如图1-43所示,设两泵自同一吸液罐吸入液体,由液面到汇合点0的两端管路阻力很小可以忽略不计。这样,两台泵并联后的总流量等于两泵在同一扬程下的流量相加，即Hl=Hll时,Qr+1 =Qi+Qu。两泵并联后总性能曲线等于两泵性能曲线在同一扬程下的各对应点叠加起来，如图1-43中(H-Q)1+日 曲线。
以上分析说明，两台不同性能的泵并联后的总流量Q1+1等于并联后各泵流量之和，即Q1←n=Q1 +Qu,但总流量又小于两泵单独工作的流量Qm,、Qm 之和，即Q:+n<Qm +Qs，其减少的量随管路特性的陡峭程度、并联泵台数的增多而增大。渣浆泵厂家
Device characteristics of slurry pump in parallel and series operation
In production practice, when a centrifugal pump can not meet the flow or head requirements, two or more pumps are often used to work together.
1. Parallel operation of centrifugal pump
When a pump is used to deliver liquid to a certain pressure pipeline and the flow cannot meet the requirements, or the delivery flow changes greatly. In order to improve the economy of the pump and make the pump work in an efficient range, two or more pumps are often used in parallel to meet the flow change requirements.
Parallel operation can be discussed in two cases, i.e. parallel operation of pumps with the same performance and parallel operation of pumps with different performance.
1) Parallel connection of pumps with the same performance
As shown in Figure 1-43, two pumps are set to suction liquid from the same suction tank, and the pipeline resistance from the liquid level to the two ends of the junction point 0 is negligible. In this way, the total flow of two pumps in parallel is equal to the sum of the flow of two pumps under the same head, that is, when HL = HLL, QR + 1 = Qi + Qu. After parallel connection of two pumps, the total performance curve is equal to the superposition of corresponding points of the performance curve of two pumps under the same head, as shown in Figure 1-43 (H-Q) 1 + daily curve.
When the pipeline characteristic H-Q is drawn, and the total performance curve (H-Q) I + I after parallel connection is intersected with point m, the flow Q11 corresponding to point m is the flow in the pipeline after parallel connection. In order to determine the working condition of each pump in parallel, make a horizontal line through point m, and submit the performance curve of single pump to point A., that is, the working point of each pump in parallel, which determines the working parameters of each pump in parallel. The working head of pump L and pump Li is equal to the working head after parallel connection; the flow after parallel connection is the sum of the flow of pump I and pump Li, which makes Q τ + n increase.
If each pump works separately in the pipeline, the working point of the pump is M1. From Fig. 1-43, it can be seen that the lift of parallel connection is higher than that of single pump, and the flow is less than 2 times of that of single pump. This is because the pipeline resistance increases with the increase of flow after parallel connection, which requires each pump to increase its head to overcome the increased resistance loss, and the corresponding flow is reduced.
It can be seen that when two pumps work in parallel, the flatter the pipeline characteristics are, the closer the flow Qi + is to each pump after parallel operation
When the pump is running alone, the flow rate is twice, so as to increase the flow rate. The steeper the performance curve of the pump is, the smaller the flow rate Q1 + π after parallel connection is, the smaller the flow rate QMI when the pump is running alone. Therefore, the performance curve of the pump should be smooth. From the perspective of the number of pumps in parallel operation, the more the number, the less the flow that can be increased after parallel operation, the less the flow delivered by each pump, so it is not economical to have too many pumps in parallel.
2) Parallel connection of pumps with different performance
Figure 1-44 shows the parallel operation of two pumps with different performance, and the curves (H-Q) 1 and (H-Q) in the figure are the performance curves of two pumps with different performance, using
The above drawing method can obtain the total performance curve after parallel connection. This curve intersects with the pipeline characteristic H-Q at point m, that is, the working point in parallel operation, and the flow rate is. 91. + e head is.
In order to determine the working point of each pump after well coupling, parallel lines can be made through point M. The performance curve of pump 1 is at point a. the performance curve of pump l l is at points A1 and A2 of point A2, which are the working points of pump L and pump LL. The head of two pumps is equal: equal to the working head after parallel connection, and the flow after parallel connection is the sum of the flow of pump I and pump IL.
If each pump works separately in the pipeline, the working point of pump I is M1, and the working point of pump IL is m2. From figure 1-44, it can be seen that the lift after parallel connection is higher than when the pump works alone, and the flow is less than the sum of the flow when the two pumps work alone on the pipeline.
The above analysis shows that the total flow Q1 + 1 of two pumps with different performance after parallel connection is equal to the sum of the flow of each pump after parallel connection, i.e. Q1 ← n = Q1 + Qu, but the total flow is smaller than the sum of the flow QM and QM of two pumps working separately, i.e. Q: + n < QM + QS, and the amount of reduction increases with the steepness of pipeline characteristics and the number of parallel pumps. Slurry pump manufacturer
It can also be seen from the figure that when two centrifugal pumps with different performance work in parallel, if the flow is less than QC, only the large pump is actually working, because the lift of the small pump is not enough, the small pump should be stopped. In the actual pump device, check valve is often installed at the outlet of two pumps to avoid the backflow phenomenon from working pump to non working pump when starting or stopping.