When the pump impeller speed is constant, a pump in the specific operating conditions provided by the liquid flow and pressure head H ~ Q curve can be used to express that. As for the specific location of this point, depending on the pipeline before and after the pump may be. Discuss pump work, should not be divorced from the specific circumstances of the pipeline. The working characteristics of the pump are determined by the characteristics of the pump and the characteristics of the piping. 1. Centrifugal Pump Piping Characteristics Consider the extra head calculation derived from the Bernoulli equation: The larger the Q, the greater the additional pressurized head required by the flow system. The relationship between the flow through a particular pipeline and its required additional head, known as the characteristics of the pipeline. The characteristic equation of the pipeline expresses the relationship between the required pressure head and pipeline flow required by the pipeline. The corresponding curve in H ~ Q coordinates is called the pipeline characteristic curve. Explanation â‘ is the intercept of the pipeline characteristic curve on the H axis, which indicates the minimum applied pressure head required by the pipeline system. â‘¡When the flow is in the resistance square area, the friction coefficient has nothing to do with the flow rate. The pipeline characteristic equation can be expressed as: â‘¢High resistance pipeline, its characteristic curve is steep; The characteristic curve of low resistance pipeline is gentle. 2. Centrifugal pump operating point of the pump H ~ Q curve and pipeline ~ Q curve drawn in the same coordinate system, the intersection of the two curves is called the pump operating point. Explain â‘ The working point of the pump is determined by the characteristics of the pump and the characteristics of the pipeline, and can be obtained by solving the equation of the characteristic of the pump and the characteristic equation of the pipeline by the simultaneous solution. â‘¡ The pump installed in the pipeline is the tube Road flow; pump at this flow is also provided by the pump head plus the required pressure head. Therefore, the pump working point corresponding to the pump head is provided both by the pump, but also the pipeline needs; The corresponding performance parameters of the operating point reflects the actual working state of a pump. 3. Centrifugal pump flow adjustment Due to changes in production tasks, the pipeline needs flow sometimes need to be changed, which is actually to change the pump operating point. Because the working point of the pump is determined by the characteristics of the pipeline and the characteristics of the pump, changing the characteristics of the pump and the characteristics of the pipeline can change the working point so as to achieve the purpose of regulating the flow. (1) to change the opening of the outlet valve - to change the characteristics of the pipeline outlet valve opening and local resistance equivalent length of the pipeline, which is related to the characteristics of the pipeline. So changing the opening of the outlet valve is actually changing the characteristics of the line. Turn off the small outlet valve, increase, the curve becomes steep, the working point from C to D, the flow rate decreases, the pump head provided by the pressure rise; on the contrary, open a large outlet valve opening, reducing, the curve slows down, the working point from C becomes E, the flow rate rises, and the pressure head provided by the pump drops. This flow control method is convenient, but not economical, in fact, artificially increase the pipeline resistance to adapt to the characteristics of the pump, and make the pump work in the low efficiency point. But it is precisely because of its convenience, is widely used in actual production. (2) change the impeller speed - change the characteristics of the pump speed increases, the flow and pressure head can increase. This method of adjusting the flow rate is reasonable and economical, but it has been considered inconvenient to operate and can not be continuously adjusted. However, with the development of modern industrial technology, the application of CVT in industry overcomes the above shortcomings. It is this kind of adjustment method that enables the pump to work in the high efficiency area, which is especially important for energy saving of large pumps. (3) turning impeller diameter: This adjustment method is not easy to implement, and the adjustment range is not large.
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