Engee documentation

Gate Valve (G)

A valve in the gas network.

blockType: EngeeFluids.Gas.Valves.FlowControl.Gate

gate valve g

Path in the library:

/Physical Modeling/Fluids/Gas/Valves & Orifices/Flow Control Valves/Gate Valve (G)

Description

Block Gate Valve (G) It is a flow control mechanism in the form of an opening with a movable gate, or gateway. The gate has a circular shape and must slide perpendicular to the flow due to the limitations of the groove of its seat. The valve seat is annular. The flow passes through an opening, the size of which corresponds to the size of the gate. The overlap of the gate and the opening determines the opening area of the valve.

The flow can be laminar or turbulent and can reach sonic velocities. The maximum velocity occurs in the valve seat, where the flow is narrowest and fastest. The flow reaches a critical mode and maximum speed when a pressure drop downstream can no longer increase the speed. The flow is blocked when the pressure drop reaches a critical value characteristic of the valve. The unit does not calculate supersonic flow.

The valves usually open quickly. Gate valves are most sensitive to gate displacement near the closed position, where a small displacement leads to a disproportionately large change in the opening area. Consequently, the valves have too much gain in this area to effectively throttle or regulate the flow. You can use this unit as a two-position switch for opening and closing gas circuits.

Shutter mechanics

In this valve, the gate is connected by a gear mechanism to the handle. When the handle is turned from the fully closed position, the shutter rises from the opening and gradually opens the valve to its maximum. Rigid stops prevent the disc from going beyond the minimum and maximum positions.

The block captures the movement of the disk, but not the details of its mechanics. The movement is set as a normalized offset in port L. The input value on the L port is the ratio of the instantaneous displacement to its value in a fully open valve.

Shutter position

This block simulates the movement of the valve, but not the dynamics of opening or closing the valve. The signal in port L sets the normalized shutter offset, . Meaning — this is the normalized value of the offset between 0 and 1, which mean a fully closed and fully open valve, respectively. If the calculation returns a number outside of this range, then this number is set equal to the nearest boundary.

Countable smoothing

When the Smoothing factor parameter has a non-zero value, the unit applies numerical smoothing to the normalized shutter offset. . Enabling anti-aliasing helps maintain the numerical stability of the simulation.

Opening Square

The valve opening area is the area of the opening adjusted by instant closure of the valve:

where

  • — instant opening area of the valve. The unit then smooths this area to remove derivative breaks in the valve limit positions.;

  • — the diameter of the shutter and the hole, which are equal, the value of the parameter Orifice diameter;

  • — the area of overlap between the shutter and the hole, which the unit calculates as a function of shutter displacement :

The picture shows the front view of the valve in the maximum closed position. ( ), partially open ( ) and fully open ( ). The figure also shows the parameters and variables for calculating the opening area.

gate valve g 2

Parameterization of the valve

The behavior of the block depends on the parameter Valve parameterization:

  • Cv flow coefficient — expense ratio determines the dependence of throughput on pressure drop;

  • Kv flow coefficient — expense ratio determines the dependence of throughput on pressure drop, ;

  • Sonic conductance — steady-state acoustic conductivity determines the throughput at critical flow, a condition in which the flow velocity is equal to the local speed of sound. The flow becomes critical when the ratio of outlet pressure to inlet pressure reaches a value called the critical pressure ratio.;

  • Orifice area based on geometry — the size of the flow limit determines the throughput.

The unit scales the set flow rate according to the degree of valve opening. When increasing the degree of valve opening from 0 before 1 The throughput indicator increases from a set minimum to a set maximum.

Conservation of momentum

Parameter Valve parameterization determines which equations will be used to calculate the flow rate. If for the parameter Valve parameterization the value is set Cv flow coefficient, then the mass consumption will be defined as

where

  • — expense ratio;

  • — valve opening area;

  • — the maximum area of the valve when it is fully open;

  • — a constant equal to 27.3 for mass flow rate in kg/hour, pressure in bar and density in kg/m33;

  • — expansion coefficient;

  • — inlet pressure;

  • — outlet pressure;

  • — density at the entrance.

The expansion coefficient is defined as

where

  • — the ratio of the adiabatic index to 1.4;

  • — parameter value xT pressure differential ratio factor at choked flow.

When is the pressure ratio exceeds the value of the parameter Laminar flow pressure ratio, , there is a smooth transition to using the linearized equation:

where

When is the pressure ratio falls lower , the flow becomes critical, and the equation is used

If for the parameter Valve parameterization the value is set Kv flow coefficient, then the block uses the same equations, but replaces on using a relationship . More detailed information about the mass flow equations when for the parameter Valve parameterization the value is set Kv flow coefficient or Cv flow coefficient, is given in [2] and [3].

