Spool Orifice - Round Holes (IL)
The hole between the spool and the sleeve with round windows or a rectangular window in the isothermal fluid network.
blockType: EngeeFluids.IsothermalLiquid.Orifices.Spool
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Spool Orifice - Round Holes (IL) Path in the library: |
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Spool Orifice - Rectangular Slot (IL) Path in the library: |
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Description
The Spool Orifice (IL) block simulates the flow through the hole between the spool and the sleeve with windows. The windows in the sleeve overlap and open when the spool is moved. They can be a series of round windows or a single rectangular window. The flow rate is calculated through the total cross-sectional area of the open holes between the sleeve with windows and the spool, which extends or slides in accordance with the signal received at port S. Multiple blocks Spool Orifice (IL) can be connected to simulate several sets of windows along several rows of windows along the axis of the spool pair.
Hydrodynamic force
The force resulting from the action of the fluid flow on the spool:
,
where
-
— mass flow through port A;
-
— density of the liquid;
-
— the area of the open hole, which is determined by the position of the spool and the geometry of the hole Orifice geometry.
-
— the angle of inclination of the jet, which is calculated using the approximate von Mises formula:
,
where — radial clearance between the spool and the sleeve Radial clearance, and — moving the spool;
-
— the direction of movement of the spool Orifice orientation, corresponding to the opening of the hole with a positive or negative signal on the port S.
The area of the open hole
Setting the Opening orientation parameter to Positive spool displacement opens the orifice means that the hole opens when the spool is extended, and in the value Negative spool displacement opens the orifice This means that the hole opens when the spool is retracted.
Gap cross-sectional area Leakage area , through which liquid can leak when the hole is closed, is considered a small area, which ensures the continuity of the numerical solution. In addition, a non-zero value of the Smoothing factor can provide increased stability of the numerical solution when the hole is in an almost closed or almost open position.
circular windows
If the Orifice geometry parameter is set to Round holes, then round windows with the same diameters and centers aligned in the same plane are defined evenly distributed around the perimeter of the sleeve.
The area of the open hole is calculated as:
,
where
-
The angle of the open hole it is determined from the control signal on port S:
;
-
— number of round windows;
-
— diameter of round windows;
-
— the cross-sectional area of the gap between the spool and the sleeve is defined as
;
-
— movement of the control element (spool):
,
where — the position of the control element when the opening is closed Control member position at closed orifice.
The maximum area of the open hole is defined as:
.
The right -angled window
If the Orifice geometry parameter is set to Rectangular slot, then a single rectangular window in the sleeve is set.
The area of the open hole is calculated as:
,
where — the width of the rectangular window Orifice width.
The maximum area of the open hole is defined as:
,
where — moving the spool between the closed and open state of the hole Spool travel between closed and open orifice.
With a minimum opening area, the leakage area is:
.
Numerical smoothing of displacement displacement
At the extreme points of the hole opening range, numerical stability of the simulation can be ensured by configuring the Smoothing factor parameter in the block. The block applies the smoothing function to the movement over the entire range, but primarily affects the modeling at the extreme points of this range.
If the Smoothing factor parameter is not equal to zero, the smooth movement of the spool is ensured, then the block smoothly saturates the opening of the hole in the range from before , where :
-
The value of the Diameter of round holes parameter, if the Orifice geometry parameter is set to
Round holes. -
The value of the Spool travel between closed and open orifice parameter, if the Orifice geometry parameter is set to
Rectangular slot.
The mass flow equation
The flow through the spool opening can be determined from the ratio of pressure and flow rate:
,
where
-
— consumption coefficient Discharge coefficient;
-
— Cross-sectional area at the entrance and exit of ports A and B Cross-sectional area at ports A and B;
-
— the average density of the liquid;
-
— the area of the open hole, except when:
-
The area of the open hole is greater than or equal to the area when moving the spool by a distance equal to Spool travel between closed and open orifice. The area of the hole in this case is defined as the maximum area of the open hole. .
-
The area of the open hole is less than or equal to the area of the minimum open hole. The area of the hole in this case is defined as .
-
-
— critical pressure drop, determined from the value of the critical Reynolds number Critical Reynolds number , which is the transition point between laminar and turbulent fluid flow:
;
-
— the coefficient of pressure loss during narrowing of the flow. Calculated as:
.
