Wyniki 1-9 spośród 9 dla zapytania: authorDesc:"Bohuš ULRYCH"

Contact Problem of Disk on Shaft Fixed by Induction Shrink Fit

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The problem of shrink fit between the disk and shaft is solved. The shrink fit realized by induction heating must transfer the prescribed torque and power. Both disk and shaft are considered elastic. The first step of the task is to find appropriate dimensions of the disk and interference. The second step is to suggest the parameters of its induction heating. The methodology is illustrated by a typical example. Streszczenie. W artykule rozwiązano problem pasowania kurczowego między tarczą a wałem. Pasowanie kurczowe zrealizowane zostało metodą indukcyjną - musi ono przenieść założone moment i moc. Zarówno tarcza jak i wał zostały potraktowane jako elastyczne. Pierwszym krokiem w rozwiązaniu zadania jest znalezienie dogodnych rozmiarów tarczy. Drugim krokiem jest zasugerowanie parametrów jej nagrzewania indukcyjnego. Ta metodyka została zilustrowana typowym przykładem. (Problem kontaktu tarczy na wale poprzez zastosowania pasowania kurczowego) Keywords: Induction shrink fit, contact problem, transfer of torque, magnetic field, field of temperature. Słowa kluczowe: indukcyjne pasowanie kurczowe, problem kontaktu, przeniesienie momentu, pole magnetyczne, pole temperatury Introduction The paper deals with the contact problem of the disk on a shaft fixed by the induction shrink fit. Shrink fits represent firm connections of two metal parts and their principal task is to transfer prescribed mechanical forces or torques. They are widely used in numerous industrial and transport technologies (shrunk-on rings, crankshafts, tires of railway wheels, armature bandages in rotating electrical machines and so on, see, for instance [1]). Their realization is based on heating of the external part of the system, which leads to an enlargement of its dimensions (i.e., the radius of the internal bore of a wheel). The second part (i.e., a shaft whose radius at the room temperature is somewhat greater than the radius of the bore) is then inserted into it an[...]

T-potential based model of induction heating of thin conductive plates in hard-coupled formulation

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Mathematical and computer models of induction heating of very thin plates are presented. The plate is supposed to be exposed by timevariable external magnetic field. Distribution of eddy currents and other quantities is modeled in terms of electric vector potential. The problem is solved in hard-coupled formulation and the methodology is illustrated by a typical example. Streszczenie. Zaprezentowano model matematyczny i model komputerowy dla problem grzania indukcyjnego bardzo cienkich płytek. Płytka wystawiona jest na działanie zmiennego pola magnetycznego. Rozkład gęstości prądów wirowych i inne wielkości zostały zamodelowane poprzez użycie elektrycznego potencjału wektorowego T. Problem został rozwiązany w warunkach silnego sprzężenia elektromagnetyczno-cieplnego a przedstawiona metodyka zilustrowana jest prostym przykładem. (Model grzania indukcyjnego cienkich płytek bazujący na potencjale T przy silnym sprzężeniu zjawisk) Keywords: induction heating, T-potential, hard-coupled formulation, numerical analysis. Słowa kluczowe: grzanie indukcyjne, potencjał T, silne sprzężenie, analiza numeryczna Introduction Nowadays, modeling of induction heating is usually performed numerically using the finite element method [1-3] and magnetic field in the system is described in terms of the magnetic vector potential A . This approach is also implemented into a number of professional codes such as OPERA [4], ANSYS [5] or FLUX [6]. From time to time, however, one must solve problems where this classical approach can fail. One class of such problems is characterized by geometrical incommensurability of some parts of the investigated system. This means that one dimension of such a part is much smaller than other dimensions, but yet, this dimension is important and its influence cannot be neglected. We can mention, for example, local induction heating of nonferromagnetic thin plates. One of the possible arrangements for realizing this technologic[...]

Magnetohydrodynamic pumps for molten salts in cooling loops of high-temperature nuclear reactors

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Possibilities of using the magnetohydrodynamic (MHD) effect for pumping molten salts in cooling loops of high-temperature nuclear reactors are analyzed. Two basic ways of producing magnetic field in the pump (saddle coils and permanent magnets) are evaluated with respect to the total Lorentz force and resultant pumping head of the device. The corresponding mathematical models are solved numerically Streszczenie. W pracy przeanalizowano możliwość zastosowania efektu magnetohydrodynamicznego (MHD) do pompowania płynnych soli w obwodach chłodzących wysokotemperaturowych reaktorów jądrowych. Zbadano dwa podstawowe sposoby wytwarzania pola elektromagnetycznego (cewki siodłowe i magnesy trwałe) pod kątem całkowitej siły Lorentza i wytwarzanego ciśnienia względnego. Do porównania wykorzystano numeryczny model efektu MHD. (Pompy magnetohydrodynamiczne do pompowania płynnych soli w obwodach chłodzących wysokotemperaturowych reaktorów jądrowych) Keywords: magnetohydrodynamic pump, molten salt, electric field, magnetic field, temperature field, numerical analysis. Słowa kluczowe: pompa magnetohydrodynamiczna, pole magnetyczne, analiza numeryczna Introduction High-temperature nuclear reactors use for transfer of heat from the active zones either molten metals and their alloys (Na, Pb, Pb-Bi, etc.) or molten salts (such as fluoride salts). Pumping of these liquid media by classical mechanical radial or axial pumps is, however, rather difficult and the lifetime of such devices is relatively low. More prospective are, therefore, electromagnetic pumps without any movable parts. The simplest devices of this kind are magnetohydrodynamic (MHD) pumps with magnetic field generated either by a system of appropriately arranged saddle coils carrying direct current or by a system of permanent magnets. Such pumps (these times applied only for molten metals) were first mentioned in 1957-1959 in both Soviet Union and United States [1-3]. The authors present[...]

