IDENTIFICATION OF THE INFLUENCE OF THE SPATIAL ORIENTATION OF THE DEPOSITED LAYERS, AS WELL AS THEIR OVERLAP COEFFICIENT ON THE SURFACE SHAPE ERROR DURING ADDITIVE SHAPING BY AN ELECTRIC ARC

Статья посвящена изучению вопросов управления процессом аддитивного формообразования изделий. Представлены результаты исследования процесса аддитивного формообразования поверхности электрической дугой в среде защитного газа. Проведен анализ погрешности формы поверхностей, полученных с различным заполнением слоев. Подтверждено экспериментально, что такие параметры процесса, как ориентация слоев, коэффициент их перекрытия являются значимыми. Так, погрешность формообразования образцов наплавки слой на слой в вертикальном направлении выше по сравнению с другими способами наплавки, реализованными в эксперименте. Средние значения погрешности формы образцов составляют 0,75 мм, 0,88 мм, 1,15 мм, соответственно, для способов наплавки слой к слою на горизонтальную поверхность с коэффициентом перекрытия 0,3, слой к слою на горизонтальную поверхность с коэффициентом перекрытия 0,5, слой на слой в вертикальном направлении. Максимальные значения погрешности определены на уровне 0,85 мм, 1,2 мм, 1,5 мм для соответствующих способов наплавки, реализованных в эксперименте. Таким образом, пространственная ориентация слоев, а также коэффициент перекрытия слоев являются значимыми, оказывают влияние на численное значение погрешности формы получаемой поверхности, должны быть учтены при проектировании алгоритмов разделения на слои, их заполнения при аддитивном формообразовании электрической дугой в среде защитного газа The article is devoted to the study of the issues of managing the process of additive shaping of products. The paper presents the results of a study of the process of additive surface shaping by an electric arc in a protective gas medium. We analyzed the error of the shape of the surfaces obtained with different filling layers. We confirmed experimentally that such process parameters as the orientation of the layers, their overlap coefficient are significant. Thus, the error of forming samples of surfacing layer on layer in the vertical direction is higher compared to other methods of surfacing implemented in the experiment. The average values of the sample shape error are 0.75 mm, 0.88 mm, 1.15 mm, respectively, for methods of surfacing layer to layer on a horizontal surface with an overlap coefficient of 0.3, layer to layer on a horizontal surface with an overlap coefficient of 0.5, layer to layer in the vertical direction. The maximum error values are determined at the level of 0.85 mm, 1.2 mm, 1.5 mm for the corresponding surfacing methods implemented in the experiment. Thus, the spatial orientation of the layers, as well as the overlap coefficient of the layers, are significant, affect the numerical value of the shape error of the resulting surface, should be taken into account when designing algorithms for dividing into layers, filling them with additive shaping by an electric arc in a protective gas medium

OuroborosBEM: a fast multi-GPU microscopic Monte Carlo simulation for gaseous detectors and charged particle dynamics

The design of gaseous detectors for accelerator, particle and nuclear physics requires simulations relying on multi-physics aspects. In fact, these simulations deal with the dynamics of a large number of charged particles interacting in a gaseous medium immersed in the electric field generated by a more or less complex assembly of electrodes and dielectric materials. We report here on a homemade software, called ouroborosbem, able to tackle the different features involved in such simulations. After solving the electrostatic problem for which a solver based on the boundary element method (BEM) has been implemented, particles are tracked and will microscopically interact with the gas medium. Dynamical effects have been included such as the electron-ion recombination process, the charging-up of the dielectric materials and other space charge effects that might alter the detector performances. These were made possible thanks to the nVidia CUDA language specifically optimised to run on Graphical Processor Units (GPUs) to minimize the computing times. Comparisons of the results obtained for parallel plate avalanche counters and GEM detectors to literature data on swarm parameters fully validate the performances of ouroborosbem. Moreover, we were able to precisely reproduce the measured gains of single and double GEM detectors as a function of the applied voltage.

Features of the Flow of a Model Liquid Into a Medium with a Variable Degree of Rarefaction

Experimental results of observing ethanol micro-jets expiring into a highly rarefied medium (vacuum) through a nozzle are presented. The study of the process was carried out both at the horizontal and vertical liquid stream from the source compared to the direction of gravity The residual background gas pressure in the vacuum chamber was maintained at a level much lower than the saturated vapor pressure of the working fluid at a given outlet temperature. The possibility of modeling complex processes of micro-fluids expiring into a medium with a given rarefied atmosphere on a compact vacuum gas-dynamic stand is shown. It is established that the long-term flow from a thin capillary or a small-diameter hole into a vacuum or a highly rarefied gas medium differs significantly from the well-studied flow modes into a dense gas medium, as well as from the pulsed flow modes into a vacuum. The paper describes the main features of the flow and the conditions for the occurrence of instability. It is shown that the long-term flow of a liquid micro-jet in a vacuum has a high degree of surface instability, with a large number of sudden changes in the direction, structure, and observed density. An explanation of the reasons for the destruction of the micro-jet is proposed. The formation of surface gas caverns causing explosive destruction of the micro-jet with the release of vapor-liquid droplets is established.

