The measurement of viscosity is divided into absolute viscosity and relative viscosity. The absolute viscosity is divided into dynamic viscosity and kinematic viscosity. Relative viscosity (conditional viscosity), viscosity, saybolt viscosity and redwood viscosity, etc. The above three conditions of viscosity measurement are commonly used in Europe and the United States. In addition to the determination of dark lubricants and residual oil, the other two viscometers are rarely used. The three conditions of viscosity represent different methods and units, but the relation between them can be converted by the chart. At the same time, the viscosity and kinematic viscosity can also be converted, so that it is more convenient and flexible.
Effect of medium viscosity on pump performance.
For vane pump, with the increase of liquid viscosity, its flow rate and head loss increase. For the volumetric pump, with the increase of medium viscosity, the general leakage volume decreases, the volume efficiency increases, the pump flow increases, but the total efficiency of the pump decreases, and the power consumption of the pump increases. For liquids, the greater the pressure, the lower the temperature, the greater the viscosity; The smaller the pressure, the higher the temperature, the smaller the viscosity. For gas, pressure doesn't matter; The higher the temperature, the greater the viscosity, the lower the temperature, the smaller the viscosity.
The viscosity of the medium has great influence on the pump performance curve. When the viscosity increases, the lift characteristic curve of the pump decreases, and the lift and flow rate of the optimal working condition decreases with the increase of viscosity, while the power increases with the increase of viscosity, thus reducing the efficiency. The wine pump
For a liquid that is mainly a viscous force, its motion state can be judged by Re number Re. When Re < 2000, it belongs to laminar movement; When Re > 1200, it belongs to turbulent motion; When Re is between 2000 and 12000, it is the transition zone. When the pump is used to transport different media, if the viscosity of the medium is very different, such as normal temperature water, ν =0.01St, crude oil ν =1.024St, the Reynolds number varies greatly, the flow state of different liquids in the pump changes, so the performance of the pump can have a great impact. However, the effect of viscosity on performance is difficult to be calculated by exact formula, and can only be converted by the curve obtained through experiments.
The calculation of influence of medium viscosity on pump performance curve.
When pumping the viscous medium, it is necessary to convert the characteristic curve of the pump pumping water to make the characteristic curve when pumping the viscous medium. In addition, if the pump needs to design the viscous medium, the design parameters of the viscous medium should also be designed.
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