The performance parameters (H, Η, p and Q) of the centrifugal pump only show the influence of the viscosity of the liquid on the pump when the kinematic viscosity ν>20×10-6m2/s, and only from this value can be obtained according to the experiment. The conversion factor is converted. The most popular conversion method is based on the standard method of the Hydraulic Society. Although the two methods use a similar chart when expressing the conversion factor, there is still a difference. That is, in the method of the Chinese Union, the influence includes the Q, H and u, and the ratio is obviously affected. Speed ns. The hydraulics method can only measure and measure various results in this limited application range at a specific speed of ns=15-20r/min. The neutral method can be tested in the range of specific speed ns = 6.5-45r/min and viscosity up to νz=4000x10-6m2/s. The use of two icons can be illustrated by an example.
When a single-stage centrifugal pump delivers water (subscript w), when the flow rate Q. head H and efficiency η of the known water are calculated to calculate the highly viscous liquid (subscript z), the following method is used to convert Qz=?Q Qw Hz=?HHw Ηz=?ηηw In HI therapy, the coefficient ? is called. Both of them are illustrated in Figure 3 and Figure 4; the pump speed is additionally explained. The specific speed of ns. Through these coefficients, the known transport data when transporting water from a centrifugal pump can be converted into data when transporting highly viscous liquids: in the normal working load area. The conversion method is as follows: 0.8Qopt There are three types of flow exceptions: flow rate is 0.8 or When 1.0 or 1.2Qopt, the above method is simplified as when Q=0. 8Qopt, Hz=1.03?HHw When the flow rate Q=0, it is simple to use: Hz-Hw and ηz=ηw=0 can be easily converted by calculating the chart Many of the above three flows can be calculated according to the following formula: Pz = ρzgHzQz / 1000ηz where ρz-density, unit: kg / m3 Qz - flow, unit: m3 / s g - gravity acceleration = 9.81m / s2 Hz - head , unit: m Ηz-0 and 1 efficiency Pz-power. Unit: kW Then, each characteristic curve can be drawn each time according to 4 or 3 flow Qz design points. If the task is reversed, given the amount of water, but the delivery parameters of the highly viscous liquid (for example, when looking for a pump that fits the desired operating point), then one needs to predict a quantity of water first. Then in the second In the step (or even the third part), the calculation is repeated according to the conversion factors ?Q, ?H and ?? to approach the solution. If the specific speed is ns. More than 20 r/min. is more suitable to use the Zhonglian calculation method, which calculates a lower operating power; below this threshold, the operating power calculated according to the HI method is too small! The effect of all fluid mechanics laws is not limited in Newtonian fluids. Therefore, the calculation method and chart of the valve tube friction coefficient and drag coefficient continue to be effective. It is only necessary to replace the water uw with the corresponding highly viscous liquid uz when calculating the Reynolds number Re=ud/ν. This gives a smaller Reynolds number and a correspondingly larger tube friction coefficient λz.
