The capability of using a linear kinetic energy harvester-A cantilever structured piezoelectric energy harvesterto harvest human motions in the real-life activities is investigated. The whole loop of the design, simulation, fabrication and test of the energy harvester is presented. With the smart wristband/watch sized energy harvester, a root mean square of the output power of 50 μW is obtained from the real-life hand-arm motion in human's daily life. Such a power is enough to make some low power consumption sensors to be self-powered. This paper provides a good and reliable comparison to those with nonlinear structures. It also helps the designers to consider whether to choose a nonlinear structure or not in a particular energy harvester based on different application scenarios.
A high-speed squirrel-cage induction machine requires a totally different design compared to the traditional squirrel cage industrial motor because of the mechanical limitations caused by the high speed. This results in a more complicated rotor construction and expensive material selection, and sets higher standards for the manufacturing precision. The objective of this paper is to demonstrate the design aspects, material selection, and manufacturing of a squirrel cage rotor for high-speed applications. In this paper, the rotor dimensioning approach based on equations and data analysis is presented. Rotor material selection and construction topology influence on the electrical machine design are discussed. The results are illustrated with the design of a 6 kW, 120 000 rpm induction machine for a turbo-circulator. The rotor parameters' influence on the electromagnetic performance of the designed machine is demonstrated. Mechanical stresses for different topologies are studied with Finite Element Method (FEM) analysis. Several manufacturing methods for producing a high precision rotor are described and compared. The presented rotor design approach, which enables high electromagnetic performance and robust construction, is verified by the testing of a prototype.
Φ Abstract --High-speed ranging requires various equipment, for example compressors, turbo-compressors and turbocirculators nowadays. Solutions using electrical drive with gearboxes is limited by technical feasibility, lifetime and maintenance of gearbox systems. Thanks to development of frequency converters is possible to build direct high-speed electrical drive. This paper is dealing with design of high-speed solid rotor cage induction machine for running 6 kW, 120 000 rpm helium turbo-circulator. Design of high speed electrical machine for TC is described from requirement specification to manufacturing. Results of mechanical, electromagnetic and thermal calculations are given. Proposed design approached can be used in various application in which high speed electrical machine is required.
Flange joints and their sealing play an important role in many industries. The gasket performance and its behaviour are influenced by a number of factors, such as non-linear material properties with permanent deformations, assembly procedures and the preparation of sealing surfaces. Additionally, a proper seal function is also affected by the design and strength design of the flanges. Determination of the respective tightening torque needed to achieve a suitable contact pressure between the seal and the flange face is equally important. This paper deals with finite element method (FEM) analyses of a flange joint designed in accordance with the modern standard EN 13445-3 Annex G and examines the influence of operating conditions on the gasket contact pressure. The article also discusses the effects of assembly on the tightness of the joint and the reason for the leakage of the operating medium that took place. The analyses show the effects of operating states on the contact pressures of gaskets and the pre-stressing of bolts. They demonstrate the contact pressure after the application of the pre-stressing of the bolts and its reduction after the temperature-field stabilization due to the start-up of the device. The results of the analyses show that only a relatively small surface of the seal achieves the compression required by the manufacturer to maintain the seal integrity during the application of the tightening forces determined in accordance with EN 13445-3 Annex G. The force of the pre-stressing of the bolts is reduced by approximately 6 % when the normal operation condition is reached. The analyses were performed due to a suspicion of a significant influence of the temperature distribution on flange joints. The main cause of the flange leakage was subsequently revealed by a physical inspection that demonstrated assembly failures when installing gasket 2. The description of these deficiencies is not a subject of this article. Keywords: flange joint, sealing, gasket, FEM, contact pressure Spoji prirobnic in njihovo tesnenje igrajo pomembno vlogo v mnogih industrijskih vejah. Lastnosti tesnila in njegovo vedenje je odvisno od mnogih faktorjev, kot so: nelinearne materialne lastnosti s stalno deformacijo, kakor tudi postopek namestitve in tesnilna povr{ina. Dodatno je pravilno tesnenje odvisno tudi od oblike in trdnosti prirobnice. Prav tako je pomembna dolo~itev tesnilnega navora za doseganje primernega kontaktnega tlaka med tesnilom in povr{ino prirobnice. V~lanku avtorji opisujejo analizo spoja prirobnice s pomo~jo metode kon~nih elementov (FEM; angl.: Finite Element Method), ki je oblikovana v skladu z modernim standardom EN 13445-3 Annex G in preiskuje vpliv delovnih pogojev na kontaktni tlak tesnila. V~lanku avtorji prav tako razpravljajo o vplivih monta`e na tesnost spoja ter podajajo mo`ne razloge za pu{~anje delovnega medija. V analizi so pokazali, kak{en je vpliv obratovalnih pogojev na kontaktni tlak tesnila in prednapetost pritrdilnih vijakov. Analiza je pokazala, kak{en je kontaktni tlak po predob...
This paper deals with the temperature field of the shell and tube heat exchanger with segmental baffles. Two different types of shell and tube heat exchangers were analysed by a numerical model for thermal-hydraulic rating called the cell method. The cell method is a numerical computational model for calculating of temperature field of a shell and tube heat exchanger with segmental baffles. A huge benefit of the cell method is especially its simplicity. The computation of temperature field by the cell method is very fast and without the necessity of powerful hardware accessories. For analyses, two different types of shell and tube heat exchangers with segmental baffles were used. First, a co-current flow heat exchanger with a floating head and second a counter-current flow heat exchanger with a fixed tubesheet. Both analysed heat exchangers are horizontal, have one tube and one shell pass and segmental baffles. The results from cell method were compared with results from the commercial software for thermal-hydraulic rating HTRI, which is one of the most widely used commercial software for solving thermal-hydraulic rating of heat exchangers. The scope of this paper is to assess how exact the cell method is and if its results are useful for a mechanical design of shell and tube heat exchanger with segmental baffles.
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