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3.2
Outlet Purge Device Measuring Principle
-Figure 2
Figure 2 Schematic Diagram of the Outlet Purge Device Measurement Principle
P2A+P3a+F
As shown in the Purge Device Schematic Diagram: (CH Outlet Constant Flow Valve)
Elastic diaphragm is subjected to downward force：
P2A+P3a+F
P2A+P3a+F= P1A+P2a
Elastic diaphragm is subjected to upward force：
P1A+P2a
When the pressure is balanced，that is (1) = (2)
P2A+P3a+F= P1A+P2a
P1-P2=F/A-(a/A)（P2-P3）
Since the magnitude of the flow depends on the difference P1-P2 of the pressure regulator
diaphragm, we can get by (3):
P1-P2=F/A- (a/A) (P2-P3)
In the case of incompressible liquids, the CH outlet constant flow valve can be used for inlet
pressure changes. For (4), P2 is constant and P1 is variable, so P1 becomes P1+△P, P2 becomes
P2+△P, so P2-P3=C is a constant value.
In the formula above：
A: Diaphragm cross-sectional area
A: Control valve spool (ball) cross-sectional area.
F/f: Spring pressure (spring force).
△P: Change in P2 or P3
