Adjustment methods of centrifugal pump and the energy consumption analysis

Through the analysis of the characteristic curves of centrifugal pump and pipeline system of centrifugal pump flow control main ways: export valve adjustment, pump variable speed adjustment and pump series, in parallel to adjust. Export was analyzed by using the characteristic curves of regulating valve and pump speed regulating energy loss in two ways, and has carried on the contrast, points out that the centrifugal pump with variable speed regulating flow than with export flow adjusting valve can better save energy consumption, and energy saving efficiency and the size of the flow changes. In practical application, you should pay attention to the range of speed regulation, can better use centrifugal pump variable speed control.

Centrifugal pump is widely used in chemical industry system of a kind of fluid machinery. It has to adapt to the wide scope of performance (including flow, pressure head and adapted to the nature of the medium), small volume, simple structure, easy operation, low operation cost, a lot of advantage. Usually, the selected centrifugal pump flow rate and pressure head may and asked for in line, or change due to the production task, technological requirements, at this time are required to adjust the discharge pump, essence is to change the working point of centrifugal pump. Centrifugal pump working point is by the characteristic curve of pump and piping system joint decision characteristic curve, therefore, any change of characteristic curve can achieve the purpose of flow control. At present, the centrifugal pump flow control ways are regulating valve, variable speed control and pump control and, series adjustment, etc. Due to all sorts of the principle of adjustment for different, in addition to have their own advantages and disadvantages, the energy loss is different also, in order to seek the best, the minimum energy consumption, the most energy-efficient way of flow control, must fully understand the flow of a centrifugal pump adjustment methods and the relationship between the energy consumption.

1 the main pump flow control

1.1 change the pipeline characteristic curve

Change the simplest method is to use centrifugal pump pump discharge valve to control the opening, the essence of which is the location of the change of pipeline characteristic curve to change the working point of the pump.

1.2 change the centrifugal pump characteristic curve

According to the proportion law and the law of cutting, change the pump rotation speed, the pump structure (such as the method of cutting impeller diameter, etc.) both methods could change characteristic curve of centrifugal pump, so as to achieve the purpose of flow adjustment, change the pressure head at the same time). But for the pump work, has changed the pump structure method is not very convenient, and because change the structure of the pump, reduces the versatility of the pump, even though it at some point adjustment convenient traffic economy [1], and rarely used in production. Just how changes in centrifugal pump flow of speed adjusting method. From figure 1, when change the pump speed adjusting flow rate decreased from Q1 to Q2, the pump speed (or motor speed) decreased from n1 to n2, speed under n2 pump characteristic curve of Q - H and the pipeline characteristic curve He = H0 + G1Qe2 (line curve does not change) to point A3 (Q2, H3), point A3 for the new speed adjusting flow after working point. The adjustment method of adjustment effect, quick, safe and reliable, can prolong the service life of the pump, save electricity, reduce speed running also can effectively reduce the NPSH of centrifugal pump NPSHr, away from the pump cavitation area, reduce the possibility of centrifugal pump cavitation occurred [2]. The disadvantage is that change the pump speed by variable frequency technology are needed to change the prime mover (usually) of the motor speed, principle of complex, investment is bigger, and the flow adjustment range is small.

1.3 pump series, and even the adjustment way

When a single centrifugal pump can't meet the delivery task, can use of centrifugal pump in parallel or in series operation. With two sets of the same type of centrifugal pump in parallel, although the head changed little, but increased the total transportation flow, the total efficiency of the pump in parallel with a single pump efficiency is the same; Centrifugal pump series when the total pressure head, flow rate change is not big, the total efficiency of the pump with single pump efficiency is the same.

Energy consumption analysis of two pumps under different adjustment modes

Analysis of energy consumption under different adjustment modes, the article in view of the present regulating valve and pump variable speed regulation is widely adopted by two types of regulation. Due to centrifugal pump and, series aims to improve the pressure head or flow, in the field of chemical industry use is not much, analyze its energy consumption can be combined with figure 2, the method is basically the same.