Needle Valve (IL)

A needle valve in an isothermal fluid network.

blockType: EngeeFluids.IsothermalLiquid.Valves.FlowControl.Needle

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/Physical Modeling/Fluids/Isothermal Liquid/Valves & Orifices/Flow Control Valves/Needle Valve (IL)

Description

Block Needle Valve (IL) simulates flow reduction using a needle valve. The valve consists of a conical needle and a round seat with sharp edges. The needle valve opens or closes according to the displacement signal in port S. A positive signal means retraction of the needle and opening of the valve.

Opening Square

The diagram of the needle valve is shown in the figure.

needle valve il 1 en

needle valve il 2 en

The valve opening area is calculated as follows:

where

— the vertical distance between the outer edge of the needle and the seat, as shown in the diagram above;
— the angle of opening of the conical seat, which always corresponds to the value of the parameter Needle cone angle;
— parameter value Seat orifice diameter;
— parameter value Leakage area.

The hole area is limited by the maximum displacement :

For any needle displacement exceeding , value is the sum of the maximum hole area and the parameter value. Leakage area:

For any combination of the input value S and the needle offset that is less than 0, the minimum valve area is Leakage area.

If the parameter Smoothing factor if it is not equal to zero, then a smooth change in the offset value between 0 and .

The equation of conservation of mass

The equation of conservation of mass:

The mass flow through the valve is calculated as:

where

— flow coefficient, the value of the parameter Discharge coefficient;
— valve opening area;
— parameter value Cross-sectional area at ports A and B;
— the average density of the liquid;
— pressure difference in the valve .

Critical pressure drop, — pressure drop, determined from the value of the critical Reynolds number , set by the parameter Critical Reynolds number, which is the transition point of the regime between laminar and turbulent flow:

Pressure loss allows you to take into account the decrease in pressure in the valve due to a decrease in its area and is calculated as:

Pressure recovery describes a positive pressure change in the valve due to an increase in area. To ignore pressure recovery, uncheck the box. Pressure recovery. In this case, the pressure loss is .

Ports

Conserving

# A — Isothermal liquid port
Isothermal liquid

Details

A hole for the entry or exit of liquid.

Program usage name

port_a

# B — Isothermal liquid port
Isothermal liquid

Details

A hole for the entry or exit of liquid.

Program usage name

port_b

Input

# S — needle displacement, m
scalar

Details

The movement of the control element in m, specified as a scalar. A positive value retracts the needle and opens the valve.

Data types	`Float64`
Complex numbers support	I don’t

Parameters

# Seat orifice diameter — seat diameter
m | cm | ft | in | km | mi | mm | um | yd

Details

The diameter of the seat opening.

Units	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`0.005 m`
Program usage name	`orifice_diameter`
Evaluatable	Yes

# Needle cone angle — angle of opening of the conical needle
deg | rad | rev | mrad

Details

Opening angle the conical needle of the valve.

Cm. Needle valve diagram.

Units	`deg` \| `rad` \| `rev` \| `mrad`
Default value	`90.0 deg`
Program usage name	`cone_angle`
Evaluatable	Yes

# Needle position when in the seat — needle displacement
m | cm | ft | in | km | mi | mm | um | yd

Details

Needle displacement when the valve is closed. A positive value other than zero indicates that the valve is partially open. A negative value other than zero indicates a closed valve, which remains closed during the initial displacement specified by the scalar at the inlet S.

Units	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`0.0 m`
Program usage name	`min_control_displacement`
Evaluatable	Yes

# Leakage area — the gap area in the fully closed position
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

The sum of all clearances when the valve is in the fully closed position. Any area less than this value is equal to the specified leakage area. This parameter contributes to the stability of the numerical solution by maintaining the continuity of the flow.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`1.0e-10 m^2`
Program usage name	`leakage_area`
Evaluatable	Yes

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

Details

The cross-sectional area at the input and output ports A and B. This area is used when calculating the mass flow through the valve.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`Inf m^2`
Program usage name	`port_area`
Evaluatable	Yes

# Discharge coefficient — expense ratio

Details

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

Default value	`0.64`
Program usage name	`C_d`
Evaluatable	Yes

# Critical Reynolds number — upper limit of the Reynolds number for laminar flow

Details

The upper limit of the Reynolds number for laminar flow through the valve.

Default value	`150.0`
Program usage name	`Re_critical`
Evaluatable	Yes

# Smoothing factor — numerical smoothing factor

Details

The continuous smoothing coefficient, which ensures smooth opening by correcting the valve characteristics in the almost open and almost closed positions. Set a non-zero value less than one to increase the stability of the simulation in these modes.

Default value	`0.01`
Program usage name	`smoothing_factor`
Evaluatable	Yes

# Pressure recovery — accounting for increased pressure during expansion of the area

Details

Determines whether an increase in pressure will be taken into account when liquid flows from an area with a smaller cross-sectional area to an area with a larger cross-sectional area.

Default value	`false (switched off)`
Program usage name	`pressure_recovery`
Evaluatable	Yes