Vibration control of resonant vibratory feeders with electromagnetic excitation

Vibracioni dodavači sa elektromagnetnom pobudom, odnosno elektromagnetni vibracioni dodavači (EMVD) su najčešće korišćeni u procesnoj industriji za obezbeđenje gravimetrijskog protoka sitnozrnih i rasutih materijala. Ovi pogoni obezbeđuju laku i jednostavnu kontrolu masenog protoka transportujućih materijala. U poređenju sa ostalim pogonima (pneumatskim, inercionim, centrifugalnim, itd.), oni su jednostavnije i kompaktnije konstrukcije, robusni i pouzdani u radu. Odsustvo habajući mehaničkih delova kao što su reduktori, kišnici, ekscentri i sl., čine EMVD veoma ekonomičnom opremom. Standardni pretvarački izlazni stepeni namenjeni za kontrolu EMVD su bazirani na SCR elementima (tiristorima i trijacima). Njihovo korišćenje podrazumeva korišćenje kontrole faznog ugla (KFU) i stoga konstantnu učestanost vibracija. Na ovaj način kontrolno kolo mora biti sinhronizovano sa mrežnom učestanošću 50(60)Hz. Uz pomoć KFU je jedino moguće ostvariti podešavanje amplitude vibracija, ali ne i njihove učestanosti. Primena prekidačkih tranzistorskih (IGBT ili MOSFET) energetskih pretvarača, omogućava amplitudsku i (ili) frekventnu kontrolu EMVD. Njihovo korišćenje podrazumeva pobudu EMVD nezavisno od mrežne učestanosti. Dodatno, frekventna kontrola dozvoljava rad u oblasti mehaničke rezonance. Rad u ovoj oblasti je veoma efikasan, pošto je moguće obezbediti značajne izlazne pomeraje, veoma malom ulaznom snagom. Optimalan i efikasan rad zahteva praćenje rezonantne učestanosti. U ovom radu su predstavljeni jedno moguće rešenje vibracione kontrole EMVD, kao i odgovarajući simulacioni i eksperimentalni rezultati.The vibratory feeders with electromagnetic excitation called electromagnetic vibratory feeders (EMVF) are commonly used for performing gravimetric flow of granular and particulate materials in processing industry. This drives offer easy and simple control the mass flow of conveying materials. In comparison with other drives (pneumatics, inertial, centrifugal, etc...), these have a more simple construction and they are compact, robust and reliable in operation. The absence of wearing mechanical part, such as gears, cams belts, bearings, eccentrics, etc., makes EMVF, most economical equipment. Standard power electronic output stages intended for control of the EMVF using SCR devices (thyristors and triacs). This implies phase angle control (PAC) and constant frequency of vibration. In this way control circuit must be synchronized to the mains supply frequency 50(60) Hz. PAC can only accomplish tuning amplitude of vibration, but not vibratory frequency. Application of transistor (IGBT or MOSFET) switch mode power converters enables accomplishing the amplitude and (or) frequency control of EMVF. Their use implies the excitation of an EMVF independent of the mains supply frequency. In addition, the frequency control ensures operation in the region of mechanical resonance. This operation is highly efficient, because large output displacement is provided by small input power. An optimal and efficient operation requires tracking of resonant frequency. This paper presents possible solution of the amplitude frequency control of EMVF and corresponding simulation and experimental results

Vibration control of resonant vibratory feeders with electromagnetic excitation

Vibracioni dodavači sa elektromagnetnom pobudom, odnosno elektromagnetni vibracioni dodavači (EMVD) su najčešće korišćeni u procesnoj industriji za obezbeđenje gravimetrijskog protoka sitnozrnih i rasutih materijala. Ovi pogoni obezbeđuju laku i jednostavnu kontrolu masenog protoka transportujućih materijala. U poređenju sa ostalim pogonima (pneumatskim, inercionim, centrifugalnim, itd.), oni su jednostavnije i kompaktnije konstrukcije, robusni i pouzdani u radu. Odsustvo habajući mehaničkih delova kao što su reduktori, kišnici, ekscentri i sl., čine EMVD veoma ekonomičnom opremom. Standardni pretvarački izlazni stepeni namenjeni za kontrolu EMVD su bazirani na SCR elementima (tiristorima i trijacima). Njihovo korišćenje podrazumeva korišćenje kontrole faznog ugla (KFU) i stoga konstantnu učestanost vibracija. Na ovaj način kontrolno kolo mora biti sinhronizovano sa mrežnom učestanošću 50(60)Hz. Uz pomoć KFU je jedino moguće ostvariti podešavanje amplitude vibracija, ali ne i njihove učestanosti. Primena prekidačkih tranzistorskih (IGBT ili MOSFET) energetskih pretvarača, omogućava amplitudsku i (ili) frekventnu kontrolu EMVD. Njihovo korišćenje podrazumeva pobudu EMVD nezavisno od mrežne učestanosti. Dodatno, frekventna kontrola dozvoljava rad u oblasti mehaničke rezonance. Rad u ovoj oblasti je veoma efikasan, pošto je moguće obezbediti značajne izlazne pomeraje, veoma malom ulaznom snagom. Optimalan i efikasan rad zahteva praćenje rezonantne učestanosti. U ovom radu su predstavljeni jedno moguće rešenje vibracione kontrole EMVD, kao i odgovarajući simulacioni i eksperimentalni rezultati.The vibratory feeders with electromagnetic excitation called electromagnetic vibratory feeders (EMVF) are commonly used for performing gravimetric flow of granular and particulate materials in processing industry. This drives offer easy and simple control the mass flow of conveying materials. In comparison with other drives (pneumatics, inertial, centrifugal, etc...), these have a more simple construction and they are compact, robust and reliable in operation. The absence of wearing mechanical part, such as gears, cams belts, bearings, eccentrics, etc., makes EMVF, most economical equipment. Standard power electronic output stages intended for control of the EMVF using SCR devices (thyristors and triacs). This implies phase angle control (PAC) and constant frequency of vibration. In this way control circuit must be synchronized to the mains supply frequency 50(60) Hz. PAC can only accomplish tuning amplitude of vibration, but not vibratory frequency. Application of transistor (IGBT or MOSFET) switch mode power converters enables accomplishing the amplitude and (or) frequency control of EMVF. Their use implies the excitation of an EMVF independent of the mains supply frequency. In addition, the frequency control ensures operation in the region of mechanical resonance. This operation is highly efficient, because large output displacement is provided by small input power. An optimal and efficient operation requires tracking of resonant frequency. This paper presents possible solution of the amplitude frequency control of EMVF and corresponding simulation and experimental results

