Centrifugal pump is a kind of general fluid machinery widely used in chemical industry system. It has many advantages, such as wide range of performance adaptability (including flow, head adaptability to the properties of conveying medium), small volume, simple structure, easy operation low operating cost. Generally, the flow pressure head of the selected centrifugal pump may be inconsistent with the requirements in the pipeline, due to the change of production task process requirements, the flow regulation of the pump is required at this time, which is essentially to change the working point of the centrifugal pump. The working point of the centrifugal pump of the full-automatic centrifuge is determined by the characteristic curve of the pump the characteristic curve of the pipeline system. Therefore, the purpose of flow regulation can be achieved by changing any characteristic curve. At present, the flow regulation methods of centrifugal pump mainly include control valve, variable speed control pump parallel series regulation. Due to the different principles of various regulating methods, in addition to their own advantages disadvantages, the resulting energy loss is also different. In order to find a flow regulating method with small energy consumption energy saving, it is necessary to fully understand the relationship between the flow regulating method energy consumption of centrifugal pump.
1： Main methods of pump flow regulation
1. Change the pipeline characteristic curve
The simple way to change the flow rate of centrifugal pump is to use the opening degree of the valve at the pump outlet to control. Its essence is to change the position of the pipeline characteristic curve to change the working point of the pump.
2. Change the characteristic curve of centrifugal pump
According to the law of proportion the law of cutting, changing the speed of the pump the structure of the pump (such as the method of cutting the outer diameter of the impeller, etc.) can change the characteristic curve of the centrifugal pump, so as to achieve the purpose of regulating the flow ( changing the head at the same time). But for the working pump, it is convenient to change the structure of the pump, because of changing the structure of the pump, the universality of the pump is reduced, although it is economical convenient to adjust the flow at some times , it is rarely used in production. Only the method of changing the speed of centrifugal pump to adjust the flow is analyzed here.
3. Serial parallel adjustment mode of pump
When a single centrifugal pump can meet the delivery task, parallel series operation of centrifugal pump can be used. When two centrifugal pumps of the same model are used in parallel, although the pressure head changes little, the total delivery flow is increased, the total efficiency of the parallel pump is the same as that of the single pump; when the centrifugal pumps are connected in series, the total pressure head increases, the flow changes little, the total efficiency of the series pump is the same as that of the single pump.
2： Analysis of energy consumption of pumps under different regulation modes
In the analysis of energy consumption under different regulation modes, this paper only analyzes two widely used regulation modes, valve regulation pump variable speed regulation. As the purpose of parallel series operation of centrifugal pump is to improve the pressure head flow, it is seldom used in chemical industry, its energy consumption can be analyzed in combination with figure 2, the method is basically the same.