Pressure recovery Pressure recovery takes into account the increase in pressure at the outlet of the hole by increasing the cross-sectional area. If there is no need to take this effect into account, then set the value for the Pressure recovery parameter turned off, in this case it will be equal to 1.
Ports
Non-directional
A isothermal fluid port
isothermal liquid
The port of the isothermal fluid corresponds to the inlet or outlet of the hole.
B isothermal fluid port
isothermal liquid
The port of the isothermal fluid corresponds to the inlet or outlet of the hole.
Parameters
Orifice geometry — pass window type:q[<br>] Round holes (by default) | Rectangular slot
The geometry of the windows in the sleeve. Options to choose from:
-
Round holes (by default)— round windows are evenly distributed around the circumference of the sleeve, have the same diameters and centers aligned in the same plane. -
Rectangular slot— there is one rectangular window in the sleeve.
Diameter of round holes — diameter of round pass windows:q[<br>] 0.005 m (default) | positive scalar
The diameter of the round windows in the sleeve.
Dependencies
To use this parameter, set the Orifice geometry parameter to Round holes.
Number of round holes — number of round pass windows:q[<br>] 6 (default) | a positive integer
The number of round windows evenly distributed around the circumference of the sleeve.
Dependencies
To use this parameter, set the Orifice geometry parameter to Round holes.
Orifice width — the width of the rectangular pass window:q[<br>] 0.01 m (default) | positive scalar
The width of the rectangular window.
Dependencies
To use this parameter, set the Orifice geometry parameter to Rectangular slot.
Spool travel between closed and open orifice — maximum movement of the spool
0.005 m (default) | positive scalar
The maximum movement (stroke) of the spool. This value determines the upper limit of displacement to ensure the adequacy (physicality) of the simulation.
Dependencies
To use this parameter, set the Orifice geometry parameter to Rectangular slot.
Spool position at closed orifice — spool offset
0 m (default) | positive scalar
A negative non-zero value indicates a longitudinal (axial) backlash — the window remains open at the initial position of the spool, set by the signal on port S.
Flow force output — calculation of the axial hydrodynamic flow force acting on the spool
disabled (by default) | enabled
The parameter value determines whether the axial hydrodynamic force acting on the spool will be calculated. When this parameter is selected, an output port F is created, which displays the value of the axial hydrodynamic force acting on the spool in N.
Radial clearance — radial clearance between the spool and the sleeve
1e−5 m (default) | positive scalar
The value of the radial gap between the spool and the sleeve.
Dependencies
To use this parameter, set the Flow force output parameter to enabled.
Leakage area — clearance area in the closed pass position:q[<br>] 1e−10 m2 (default) | positive scalar
The sum of the areas of all the gaps when the windows are completely blocked. Any area less than this value is equal to the specified leakage area. This contributes to the stability of the numerical solution by maintaining the continuity of the flow.
Cross-sectional area at ports A and B — area at the entrance and exit of ports
Inf (default) | positive scalar
The cross-sectional area at the input and output ports A and B. This area is used when calculating the mass flow through the hole.
Opening orientation — the direction of movement of the spool corresponding to the opening of the pass hole:q[<br>] Positive spool displacement opens the orifice (by default) | Negative spool displacement opens the orifice
The direction of movement of the element corresponding to the opening of the hole. A positive orientation means that a positive signal on S opens the hole. A negative direction means that a negative signal on S opens the hole.
Discharge coefficient — flow rate
0.64 (default) | positive scalar
The correction factor is the ratio of the actual mass flow to the theoretical mass flow through the hole.
Critical Reynolds number — upper limit of the Reynolds number for laminar flow
150 (default) | positive scalar
The Reynolds number, at which the laminar flow regime through the hole is maintained.
Smoothing factor — numerical smoothing coefficient of
0.01 (default) | a positive scalar in the range [0,1]
A continuous smoothing coefficient that ensures smooth movement when the valve introduces a level of gradual change based on the flow characteristic when the valve is in the nearly open and nearly closed positions. Set a non-zero value less than one to increase the stability of the simulation in these modes.
Pressure recovery — accounting for pressure increase during expansion of the pass area:q[<br>] disabled (by default) | enabled
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.
If you uncheck Pressure recovery, this increase in pressure is not taken into account.