Low specific speed pump design principles

Low specific speed pump refers to the speed of the ns = 30 ~ 80 centrifugal pump, which has a small flow, high lift characteristics. Low specific speed pump is widely used in agricultural irrigation and drainage, urban water supply, boiler feed water, mining, petroleum and chemical and other fields.
Pump performance parameters of this type are characterized by: lower than the speed, small flow, high head.
Geometric features are: the blade outlet width b2 smaller, larger impeller diameter D2, axial flow narrow and long.
Performance characteristics of the features: the pump shut-off head is about 1.1 to 1.3 times the design conditions, the head increases with the flow rate decreases, the change is relatively slow, and sometimes hump; pump power is small, the shaft power increases with the flow While increasing; the efficiency curve is relatively flat and the range of high efficiency is wider.
For a long time, due to the lack of special theory and design method, people can only design low specific speed pump according to the theory of ordinary centrifugal pump, so the efficiency of the pump is low. Nearly 20 years, the research on low specific speed pump has been one of the key issues of the pump industry, many experts and engineers have done a lot of theoretical analysis and experimental research, developed a number of excellent hydraulic model, And gradually formed on the basis of practice and developed into a design method to improve its hydraulic efficiency, that is, to increase traffic design law. However, with the increase of efficiency, the lift curve is more prone to hump, and the running stability of the pump is worsened in the system. At the same time, due to the steeper shaft power curve, the pump is prone to overloading when operating in a large flow area.
Compared with other countries, the hydraulic efficiency of low specific speed centrifugal pumps in our country has basically reached the level of similar foreign products, and its testing techniques and methods are closely following the pace of foreign countries. However, there is still a big gap between the accuracy of ternary performance prediction, the practicability of CAD, the depth and breadth of in-flow field test, the manufacturing technology of impeller, the reliability of products and the research of material and structure. In some special applications Areas can not meet the needs of economic construction.

Features: