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We propose a method for calculating the kinetics of ultrasonic coagulation of PM2.5 during fine gas cleaning that provides an order of magnitude higher calculation performance. Increased productivity is achieved through the proposed and justified method of reducing the original three-dimensional problem to a two-dimensional one. The proposed reduction method is based on the fact that the time of complete rotation of vortex acoustic flows turns out to be much shorter than the characteristic coagulation time during fine gas cleaning. This makes it possible to present the fractional composition of aerosol particles as a function of two stream functions instead of three coordinates. Calculations carried out using the proposed method make it possible to identify the possibility of increasing the efficiency of coagulation in three-dimensional flows due to the following mechanisms: a local increase in concentration caused by the inertial transfer of particles to the periphery of three-dimensional vortices in the gas phase, increasing the frequency of particle collisions due to three-dimensional turbulent disturbances in ultrasonic fields with a high amplitude of oscillatory velocity (more than 10 m/s), and increasing productivity and ensuring the possibility of continuous implementation of the process in flow mode due to the transfer of particles between the streamlines of the main vortices initiated by ultrasonic vibrations as well as due to external flows perpendicular to the plane of the vortices in three-dimensional space. The developed set of programs for implementing calculations can be used in the design of gas cleaning equipment. [ABSTRACT FROM AUTHOR]

This study aims to investigate the impact of cavitation states on the stability of cryogenic pumps. Steady and unsteady simulations of the internal flow were conducted based on an SST k–ω turbulence model and a modified Zwart cavitation model considering thermodynamic effects. The modified cavitation model was verified using the hydrofoil model and compared with the Hord test results. The results indicate that the variation in pressure at the pump inlet has a significant influence on the cavitation in the pump. The cavitation states and fluid flow directions vary across the different spans in the impeller channel. The smaller the distance from the front cover of the impeller, the more severe is the cavitation, in addition to the appearance of a vortex. The influence of the formation of a longitudinal vortex at the impeller outlet on the pressure fluctuation in the cavitation state was revealed. The rotation of the impeller has negligible influence on the pressure load distribution at the blade inlet. However, it has a higher influence on that of the second half of the blade, particularly when the blade passes through the volute tongue. Cavitation can exacerbate the instability of pump operation. The research results are significant for accurately predicting cavitation performance and improving the anti-cavitation capability of cryogenic pumps. [ABSTRACT FROM AUTHOR]

A numerical study of the aerodynamics of a swirling turbulent flow and of the classification of particles in the vortex chamber of a pneumatic combined apparatus has been performed. The obtained results indicate the possibility of achieving a uniform distribution of the radial flow velocity along the height of the chamber in the particle separation zone in it by changing the shape of the rotor blades of the apparatus, which is a prerequisite for its efficient operation. The trajectories of motion of single particles in the vortex chamber are determined. A significant effect of turbulent flow pulsations on the efficiency of particle separation in it has been established. The reliability of the obtained results is confirmed by test studies and by their comparison with experimental data. [ABSTRACT FROM AUTHOR]