Abstract
Fluid flow occurring in a venturi tube was numerically simulated with the Fluent software, and several factors to affect the mass flux and an asymmetric flow were analyzed, including the contraction ratio, ratio of the throat section length to diameter, the diffusion angle and the inlet and outlet pressure difference. Results show that the minimum pressure point occurs at the intersection between the contraction and throat sections in the venturi tube. As the contraction ratio increases, vacuum degree ascends, and mass flux rises. While both vacuum degree and mass flux reduces as the diffusion angle increases. In addition, an increment in the contraction ratio shortens a fully developed section of velocity in the diffusion section. At the contraction ratio less than 0.2 or the diffusion angle less than 35°, velocity in the diffusion section shows an asymmetric and skewed flow. However, as the inlet and outlet pressure difference increases, mass flux goes up, and thereby occurring a back-flowing in the throat section. The calculated results were compared with the reference’s data, both error is within 0.5% – -28%.
Highlights
A venturi tube, of which the cross-section contracts firstly and gradually expands, is composed of a contraction section, a throat section and a diffusion section
Fluid flow was numerically simulated at the contraction ratio of 0.2–0.8, the diffusion angle of 15°– 60° and the inlet and outlet pressure differences of 10–310kPa
Pressure in diffusion section increases along the flow direction. The difference between this minimum pressure and atmosphere is defined as a vacuum degree, and it is 78kPa at the contraction ratio of 0.5
Summary
A venturi tube, of which the cross-section contracts firstly and gradually expands, is composed of a contraction section, a throat section and a diffusion section. When the fluid flows through the throat section, the shrunken cross-section will accelerate the fluid accompanied by a pressure drop This phenomenon is called as a Venturi effect, which will cause the fluid to occur a vacuum draw. Sun and Niu.[13] numerically analyzed the effects of the contraction ratio and the diffusion angle on mass flux and vacuum degree in the venturi tube, and they suggested that the minimum pressure occurs at the intersection between the contraction and throat sections. A Fluent software was applied to numerically analyze the influences of the structural parameters on fluid flow and pressure in the Venturi tube, including the contraction ratio, the diffusion angle, the ratio of the throat section length to diameter and the pressure difference between the inlet and the outlet of venture tube. The characteristics of mass flux, vacuum degree and asymmetric flow were analyzed
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