drawing of impeller shaft surface

When the values of B, D2 and D. are known, draw the impeller shaft surface section. Because the coefficient K of the impeller of the pump is very large (1.6-2.5) (for the pump of homogeneous liquid, when n, = 80-120, KUs = 0.6-0.8), the impeller structure can not be made to shrink to the outlet (for example, this can be generally done on the impeller of homogeneous liquid), and it is usually made into parallel wall form.

It has been pointed out that the shape of the shaft and section at the inlet of the impeller has an important influence on the forming of the convective flow, because it has an important influence on the wear characteristics and strength of the blade inlet section and the rear cover plate (see Chapter 7 of this chapter). Therefore, the section radius of the axial surface at the inlet of the impeller is described and selected according to the condition of the minimum wear of the rear cover plate and the inlet edge of the impeller. According to the existing data, it is determined that the radius of the front cover plate wheel seat is Ru = KXD.. where KX is the axial section coefficient, KX = 0.46 ~ 0.55. When the coefficient kn is increased, the wear amount decreases little, but the size of the impeller in the direction of pump oil increases sharply.

The radius of the shape of the rear cover plate is determined by considering the smooth change of the required channel size and area. Generally, Ru. S < Ru + B (where, R-1 is the radius of the rear cover plate wheel seat; B, is the channel width of the impeller inlet section).

The correctness criterion for drawing the axial section is that the flow passage area between the cover plates varies smoothly from the inlet to the outlet, which can be determined by the method described in reference [179, 202].