Abstract:The article describes the theory of cavitation at high values of shear stress in a viscous liquid. For this purpose, a spatial model of two cylindrical shells imposed concentrically was designed. In the narrow gap between the cylinders the temperature, density and viscosity of liquid is constant. Shear stress is induced by the rotary motion of the inner cylinder, resulting in a change of velocity and pressure fields. Due to the pressure drop between the cylinders there is a precondition to the formation of cavitation bubbles at the point of the lowest static pressure. To verify the assumption was made CFD model based on simplified physical model, through which cavitation was qualitatively and quantitatively assessed. In this paper the results of the numerical solution will be presented alongside with basic form of experimental device for physical generation of cavitation at high values of shear stress.

Abstract. A supersonic gas ejector in conjunction with a liquid ring vacuum pump is used for creating and maintaining vacuum in a chamber for technological purposes. In this paper the authors submit an overview about the problematics of suction pressure reduction with a supersonic gas ejector used as a pre-stage of a liquid ring vacuum pump. This system has also the function of a cavitation protection due to the higher pressure present at the suction throat of the vacuum pump. A part of this paper is devoted to the governing equations used at the definition of the flow through an ejector. The experimental studies are then carried out in or own laboratory for verification purposes.

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The article describes the theory of cavitation at high values of shear stress in a viscous liquid. For this purpose, a spatial model of two cylindrical shells imposed concentrically was designed. In the narrow gap between the cylinders the temperature, density and viscosity of liquid is constant. Shear stress is induced by the rotary motion of the inner cylinder, resulting in a change of velocity and pressure fields. Due to the pressure drop between the cylinders there is a precondition to the formation of cavitation bubbles at the point of the lowest static pressure. To verify the assumption was made CFD model based on simplified physical model, through which cavitation was qualitatively and quantitatively assessed. In this paper the results of the numerical solution will be presented alongside with basic form of experimental device for physical generation of cavitation at high values of shear stress.

Single-blade centrifugal pumps with a screw-shaped blade are perspective hydraulic machines with possible usage in many areas. According to the non-symmetrical impeller shape, mechanical properties, resulting from a dynamic balancing, are not fulfilled automatically. The way of designing of an impeller which enables fulfilled main requests such as good hydraulic, mechanical properties and the ball passage diameter, is described in this academic paper.