Pressure compensator (TL)#

The Pressure compensator (TL) block has 4 ports:

A and B - hydraulic ports through which liquid flows through the network under consideration;
X and Y - hydraulic ports of the third-party hydraulic network. The characteristics of this network (for example, the dependence of the flow rate on the difference on each component of the network or the network as a whole) are not involved in the calculation of the main hydraulic network, and points X and Y are used only to monitor the pressure in the third-party network using the block in question.

The block describes the flow of liquid through the valve cross-section, which controls the pressure if the current drop at ports X and Y exceeds the setpoint, but does not exceed the maximum pressure.

The maximum pressure is the sum of the setpoint and the control range.

The pressure setpoint can be zero, the control range is strictly greater than zero. The smaller the monitoring range, the faster the valve position changes at pressure change (the control speed increases).

There are two modes of valve operation:

The Constant mode, the pressure setpoint remains unchanged and is set through the block property Set pressure drop;
The Controlled mode, the setpoint is set by the external signal via the automation port.

Simulated valve can be:

Normally open (for example, reducing valve), maintaining the downstream pressure not higher than the set one;
Normally closed (for example, safety valve), maintaining the upstream pressure not higher than the set one.

Leakage area is the area of the hole when the valve is fully closed.

Note

Can be set to zero

Maximum area is the area of the hole when the valve is fully open.

Note

Should be set strictly less than valve port area

Provision is made for selecting a pressure recovery option.

Valve opening can be parameterized linearly or using tabular data.

If Opening parametrization is set to Linear, the hole area is a linear function of the piston valve travel distance (1) :

(1)#\[ A_{orifice}\:=\:\frac{(A_{max}-A_{leak})}{\Delta S}\:*\:\Delta S + A_{leak} \]

where:

\(A_{orifice}\) - open area;

\(ΔS\) is a piston valve travel distance entered into port S (2) :

(2)#\[Δ S = S -S_{max}+ ΔS_{max}\]

\(ΔS_{max}\) is the value of the parameter movement of the piston valve between the closed and open holes;

\(A_{leak}\) - value of parameter Leakage area;

\(A_{max}\) — value of parameter Maximum valve area.

Scaling from \(A_{Leak}\) to \(A_{max}\) is implemented linearly.

If set Opening parametrization to Tabulated, the clock uses piston valve travel vector and parameters Valve area vector, to determine the relationship between \(A_{orifice}\) and \(ΔS\) by interpolation. \(A_{leak}\) and \(A_{max}\) are the first and last parameter Valve area vector respectively.

Law of mass conservation (3) :

(3)#\[Min_1+Min_2+M_{out}=0\]

Dependence of mass on pressure drop (4) :

(4)#\[\dot{m}=\frac{C_d \cdot A_{valve} \cdot \sqrt{2 \cdot \bar \rho}}{\sqrt{PR_{loss}\cdot (1-(\frac{A_{valve}}{A_{port}})^2)}}\cdot \frac{\Delta p}{(\Delta p^2+\Delta p^2_{crit})^{1/4}}\]

where:

\(A_{valve}\) – valve cross-sectional area, [m\(^2\)];

\(A_{port}\) – port cross-sectional area, [m\(^2\)];

\(PR_{loss}\) – loss ratio;

\(\Delta p_{crit}\) – critical pressure drop, [Pa];

\(\Delta p\) – pressure drop between input and output port, [Pa].

Note

Calculated in the model core at each cycle of its operation

Note

Calculated further

Note

For this block \(\Delta p_1\) is defined as the difference between input port 1 and output port, ‘dp2’ is the same for port 2. \(Min_1\) and \(Min_2\) values - mass flows through input ports 1 and 2, respectively, are calculate аrom the values of these two differences.

Calculation of critical drop (5) :

(5)#\[\Delta p_{crit}=\frac{\pi \cdot \bar \rho}{8 \cdot A_{valve}}\cdot (\frac{\nu \cdot Re_{crit}}{C_d})^2\]

where:

\(C_d\) – recovery factor;

\( u\) – liquid kinematic viscosity, [mm\(^2\)/s];

\(Re_{crit}\) – Critical Reynolds number, the boundary between laminar and turbulent flow.

Calculation of loss coefficients (6) :

(6)#\[PR_{loss}\:=\:\frac{\sqrt{1-(\frac{A_{valve}}{A_{port}})^2\cdot (1-C_{d}^2)}-C_{d}\cdot \:\frac{A_{valve}}{A_{port}}}{\sqrt{1-(\frac{A_{valve}}{A_{port}})^2\cdot (1-C_{d}^2)}+C_{d}\cdot \:\frac{A_{valve}}{A_{port}}}\]

Law of conservation of energy (7) :

(7)#\[\phi_А+\phi_В=0\]

where:

\(\phi_A\) - energy flow at the input, [W];

\(\phi_B\) - energy flow at the output, [W].

1. Properties#

Property	Default value	Description	Units of measurement
Valve specification: Normally open; Normally close	Normally open	-	-
Set pressure drop: Constant; Controlled	Constant	-	-
Opening parametrization: Linear; Tabulated	Linear	-	-
Pressure recovery	Off	-	-
Pressure drop set, available when selecting `Set pressure drop` - `Constant`	500	-	Pa
Pressure range, available when selecting `Opening parametrization` - `Linear`	10000	-	Pa
Critical Reynolds number	150	-	-
Discharged coefficient, available when selecting `Pressure recovery` - `On`	0.64	-	-
Leakage area, available when selecting `Opening parametrization` - `Linear`	1e-10	-	m\(^2\)
Maximum valve area, available when selecting `Opening parametrization` - `Linear`	0.01	-	m\(^2\)
Port area	0.1	-	m\(^2\)
Smoothing factor	0.01	-	-
Presure drop vector, available when selecting `Opening parametrization` - `Tabulated`	2e5; 4e5; 6e5; 8e5; 1e6; 1.2e6	-	Pa
Valve area vector, available when selecting `Opening parametrization` - `Tabulated`	1e-5; 8e-6; 6e-6; 4e-6; 2e-6; 1e-10	-	m\(^2\)

2. Inputs and outputs#

Parameters	Input/Output	Description	Units of measurement	Port type
Input	Input	-	-	Thermohydraulics
Control port X	Input	-	-	Thermohydraulics
Control port Y	Input	-	-	Thermohydraulics
Pressure drop	Input	Available, when `Set pressure drop` - `Constant`	Pa	Automation
Output	Output	-	-	Thermohydraulics

In order to see the connection capabilities of the block, you need to go to page Description of block ports