Classification of axial flow pump fan losses

 Fluid flow through the leaf type, leaf type on the surface will produce friction loss, leaf type tail will wake vortex loss. At the same time, the impeller of axial flow pump and fan is subjected to axial force, the axial force direction points to the inlet of the pump and the blower. 

 The loss of resistance is related to the relative thickness of the leaf blade, and the relative increase of the relative thickness of the leaf blade. In a certain range near the impact angle, the leaf type loss is small. When the impact angle increases, the thickness of the upper boundary layer increases sharply, which causes the separation of boundary layer and the loss of the boundary layer. 

 In a word, the size of the leaf type loss is related to the shape of the airfoil, the roughness of the airfoil surface, the angle of installation, the consistency of the blade and the impact angle. 

 At both ends of the blade on the surface of the annular channel, the fluid friction and eddy current induced losses are called toroidal losses. The size of the torus loss is related to the height of the blade and the pitch of the blade. 

 The fluid flow through the cascade passage, in the leaves of the concave (working face) and convex (non working surface) on the pressure difference exists, and the pressure is greater than the leaf blade concave convex pressure. The pressure difference between the concave and convex blades and blade load (lift coefficient) is related to the size of the. In the middle part of the channel (along the high direction), the pressure difference is balanced by the inertia force generated by the refraction of the fluid. But at the root of the blade and the end face of the top, because there is a boundary layer, near the wall of the fluid pressure and the mainstream of the same pressure, and the speed tends to zero. The inertial force generated by the fluid and turn almost disappeared. At this time, in the transverse pressure gradient exists in the end regions of the fluid flow from the concave convex form, two flow. The formation of the two flow is taken away by the mainstream, in the back of the blade gradually become heat loss. 

 There is a certain radial clearance between the rotating impeller and the impeller casing. The value of radial clearance affects the performance of axial flow pump and fan. 

 When the impeller rotates, the fluid pressure because the blade working surface is larger than that on the non working surface of the pressure, so the area of low pressure portion of the fluid flow back to the blade through the radial clearance (non working surface), and the resulting vortex induced losses, this is similar to the finite length of isolated airfoils. Induced loss of the vortex will flow along with the main flow cascade, the formation of a complex three yuan flow. 

 At the same time, the cascade exit fluid pressure above the cascade inlet pressure and outlet pressure fluid through the inlet flow, the radial clearance of cascade, against the flow direction, the impact of the mainstream, increase flow resistance. 

 The loss caused by the radial clearance reduces the head and the total pressure of the pump and the blower, and reduces the efficiency of the pump and the fan.