Axial hydraulic static force exerted on valve
The Valve Hydraulic Force block simulates axial hydraulic static force exerted on a valve by fluid flowing through the orifice. The relationship between the valve opening, the pressure drop, and the force is provided as a two-dimensional table, which is processed by the PS Lookup Table (2D) block. The table can be obtained experimentally or analytically and can represent both the hydraulic static axial force and pressure forces. The force matrix must be rectangular and contain as many rows as there are pressure differential measurements and as many columns as there are valve openings. The pressure differential and opening vectors must be arranged in strictly ascending order and cover the whole range of valve operation. Connect the block in parallel with the orifice whose flow induces the force.
Connections A and B are hydraulic conserving ports that should be connected to the valve block ports in such a way as to monitor the pressure differential across the valve. Connection S is a physical signal port that provides the valve control member displacement. Connection F is a physical signal port that outputs the hydraulic axial force value. This port should be connected to the control port of an Ideal Force Source block. The pressure differential inside the block is determined as . The force orientation is specified by the table values and can be positive or negative with respect to the globally assigned positive direction, depending on the value of the Orifice orientation parameter.
No transient effects can be simulated.
Orifice initial opening. The parameter can be positive (underlapped
orifice), negative (overlapped orifice), or equal to zero for zero
lap configuration. The default value is
The parameter is introduced to specify the effect of the valve
opening on the valve force. The parameter can be set to one of two
Opens in positive direction or
in negative direction. The value
Opens in positive
direction specifies an orifice that opens when the valve
is shifted in the globally assigned positive direction. The default
Opens in positive direction.
Specify the vector of input values for valve openings as a one-dimensional
array. The input values 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 cubic or spline interpolation.
The default values, in meters, are
The Tabulated valve openings values will be used
together with Tabulated pressure differentials for
two-dimensional table lookup in the Hydraulic axial force
Specify the vector of input values for pressure differentials
as a one-dimensional array. 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 cubic or
spline interpolation. The default values, in Pa, are
Specify the hydraulic axial force as an
m is the number of valve openings and
the number of pressure differentials. Each value in the matrix specifies
an axial force corresponding to a specific combination of valve opening
and pressure differential. The matrix size must match the dimensions
defined by the input vectors. The default values, in N, are:
[0, -127.3576, -27.8944, 227.2513, 575.3104; ... 0, -95.5182, -20.9208, 170.4385, 431.4828; ... 0, -63.6788, -13.9472, 113.6256, 287.6552; ... 0, -31.8394, -6.9736, 56.8128, 143.8276; ... 0, 0, 0, 0, 0; ... 196.3495, 120.7506, 97.5709, 111.9898, 150.9306; ... 392.6991, 241.5013, 195.1418, 223.9797, 301.8613; ... 589.0486, 362.2519, 292.7126, 335.9695, 452.7919; ... 785.3982, 483.0025, 390.2835, 447.9594, 603.7225]
Select one of the following interpolation methods for approximating the output value when the input value is between two consecutive grid points:
Linear — Uses a
bilinear interpolation algorithm, which is an extension of linear
interpolation for functions in two variables.
Cubic — Uses the
bicubic interpolation algorithm.
Spline — Uses the
bicubic spline interpolation algorithm.
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 — Extrapolates
using the linear method (regardless of the interpolation method specified),
based on the last two output values at the appropriate end of the
range. That is, the block uses the first and second specified output
values if the input value is below the specified range, and the two
last specified output values if the input value is above the specified
Nearest — Uses the
last specified output value at the appropriate end of the range. That
is, the block uses the last specified output value for all input values
greater than the last specified input argument, and the first specified
output value for all input values less than the first specified input
The block has the following ports:
Hydraulic conserving port associated with a valve port.
Hydraulic conserving port associated with another valve port to monitor the pressure differential.
Physical signal port that provides the valve control member displacement.
Physical signal port that outputs hydraulic axial force.
The following example shows a model of a poppet valve built of a Poppet Valve block and a Valve Hydraulic Force block. The Valve Hydraulic Force block is connected in parallel and provides tabulated data to compute hydraulic force acting on the valve. The force value is exported through the F port.