flowcontrolvalve

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flowcontrolvalve

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Iconic Diagrams\Hydraulics\Valves\Basic Valves

Use

Domains: Continuous. Size: 1-D. Kind: Iconic Diagrams (Hydraulics).

Description

Flow control valves have the purpose to provide a constant flow, independent of the downstream pressure. The flow is obtained by means of a pressure difference controller using the pressure drop over an orifice. Therefore flow control valves always need a certain pressure drop before the desired flow can be achieved.

FlowControlValve

 

In this model the flow is modeled by an tanh function. The pressure drop is defined as the pressure where 95% of the desired flow rate is achieved.

 

dp = pa.p - pb.p

phi = if dp > 0 then

 phi*arctanh( (arctan(0.95)/p_drop) * dp) + GLeak * dp;

else

 GLeak * dp

end;

 

Here phi is the desired flow and p_drop is the 95% pressure drop. Gleak is the conductance of laminar leakage flow when the valve is closed. The pressure at both ports has a lower limit that is equal to the vapour pressure. Therefore the actual equations used in this model are:

 

p1_lim = if pa.p < p_vapour then p_vapour else pa.p end;

p2_lim = if pb.p < p_vapour then p_vapour else pb.p end;

dp = p1_lim - p2_lim;

Interface

Ports

Description

pa, pb

Both terminals of the hydraulic component.

Causality

 

fixed volume flow out pa

fixed volume flow out pb

 

Parameters

 

phi

p_drop

GLeak

 

Desired flow [m3/s]

pressure drop at 95% flow [Pa]

Conductance of the laminar leakage flow [m3/s.Pa], GLeak >= 0!