多级串联渣浆泵的叶轮平衡怎么

(1)对称布置叶轮。

如图1-69所示,对称布置叶轮适用于级数为偶数,若级数为奇数，则第一级可采用双吸叶轮。由于多级泵各级漏损不同，各级轮毂大小不同，故叶轮对称布置不能完全平衡轴向力，仍有一部分轴向力需由轴承来承受。这种平衡方法的优点是不增大容积损失，缺点是泵体结构较复杂。它多应用于单吸两级悬臂泵和蜗壳式多级泵上。
    (2)采用平衡鼓。图1- 70是平衡鼓的示意图，装在末级叶轮之后。平衡鼓后面为平衡室,通过平衡管与第I级叶轮的吸入室相通。因此,平衡鼓前面的压力接近于末级叶轮的排出压力，而平衡鼓后面的压力等于吸入室中的压力与平衡管中阻力之和。这样就产生了平衡鼓前后的压力差，以平衡泵的轴向力。平衡鼓外缘与泵体上平衡套间的间隙很小，为0.2~

0.3mm。由于泵的工况经常变化，平衡鼓的平衡状态要受到影响，仍需止推轴承承受剩余的轴向力。
    (3)采用自动平衡盘。自动平衡盘在离心泵中习惯简称为平衡盘.其优点是在不同工况下可自动平衡全部轴向力，故广泛用于多级分段式离心泵中，其结构如图1-71所示。它结构上的特点是除了轮毂(或轴套)与泵体之间有一个径向间隙b外，平衡盘端面与泵体间还有一个轴向间隙bo，平衡盘后面是与泵吸入口相通的平衡室。径向间踪b前的液体压力是末级叶轮普面的压力p，液体流过径向间院b后压力降到p,径向间院的压力降为:
                                △p1=p-p
液体流过轴向间家b0后压力再下降到p0，轴向间隙两端的压力降为，
Ap2=p- Pu

这样,在平衡盘上作用一个平衡力，其方向与轴向力相反。

自动平衡低工作原理如下:当轴向为大于平衡力时:转子向左移动、轴向间隙b0减小，流过该间隙的阻力系数增大。当然整个平衡装置的总阻力系数也随之而增大，但△p并不改变，可见泄漏量q减少.结果是△p1，减小而△p2增大,从而增大了平衡力。转子不断向左移动，平衡力不断增加,到某一位置，平衡力和轴向力相等而达到平衡。
    同理，当轴向力小于平衡力时,转子将向右移动,b0增大, △p2减小，平衡力变小。当转子移动到一定位置时，平衡力也减小到与轴向力相等而重新达到平衡。所以装有平衡盘装置的离心泵一般不配止推轴承。
    (4)采用平衡盘与平衡鼓组合的平衡装置。由于平衡鼓可以平衡50% -80%的轴向力，这祥就减轻了渣浆泵平衡盘的负荷，从而可采用较大的轴向间隙，避免因转子审动而引起平衡盘与泵休的摩擦。实践证明，这种平衡装置用于大容量，高参数的分段式多级须中效果良好，

How to balance the impeller of multistage series slurry pump

(1) Arrange impellers symmetrically.

As shown in figure 1-69, impeller with symmetrical arrangement is suitable for even number of stages. If the stage is odd, double suction impeller can be used for the first stage. Due to the different leakage and hub sizes of different stages of multistage pump, the impeller symmetrical arrangement can not completely balance the axial force, there is still a part of the axial force to be borne by the bearing. The advantage of this balance method is not to increase the volume loss, but the disadvantage is that the structure of the pump body is complex. It is mainly used in single suction two-stage Cantilever Pump and volute type multistage pump.

(2) Use balance drum. Figure 1-70 is a schematic diagram of the balancing drum, installed behind the last stage impeller. The balance chamber is behind the balance drum, which is connected with the suction chamber of the stage I impeller through the balance pipe. Therefore, the pressure in front of the balance drum is close to the discharge pressure of the last stage impeller, while the pressure behind the balance drum is equal to the sum of the pressure in the suction chamber and the resistance in the balance pipe. This creates a pressure difference before and after the balance drum to balance the axial force of the pump. The gap between the outer edge of the balance drum and the balance sleeve on the pump body is very small, which is 0.2~

0.3mm. Due to the frequent changes of pump working conditions, the balance state of balance drum will be affected, and the thrust bearing is still required to bear the remaining axial force.

(3) Automatic balancing plate is adopted. In centrifugal pumps, the automatic balancing disk is commonly referred to as the balancing disk. Its advantage is that it can automatically balance all axial forces under different working conditions, so it is widely used in multistage segmented centrifugal pumps. Its structure is shown in Figure 1-71. Its structure is characterized by a radial clearance B between the hub (or shaft sleeve) and the pump body, and an axial clearance Bo between the end face of the balance plate and the pump body. Behind the balance plate is the balance chamber which is connected with the suction port of the pump. The liquid pressure before the radial trace B is the pressure P on the general surface of the last stage impeller. After the liquid flows through the radial chamber B, the pressure drops to P. the pressure drop of the radial chamber is as follows:

Delta p1=p-p

After the liquid flows through the axial gap, the pressure drops to P0, and the pressure at both ends of the axial gap drops to,

Ap2=p- Pu

In this way, a balance force is applied on the balance plate, and its direction is opposite to the axial force.

The principle of auto balance is as follows: when the axial direction is greater than the balance force, the rotor moves to the left, the axial clearance B0 decreases, and the resistance coefficient through the clearance increases. Of course, the total resistance coefficient of the whole balancing device also increases, but △ P does not change, so the leakage Q decreases. As a result, △ P1 decreases, while △ P2 increases, thus increasing the balancing force. The rotor moves to the left continuously, and the balance force increases continuously. When it reaches a certain position, the balance force and the axial force are equal and reach balance.

Similarly, when the axial force is less than the balance force, the rotor will move to the right, B0 increases, △ P2 decreases, and the balance force decreases. When the rotor moves to a certain position, the balance force is reduced to the same as the axial force, and the balance is achieved again. Therefore, the centrifugal pump equipped with balance plate device is generally not equipped with thrust bearing.

(4) The balance device is composed of balance plate and balance drum. Since the balance drum can balance 50% - 80% of the axial force, it can reduce the load of the balance plate, so a large axial clearance can be used to avoid the friction between the balance plate and the pump due to the rotor movement. It has been proved that this kind of balancing device has a good effect in large capacity and high parameter segmented multistage whiskers,