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渣漿泵泵中的徑向力、軸向力及其平衡
一、徑向力的產(chǎn)生及其平衡
在設計流量時，蝸室內(nèi)液體流動速度和液體流出葉輪的速度(大小和方向)基本上是一致的，因此從葉輪流出的液體能平順地流入蝸室，在葉輪周圍液體的流動速度和壓力分布是均勻的，此時無徑向力。但在小于設計流量時，蝸室內(nèi)液體流動速度將減慢。從圖2-49葉輪出口速度三角形中可以看出，此時液體流出葉輪的絕對速度2并不是減小了反而是增加了，吃>，并且方向也發(fā)生了改變。一方 面蝸室里的流動速度減慢，而另一方面葉 輪出口的流動速度增加，就發(fā)生了撞擊，結(jié)果使流出葉輪液體的速度下降到蝸室里的流動速度，同時，把一部分動能通過撞擊傳給了蝸室內(nèi)液體，使蝸室里的波體壓力升高。液體從蝸室前端(隔舌)流到蝸室后端過程中，不斷受到推擊，不斷增加壓力，使蝸室里壓力分布成逐漸上升分布。同樣在大于設計流量時，蝸室里液體壓力從隔舌開始是不斷下降的分布。
由于蝸室各斷面中的壓力不相等，液體作用于葉輪出口處的圓周面上的壓力不相等，于是在葉輪上就產(chǎn)生了一個徑向力。又因為蝸室里液休的壓力對流出葉輪的液體起著阻礙作用，由于壓力不均勻，液體流出葉輪的速度也是不一致。因此，葉輪周圍上受液體流出時的反沖力也是不均勻的。這又形成了徑向力產(chǎn)生的另一個原因。 總之徑向力是因為在非設計工況時由于蝸室壓力分布不均勻而產(chǎn)生的。
徑向力會使軸產(chǎn)生較大的撓度，致使葉輪密封環(huán)、軸套等處卡死或磨損。同時會使軸因疲勞而破壞，在泵的運轉(zhuǎn)中產(chǎn)生振動噪聲。因此，消除徑向力是十分必要的，特別是口徑較大、揚程較高的泵。
徑向力平衡方法是將蝸室分成兩個對稱的部分，即雙層蝸室或雙蝸室，如圖2-50所示。在雙層蝸室里，雖然每個蝸室里壓力分布仍是不均勻的，但由于兩個蝸室相互對稱，所以作用在葉輪上的徑向力相互抵消。
在蝸殼式多級泵里，采用相鄰兩個蝸室旋轉(zhuǎn)180°布置的辦法， 也可減弱徑向力對軸的作用。
采用導葉式泵，由于導葉葉片沿圓周均勻分布，各個導葉所產(chǎn)生的徑向力相互平衡了.渣漿泵廠家
Radial force, axial force and balance in slurry pump
I. generation and balance of radial force
In the design flow, the liquid flow velocity in the volute chamber is basically the same as that of the liquid flowing out of the impeller (size and direction). Therefore, the liquid flowing out of the impeller can flow smoothly into the volute chamber. The distribution of the liquid flow velocity and pressure around the impeller is uniform, and there is no radial force at this time. However, when the flow rate is less than the design flow rate, the liquid flow rate in the cochlear chamber will slow down. As can be seen from the triangle of impeller outlet speed in Figure 2-49, the absolute speed 2 of liquid flowing out of impeller at this time is not reduced but increased, and the direction is also changed. On the one hand, the flow speed in the cochlear chamber slows down, and on the other hand, the flow speed at the outlet of the impeller increases, resulting in an impact. As a result, the flow speed of the liquid flowing out of the impeller decreases to the flow speed in the cochlear chamber. At the same time, a part of the kinetic energy is transmitted to the liquid in the cochlear chamber through the impact, which increases the pressure of the wave body in the cochlear chamber. In the process of fluid flowing from the anterior end of the cochlear chamber (septum tongue) to the posterior end of the cochlear chamber, the pressure is constantly pushed and increased, which makes the pressure distribution in the cochlear chamber gradually increase. Similarly, when the flow rate is larger than the design flow rate, the liquid pressure in the cochlear chamber begins to decrease from the septum tongue.
Because the pressure in each section of the volute chamber is not equal, and the pressure of the liquid acting on the circular surface at the outlet of the impeller is not equal, a radial force is generated on the impeller. And because the pressure of the liquid rest in the volute chamber hinders the liquid flowing out of the impeller, the speed of the liquid flowing out of the impeller is also inconsistent due to the uneven pressure. Therefore, the reaction force around the impeller when the liquid flows out is also uneven. This is another reason for the radial force In a word, the radial force is caused by the uneven pressure distribution in the cochlear chamber.
Radial force will make the shaft produce larger deflection, resulting in the impeller seal ring, shaft sleeve and other places stuck or worn. At the same time, the shaft will be damaged due to fatigue, resulting in vibration and noise during the operation of the pump. Therefore, it is necessary to eliminate the radial force, especially for the pump with large diameter and high head.
The radial force balance method is to divide the cochlear chamber into two symmetrical parts, i.e. double or double cochlear chambers, as shown in Figure 2-50. In the double-layer volute chamber, although the pressure distribution in each volute chamber is still uneven, the radial forces acting on the impeller cancel each other because the two volutes are symmetrical to each other.
In the volute type multistage pump, the radial force on the shaft can also be weakened by adopting the method of 180 ° rotation of two adjacent volute chambers.
With guide vane pump, the radial force produced by each guide vane is balanced due to the uniform distribution of the guide vane along the circumference. Slurry pump manufacturer
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