If for the parameter Valve parameterization the value is set Sonic conductance, then the mass consumption defined as

where

  • — acoustic conductivity;

  • — critical pressure ratio;

  • — parameter value Subsonic index;

  • — parameter value ISO reference temperature;

  • — parameter value ISO reference density;

  • — temperature at the entrance.

When is the pressure ratio exceeds the value of the parameter Laminar flow pressure ratio, , there is a smooth transition to using the linearized equation:

When is the pressure ratio falls below the critical pressure ratio , the flow becomes critical, and the equation is used

More detailed information about the mass flow equations when for the parameter Valve parameterization the value is set Sonic conductance, is given in [1].

If for the parameter Valve parameterization the value is set Orifice area based on geometry, then the mass consumption defined as

where

  • — valve opening area;

  • — parameter value Cross-sectional area at ports A and B;

  • — parameter value Discharge coefficient;

  • — the adiabatic index.

When is the pressure ratio exceeds the value of the parameter Laminar flow pressure ratio, , there is a smooth transition to using the linearized equation:

When is the pressure ratio falls lower , the flow becomes critical, and the equation is used


More detailed information about the mass flow equations when for the parameter Valve parameterization the value is set Orifice area based on geometry, is given in [4].

Conservation of mass

It is assumed that the volume and mass of gas inside the valve are very small, and these values are not taken into account, so gas cannot accumulate in the valve. According to the principle of conservation of mass, the mass flow rate of gas entering through one port is equal to the flow rate of gas exiting through another port.:

where and — the mass flow rate at ports A and B respectively.

Energy conservation

The valve is an adiabatic component. There is no heat exchange between the gas and the valve wall. When the gas passes through the valve, no work is performed on it. Under these assumptions, energy can enter and exit the valve only through convection through ports A and B. According to the principle of energy conservation, the sum of energy flows through ports is always zero:

where and — the flow of energy entering the valve through ports A and B, respectively.

Assumptions and limitations

  • Meaning Sonic conductance the parameter Valve parameterization designed for pneumatic systems. If this parameter is used for gases other than air, it may be necessary to adjust the acoustic conductivity value by the square root of the relative density.

  • The equation for parameterization Orifice area based on geometry it has lower accuracy for gases that are far from ideal.

  • This block does not simulate supersonic flow.

Ports

Conserving

# A — gas port
gas

Details

A hole for gas entry or exit. The flow direction depends on the pressure drop in the valve. The block allows both forward and reverse flow directions.

Program usage name

port_a

# B — gas port
gas

Details

A hole for gas entry or exit. The flow direction depends on the pressure drop in the valve. The block allows both forward and reverse flow directions.

Program usage name

port_b

Input

# L — normalized shutter offset
scalar in the range [0,1]

Details

Normalized shutter offset. The shutter position is normalized to the maximum offset. Meaning 0 corresponds to a fully closed valve, and the value of 1 — completely open.

Data types

Float64
Complex numbers support

No

Parameters

Parameters

# Orifice diameter — valve opening diameter
m | um | mm | cm | km | in | ft | yd | mi | nmi

Details

The diameter of the valve opening and the diameter of the gate, which regulates the opening area. It is assumed that the hole has a constant cross-section along its entire length from one port to the other.

Units

m | um | mm | cm | km | in | ft | yd | mi | nmi
Default value

0.01 m
Program usage name

orifice_diameter
Evaluatable

Yes

# Valve parameterization — the method of defining the characteristics of the flow through the hole
Orifice area based on geometry | Cv flow coefficient | Kv flow coefficient | Sonic conductance

Details

The method of calculating the mass flow is based on:

  • Cv flow coefficient — the expense ratio ;

  • Kv flow coefficient — the expense ratio , which is defined as ;

  • Sonic conductance — acoustic conductivity in steady state;

  • Orifice area based on geometry — the size of the flow restriction.

Values

Orifice area based on geometry | Cv flow coefficient | Kv flow coefficient | Sonic conductance
Default value

Orifice area based on geometry
Program usage name

valve_parameterization
Evaluatable

No

# Discharge coefficient — expiration rate

Details

The correction factor is the ratio of the actual mass flow to the theoretical mass flow.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Orifice area based on geometry.

Default value

0.64
Program usage name

C_d
Evaluatable

Yes

# Leakage flow fraction — cost ratio

Details

The ratio of flow through a closed and through an open hole.

Default value

1.0e-6
Program usage name

leakage_fraction
Evaluatable

Yes

# Smoothing factor — numerical smoothing factor

Details

The continuous smoothing coefficient, which ensures smooth opening by correcting the characteristic of the hole in the almost open and almost closed positions.

Default value

0.01
Program usage name

smoothing_factor
Evaluatable

Yes

# Laminar flow pressure ratio — the pressure ratio at which the flow transitions between laminar and turbulent modes

Details

The ratio of outlet pressure to inlet pressure at which the flow transitions between laminar and turbulent flow modes.

