Centrifugal pumps are widely used in water conservancy and chemical industries. The selection of working conditions and the analysis of energy consumption are also receiving more and more attention. The so-called working conditions refer to the working capacity of pumps.
Centrifugal pumps are widely used in water conservancy, chemical industry, etc. The selection of working conditions and the analysis of energy consumption are also receiving more and more attention. The so-called operating point refers to the working capacity of the pump. Usually the flow rate and pressure head of the centrifugal pump may be Inconsistent with the pipeline system or due to changes in production tasks and process requirements, it is necessary to adjust the flow rate of the pump to change the operating point of the centrifugal pump. In addition to the correctness of the centrifugal pump selection in the engineering design stage, the actual use of the centrifugal pump The choice of the situation will also directly affect the user's energy consumption and cost. Therefore, how to properly change the operating point of the centrifugal pump is particularly important.
The working principle of the centrifugal pump is to convert the mechanical energy of the high-speed rotation of the motor into the kinetic energy and potential energy of the liquid to be lifted. It is a process of energy transfer and conversion. According to this feature, the operating point of the centrifugal pump is based on the change of the characteristic curve of the pump itself. Such as frequency control, cutting impeller,
Here are some ways to analyze and compare:
First, the valve throttle
The simplest way to change the flow rate of the centrifugal pump is to adjust the opening degree of the pump outlet valve, and the intersection point A of the pump characteristic curve QH and the pipeline characteristic curve Q-∑h is the shift of the pump operating point to the left when the valve is fully open. The flow rate is reduced. When the valve is fully closed, the flow is equivalent to the infinite flow of zero, and the pipe characteristic curve coincides with the ordinate.
Second, frequency control
The operating point deviates from the high efficiency zone. The pump balance operating point (also called the operating point) corresponds to the efficiency ηa. To reduce the flow rate, the speed can be reduced. At this time, the operating point is B. The efficiency of the pump corresponding to the efficiency ηb/ηc decreases. When the required flow rate is less than the rated flow rate, the head of the variable frequency speed regulation is smaller than the throttle of the valve, so the water supply power required for the frequency conversion speed regulation is also smaller than the throttle of the valve. Compared with the valve throttling, the working efficiency of the centrifugal pump is more High. In addition, the use of variable frequency speed control not only helps to reduce the possibility of cavitation of the centrifugal pump, but also can extend the start/stop process by setting the speed up/down time to greatly reduce the dynamic torque. , thus largely eliminating the extremely destructive water hammer effect has been greatly extended.
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China Hardware Business Network http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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