Hydraulic ball valve
Flow Control Valves
The Ball Valve block models a variable orifice created by a spherical ball and a round sharp-edged orifice.
The flow rate through the valve is proportional to the valve opening and to the pressure differential across the valve. The flow rate is determined according to the following equations:
|pA, pB||Gauge pressures at the block terminals|
|CD||Flow discharge coefficient|
|A(h)||Instantaneous orifice passage area|
|x||Ball displacement from initial position, controlled by the physical input signal at port S|
|ν||Fluid kinematic viscosity|
|pcr||Minimum pressure for turbulent flow|
|Recr||Critical Reynolds number|
|DH||Valve instantaneous hydraulic diameter|
|Aleak||Closed valve leakage area|
|Amax||Maximum valve open area|
|hmax||Maximum valve opening|
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 . Positive signal at the physical
S opens the valve.
Fluid inertia is not taken into account.
The flow passage area is assumed to be equal to the side surface of the frustum of the cone located between the ball center and the orifice edge.
The diameter of the valve ball. It must be greater than the
orifice diameter. The default value is
The diameter of the orifice of the valve. The default value
The initial opening of the valve. Its value must be nonnegative.
The default value is
Semi-empirical parameter for valve capacity characterization.
Its value depends on the geometrical properties of the orifice, and
usually is provided in textbooks or manufacturer data sheets. The
default value is
The maximum Reynolds number for laminar flow. The transition
from laminar to turbulent regime is assumed to take place when the
Reynolds number reaches this value. The value of the parameter depends
on the orifice geometrical profile. You can find recommendations on
the parameter value in hydraulics textbooks. The default value is
The total area of possible leaks in the completely closed valve.
The main purpose of the parameter is to maintain numerical integrity
of the circuit by preventing a portion of the system from getting
isolated after the valve is completely closed. The parameter value
must be greater than 0. The default value is
Parameters determined by the type of working fluid:
Fluid kinematic viscosity
The block has the following ports:
Hydraulic conserving port associated with the valve inlet.
Hydraulic conserving port associated with the valve outlet.
Physical signal port to control ball displacement.