Circulation capacity Cv is one of the main parameters for selecting a regulating valve. Its circulation capacity is defined as: when the regulating valve is fully opened, the pressure difference between the two ends of the valve is 0.1MPa and the fluid density is 1g/cm3, the hourly flow rate of the regulating valve , Known as the circulation capacity, also known as the flow coefficient, expressed in Cv, the unit is t/h.
According to the size of the flow rate Cv value, the nominal diameter DN of the regulating valve can be determined. The flow characteristic of the regulator is the relationship between the relative flow of the medium flowing through the regulator and the opening amount under the condition that the pressure difference between the two ends of the regulator remains unchanged. There are three types of flow characteristics of the governor: linear, equal percentage characteristics and parabolic characteristics. The meanings of the three characteristics of fluence are as follows:
(1) Equal percentage feature (logarithm)
The relative stroke and the relative flow are not linear. At each point of the stroke, the flow change caused by the change of the cylinder solenoid valve stroke is proportional to the flow change at that point, and the percentage of the flow change is equal. Therefore, its advantage is that when the flow is small, the flow change is small, and the flow is large, the flow change is large, that is, different opening degrees have the same adjustment accuracy.
(2) Linear feature (linear)
The relative stroke and relative flow have a linear relationship on the linear characteristic. The flow change caused by the unit stroke change is constant. When the flow rate is large, the relative value of the flow rate changes little; when the flow rate is small, the flow rate changes more.
(3) Parabolic characteristics.
The flow field changes proportionally in two directions, roughly having linear and equal percentage intermediate characteristics. From the analysis of the above three characteristics of the solenoid valve pulse, it can be seen that in terms of adjustment performance, the equal percentage characteristic is the best, its adjustment is stable, and the adjustment performance is better. Compared with the linear characteristic, the parabolic characteristic has better adjustment performance, and any one of the flow characteristics can be selected according to the different requirements of the use occasion.