Non Return Override Valve
Non return override valve
Description
Equations
Variables
Connections
Parameters
The Non Return Override Valve component is a check valve with a pilot pressure that can be used to assist in opening or closing the valve.
The sonic conductance of the valve is assumed to be a piecewise linear function of the pressure difference between port A and port B.
Based on the orifice area, the pressure vs. flow rate relationship is calculated by the formulation used in the Orifice ISO 6358 component.
Formulation Approaches
Two approaches were taken for formulation of the flow equation inside the device. When the boolean parameter UseRestrictionArea is true, the flow area at the local restriction can be provided which will be converted to sonic conductance using Gidlund's approximation.
p=pA−pBhflow__X = inStreamportX⋅hflow
Orifice Gas Equations
mflow = {k⋅p1⋅1−p__2p__1T__envT__refp2p1≥b__lamregp__1⋅C⋅ρ__0⋅T__envT__ref⋅ (1−p__2p__1−b1−b2b__lamreg> p__2p__1>bp__1⋅C⋅ρ__0⋅T__0T__1p__2P__1≤b p__1 → Upstream pressure, p__2 → Downstream pressure Linear Gain k is given by
k = C1−b__lamreg⋅ρ__01− b__lamreg−b1−b2
When UseRestrictionArea is checked, Gidlund's approximation is used to calculate C using Ar__max
C=0.125⋅4⋅Ar__maxπ
Pilot Equations
Ct={Cminptot≤pcloseCmin+ptot−pcloseCmax−Cminpopen−pcloseptot<popenCmaxotherwise
ptot=p+{kppCdir=1−kppCotherwise
mflowC=0
Name
Units
Modelica ID
p
Pa
Pressure drop from A to B
pX
Pressure at port X
mflow
kgs
Mass flow rate from A to B
hflowX
Jkg
Specific Enthalpy into port X
portA
Pneumatic port on left side
portB
Pneumatic port on right side
portC
Pneumatic port on the bottom (no volume, used as pilot)
Fluid Medium Parameters
The Gas parameters used in the equations are properties defined in the Gas Model component used in the model.
Default
Use default medium
true
When true the default gas properties defined for Air will be used.
useDefaultMedium
medium
−
When Use default medium is false this option gets turned on. The user can specify the name of the Gas model dragged into the canvas.
Orifice Parameters
b__lamreg
0.999
Flow transition constant from turbulent to laminar zone
blamreg
UseRestrictionArea
false
True (checked) means flow restriction area can be given which will be converted to sonic conductance based on Gidlund's approximation
Valve Parameters
pcrack
2⋅ 105
Pressure at which valve is fully closed (C = Cmin)
pclose
popen
2.05 ⋅ 105
Pressure at which valve is fully open (C = Copen)
Cmin
1 ⋅ 10−13
m3s⋅Pa
Valve Sonic Conductance when closed (leakage)
Cmax
1.6 ⋅ 10−8
Valve Sonic Conductance when fully open
Amin
0
m2
Restriction Area when closed (leakage); used when Use Restriction Area is true
Ar__max
0.00001
Valve restriction area when fully open; used when Use Restriction Area is true
Armax
b
0.54
Critical pressure ratio
bcr
Pilot action
Open
Select whether the pilot operates to open or close the valve
dir
kpilot
3
Pilot ratio
kp
See Also
Pneumatics Library
Valves
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