Influence of gaz modified medium on the safety of flour confectionery products

С целью увеличения срока годности мучных кондитерских изделий проведены исследования влияния газовой модифицированной среды на их органолептические свойства. Изделия были упакованы в лотки из полипропилена и среднебарьерную многослойную пленку на основе полиэтилентерефталата под запайку лотков. Газовая модифицированная среда была представлена смесью углекислого газа и азота в соотношениях 20:80; 30:70; 50:50. Хранение образцов осуществлялось в течение 60 дней. Установлено, что замена воздушной среды на смесь углекислого газа и азота положительно влияла на их сохранность. Показано, что основным критерием сохранности изделий являются органолептические показатели, изменение которых происходят значительно раньше появления признаков микробиологической порчи. Использование газовой модифицированной среды при упаковывании кондитерских изделий позволило увеличить срок годности изделий в 3-6 раз. Наилучшие результаты были получены при использовании газов в соотношении 50:50. Таким образом, использование газовой модифицированной среды может рассматриваться в качестве альтернативы применению пищевых добавок для продления срока годности упакованных мучных кондитерских изделий. In order to increase the shelf life of flour confectionery products, studies have been conducted on the effect of a modified gas medium on their organoleptic properties. The products were packed in trays made of polypropylene and a medium-barrier multilayer film based on polyethylene terephthalate for sealing the trays. The gas modified medium was represented by a mixture of carbon dioxide and nitrogen in the ratios 20:80; 30:70; 50:50. The samples were stored for 60 days. It was found that the replacement of the air environment with a mixture of carbon dioxide and nitrogen positively affected their safety. It is shown that the main criterion for the safety of products are organoleptic properties, the change of which occurs much earlier than the appearance of signs of microbiological spoilage. The use of a modified gas medium in the packaging of confectionery products allowed to increase the shelf-life of products by 3-6 times. The best results were obtained when using gases in a 50:50 ratio. Thus, the application of a modified gas medium can be considered as an alternative to the use of food additives to extend the shelf-life of packaged flour confectionery products.

Investigation of service life characteristics of hot cathodes in arc plasmatrons

Among the applied challenges associated with the use of electric-arc plasma, the most urgent is the erosion of electrodes in plasmatrons, which determine the continuous operation of an electric-plasma device. Investigation results on the thermal state of hot cathodes and their erosion are presented depending on the main defining parameters, namely geometrical dimensions of electrodes, Joule heating, current of the arc discharge, and the gas medium. The conditions for the minimum specific erosion and long service life of tungsten thermionic cathodes are established experimentally.

Collisions of Two-Phase Liquid Droplets in a Heated Gas Medium

The paper presents the experimental research findings for the integral characteristics of processes developing when two-phase liquid droplets collide in a heated gas medium. The experiments were conducted in a closed heat exchange chamber space filled with air. The gas medium was heated to 400–500 °C by an induction system. In the experiments, the size of initial droplets, their velocities and impact angles were varied in the ranges typical of industrial applications. The main varied parameter was the percentage of vapor (volume of bubbles) in the droplet (up to 90% of the liquid volume). The droplet collision regimes (coalescence, bounce, breakup, disruption), size and number of secondary fragments, as well as the relative volume fraction of vapor bubbles in them were recorded. Differences in the collision regimes and in the distribution of secondary fragments by size were identified. The areas of liquid surface before and after the initial droplet breakup were determined. Conditions were outlined in which vapor bubbles had a significant and, on the contrary, fairly weak effect on the interaction regimes of two-phase droplets.

Determination of the concentration of CO2 and H2O vapor under conditions of overlapping spectral lines

The efficiency of determining the concentration of CO2 and H2O vapors in the atmosphere has been investigated taking into account the overlap of their spectral lines. It is proposed to use regression relationships established between the determined and measured parameters of the investigated medium. These ratios can be set both for fixed values of temperature and pressure, and for a set range of their values. When calculating the absorption value, all overlaps of spectral lines are taken into account, taking into account their broadening at different temperatures and pressures. This allows the method to be used in multicomponent media with strongly overlapping spectral lines. The established regression relations are resistant to errors in the measurement information, which also improves the accuracy of determining the concentrations of the component composition of the gas medium. In addition, they are determined promptly (in real time), since the calculation of concentrations using established relationships (analytical expressions) between the determined and measured values does not present computational difficulties.

Numerical investigation of a high-pressure gas medium preionization by runaway electrons

A comparative simulation of the generation and acceleration of runaway electrons in the discharge gap during the initiation of the discharge by nanosecond and subnanosecond pulses is carried out. We used a numerical model based on the PIC-MCC method. Calculations were carried out for N2 6 atm pressure. Numerical simulation of a formation process of the electron avalanche initiated by an electron field-emitted from the top of the cathode microspike was carried out taking into account the motion of each electron in the avalanche. Characteristic runaway electron trajectories, runaway electron energy gained during the motion through the discharge gap, times required for runaway electrons to reach the anode were calculated. We compared our results with calculations using well-known differential equation of electron acceleration using braking force in Bethe approximation. We solved this equation also for braking force based on real (experimental) ionization cross section. The reasons for the discrepancy in the calculation results are discussed.