Markov models for mixing of powders in static mixers

Mixing of powders is important in many different industries as it adds significant value to the product. The research on this operation in industry goes through simulation of continuous mixing and mixing in general. The objective of this thesis is a development of a unified model representing samples of the particulate flow in different types of static mixers operating with materials that tend to segregate. One and two dimensional models of static mixers based on the theory of Markov chains are developed and the procedure of model parameter identification is proposed. The results of simulation have shown how the value of transition probabilities and initial distribution of the components influence mixture quality. The experimental results have proved the adequacy of the developed models. It has been shown that there is an optimum number of material passages through the mixer that gives maximal mixture quality while mixing components that tend to segregate

Spacecraft reflectors thermomechanical analysis

In this article, thermo-mechanical analysis results of the composite reflectors for the use on the geostationary Earth orbit possibility studies are described. The behavior of two different space reflector structures manufactured on composite materials is investigated. The estimates of reflecting surfaces RMS deviations for the two extreme cases orbital inclinations are presented

Plasma chemical purification of flue gases using pulsed electron beams

The article presents the study of the pulsed electron beam propagation in oxygen and nitrogen. The researches were performed using the TEA-500 pulsed electron accelerator and drift tube. Parameters of the TEA-500 pulsed electron accelerator are as follows: the electron energy (varies) is 200-450 keV, the beam current is 10 kA, the half-amplitude current pulse duration is 60 ns, the pulse repetition rate is up to 10 Hz (in the pulse burst). The accelerator is equipped with the necessary means of diagnostics of the beam parameters: particle energy, current and current density, the total energy transferred by the beam. The drift tube includes a chamber consisting of two sections of reverse current shunts located along the entire length of the drift tube. The following precursors used N2 and O2. The specified types of gases were chosen as they are among the main components of the flue gases, whose treatment has been widely reported recently

Propagation of the pulsed electron beam of nanosecond duration in gas composition of high pressure

This paper presents the results of the investigation of the propagation of an electron beam in the high-pressure gas compositions (50, 300, and 760 Torr): sulfur hexafluoride and hydrogen, sulfur hexafluoride and nitrogen, sulfur hexafluoride and argon. The experiments have been performed using the TEA-500 laboratory accelerator. The main parameters of the accelerator are as follows: an accelerating voltage of 500 kV; an electron beam current of 10 kA; a pulse width at half maximum of 60 ns; a pulse energy of 200 J; a pulse repetition rate of up to 5 pulses per second, a beam diameter of 5 cm. The pulsed electron beam was injected into a 55 cm metal drift tube. The drift tube is equipped with three reverse-current shunts with simultaneous detecting of signals. The obtained results of the investigation make it possible to conclude that the picture of the processes occurring in the interaction of an electron beam in the high-pressure gas compositions is different from that observed in the propagation of the electron beam in the low-pressure gas compositions (1 Torr)

A 2D Markov chain for modelling powder mixing in alternately revolving static mixers of Sysmix (R) type

International audienceA two-dimensional model of the flow and mixing of particulate solids has been developed on the basis of the Markov chain theory for an alternately revolving static mixer of Sysmix (R) type. In such a system, mixing occurs in both vertical and horizontal directions. Simulations are presented here to investigate the effect of the initial loading of the components, as well as the effect of the values of the transition probabilities that constitute the main parameters of the model. It is shown that a horizontal arrangement of the components always leads to better mixture quality and improved mixing kinetics. This research is presented for non-segregating mixtures, as well as potentially segregating mixtures. for which the empirically well-known oscillations in variance are represented by the model. Results suggest that there is a rational way of approaching a static-mixing problem with regard to the initial loading of the component and the optimal number of revolutions. Comparison of model results with experimental data published previously for a Sysmix (R) apparatus contributes to validating the viability of the model

Electrospark method for obtaining nanopowders

In the paper, a metallic FexOy nanopowder was obtained by the electrospark method. The used electrospark installation consists of the electrode system, mobility system, system for measuring processing parameters (oscilloscope and current sensor, HV voltage divider, manovacuum meter), source of current pulses, vacuum system (vacuum pump, gas cylinders with working gas, gas routes, gas taps). The specific feature of the installation is the use of a power supply circuit of two generators with different voltage levels operating for one interelectrode gap. This generator circuit makes it possible to change the treatment parameters in wide ranges (pulse duration 10–100 ?s, pulse energy 0.1–0.6 J, pulse repetition rate 0.1–5 kHz). It will enable to choose the optimal ratio between the energy expended and the maximum yield of the product, as well as to study the influence of treatment parameters on the composition and properties of the resulting powder. The morphology and phase composition of the FexOy synthesized metal powder was studied

Optical properties of SixTiyCzOw composite nanopowder obtained by pulsed plasma chemical method

This paper presents the results of an experimental investigation on the optical properties of the SixTi<yCzOw nanopowders, produced by the pulsed plasma chemical method. Pulsed plasma chemical synthesis is realized on the laboratory stand, including a plasma chemical reactor (6 l) and TEA-500 electron accelerator. The parameters of the electron beam are as follows: 400-450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. The spectrum of the diffuse reflection coefficient R(hv) was measured using the AvaSpec-2048-2 (Avantes) spectrometer with the AvaLight-DHS light source (deuterium and halogen-tungsten lamp) and an integrating sphere. The band gap of the obtained composite is 2.03–3.12 eV

Investigation of the effect of condensed phase on the energy conditions for the initiation of the plasma-chemical process of flue gas cleaning by a pulsed electron beam

This work investigates the processes of dissipation of the charge and energy of a pulsed electron beam in gas compositions (nitrogen, carbon dioxide and oxygen) in the presence of ammonium sulphate and nitrate. A pulsed electron beam generated by the TEA500 accelerator (Tomsk, Russia) with an electron energy of up to 410 keV, a beam current of up to 5 kA (I0), and a half-amplitude voltage pulse duration of 60 ns was injected into a 46 cm long drift chamber filled with a gas mixture. The pulsed electron beam current (IF?) passing through the drift chamber was registered using a sectioned calorimeter with beam charge monitor function, and the efficiency of the current passage of the beam was determined as the ratio qF?/q0, where q0 is the beam charge measured at the place of its injection into the chamber drift. The pressure in the drift chamber varied (375, 560 and 760 Torr, humidity value 15% ± 5% and 50% ± 5%). The geometric dimensions of the plasma-chemical reactor for initiating plasma-chemical reactions of flue gas cleaning were determined