Theory And Design Method On The Non-overload Sewage Pumps

In recent twenty years, the sewage pump is widely applied and the research of it has been developed rapidly. But there is still a difficult problem present in the low specific speed sewage pumps: with changeable operation points, the motor is often destroyed by overload, which restricts the application of the pump in many fields.This paper systematically studies the theory and hydraulic design of the non-overload sewage pump, the research work and its results are mainly following:1. By discussing in detail the shapes and types of pump characteristic curves and the effects of geometrical parameters on them, this paper points out that the main reason of the brake horsepower of the low specific speed sewage pump increasing with capacity rapidly is that we often select larger geometrical parameters such as b2, Ft and so on to enhance the capacity of the sewage pump. Under the premise of no affecting the function, the brake horsepower curves can be flattened by decreasing 62, D2,Z, β2 and F,2. This paper derives the theoretical conditions of producing the saturation brake horsepower of a sewage pump, it also derives the fundamental principles of the non-overload sewage pump design. Under the premise of ensuring the pump's normal performance, and its non-overload characteristics and aimed at lowering the maximum brake horsepower,, the author also analysis the problem resulted from the saturation brake horsepower of the low specific speed sewage pumps and the solution to it.3. After studying the effects of the geometrical parameters on the characteristics of the non-overload sewage pumps by Latin Spare Test thoroughly, the paper arrives at some research results: The higher the Ns, the larger the b2; and the lower the Ns, the smaller the 62.The order of the effects of geometrical parameters on the maximum brake horsepower Pmax is D2, b2, Z, ψ , β2 and Ft .and the order of the effects of geometrical parameters on the Qpmax is 2, b2, D2, Z, ψ and Ft4 .The formula to predict the maximum brake horsepower and its location of a sewage pump are given, the Latin Spare Test shows that the precision of the formula predicting meets to the requirement of engineering.5. The paper also puts forward the design method of the non-overload sewage pump. Certain parameters should be selected to make sure that the maximum brake horsepower occurs near the design point. The experiments show that the design method and procedure are correct, scientific and practicable.6. The research results in the paper shows that the brake horsepower overload resulting from the design of larger capacity of sewage pump can be solved by reasonable design.