Method for adjusting the flow rate using a rotational speed when a gear pump is used

The speed (or motor speed) of the gear pump drops from n1 to n2, the characteristic curve QH of the pump at speed n2 and the line characteristic He=H0+G1Qe2 (the line curve does not change) intersect at point A3 (Q2, H3) ), point A3 is a new working point after adjusting the flow rate through speed regulation. This adjustment method has obvious, fast, safe and reliable adjustment effect, can prolong the service life of the pump and save electric energy. In addition, reducing the speed operation can effectively reduce the NPSHr of the heat transfer oil pump, keep the pump away from the evaporative area and reduce the heat transfer oil pump. The possibility of cavitation occurs. The disadvantage is that changing the rotational speed of the pump requires changing the rotational speed of the prime mover (usually the motor) through frequency conversion technology, the principle is complex, the investment is large, and the flow regulation range is small.

Through the characteristic curve diagram of the heat transfer oil pump and the pipeline system, several main methods of flow regulation of the heat transfer oil pump are analyzed: the outlet valve adjustment, the pump speed adjustment and the serial and parallel adjustment of the pump. The energy loss of the two methods of outlet valve regulation and pump speed regulation was analyzed by using the characteristic curve diagram, and a comparison was made. It was pointed out that the heat transfer oil pump can adjust the flow rate with the outlet valve better than the outlet valve to save the energy consumption, and the energy-saving efficiency can be achieved. Related to the size of the flow changes. In practical applications, attention should be paid to the range of variable speed adjustments in order to better apply variable speed control of the heat transfer oil pump.
The operating point of the heat transfer oil pump is determined by the characteristic curve of the pump and the characteristic curve of the pipeline system. Therefore, changing any of the characteristic curves can achieve the purpose of flow regulation. At present, the flow adjustment methods of the heat-conducting oil pump mainly include the control of the regulating valve, the variable-speed control, and the parallel and series adjustment of the pump. Because of the different principles of various adjustment methods, in addition to their own advantages and disadvantages, the resulting energy loss is not the same. In order to seek out excellent, low energy consumption, energy-saving flow adjustment methods, we must fully understand the flow regulation method of the thermal oil pump and The relationship between energy consumption. The heat transfer oil pump is a general-purpose fluid machine widely used in chemical industry systems. It has a wide range of performance adaptation (including flow, pressure head and adaptability to the nature of the transmission medium), small size, simple structure, easy operation, low operating cost and many other advantages. Generally, the flow and pressure head of the selected heat-conducting oil pump may be inconsistent with the requirements in the pipeline, or due to changes in production tasks and process requirements. At this time, flow adjustment of the pump is required, which essentially changes the working point of the heat-conducting oil pump.