On some important quantities influencing proper functioning of the differential pneumatic comparator

Back-pressure air gauging is an effective and practical way of controlling machine parts in large-scale production. It is a non-contact measuring technique based on the flapper-nozzle effect. The proper functioning of a differential pneumatic comparator depends on several geometric parameters as well as flow conditions inside the device. The main problems of this controlling technique are the fouling of the measuring nozzle head and changes in the accuracy of the comparator. This paper examines the influence of the supply pressure, the diameter of the orifice in the measuring branch, and the axial distance in the flapper-nozzle area on pneumatic comparator performance. In a way, we are trying to optimize the performance of a given pneumatic comparator with respect to the tolerance field for which it is intended. The size, strength, and position of the vacuum in the flapper-nozzle area depend on the supply pressure and the axial distance between the measuring nozzle outlet cross-section and the workpiece surface. For a certain combination of these two parameters, we can influence the vacuum quantities. A pneumatic sensitivity of a comparator can be increased by increasing the supply pressure. The greater accuracy of the back pressure air gauge, the smaller the application range, i.e. the tolerance field that we can control with a given device

An experimental investigation and statistical analysis of turbulent swirl flow in a straight pipe

This paper presents results of our own velocity field measurements in a straight pipe swirl flow. These studies were conducted using an originally designed hot wire probe. Due to the specially tailored shape of the probe, it was possible to get four measurement points in the viscous sublayer. The time-averaged velocity field and the statistical moments of the second and third order are calculated based on the measured velocity components. Mathematical and physical interpretations of statistical characteristics and structures of turbulent swirl flow in the time domain are presented. On the basis of these results, deeper insight into turbulent transport processes can be obtained, as well as useful conclusions necessary for turbulent swirl flows modeling. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 35046

Numerical research of the compressible flow in a vortex tube using OpenFOAM software

The work presented in this paper is dealing with numerical simulation of energy separation mechanism and flow phenomena within a Ranque-Hilsch vortex tube. Simulation of turbulent, compressible, highly swirling flow inside vortex tube is performed using RANS approach, with Favre averaged conservation equations. For turbulence closure, k-ε and k-ω shear-stress transport models are used. It is assumed that the mean flow is axisymmetric, so the 2-D computational domain is used. Computations were performed using open-source CFD software Open- FOAM. All compressible solvers available within OpenFOAM were tested, and it was found that most of the solvers cannot predict energy separation. Code of two chosen solvers, which proved as the most robust, is modified in terms of mean energy equation implementation. Newly created solvers predict physically accepted behavior in vortex tube, with good agreement with experimental results. Comparison between performances of solvers is also presented. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 35046

The school of the turbulent swirling flow at the Faculty of Mechanical Engineering University of Belgrade

This review paper provides data about research activities at the School of the turbulent swirling flow at the Faculty of Mechanical Engineering, University of Belgrade, conducted in the period 1941 up to date. An overview is provided of the main directions in this research area. First papers dealt with the turbulent swirling flow in hydraulic turbines to be continued by the experimental and analytical approaches on the axial fans pressure side. The complexity of 3-D, non-homogeneous, anisotropic turbulent velocity fields required complex experimental and theoretical approach, associated with the complex numerical procedures. Analytical approaches, complex statistical analyses and experimental methods and afterwards CFD employed in the research are presented in this paper. The 150 scientific papers, numerous diploma works, several master of science (magister) theses, six Ph. D. theses and two in progress, 40 researchers, national and international projects are the facts about the School. Scientific references are chronologically presented. Numerous abstracts from scientific conferences, presentations, projects with industry and lectures are not given here. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 35046