Axial flow calculation of 2QV-AF foam pump

1. Determine the initial axial surface flow channel contour

The design of centrifugal pump is a medium specific speed centrifugal pump. Its impeller axial surface flow channel is narrow and long, and most of the axial plane section lines of the front and rear cover plates are non parallel straight lines. The free-form curve is used to generate the initial axial surface profile, as shown in Fig. 1-100.

2. Calculation of axial flow

Based on the method of the axial velocity gradient equation along any quasi orthogonal line and the continuity equation of fluid motion, the quasi orthogonal method is used to iteratively calculate the axial streamline. The axial velocity of each particle is obtained by solving the gradient equation of the axial velocity along the quasi orthogonal line [equation (1-108), in which the symbols are shown in Fig. 1-101]. Finally, the intersection of the flow line and the flow line can be determined by iteration. The initially determined axial flow network does not necessarily meet the required axial velocity distribution law. Therefore, iterative calculation is needed to constantly modify the shape of the axial streamline position until the requirements are met, and the final axial flow network is obtained, as shown in Fig. 1-102.

Bony line drawing

Based on the assumption that there are infinite blades in the impeller, the blade profile line on the calculated flow surface should coincide with the calculated streamline. In order to determine the blade skeleton line, it is necessary to determine the relationship between blade contour and axial streamline. The relationship between blade wrap angle and axial streamline length is established by point by point integration method, and the differential equation of blade contour is obtained. The blade contour is finally determined by integrating along the axial streamline to calculate the corresponding wrap angle of each calculation point on the flow line. The motion of the particle in the axial plane is shown in Fig. 1-103. The equation of blade bone line is as follows:

4. Blade bone line thickening and head and tail rounding

In order to meet the needs of energy transfer, the blade must meet certain strength requirements, so it is necessary to thicken the blade. There are three main methods of blade thickening: the thickening on conformal transformation plane, the axial surface thickening and the rotary flow surface thickening. In order to reduce the impact loss of blade head, it is necessary to round the blade head. The traditional rounding method is to round on the conformal transformation plane or on the flow surface. Here, the four point "Bessel" curve is used to round the design blade head, as shown in Fig. 1-104. Compared with the traditional design method, this method is more flexible. Finally, the blade model is shown in Fig. 1-105, and the impeller with the front cover removed is shown in Fig. 1-106.

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With the development of theoretical and experimental hydrodynamics, the continuous expansion of computer capacity and the rapid improvement of running speed, the two kinds of relative flow surface methods are mainly used in the study of inverse problems of fluid machinery, and rarely used for forward problems. Computational fluid dynamics (CFD) is one of the most important methods in fluid mechanics. CFD is one of the main research directions of fluid mechanics. Through computer numerical calculation and image display, CFD is the analysis of the system including fluid flow and heat conduction. Compared with the computational fluid mechanics, the computational fluid mechanics model is the most suitable method for the study of fluid mechanics