Ilya A. Lysak

The efficiency of annular-nozzle ejectors serving as components of complex technical systems interacting with high-temperature media in engines and in the field of energy technologies is not linearly related to the gas-dynamic characteristics of the flows formed in the device. In this paper, we have analyzed the results of numerical and experimental studies of gas jets in an annular-nozzle air ejector. The regression equations built according to the circumscribed central composite design described the relationship between a pressure drop and the structural parameters of the nozzle with the speed and mass flow rates of the airflows, including error rates of no more than 15 percent. A two-factor optimization based on Harington’s generalized desirability function was performed to obtain a relatively accurate estimate of the ejector efficiency under the influence of the structural and operating parameters. An optimization method based on the combination of response surface methodology and the desirability function approach, allowing simultaneous consideration of all responses, made it possible to simultaneously optimize multiple conflicting objectives.

Background: The formation and modification of the surface of polypropylene fibers provide a versatile material for a variety of applications. Objective: This research examines the production of new materials by pneumatic spraying of a polypropylene melt jet, on the surface of which metal and metal oxide nanoparticles are prepared using the sol-gel technique and photoreduction followed by ultra-high frequency processing. We used the obtained materials to remove Bisphenol A in the photoreactor. Method: Based on an analysis of the obtained values of the numerical characteristics in the spray zone and the physical essence of the criteria under consideration, a mechanism for the destruction of the melt jet from the formation of a fiber-forming system is proposed. Analysis of the degradation of Bisphenol A was carried out by electron spectroscopy and fluorescence. Results: A composite active layer, “polymer – inorganic nanoparticles”, on the surface of polypropylene fibers has been demonstrated to create new photocatalytic materials. Bisphenol A in water was examined as a toxicant. Conclusion: Based on the analysis of the obtained values of the numerical characteristics in the spray zone and the physical essence of the considered criteria, it was found that the pressure drop in the nozzle, the nozzle critical section area, and the rheological properties of the melt are dominating factors in the influence on the morphology and size of the ultra-fine fibers obtained by pneumatic spraying. It was determined that materials based on a polypropylene carrier with the largest diameter of 6.71 μm have the best sorption capacity for Bisphenol A. A decrease in the concentration of bisphenol A in water by more than two times in 30 minutes of UV irradiation in the presence of polypropylene was achieved without additional injection of oxidants.

Предложены новые принципы формирования и закрепления наночастиц серебра на поверхности ультратонких волокон с использованием электромагнитного излучения деци- и нанометрового диапазонов для бактерицидной модификации жидких сред. Получение покрытий включает образование наночастиц серебра при фотовосстановлении из водного раствора AgNO₃ с концентрацией 0,001М в присутствии ультратонких полипропиленовых волокон с последующей их стабилизацией на поверхности волокон микроволновым излучением материала волокон, которые препятствует агломерации и обеспечивают стабилизацию наночастиц серебра на их поверхности. Ультратонкие полипропиленовые волокна, полученные в результате пневматического распыления расплава, представлены средним диаметром d_ср=1,5-6мкм и достаточно широким логнормальным распределением. Методом численного моделирования самосборки и самоорганизации наночастиц серебра с учетом экситонного и фононного механизмов их квантовой релаксации за счет диссипации энергии в матрицу полимера продемонстрирована возможность двухстадийного создания покрытий на поверхностях полимерных матриц. Установлено, что в результате локального микроволнового нагрева наночастиц серебра инициируются процессы образования надмолекулярных структур материала волокон, которые препятствует агломерации и обеспечивают стабилизацию наночастиц серебра на их поверхности. Полученные покрытия охарактеризованы методами просвечивающей электронной микроскопии и спектроскопии. Например, наночастицы серебра, сформированные и закрепленные на поверхности волокон в результате десятиминутной экспозиции ультрафиолетового облучения, имеют размер 50±18нм. Проведенные исследования бактерицидной активности показали, что ультратонкие полипропиленовые волокнистые материалы с покрытиями на основе наночастиц серебра позволяют эффективно производить антибактериальную очистку природных вод с высоким уровнем микробиологической загрязненности. После проведения 10 циклов очистки воды количество серебра в образцах, по данным атомно-эмиссионной спектроскопии, остается неизменным.

In this paper, we present a method of formation of polymer fibre materials comprising dispersed oxides of rare and trace elements. The results of X-ray diffraction and spectral analyses show that the optimum synthesis conditions of the antimony-doped tin oxide, indium-doped tin oxide, and bismuth-doped tin oxide particles are provided using the "reverse" hydrolytic co-precipitation of hydroxides from chloride solutions combined with the subsequent thermal treatment at 1000°C. Durable fixation of nanoparticles on the fibre surface is confirmed by the atomic emission spectrometry with inductively coupled plasma and transmission electron microscopy. The results show that spraying of a free stream of the thermoplastic polymer melt with a gas stream containing nanoparticles allows obtaining fibre materials, which possess catalytic, photosensitive, as well as heat and sound insulating properties.

The aim of the work was to study jet flows produced by gas-gas ejector with annular primary flow nozzle and central duct for secondary flow in case of its consequent usage as a liquids atomizer. A complex experimental and numerical study of a coaxial jet has been performed. A set of probe methods for diagnosing flows provides new data on the characteristic of the flow: the effective area of the ejector nozzle critical section, the gas velocity profiles and the ejection coefficient. Experimental data on the coaxial flows are extremely important for the verification of developing theoretical models of liquid destruction by a gas flow using annular ejectors.

A physicochemical research of the processes of phase composition formation in the materials of the Dy-Sn-O system was performed. Phase composition was taking place in the course of thermal treatment of dysprosium (III) and tin (IV) codeposition products. These were codeposited from nitrate solutions at pH 7, and 25% ammonia water was used as the precipitant. Using thermal and X-ray diffraction analysis, it was found that in the above system at 90 wt. % of Dy₂O₃ and 10 wt. % of SnO₂, when the precursors were heated above 600°C there are no solid solutions. In the meanwhile, at temperatures below 1000°C there is only one phase, Dy₂O₃. At temperatures above 1000°C, the system becomes bi-phase and includes Dy₂O₃ and Dy₂Sn₂O₇.