Typical values range from 0.995 before 0.999.

Default value

0.999
Program usage name

B_laminar
Evaluatable

Yes

# Cross-sectional area at ports A and B — the area at the inlet or outlet of the valve
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

This area is used when calculating the mass flow through ports.

The ports have the same size. The value of this parameter must correspond to the area of the inlet of the component to which the unit is connected.

Units

m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac
Default value

0.01 m^2
Program usage name

port_area
Evaluatable

Yes

# Maximum Cv flow coefficient — the flow rate corresponding to the maximum opening area

Details

The value of the flow coefficient , when the cross-sectional area of the hole is maximal. The flow coefficient determines the dependence of the throughput on the pressure drop.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Cv flow coefficient.

Default value

4.0
Program usage name

C_v_max
Evaluatable

Yes

# xT pressure differential ratio factor at choked flow — critical pressure drop ratio

Details

The ratio between inlet pressure and the outlet pressure , defined as at which point the flow becomes critical. If this value is not known, it can be found in Table 2 in ISA-75.01.01. [3]. Default value 0.7 suitable for many valves.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Cv flow coefficient.

Default value

0.7
Program usage name

delta_p_ratio_C_v
Evaluatable

Yes

# Maximum Kv flow coefficient — the flow rate corresponding to the maximum opening area

Details

The value of the flow coefficient, , when the cross-sectional area of the hole is maximal. The flow coefficient determines the dependence of the throughput on the pressure drop.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Kv flow coefficient.

Default value

3.6
Program usage name

K_v_max
Evaluatable

Yes

# xT pressure differential ratio factor at choked flow — critical pressure drop ratio

Details

The ratio between inlet pressure and the outlet pressure , defined as at which point the flow becomes critical. If this value is not known, it can be found in table 2 in ISA-75.01.01 [3]. Default value 0.7 suitable for many valves.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Kv flow coefficient.

Default value

0.7
Program usage name

delta_p_ratio_K_v
Evaluatable

Yes

# Maximum sonic conductance — acoustic conductivity corresponding to the maximum hole area
l/(bar*s) | gal/(min*psi) | m^3/(Pa*s)

Details

The value of acoustic conductivity, when the cross-sectional area of the hole is maximum.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Units

l/(bar*s) | gal/(min*psi) | m^3/(Pa*s)
Default value

12.0 l/(bar*s)
Program usage name

C_max
Evaluatable

Yes

# Critical pressure ratio — critical pressure ratio

Details

The pressure ratio at which the flow becomes critical and the flow velocity reaches a maximum determined by the local speed of sound. The ratio between the outlet pressure and inlet pressure : .

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Default value

0.3
Program usage name

B_critical_linear
Evaluatable

Yes

# Subsonic index — the value of the degree used to calculate the mass flow rate in subsonic flow mode

Details

An empirical value used for more accurate calculation of mass flow rate in subsonic flow mode.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Default value

0.5
Program usage name

m
Evaluatable

Yes

# ISO reference temperature — reference temperature according to ISO 8778
K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR

Details

The temperature in the standard reference atmosphere in the ISO 8778 standard.

The ISO reference parameter values need to be adjusted only if acoustic conductivity values obtained with excellent reference values are used.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Units

K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR
Default value

293.15 K
Program usage name

T_reference
Evaluatable

Yes

# ISO reference density — reference density according to ISO 8778
kg/m^3 | g/m^3 | g/cm^3 | g/mm^3 | lbm/ft^3 | lbm/gal | lbm/in^3

Details

The density in the standard reference atmosphere in the ISO 8778 standard.

The ISO reference parameter values need to be adjusted only if acoustic conductivity values obtained with excellent reference values are used.

Dependencies

To use this parameter, set for the parameter Valve parameterization meaning Sonic conductance.

Units

kg/m^3 | g/m^3 | g/cm^3 | g/mm^3 | lbm/ft^3 | lbm/gal | lbm/in^3
Default value

1.185 kg/m^3
Program usage name

rho_reference
Evaluatable

Yes

Literature

  1. ISO 6358-3. «Pneumatic fluid power — Determination of flow-rate characteristics of components using compressible fluids — Part 3: Method for calculating steady-state flow rate characteristics of systems». 2014.

  2. IEC 60534-2-3. «Industrial-process control valves — Part 2-3: Flow capacity — Test procedures». 2015.

  3. ANSI/ISA-75.01.01. «Industrial-Process Control Valves — Part 2-1: Flow capacity — Sizing equations for fluid flow underinstalled conditions». 2012.

  4. P. Beater. «Pneumatic Drives.» Springer-Verlag Berlin Heidelberg. 2007.