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渣漿泵并聯(lián)和串聯(lián)工作時的裝置特性
生產(chǎn)實際中，當采用一臺離心泵不能滿足流量或能頭要求時，往往用兩臺或兩臺以上的泵聯(lián)合工作。
1. 離心泵并聯(lián)工作
當使用一臺泵向某一壓力管路輸送液體而流量不能滿足要求時，或輸送流量變化很大，為提高泵的經(jīng)濟性,使得泵處在高效范圍內(nèi)工作等，常采取兩臺或數(shù)臺泵并聯(lián)工作，以滿足流量變化要求。
并聯(lián)工作可分兩種情況來討論，即相同性能的泵并聯(lián)和不同性能的泵并聯(lián)。
1) 相同性能的泵并聯(lián)
如圖1-43所示，設兩泵自同一吸液罐吸入液體，由液面到匯合點0的兩端管路阻力很小可以忽略不計。這樣,兩臺泵并聯(lián)后的總流量等于兩泵在同一揚程下的流量相加，即Hl=Hll時,Qr+1 =Qi+Qu。兩泵并聯(lián)后總性能曲線等于兩泵性能曲線在同一揚程下的各對應點疊加起來，如圖1-43中(H-Q)1+日 曲線。
當畫出管路特性h-Q后,與并聯(lián)后總性能曲線(H-Q)I+I交于M點,M點對應的流量Q11即為并聯(lián)后管路中的流量。為了確定并聯(lián)時每臺泵的工況，過M點作水平線,交單泵性能曲線于A.點，即每臺泵并聯(lián)工作時的工作點，該點決定了并聯(lián)時每臺泵的工作參數(shù)。泵l、泵lI工作揚程相等,等于并聯(lián)后工作揚程;并聯(lián)后流量為泵I與泵lI流量之和，使Qτ+n提高了。
若每臺泵單獨在管路中工作，則泵的工作點為M1。從圖1-43可以看出并聯(lián)后揚程比單泵工作時高，而流量小于一臺泵單獨工作時流量的2倍。這是因為并聯(lián)后管路阻力由于流量的增加而有所增大，這就要求每臺泵都提高它的揚程來克服增加的阻力損失，相應的流量就減少了。
由此可知，兩臺泵并聯(lián)工作時，管路特性越平坦，則并聯(lián)后的流量QI+就越接近每臺泵
單獨運行時流量的2倍，達到增加流量的目的;泵的性能曲線越陡峭，并聯(lián)后的流量Q1+π就越小于單獨工作時流量QMI的2倍。為此，泵的性能曲線應平緩一些為好。從并聯(lián)工作的泵臺數(shù)來看，數(shù)量越多,并聯(lián)后所能增加的流量越少，則每臺泵輸送的流量越少,故并聯(lián)臺數(shù)過多并不經(jīng)濟。
2)不同性能的泵并聯(lián)
圖1-44為兩臺不同性能泵并聯(lián)工作時的情況，圖中曲線(H-Q)1和(H-Q)為兩臺不同性能泵的性能曲線，利用
前述畫法，可以得到并聯(lián)后的總性能曲線。此曲線與管路特性h-Q相交于M點，即并聯(lián)工作時的工作點，此時流量為.91.+e 揚程為。
為確定井聯(lián)后每臺泵的工作點，可過M點作平行線。交泵1性能曲線于A點.交泵ll性能曲線于A2點A1和A2點即為泵l和泵ll的工作點。兩泵的揚程相等:等于并聯(lián)后的工作揚程，并聯(lián)后的流量為泵I和泵Il流量之和。
若每臺泵單獨在管路中工作則泵I的工作點為M1，泵Il的工作點為M2。從圖1-44可以看出，并聯(lián)后揚程比泵單獨工作時高，而流量小于兩泵單獨在管路上工作時的流量之和。
以上分析說明，兩臺不同性能的泵并聯(lián)后的總流量Q1+1等于并聯(lián)后各泵流量之和，即Q1←n=Q1 +Qu，但總流量又小于兩泵單獨工作的流量Qm,、Qm 之和，即Q:+n<Qm +Qs，其減少的量隨管路特性的陡峭程度、并聯(lián)泵臺數(shù)的增多而增大。渣漿泵廠家
由圖還可看出，當兩臺性能不同的離心泵并聯(lián)工作時，若流量小于Qc，則實際上僅大泵在工作，因為小泵的揚程不夠，應停止小泵運轉(zhuǎn)。在實際泵裝置上，往往在兩泵出口安裝止回閥，以免在啟動或停車時，造成從工作泵到非工作泵的倒灌現(xiàn)象。
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.
