Pressure Reducing Valve

Description

The Pressure Reducing Valve component allows fluid flow in one direction, from port A to port B. The flow is controlled by an adjustable orifice whose area is controlled by the pressure difference from port A to port B.

The Conductance increases linearly from $\mathrm{C__max}$ to ${C}_{\mathrm{min}}$ as the pressure increases from ${p}_{\mathrm{contract}}$ to ${p}_{\mathrm{close}}$.

The pressure drop vs. flow rate, for the computed area, comes from the Orifice ISO 6358 model.

 Formulation Approaches Two approaches were taken for formulation of the flow equation inside the device. When the boolean parameter $\mathrm{UseRestrictionArea}$ is true, the flow area at the local restriction can be provided which will be converted to Sonic conductance using Gidlund's approximation.
 Equations $p={p}_{A}-{p}_{B}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}$ Orifice Gas Equations Linear Gain k is given by When UseRestrictionArea is checked, Gidlund's approximation is used to calculate C using $\mathrm{Ar__max}$ Orifice Opening

Variables

 Name Units Description Modelica ID ${C}_{}$ $\frac{{m}^{3}}{s\cdot \mathrm{Pa}}$ Sonic Conductance Cmax $p$ $\mathrm{Pa}$ Pressure difference p $\mathrm{mflow}$ $\frac{\mathrm{kg}}{s}$ Mass flow rate across the ports mflow ${\mathrm{hflow}}_{X}$ $\frac{\mathrm{kJ}}{\mathrm{kg}}$ Specific Enthalpy into port X hflowX

Connections

 Name Description Modelica ID $\mathrm{portA}$ Pneumatic port on left side portA $\mathrm{portB}$ Pneumatic port on right side portB

Parameters

Fluid Medium Parameters

The Gas parameters used in the equations are properties defined in the Gas Model component used in the model.

 Name Default Units Description Modelica ID $\mathrm{true}$  When true the default gas properties defined for Air will be used. useDefaultMedium $\mathrm{medium}$ $-$  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. medium

Orifice Parameters

 Name Default Units Description Modelica ID $\mathrm{b__lamreg}$ $0.999$ Flow transition constant from turbulent to laminar zone blamreg $\mathrm{UseRestrictionArea}$ $\mathrm{false}$ True (checked) means flow restriction area can be given which will be converted to sonic conductance based on Gidlund's approximation UseRestrictionArea

Valve Parameters

 Name Default Units Description Modelica ID ${p}_{\mathrm{close}}$ $2.1\cdot {10}^{5}$ $\mathrm{Pa}$ Pressure at which valve is fully closed (C = Cmin) [1] pclose ${p}_{\mathrm{contract}}$ $1.9\cdot {10}^{5}$ $\mathrm{Pa}$ Pressure at which valve is fully open (C = Copen) [1] pcontract ${C}_{\mathrm{min}}$ $\frac{{m}^{3}}{s\cdot \mathrm{Pa}}$ Valve Sonic Conductance when closed (leakage) Cmin ${C}_{\mathrm{max}}$ $\frac{{m}^{3}}{s\cdot \mathrm{Pa}}$ Valve Sonic Conductance when fully open Cmax ${A}_{\mathrm{min}}$ $0$ ${m}^{2}$ Restriction Area when closed (leakage); used when  is true Amin $\mathrm{Ar__max}$ $0.00001$ ${m}^{2}$ Valve restriction area when fully open; used when  is true Armax $b$ $0.54$ Critical pressure ratio bcr

[1] $\mathrm{p__contract}<\mathrm{p__close}$

[2] $\mathrm{C__min}<\mathrm{C__max}$