Flow control valve actuated by transverse motion of circular gate
Thermal Liquid/Valves/Flow Control Valves
The Gate Valve (TL) block represents a flow control valve with a circular opening and a circular gate. The gate moves in a direction orthogonal to the fluid flow. The opening and gate are equal in diameter. The figure shows a schematic of the gate valve in three different positions—closed, partially open, and fully open.
Gate Valve in Different Positions
A smoothing function allows the valve opening area to change smoothly between the fully closed and fully open positions. The smoothing function does this by removing the abrupt opening area changes at the zero and maximum ball positions. The figure shows the effect of smoothing on the valve opening area curve.
Opening-Area Curve Smoothing
The block computes the valve opening area directly from valve geometry parameters using the expression
A is the valve opening area.
d0 is the valve orifice diameter.
ACovered is the portion of the valve orifice area covered by the gate:
Δl is the net displacement of the gate center relative to the orifice center.
x0 is the Gate displacement offset specified in the block dialog box.
Sd is the gate displacement specified through physical signal input port S.
The valve opening expressions introduce undesirable discontinuities at the fully open and fully closed positions. The block eliminates these discontinuities using polynomial expressions that smooth the transitions to and from the fully open and fully closed positions. The valve smoothing expressions are
λL is the smoothing expression for the fully closed portion of the valve opening curve.
λR is the smoothing expression applied to the fully open portion of the valve opening curve.
Δlsmooth is the gate displacement smoothing region:
The smoothed valve opening area is given by the piecewise conditional expression
SR is the smoothed valve opening area.
SLeak is the valve leakage area.
SMax is the maximum valve opening area:
The mass conservation equation in the valve is
is the mass flow rate into the valve through port A.
is the mass flow rate into the valve through port B.
The energy conservation equation in the valve is
ϕA is the energy flow rate into the valve through port A.
ϕB is the energy flow rate into the valve through port B.
The momentum conservation equation in the valve is
pA and pB are the pressures at port A and port B.
is the mass flow rate.
is the critical mass flow rate:
ρAvg is the average liquid density.
Cd is the discharge coefficient.
S is the valve inlet area.
PRLoss is the pressure ratio:
Diameter of the valve flow area in the fully open position.
The default value is
Gate offset from the zero position. The instantaneous gate displacement
is the sum of the gate offset and input signal S. The default value
Aggregate area of all fluid leaks in the valve. The leakage
area helps to prevent numerical issues due to isolated fluid network
sections. For numerical robustness, set this parameter to a nonzero
value. The default value is
Portion of the opening-area curve to smooth expressed as a fraction.
Smoothing eliminates discontinuities at the minimum and maximum flow
valve positions. The smoothing factor must be between
Enter a value of
0 for zero smoothing. Enter a
1 for full-curve smoothing. The default
Flow area at the valve inlets. The inlets are assumed equal
in size. The default value is
Approximate length of the valve. This parameter provides a measure
of the longitudinal scale of the valve. The default value is
Semi-empirical parameter commonly used as a measure of valve performance. The discharge coefficient is defined as the ratio of the actual mass flow rate through the valve to its theoretical value.
The block uses this parameter to account for the effects of
valve geometry on mass flow rates. Textbooks and valve data sheets
are common sources of discharge coefficient values. By definition,
all values must be greater than 0 and smaller than 1. The default
Reynolds number corresponding to the transition between laminar
and turbulent flow regimes. The flow through the valve is assumed
laminar below this value and turbulent above it. The appropriate values
to use depend on the specific valve geometry. The default value is
Mass flow rate into the component through port A
at the start of simulation. The default value is
A — Thermal liquid conserving port representing valve inlet A
B — Thermal liquid conserving port representing valve inlet B
S — Physical signal input port for the control member displacement