DCV_3_2_PAT $—$ Directional Control Valve with first-order spool dynamics, a spool with 3 ports, and 2 stable positions; when in the not activated position, ports P and A are connected and port T is closed

The DCV_3_2_PAT component describes a directional control valve with first-order spool dynamics, a spool with 3 ports, and 2 stable positions. When in the not activated position, ports P and A are connected and port T is closed.

The laminar/turbulent flow through the valve is modeled as flow through orifices without cavitation. The commanded opening of the valve is input at $\mathrm{commandB}$.

The parameter qnom gives the nominal flow rate of the fully opened flow path at the pressure drop ${\mathrm{Δp}}_{\mathrm{nom}}$.

${A}_{\mathrm{max}}={q}_{\mathrm{nom}}\sqrt{\frac{1}{2}\frac{\mathrm{\rho }{k}_{2}}{{\mathrm{Δp}}_{\mathrm{nom}}}}$

${d}_{\mathrm{max}}=2\sqrt{\frac{{A}_{\mathrm{max}}}{\mathrm{\pi }}}$

For example, the maximum diameter for the flow path from P to T is given by ${d}_{\mathrm{max}\left(\mathrm{PB}\right)}$:

${A}_{\mathrm{max}\left(\mathrm{PT}\right)}={q}_{\mathrm{nom}\left(\mathrm{PT}\right)}\sqrt{\frac{1}{2}\frac{\mathrm{\rho }{k}_{2}}{{\mathrm{Δp}}_{\mathrm{nom}}}}$

${d}_{\mathrm{max}\left(\mathrm{PT}\right)}=2\sqrt{\frac{{A}_{\mathrm{max}\left(\mathrm{PB}\right)}}{\mathrm{\pi }}}$

There is leakage flow modeled when the respective flow path is nominally closed. The position of the spool is modeled as a first-order system.

Input signal: $\mathrm{commandB}$.

 Command signals Flow paths and diameter of metering orifice $\mathrm{commandB}=\mathrm{false}$ Flow from P $\to$ A. T is closed. Flow diameter from P $\to$ T: $\mathrm{dleak}$. Flow diameter from P $\to$ A: $\mathrm{dmax_P_A}+\mathrm{dleak}$. $\mathrm{commandB}=\mathrm{true}$ Flow from P $\to$ T. A is closed. Flow diameter from P $\to$ T: $\mathrm{dmax_P_T}+\mathrm{dleak}$. Flow diameter from P $\to$ A: $\mathrm{dleak}$.

When the pump pressure and the flow rate are high, the unbalanced forces and flow forces acting on the spool are higher than the force generated by the solenoid and the valve is partially closed. The effect can be modeled by the parameters P_max and coeff_P. Specify the maximum hydraulic power in $W$ (where the valve is still completely open) and use coeff_P to adjust the model to the manufacturer's data. When the specified hydraulic power is exceeded, a warning is printed in the log window (Mode Simulation / Simulation / Show Log).

The movement of the spool is described by a first-order system. This is appropriate for valves that are directly actuated by a spool. The time to shift from the neutral position to an end position (${\mathrm{\tau }}_{\mathrm{opening}}$) may be different than the time to shift to the neutral position (${\mathrm{\tau }}_{\mathrm{closing}}$).

Use the modifier(s)

VolumeA(port_A(p(start=1e5,fixed=true)))

and/or

VolumeB(port_A(p(start=1e5,fixed=true)))

and/or

VolumeP(port_A(p(start=1e5,fixed=true)))

to set the initial condition(s) for the pressure of the lumped volume(s) $\left[\mathrm{Pa}\right]$.

Note: There are also valves that close all three ports in the intermediate position.

Events

There is a new boolean reduceEvents (selected by default) in the Advanced section under the Properties tab ( ). Selecting reduceEvents lets the model use noEvents(expr) to generate fewer events for boolean expressions that should not generate events. In some cases the solver might reduce the stepsize too much and generate a lot of steps. If this happens, try clearing reduceEvents.

