A. Effect of sediment concentration on pump efficiency
Theoretically, due to the existence of sediment solid particles, the density ρs of the solid particles is greater than the density ρf of the water, so the movement speed and movement trajectory of the sediment solid particles are not synchronized with the movement of the water quality point, which increases the internal impeller. The impact loss and the diffusion loss of the impeller outlet reduce the pump efficiency. Figure 4.22 shows that the highest efficiency point of the lOSH-13 double-suction centrifugal pump moves downward with the increase of sediment concentration, which indicates that when the sediment concentration increases, the design flow rate of the pump decreases, and the pump has the highest efficiency. Decrease, if the maximum efficiency of the pump is zero when the sediment concentration is zero, then the correction formula for the efficiency of the water in the drowning should be
?=K? ?0
In the formula, K?, the efficiency correction factor, is found in Figure 4.23.
B. Influence of sediment concentration on pump shaft power
The shaft power of the pump is expressed by:
Where r - the weight (specific gravity) of the transported liquid, kg / m3; Q - the flow through the pump, m3 / s; H - the pump lift, m; ? - pump efficiency, %. From the shaft power formula, the shaft power of the pump is related to the gravity r of the delivered liquid, the pump flow Q, the head H, and the pump efficiency. y, Q, H are related to the sediment concentration of the water. Therefore, the water flow The amount of sediment will inevitably affect the power of the shaft.
It can be seen from the test curve in Figure 4.24 that as the amount of sediment increases, the shaft power also increases. This is consistent with the theoretical analysis. In the case of the same head and flow rate, the shaft power consumed by pumping sandy water is greater than that of fresh water, and should be properly considered in the design configuration. In actual situations, it may be encountered that when the lift is constant, when the liquid concentration of the pumped liquid increases, the flow rate will also decrease accordingly. It is not sensitive to the shaft power response. Some engineering designs often do not consider the sediment concentration. The effect on the shaft power.
