Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 3. The picture of bath blowing at application two-level oxygen lances

Further increase of resources- and energy-saving efficiency of BOF processes is unthinkable without development of new methods of blowing and designs of blowing devices. It requires information on the real physicochemical phenomena in the converter cavity accompanying the blowing of the converter bath using new designs of oxygen lances in order to assess the possible risks in the mastering of the proposed developments in industrial conditions. The paper presents the results of video filming of the top blowing of a 80-kg converter bath by groups of multi-pulse supersonic and sonic oxygen jets formed, respectively, by Laval and cylindrical two-level nozzles of two designs equipped with double-row tips with a circular arrangement of Laval nozzles and cylindrical ones and upper block with cylindrical nozzles. Previously unknown information was obtained on the picture of the bath blowing with the formation of a reaction zone of interaction of supersonic and sonic oxygen jets with a metal melt with a flow of carbon monoxide going out the bath and afterburning of CO to CO2 under conditions of a counter-directed double curtain of sonic oxygen jets at different levels of location of the foamed slag-metal emulsions. It was established that in the initial period of blowing during slag formation most of the thermal energy of CO to CO2 combustion flares is transferred to the surface of the bath with lumps of added lime, and the rest is transferred by forced convection to the converter walls and gases escaping from the bath to the neck. In the case of the location of the foamed slag level at the upper tier of the cylindrical nozzles of the lance, heat transfer from high-temperature flares of localized afterburning of CO to CO2 within a limited in size near-lance flow of exhaust gases from the reaction zone is carried out according to the laws of submerged combustion and is completed completely in foamed slag-metal emulsion with the prevention of aggressive action of afterburning flares and volumes of overheated slag on the converter lining. Revealed and recorded by video recording modes of blowing the converter bath, contributing to the development of such undesirable phenomena during smelting as the appearance of intense emissions of slag-metal suspension from the facility, coagulation of the slag with the cessation of dephosphorization of the metal melt, the development of intense dust formation and the removal of small metal particles and slag with the formation of crust on the lance barrel. A variant of the final stage of blowing with a transition to supplying nitrogen instead of oxygen through cylindrical nozzles of two-level lances was experimentally tested, which provides an effective reduction in the level of foamed slag-metal emulsion before the converter turning down. The data obtained were used in the development of an industrial design of a two-level lance with a double-row tip, blowing and slag modes of blowing a converter bath with its use.

The potential air flow through diver’s breathing apparatus

The gas admission through the divers' breathing apparatus is done with a critical flow. The gas storage pressure is reduced to the value of the external pressure 𝑝𝑒 . The paper approaches the gas-dynamic phenomena that occur when the gas flows through the second stage regulator, respectively: the variable restrictor A (between the seat and the cylindrical piston) and the fixed restrictor B (the orifice of cylindrical piston). The two main pressure restrictors can be considered Laval nozzles. Mathematical modeling of airflow through restrictors was done following the notions of the theory of potential gas flow through tubes and nozzles. The air flow was calculated numerically and by CFD simulation and was experimentally verified at a professional stand for the second stage.

PROCESSES AND TECHNOLOGIES OF COLD GAS DYNAMIC SPRAYING OF AGRICULTURAL EQUIPMENT

The article is devoted to the technology of cold gas-dynamic spraying - a relatively new technology for creating functional coatings in which narrowed-expanding nozzles (De Laval nozzles) are used, in which solid powders are sprayed at or close to supersonic speed in the direction of the substrate, where they plastically deform and adhere. Cold gas dynamic spraying is an innovative process that has received widespread scientific interest and industrial applications in the automotive, aerospace and biotechnology industries in recent years. Spraying various powder materials in this way provides protection against corrosion and can increase the mechanical strength and wear resistance of details. With that method it is possible to create functional coatings with different thermal conductivities and electrical conductivities, which can be used as insulation materials, conducting and isolation surface layers of parts, coatings for controlling gaps, restoring and repairing details. The article discusses modern developments in the field of experimental analysis of technologies and processes of cold gas-dynamic spraying, the systems of cold gas-dynamic spraying and coating formation are determined and the parameters and principles of the process are described. The installation for spraying surfaces developed at VNAU is presented and researches and the analysis of possibility of use of a method of a cold gas-dynamic spraying for restoration of details of autotractor equipment of agricultural purpose are carried out.

Numerical simulation of the dimensional transformation of atomization in a supersonic aerodynamic atomization dust-removing nozzle based on transonic speed compressible flow

To simulate the transonic atomization jet process in Laval nozzles, to test the law of droplet atomization and distribution, to find a method of supersonic atomization for dust-removing nozzles, and to improve nozzle efficiency, the finite element method has been used in this study based on the COMSOL computational fluid dynamics module. The study results showed that the process cannot be realized alone under the two-dimensional axisymmetric, three-dimensional and three-dimensional symmetric models, but it can be calculated with the transformation dimension method, which uses the parameter equations generated from the two-dimensional axisymmetric flow field data of the three-dimensional model. The visualization of this complex process, which is difficult to measure and analyze experimentally, was realized in this study. The physical process, macro phenomena and particle distribution of supersonic atomization are analyzed in combination with this simulation. The rationality of the simulation was verified by experiments. A new method for the study of the atomization process and the exploration of its mechanism in a compressible transonic speed flow field based on the Laval nozzle has been provided, and a numerical platform for the study of supersonic atomization dust removal has been established.