Electromagnetic-thermoelastic actuator for accurate wide-range setting of position

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A novel actuator for accurate setting of position is presented, allowing a wide-range shift. While the rougher setting of position is realized electromagnetically, its fine tuning is performed on the principle of thermoelastic dilatation of the nonferromagnetic part of the plunger. The complete mathematical model of the problem (representing a triply coupled task) is solved numerically. The methodology is illustrated by an example whose results are discussed. Streszczenie. W artykule przedstawiono nowy projekt aktuatora o szerokim zakresie przemieszczeń. Zgrubne pozycjonowanie jest realizowane za pomocą sterowania elektromagnetycznego, natomiast precyzyjne dostrojenie pozycji osiąga się przez termoelastyczną dylatację nieferromagnetycznego elementu trzpienia. Rozwiązano numerycznie kompletny matematyczny model urządzenia (uwzględniający sprzężenia pól). Zaprezentowana metody została zilustrowana przykładowymi obliczeniami, których wyniki zostały starannie przeanalizowane. (Siłownik termoelastyczny o szerokim zakresie przemieszczeń) Keywords: actuator, electromagnetic field, temperature field, field of thermoelastic displacements, setting of position, numerical analysis. Slowa kluczowe: siłownik, pole elektromagnetyczne, odkształcenie termoelastyczne. Introduction Setting of position in technical practice may be realized by a number of ways derived from numerous mechanical, hydraulic, pneumatic, electromagnetic and other principles. The main disadvantage of these systems consists in the presence of movable parts (screws, pistons, plungers, etc.) whose movement negatively affects the available accuracy of such devices. In their previous papers (see, for example [1], [2]) the authors proposed a purely thermoelastic actuator that worked sufficiently accurately without any movable parts, but only with extremely small shifts (10-5-10-3 m). Possibilities of applications of such actuators, therefore, suffered from rather high setting limita[...]

Monolithic Model of Induction Heating of Thin Conductive Plate with Respecting Thermoelasticity

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A new approach to modeling of induction heating of thin plates is presented. The model of magnetic field is based on the electric vector potential T and the distribution of temperature is described by a modified equation including heat sources and sinks. The thermoelastic displacements are also respected. The methodology is illustrated by an example whose results are discussed. Streszczenie. W artykule przedstawiono nowe podejście do modelowania grzania indukcyjnego w cienkiej płytce. Model pola magnetycznego wykorzystuje elektryczny potencjał wektorowy T a rozkład temperatury opisany jest zmodyfikowanym równaniem, zawierającym źródła ciepła i wydatki ciepła. Uwzględniono również przesunięcia termoelastyczne. Metodyka tego podejścia została zilustrowana przykładem obliczeniowym z dyskusją wyników. (Model monolityczny grzania indukcyjnego cienkiej płytki przewodzącej z uwzględnieniem przesunięcia termoelastycznego) Keywords: induction heating, thin plate, electric vector T-potential, thermoelastic displacements, numerical modeling. Słowa kluczowe: grzanie indukcyjne, cienka płytka, elektryczny potencjał wektorowy, przesunięcia termoelastyczne, modelowanie numeryczne Introduction Induction heating is a technological process that is employed in numerous industrial, transport, and other applications. Its goal is to prepare the heated metal element for its further heat treatment (for instance forming, hardening, hot pressing, melting, etc.). A typical heat treatment used in case of thin plates is their annealing performed after hot forming whose aim is to suppress internal mechanical strains and stresses. An example is depicted in Fig. 1 showing a set of plate springs made of phosphor bronze by a Swiss company Grewis [1]. Fig. 1. Thin plate springs manufactured by Swiss company Grewis Usually, such thin plates are heated only locally, at the places where the internal mechanical strains and stresses occur. The process itself is realized mo[...]

