Relationship of energy conversion for Venturi injector
(1.Institute of Soil and Water Conservation, CAS & MWR, Yangling, Shaanxi 712100, China; 2.Institute of Watersaving Agriculture in Arid Areas of China, Northwest A＆F University, Yangling, Shaanxi 712100, China; 3.University of Chinese Academy of Sciences, Beijing 100049, China)
To understand the causal conditions and processes of negative pressure in the throat of Venturi injector, by measuring pressures at the inlet, outlet and throat for Venturi injector respectively, the energy conversion relations of water flow at different feature sections were studied. The results show that the inlet pressure energy is translated into the throat kinetic energy when water flows through the Venturi injector. As the inlet pressure energy and the discharge increase, the kinetic energy in the throat increases, when the kinetic energy in the throat reaches a certain value, the pressure energy at the throat disappears completely and the negative pressure occurs. When the negative pressure reaches the minimum value and remains stable, the flow velocity increases significantly as the inlet pressure increases. The kinetic energy and head loss in the throat also increases very quickly as the flow rate increases. At the same flow rate, the differences between actual and theoretical flow velocity could indicate the size of throat vacuum space. Compared with freeoutflow conditions, under nonfreeoutflow conditions, the starting pressure causing the negative pressure in the throat increases, and the flow volume is relatively great. To obtain the same negative pressure, the inlet pressures and flow rate under nonfreeoutflow conditions are significantly greater than those under freeoutflow conditions.
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