Flow of foam pump in impeller

The flow of liquid in the impeller passage is complex. In order to facilitate the theoretical analysis, there are usually three assumptions as follows:

(1) The flow of liquid in impeller is stable, that is, the flow field does not change with time.

(2) The liquid passing through the impeller is an ideal liquid, that is, there is no energy loss when the liquid flows in the impeller.

(3) The impeller is composed of infinite and infinite sea blades. When the liquid moves in the impeller channel, its trajectory is exactly the same as the shape of the blade curve, and the speed of the liquid particles on the same radius circle of the impeller is equal.

When the impeller rotates, on the one hand, the wave body moves relative to the blade outwards along the blade inside the impeller, and its moving speed is called relative speed, which is represented by vector W. under the assumption of infinite number of blades, its direction is tangent to the blade as shown in Figure 1-6 (a). Meanwhile, the liquid rotates with the impeller to make circular motion (implicated motion), and its moving speed is circular speed (implicated speed) Represented by vector u, its size and direction are the same as the peripheral speed of impeller, as shown in Fig. 1-6 (b).

Therefore, the motion of the liquid in the impeller is a kind of motion composed of circular motion and relative motion. Its motion speed is called absolute velocity, which is represented by vector C, as shown in Figure 1-6 (c). Then C is equal to the vector sum of relative velocity W and circular velocity u, that is

C=u+w

The vector diagram composed of these three velocity vectors is called velocity triangle, as shown in Figure 1-7.

Absolute velocity C can be divided into two components: one is the component perpendicular to the circumferential velocity, expressed in C, which is called radial velocity of absolute velocity of liquid, or axial velocity; the other is the component parallel to the circumferential velocity, expressed in Cu, which is called absolute velocity of liquid

The circumferential velocity of degrees.

The angle between the liquid velocity and the geometric parameters of the impeller can be expressed by the following symbols:

A -- absolute flow angle, which is the angle between the absolute velocity direction of liquid and the circumferential velocity direction;

β - relative flow angle, that is, the angle between the relative velocity direction of the liquid and the reverse direction of the circular velocity;

β a -- blade angle, that is, the angle between the tangent line of the blade at this point and the reverse direction of the peripheral speed.

Under the assumption of infinite number of blades, the relative flow angle is the same as the blade angle, that is, β = β a. Foam pump

The lower angle scale 1.2 is used to represent the parameters of blade inlet and blade outlet respectively, and the lower angle scale ∞ is used to represent the parameters of liquid flowing in the impeller with infinite number of blades.