How to design and practice the hydraulic model of submersible axial flow pump

1. Determination and calculation of blade geometrical parameters
(1) the determination of the hub than dh In the diving axial flow pump structure design, because the motor and the axial flow pump impeller and guide vane close combination, in order to make the flow channel smooth, the outer diameter of the motor and guide leaf body diameter the same. Then the impeller export of the fluid is bound to directly hit the inner wall of the guide vane. Therefore, for the submersible axial flow pump, in order to improve the hydraulic efficiency, the hub than dh need to get bigger. This is the first condition that determines dh.
(2) Determination of impeller outer diameter D Axial flow pump impeller diameter D is an important design parameter, the current widely used empirical formula.
(3) Determination of speed n In determining the speed of the submersible axial flow pump, by calculating the cavitation than the speed C and the speed ns, to determine n, so choose n there are two principles:
1) makes the cavitation ratio C not exceed the predetermined value, usually C <1 100.
2) the ratio of speed ns, as far as possible within the efficient range, that is, ns = 850 ~ 1 250. But also in a larger range, that is, ns = 500 ~ 2000.
2. Design guidelines for hydraulic models
(1) variable ring volume, variable axis surface lift lift method design based on the lifting method from the cascade theory, for axial flow pump blade design, made the following assumptions:
1) When the fluid medium passes through the blade, the cylindrical flow layers do not interfere with each other.
2) In calculating the lift, assume that the blade is infinite wingspan, you can use the binary airfoil test or theoretical calculation, plus the inline wing grid revision.
3) The hydraulic efficiency or hydraulic loss of the axial flow pump can be estimated by the existing hydraulic model efficiency.
(2) The radial distribution of the annular flow of the diving axial flow The main focus of the design of the variable ring is the change of the distribution of the ring along the radial direction of the blade, that is, the root and the shoot Margin) is small and the middle load is large. Therefore, the use of variable ring design, it is to adapt to the actual flow of submersible axial flow of an effective means. And this means to use good or bad, the key lies in the specific design requirements, a reasonable choice of the distribution of the law of the ring.
In the design practice, combined with theoretical analysis and model test situation, it is recommended to use the author to calculate the regression formula:
Γ (r) = ΚrΓ0
Γr (r) - cyclic distribution function, r is the impeller radius; Γ0 - the average distribution of the loop; Κr - radial ring distribution coefficient, Κr = -2.83r2i + 4.64ri-0.8, ri for each The radius of the cylinder.
(3) Distribution law of axial velocity of submersible axial flow pump In the design practice, combined with theoretical analysis and model test, the axial cyclic distribution coefficient Κm is recommended by the formula:
Κm = -1.807r2i + 3.037ri-0.215 (2)