Modeling of Induction Shrink Fit of Action Wheel in Gas Turbine

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Induction shrink fit in a gas turbine is modeled. The fit is realized by pressing of a heated steel wheel carrying the blades on shaft and its purpose is to transfer a relatively high torque in specific operation conditions. The paper deals with the numerical solution of the process that represents a nonlinear and nonstationary coupled problem characterized by interaction of magnetic field, temperature field and field of thermoelastic displacements. The methodology is illustrated by a typical example whose results are discussed. Streszczenie. Zaproponowano modelowanie indukcyjnego dopasowania koła w turbinie gazowej. Dopasowanie to polega na naprężaniu rozgrzanego koła w celu ułatwienia transferu dużego momentu. Przedstawiono model numeryczny procesu uwzględniający pola magnetyczne i temperaturpowe oraz odkształcenie termoelastyczne. (Modelowanie indukcyjnego dopasowania wymiarów koła w turbinie gazowej) Keywords: induction shrink fit, coupled problem, numerical analysis, magnetic field, temperature field, thermoelastic displacements. Słowa kluczowe: dopasowanie indukcyjne, analiza numeryczna, zjawiska termoplastyczne. Introduction One of the most mechanically and thermally exposed parts of gas turbines are blade-carrying wheels rotating at high velocities in very hot environment. These wheels are fixed to a shaft by means of shrink fits. Every shrink fit has to transfer a relatively high torque, which is secured by an appropriate interference whose selection must also take into account the centrifugal force acting on the wheel and environmental temperature. The process of hot pressing leading to the shrink fit starts with induction heating of the wheel. This brings about an enlargement of the diameter of its internal hole, the wheel is put on the shaft and the whole system is cooled. The particular steps of the process are depicted in Fig. 1. Fig. 1. Particular steps of the process As the above process requires a lot of energy, its[...]

Load-Bearing Actuator with Permanent Magnet for Transport of Rails

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A new solution for transporting long ferromagnetic bodies is presented, based on a system of permanent magnets whose attractive force at the moment of releasing the load is reduced by pulse magnetic field produced by appropriately arranged coils. The continuous mathematical model of the device is solved numerically. Its operation characteristics illustrated by an example are evaluated and discussed. Streszczenie. W artykule przedstawiono metodę transportu długich obiektów ferromagnetycznych. W rozwiązaniu wykorzystane zostało zjawisko osłabiania siły z jaką magnesy trwałe przyciągają obciążenie, poprzez wytworzenie impulsowego pola magnetycznego, wytworzonego przez odpowiednio ustawione cewki. Zastosowano model matematyczny urządzenia o dziedzinie ciągłej, który poddano analizie numerycznej. Przedstawiono i omówiono wynikowe charakterystyki pracy. (Siłownik nośny z magnesami trwałymi to transportu szyn). Keywords: transport of ferromagnetic bodies, permanent magnet, magnetic field, numerical analysis Słowa kluczowe: transport korpusów ferromagnetycznych, magnesy trwałe, pole magnetyczne, analiza numeryczna. Introduction Transport of long massive steel bodies (for example rails, rods or pipes) is commonly realized by mobile cranes to which such bodies are fastened by steel ropes. The process of their binding and manipulation with them, however, are laborious and dangerous. That is why new possibilities in the domain are intensively looked for. The paper represents an introductory study of a fixing device for transport of steel rails (or other long bodies) equipped with a system of load-bearing transport actuators with permanent magnets producing the necessary attractive force. The device does not need any external source of electric energy. It just works with short current pulses (causing a short-time demagnetization of the permanent magnets) at the moment of releasing the body that may be, for example, delivered from a sufficiently [...]

Control of movement of artificial satellites by geomagnetic field

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The paper deals with a possibility of influencing the movement of artificial satellites of the Earth by its geomagnetic field using "tethers", i.e. long, direct current carrying superconductive cables moving together with the satellite. Derived is the continuous mathematical model of the problem consisting of an ordinary nonlinear differential vector equation. Its solution is carried out n[...]

Experimental Verification of Device for Setting of Position Based on Induction Heating-Produced Thermoelastic Effect

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Experimental verification of thermoelastic effect is performed with the aim to calibrate the device for accurate setting of position built in our laboratory. The time evolution of temperature and dilatation of the action element was measured for a sufficient spectrum of field current parameters (amplitude and frequency). The resultant graphs were compared with results obtained by numerical simulation. Streszczenie. W pracy opisano eksperymentalną weryfikację modelu numerycznego nagrzewania indukcyjnego. Zmiana rozmiaru elementu wykonawczego została zmierzona dla szerokiego zakresu amplitudy i częstotliwości prądu wzbudzającego. Wyniki uzyskane z pomiarów zostały porównane z rezultatami symulacji numerycznych. (Eksperymentalna weryfikacja urządzenia do precyzyjnego pozycjonowania zbudowanego w oparciu o efekt termoplastyczny z podgrzewaniem indukcyjnym) Keywords: experimental verification, setting of position, thermoelastic effect, numerical analysis. Słowa kluczowe: weryfikacja eksperymentalna, ustawianie pozycji, efekt termoplastyczny, analiza numeryczna. Introduction Accurate setting of position on the order of 10-5-10-3 m may be realized by a number of techniques based on mechanical, hydraulic, pneumatic, electromagnetic and other principles. All these systems, however, contain movable parts, whose presence often makes complications. Qualitatively much better results can be achieved using the principle of thermoelasticity produced by induction heating. Our team proposed a device [1] that was modelled numerically, and that exhibits very prospective results. That is why we decided to build a real device and verify these results experimentally. Description of the device The arrangement of the device is depicted in Fig. 1. The dilatation element 2 made of a suitable metal is inserted into a harmonic current-carrying coil 3 fixed in fr[...]

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