The Application Of Boundary Layer Theory In The Low Specific Speed Centrifugal Pump Blade Design

Low specific speed centrifugal pump is used in agriculture and industry in large range . In long time, as the efficiency of low specific speed centrifugal pump is low and Q-H characteristic curve is unstable, the research of the fluid flow law in the pump is an important project of fluid machinery researchers in order to improve the efficiency and the stabilization of Q-H characteristic curve.A method is given that the theory of turbulent boundary layer is used to design cylindrical vane in order to gain the equations of vane' s modular curve that can not cause boundary layer separateness in the papero Reyonds equations is given on the basis of N-S equation, the relevant quantities are analyzed and momentum integral equation is given. By transitional momentum integral equation the approximate expression of momentum thickness is presented, velocity distributing in turbulent boundary layer is analysed. Wake laws are applied to deduce corressioning expressions of turbulent boundary layer thickness, the expressions are regarded as the auxiliary relational expressions to solve momentum thickness. Amethod is applied that by boundary layer thickness coefficient ks and momentumthickness d2 the fluid calculation without centrifugal force approaches the fluidcalculation with centrifugal force in order to solve momentum thickness . these will be the basis of further analyzing boundary layer separateness. according to the analysis velocity field of main fluid zone, the parameter equations of vane' s modular curve of low specific speed centrifugal pump are given. The relation of velocity coefficient and boundary layer separateness and theory head is analysed. Finally, the calculation process is given in vane design as the applications on boundary layer theory. Through above study, the following conclusions can be made: In designing process of cylindrical vane' s modular curve , not only the parameter but also flow properties on vane surface should be considered. Total consideration is very important to design cylindrical vane' s modular curve, especially the method to study the output and input parameter according to flow properties on vane surface is very valuable.