savings and implementation advantages over traditional vibration monitoring. This paper represents a mathematical model for electromechanical systems and for rolling-element bearing faults to study the influence of mechanical defects on electrical variables (stator current). The novelty in this work involves three contributions: modelling of rolling bearing faults by external forces applied on the electromechanical system; Physical representation of rolling bearing fault allowing the modeling of the studied system functionality and, the influence of mechanical fault (inner race) in the electrical variables (stator current). Simulation results at the end of this paper demonstrate the effectiveness of the proposed mathematical model to detect gearbox’ bearing fault based on the electrical stator current signal with high sensitivity using fast Kurtogram approach

Potential of power recovery of a subsonic axial fan in windmilling operation

During the last decades, efforts to find efficient green energy solutions have been widely increased in response to environmental concerns. Among all renewable energies, this paper is focused on wind power generation. To this end, a windmilling axial fan in turbine operation is experimentally and numerically investigated. Under specific conditions, the studied fan is naturally freewheeling. Consequently, the main objective of this analysis is to determine whether or not this intrinsic windmilling behavior can be optimized for power generation. A preliminary study of the fan is dedicated to the knowledge of the fan characteristics in normal operating conditions. Then, two windmilling configurations (direct and reverse flow direction) are tested and compared on the basis of the output power. An analysis of the velocity triangle gives the opportunity to evaluate the energy recovery potential of both solutions. Of the two, the reversed configuration showed a higher level of output power than the direct one

Технічна еволюція та надійність тягової трансмісії тролейбуса

Based on the analysis of the indicators of functionality and structure of the trolleybus’s traction transmission (TT), some characteristic differences have been established for the classification of 4 generations of drive axles (DA) structures of known world manufacturers. The calculation models and methods for increasing the probability of a fail-safe transmission’s and DA system work, consisting of aggregates, modules, mechanisms, parts and connections, are analyzed. A method is proposed and example is given of predicting the parametric reliability of a planetary wheel gear (PWG) in DA system by two criteria: fatigue strength and vibration resistance of "criteria element" – thin-walled epicycle of "weak link" – PWG.На підставі аналізу показників функціональності і структури тягової трансмісії (ТТ) тролейбусів встановлено характерні відмінності для класифікації 4-х поколінь конструкцій тягових мостів (ТМ) відомих світових виробників. Проаналізовано розрахункові моделі та методи підвищення ймовірності безвідмовної роботи систем ТТ і ТМ, що складаються з агрегатів, модулів, механізмів, деталей, з'єднань. Запропоновано методику та наведено приклад прогнозування параметричної надійності планетарного колісного редуктора (ПКР) за двома критеріями: втомної міцності та вібростійкості "критеріального елементу" – тонкостінного епіциклу у складі "слабкої ланки" – ПКР

The technical assessment of the level of innovative traction transmission of railway vehicle

The article deals with the development of an innovative model of traction transmissions of railway vehicles with a higher technical level, which allows to eliminate the existing shortcomings of the mechanical system, simplify the repair processes and reduce the cost, and evaluate its technical level. By reducing the overall dimensions and weight of the mechanical system, increasing reliability due to equal distribution of the load and shortening the power arm, as well as reducing the number of structural elements, increasing the useful work coefficient due to the reduction of the mass of double sliding pads and rotating parts, saving electricity and thereby improving the technical level of rail transport. Traction transmissions consisting of an innovative reducer are offered that ensure the increase. The technical level of the proposed dart transmission is determined based on three compatibility parameters with a creative approach. Compatibility parameters are determined according to the minimum value of the geometric dimensions characterizing the mass of the mechanical system, the maximum value of the useful work coefficient characterizing economic efficiency, as well as the maximum values of the degree of reliability characterizing safety. The technical level of the proposed project transmitter is determined and compared with existing buildings, its technical and economic advantages are highlighted. As a result of the application of the proposed innovative reducers in the traction drives of railway vehicles, the basis is created for reducing the cost and maintenance costs of traction vehicles, increasing the level of traffic safety, as well as improving the traction and braking characteristic

OPPORTUNITIES OF INTEGRATING DESALINATION TO COGENERATION FOR BRAZILIAN CONDITIONS

One of the major problems in this century refers to the availability of potable water, necessary to the survival of populations. The world population is continually increasing and natural resources are proportionally decreasing, and the development of potable water production techniques demands intensive efforts. Electric power requirement is also necessary to the development of nations. Desalination processes are widely used in countries with low offer of potable water. Technologies nowadays in use are multi-stage-flash distillation (MSF), multi-effect distillation (MED) and reverse osmosis (RO) process. In MSF and MED processes, the main technique is distillation. Reverse osmosis technique relies on the osmotic principle, in which a solvent passes through a membrane. Since the middle of 1950, these desalting techniques are widely used mainly in the Middle East countries, where water shortage is almost absolute. Although uncommonly conceived, discussing the implementation of desalination processes in association to cogeneration systems in Brazil is a necessary task for the long-term planning. In this way, this paper proposes to reviewthe successful experiences presented in the literature as a way of  establishing how electric power and fresh water production can be produced from seawater desalting processes in an optimized way. Another objective pursued in this paper is stimulating more attention to this matter, that deserves discussing the skill staff formation and the know-how of such technologies in the strategic planning to the water resource management, specially because these investments require a considerable time for human resources development and the knowledge of the most adequate technology to be implemented for the integration of desalting and cogeneration units

Multiphysic Design and Modeling of Rotating Electrical Machines

This paper presents a general overview on design process of electrical machines considering a multiphysic point of view, and a road map for a comprehensive design approach is drawn. The objective multi-physical criterion including electromagnetism and mechanics physics, thermodynamics, fluid dynamics, structural dynamics, noise and vibration are discussed. Also, various modelling methodologies are presented and compared in terms of computational-time resources and accuracy. Current state of art in this approach will be presented highlighting the advantages and disadvantages of such methodologies

Space station gas compressor technology study program, phase 1

The objectives were to identify the space station waste gases and their characteristics, and to investigate compressor and dryer types, as well as transport and storage requirements with tradeoffs leading to a preliminary system definition

Comparative study on Double-Rotor PM brushless motors with cylindrical and disc type slot-less stator

Among brushless permanent magnet machines, the torus motors (also called Axial Flux Double-Rotor Permanent Magnet (AFTR PM) motors) are most compact and highly efficient. A cylindrical counterpart of this motor is a newly proposed Radial Flux Double-Rotor Permanent Magnet (RFTR PM) motor. The objectives of this thesis are to optimize the magnetic circuit of both AFTR PM and RFTR PM motors and to compare their electromechanical parameters on the basis of the results obtained from magnetic field simulation using Finite Element Method (FEM). To reach these objectives, FEM models are developed for both the motors, for particular given data. Applying the magnetic field simulation with the help of FEMM 4.0 software package, optimized stator and rotor core dimensions were determined as well as electromechanical parameters such as electromechanical torque, electromotive force, resistance and inductance of the stator windings. Next, the efficiency and torque to volume ratio along with the torque to mass ratio were calculated. Comparing the parameters of both motors, the following conclusions are obtained: • Both slot-less motors developed electromagnetic torque with very low torque ripple contents. • The torque to mass ratio of RFTR PM motor is almost equal to the torque per mass of AFTR PM machine. • AFTR PM motor is more compact than its cylindrical counterpart because its torque to volume ratio is higher. • The efficiency of RFTR PM motor is relatively higher than that of AFTR PM motor, particularly if multi disc motor is considered, mainly due to the smaller percentage of end connection in the entire volume of the winding