Measures to avoid the influence of dynamic pressure should avoid the influence of dynamic pressure. As long as the valve seat is separated from the lower cavity of the diaphragm, the outlet airflow cannot directly act on the diaphragm. For direct-acting regulators, use a signal tube or dedicated channel to transfer P2 to the lower diaphragm cavity, avoiding the effects of dynamic pressure as much as possible.
As shown in b, the valve seat is separated from the lower cavity of the diaphragm by a partition plate, and the feedback pressure P2 at the lower end of the diaphragm is from the downstream pipeline, thereby avoiding the influence of dynamic pressure. However, it is necessary to pay attention to the matching clearance between the diameter d of the valve stem and the guide hole D of the partition plate. For the medium-low pressure regulator, the clearance of the base hole should be selected, and the precision should be higher than H10/d9. Of course, the smaller the fit clearance, the smaller the effect of dynamic pressure. For high pressure regulators, rubber seals can be installed for gapless dynamic sealing.
It is also possible to use a method as shown in c to isolate the valve seat from the lower cavity of the diaphragm with a balanced diaphragm, which not only solves the imbalance force of the valve core but also solves the problem of isolation, while the opening of the signal tube faces the gas flow. The direction avoids the entry of dynamic pressure. All of the above are common measures for voltage regulator products.
The working principle of the voltage regulator is mainly reflected in the spring-loaded direct-acting voltage regulator. The voltage regulator with weight and pressure is not discussed in this paper.
It can be seen from Equation 2 that when the force receiving area A of the diaphragm is constant, the outlet pressure P2 of the pressure regulator is proportional to the spring force F of the upper end of the diaphragm. If the spring force F is fixed, the regulator outlet pressure P2 will be stable. By adjusting the spring to change the spring force, the outlet pressure of the regulator can be adjusted within a certain range.
It shows two working states of the same regulator fully open and critically closed. a, the regulator spool is at the maximum opening, working in the maximum flow state, the working height of the pressure regulating spring is H1, the spring force is F1; the b spool is at the minimum opening, and the regulator works in a small flow state. The working height of the pressure regulating spring is H2, and the spring force is F2; ​​the height difference of the spring in both states is x, which is equal to the stroke of the spool.
The adverse effect of the spring effect is described in Equation 5. The relationship between the spring effect is described. When the effective area A of the regulator diaphragm and the stroke x of the spool are determined, the magnitude of the spring effect is related to the stiffness of the spring. The greater the stiffness, the more adverse the effect of the spring effect. Big. From the static characteristic curve of the regulator, it can be seen that the static characteristic curve and the ideal static characteristic curve are affected by the spring effect. The spring effect will cause the slope of the static characteristic curve to be relatively large, the head is upturned, the tail is drooping, and the voltage regulation precision is low. The flow rate within the range of the regulation accuracy becomes small. If the flow load of the regulator frequently fluctuates during actual use, the output pressure will also follow the fluctuation, which is the adverse effect of the spring effect.
The curve affected by the spring effect is different from the curve affected by the dynamic pressure. Although the slope of the curve is large, the linearity is better. The ΔP corresponding to the middle ordinate is the maximum value of the spring effect in Equation 5.
The result of the compensation of the spring effect by the negative pressure compensation method is to raise the tail of the curve affected by the spring effect, reduce the slope of the curve, try to make it coincide with or close to the ideal static characteristic curve, thereby improving the voltage regulation accuracy and flow rate. Scope, several practical compensation measures are described below.
The effect of the spring effect can be reduced by reducing the spring rate, increasing the effective area of ​​the diaphragm, and the like. However, it has been proved that the above method is only applicable to occasions where the spring effect is not serious. The output pressure of the pressure regulator determines the load force of the pressure regulating spring. If the spring stiffness is excessively reduced, the free height of the spring is bound to increase. The length to diameter ratio of the spring will exceed the design requirements of the spring, causing the spring to be unstable and the spring Bending deformation occurs after compression; excessively increasing the diaphragm area also increases the size and weight of the upper and lower membrane shells, causing the regulator to be too bulky and uncoordinated in appearance.
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