Fixed hydraulic orifice based on empirical data
Orifices
The Fixed Orifice Empirical block models a fixed orifice in hydraulic systems with data obtained from experimental testing. The data required for characterization is the set of pressure differentials across the orifice, together with associated flow rates determined for a particular fluid and temperature.
The flow rate through the orifice is determined with the table lookup block from the set of experimental measurements
q = f
(p)
where
q | Volumetric flow rate |
p | Pressure differential |
You can select from two interpolation and two extrapolation methods.
Note Extrapolation could result in large errors if the operating point deviates significantly from the area of experiments. |
The block positive direction is from port A to port B. This means that the flow rate is positive if it flows from A to B, and the pressure differential is determined as $$p={p}_{A}-{p}_{B}$$.
Specify the pressure differential vector as a one-dimensional
array. The vector contains values of pressure differentials obtained
during experimental characterization of the orifice. The vector must
be strictly increasing. The values can be nonuniformly spaced. The
minimum number of values depends on the interpolation method: you
must provide at least two values for linear interpolation, at least
three values for smooth interpolation. The default values, in bar,
are [-40.0, -30.0, -20.0, -10.0, -5.0, 0.0, 5.0, 10.0, 20.0,
30.0, 40.0]
.
Specify the vector of flow rates through the orifice, corresponding
to these pressure differentials, as a one-dimensional array. The vector
must be of the same size as the Tabulated pressure differentials vector.
The default values, in m^3/s, are [ -0.0024436 -0.0021248
-0.0016852 -0.0012248 -8.4476e-4 0 8.5333e-4 0.0012068 0.0017067 0.0020902
0.0024136 ]
.
Select one of the following interpolation methods for approximating the output value when the input value is between two consecutive grid points:
Linear
— Select
this option to get the best performance.
Smooth
— Select
this option to produce a continuous curve with continuous first-order
derivatives.
For more information on interpolation algorithms, see the PS Lookup Table (1D) block reference page.
Use extrapolation with extreme caution, because moving beyond the measurement limits could result in large errors. Select one of the following extrapolation methods for determining the output value when the input value is outside the range specified in the argument list:
Linear
— Select
this option to produce a curve with continuous first-order derivatives
in the extrapolation region and at the boundary with the interpolation
region.
Nearest
— Select
this option to produce an extrapolation that does not go above the
highest point in the data or below the lowest point in the data.
For more information on extrapolation algorithms, see the PS Lookup Table (1D) block reference page.
The block has the following ports:
A
Hydraulic conserving port associated with the orifice inlet.
B
Hydraulic conserving port associated with the orifice outlet.