Variables

 Name Value Units Description Modelica ID $\mathrm{p_A}\left(\mathrm{summary}\right)$ $\mathrm{spool_32.p_A}$ $\mathrm{Pa}$ Pressure at port A summary_pA $\mathrm{p_P}\left(\mathrm{summary}\right)$ $\mathrm{spool_32.p_P}$ $\mathrm{Pa}$ Pressure at port P summary_pP $\mathrm{p_T}\left(\mathrm{summary}\right)$ $\mathrm{spool_32.p_T}$ $\mathrm{Pa}$ Pressure at port T summary_pT ${\mathrm{Δp}}_{\mathrm{PA}\left(\mathrm{summary}\right)}$ [1] $\mathrm{Pa}$ Pressure drop summary_dp_PA ${\mathrm{Δp}}_{\mathrm{AT}\left(\mathrm{summary}\right)}$ [2] $\mathrm{Pa}$ Pressure drop summary_dp_AT ${V}_{A}$ VolumeA ${V}_{P}$ VolumeP $\mathrm{coil}$ coil $\mathrm{spool_32}$ spool_3_2 ${V}_{T}$ VolumeT $\mathrm{q_PA}\left(\mathrm{summary}\right)$ $\mathrm{spool_32.mor_PA.q}$ $\frac{{m}^{3}}{s}$ Flow rate flowing port_P to port_A summary_qPA $\mathrm{q_AT}\left(\mathrm{summary}\right)$ $\mathrm{spool_32.mor_AT.q}$ $\frac{{m}^{3}}{s}$ Flow rate flowing port_P to port_A summary_qAT

[1] $\mathrm{spool_32.port_P.p}-\mathrm{spool_32.port_A.p}$

[2] $\mathrm{spool_32.port_A.p}-\mathrm{spool_32.port_T.p}$

Connections

 Name Description Modelica ID ${\mathrm{port}}_{A}$ Port A, one of valve connections to actuator or motor port_A ${\mathrm{port}}_{P}$ Port P, where oil enters the component from the pump port_P ${\mathrm{port}}_{T}$ Port T, where oil flows to the tank port_T $\mathrm{commandB}$ Command signal for valve commandB $\mathrm{oil}$ oil

Parameters

General Parameters

 Name Default Units Description Modelica ID use volume A $\mathrm{true}$ If true, a volume is present at port_A useVolumeA use volume B $\mathrm{true}$ If true, a volume is present at port_B useVolumeB use volume P $\mathrm{true}$ If true, a volume is present at port_P useVolumeP use volume T $\mathrm{true}$ If true, a volume is present at port_T useVolumeT ${V}_{A}$ ${10}^{-6}$ ${m}^{3}$ Geometric volume at port A volumeA ${V}_{B}$ ${10}^{-6}$ ${m}^{3}$ Geometric volume at port B volumeB ${V}_{P}$ ${10}^{-6}$ ${m}^{3}$ Geometric volume at port P volumeP ${V}_{T}$ ${10}^{-6}$ ${m}^{3}$ Geometric volume at port T volumeT ${\mathrm{ΔT}}_{\mathrm{system}}$ $0$ $K$ Temperature offset from system temperature dT_system

 Name Default Units Description Modelica ID reduce events $\mathrm{true}$ If true, reduce event generation reduceEvents

Dynamic Parameters

 Name Default Units Description Modelica ID ${\mathrm{\tau }}_{\mathrm{opening}}$ $0.03$ $s$ Switching time to open valve 95 % tau_opening ${\mathrm{\tau }}_{\mathrm{closing}}$ $0.02$ $s$ Switching time to close valve 95 % tau_closing

Flow Parameters

 Name Default Units Description Modelica ID ${\mathrm{Δp}}_{\mathrm{nom}}$ $7.·{10}^{5}$ $\mathrm{Pa}$ Pressure drop at nominal flow rate qnom dpnom ${q}_{\mathrm{nom}\left(\mathrm{PA}\right)}$ $0.00158$ $\frac{{m}^{3}}{s}$ Nominal flow rate from P -> A qnom_P_A ${q}_{\mathrm{nom}\left(\mathrm{AT}\right)}$ ${q}_{\mathrm{nom}\left(\mathrm{PA}\right)}$ $\frac{{m}^{3}}{s}$ Nominal flow rate from A -> T qnom_A_T ${P}_{\mathrm{max}}$ $1.26·{10}^{5}$ $W$ Max. hydraulic power P_max ${\mathrm{coeff}}_{P}$ $10$ Influence of hydraulic power on flow rate coeff_P ${k}_{1}$ $10$ Laminar part of orifice model k1 ${k}_{2}$ $2$ Turbulent part of orifice model, ${k}_{2}=\frac{1}{{C}_{d}^{2}}$ k2

Spool Geometry Parameters

 Name Default Units Description Modelica ID ${d}_{\mathrm{leak}}$ $1.67·{10}^{-5}$ $m$ Diameter of equivalent orifice to model leakage of closed valve dleak