Aerodynamics of two-phase gas-solid flow in a flat suction nozzle during vacuum pneumatic transport.

The paper reports the results of research on the effect of the design of a suction nozzle with a rectangular section under horizontal and vertical pneumatic conveying conditions in a pipe with a diameter of D = 30 mm. Five unmanned truncated pyramid-shaped suction nozzles were tested, which differed in height and cone opening angle 25°-120° while maintaining a constant ratio of the inlet to the outlet surface area of 8.5. The working media in the research were air and ten types of bulk materials commonly used in the industry with a variable equivalent particle diameter of d s = 0.2–2.4 mm and the specific density ρ s = 495–6730 kg/m3. The materials used in the research were characteristic of bulk materials of type A, B and D defined according to Geldart's classification. The study was carried out at the superficial velocities of air u g = 2.8–46 m/s and solids u s = 0.002–2 m/s. This ensured obtaining the mass concentration of the solid in relation to the mass flow of air in the range of μ s = 0.6–290. As a result of the analysis of experimental data obtained by means of a high-speed camera and a computer system for archiving experimental data and image analysis, seven flow structures were identified and described. Also an original two-phase gas-solid flow map was developed. A new method has been proposed to calculate pressure drop ΔP 2P during two-phase gas-solid flow for different geometries of rectangular suction nozzles with the accuracy mean relative error MRE = −0.83% and mean absolute error MAE = 29.5%. It is the first model of this type described in the literature. [Display omitted] • Conditions of vacuum pneumatic transport in flat suction nozzle were investigated. • Loose materials of type A, B and D according to Geldart's classification were used in the study. • New two-phase gas-solid flow structures were identified and described. • New map of air-solids two-phase flow was created. • New calculation model of pressure drop in flat suction nozzle was proposed. [ABSTRACT FROM AUTHOR]