Poppet with Seat at B (IL-PB)

R2026b

Poppet with seat at port B for hydromechanical valves

Since R2026b

• 

Poppet with Seat at B (IL-PB) block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Simscape / Fluids / Isothermal Liquid / Valves & Orifices / Hydromechanical Valves

Description

The Poppet with Seat at B (IL-PB) block represents a poppet and valve seat with the poppet at port B. The metering area increases as the poppet moves in the positive direction relative to the valve seat, which is toward port F. This movement creates a flow path between ports Af and B. To model this component with the poppet on the opposite side, use the Poppet with Seat at F (IL-PB) block.

Use the Flow momentum force model parameter to specify the method the block uses to calculate the flow momentum force. The block always models the pressure force. When you select Liquid flows around poppet to port F, the block calculates the pressure force by multiplying by the seat area by the fluid pressure difference across the block. Otherwise, the block calculates the pressure force from the seat area and the gauge pressure at B.fluid. A positive fluid force pushes the poppet in the positive direction, and a negative fluid force pushes the poppet in the negative direction.

Port Relations

Ports F and B are hydromechanical valve composite ports that have valve_body, spool, and fluid nodes, where:

• The position of B.valve_body is equal to the position of F.valve_body.

• The position of F.spool relative to B.spool is equal to the value of the Poppet length along valve axis parameter.

• The valve lift is the position of B.spool relative to B.valve_body. When the valve lift is 0, a hard stop engages.

Governing Equations

The mass flow rate through the fluid flow path is

$$\dot{m}=\frac{\Delta p}{{\left(\Delta p^2+\Delta p_{crit}{}^2\right)}^{1/4}}{\left(\frac{2{\rho }_{avg}}{1-A_r{}^2}\right)}^{1/2}{C}_{d}A,$$

where:

• Δp is the pressure differential.

• Δp_crit is the critical pressure differential.

• ρ_avg is the average fluid density.

• A_r is the ratio from the metering area to the connecting area.

• C_d is the value of the Discharge coefficient parameter.

• A is the metering area.

The critical pressure differential is

$$\Delta p_{crit}=\frac{\pi }{4}\frac{{\rho }_{avg}}{2A}{\left(\frac{R{e}_c\nu }{C_d}\right)}^2,$$

where:

• Re_c is the value of the Critical Reynolds number parameter.

• ν is the fluid kinematic viscosity.

When you set Flow momentum force model to Based on poppet and seat geometry or Based on tabulated jet angle, the flow momentum force is

$$F_{Flow}=\frac{{\dot{m}}^2}{{\rho }_{\text{avg}}}\left(\frac{1}{A_{\max }}-\frac{\cos (\alpha )}{A}\right),$$

where A_max is the maximum metering area and α is the jet angle. If Flow momentum force model is Based on poppet and seat geometry, the block calculates α depending on the block geometry. If Flow momentum force model is Based on tabulated jet angle, the block interpolates α from the Poppet lift vector for jet angle, Jet angle vector for inflow through seat, and Jet angle vector for outflow through seat parameters.

When you set Flow momentum force model to None, F_Flow is 0. However, the block still models the pressure force.

Metering Area

The metering area depends on the poppet and seat geometry.

Conical Poppet

When Poppet geometry is Conical, the metering area for both seat geometries is

$$A=\pi x\sin \frac{\gamma }{2}\left(d_s-\frac{x}{2}\sin \gamma \right),$$

where:

• γ is the value of the Poppet cone angle parameter.

• d_s is the value of the Seat hole diameter parameter.

• x is the lift between poppet and seat.

The maximum metering area is

$$A_{max}=\frac{\pi d_s^2}{4}.$$

The maximum metering area occurs when the valve lift is greater than or equal to

$$x_{max}=\frac{d_s}{\sin \gamma }\left(1-\sqrt{1-\cos \frac{\gamma }{2}}\right).$$

The jet angle is ɑ = γ/2.

Cylindrical Poppet

When Poppet geometry is Cylindrical and Seat geometry is Sharp-edged, the metering area is

$$A=\pi d_{s}x.$$

The maximum metering area is

$$A_{max}=\frac{\pi d_s^2}{4}.$$

The maximum metering area occurs when the valve lift is greater than or equal to x_max = d_s/4. The block assumes that the jet angle is 90°.

When Poppet geometry is Cylindrical and Seat geometry is Conical, the metering area is

$$A=\pi x\sin \frac{\gamma }{2}(d_p+\frac{x}{2}\sin \gamma )\text{ ,}$$

where d_p is the value of the Poppet diameter parameter.

The maximum metering area is

$$A_{max}=\frac{\pi d_s^2}{4}.$$

The maximum metering area occurs when the valve lift is greater than or equal to

$$x_{max}=\frac{d_p}{\sin \gamma }\left(-1+\sqrt{1+{\left(\frac{d_s}{d_p}\right)}^2\cos \frac{\gamma }{2}}\right).$$

The jet angle is ɑ = γ/2.

Spherical Poppet

When Poppet geometry is Spherical and Seat geometry is Sharp-edged, the metering area is

$$A=\pi r_s\sqrt{{\left(x+G\right)}^2+r_s^2}\left(1-\frac{r_p^2}{r_s^2+{(x+G)}^2}\right),$$

where:

• r_s is the seat radius.

• r_p is the poppet radius.

• $$G=\sqrt{r_p^2-r_s^2}.$$

The maximum metering area is

$$A_{max}=\frac{\pi d_s^2}{4}.$$

The maximum metering area occurs when the valve lift is greater than or equal to

$$x_{max}=\sqrt{\frac{2r_p^2-r_s^2+r_s\sqrt{4r_p^2+r_s^2}}{2}}-G.$$

The jet angle is

$$\alpha =\arctan \frac{x+G}{r_s}.$$

When Poppet geometry is Spherical and Seat geometry is Conical, the metering area equations vary depending on the expression $$r_p\cos \frac{\gamma }{2}.$$

If $$r_p\cos \frac{\gamma }{2}\ge r_s,$$ the metering area and maximum metering area are

$$\begin{array}{l}A=\frac{\pi }{2}\sin \gamma \left(d_{p}x+x^2\sin \frac{\gamma }{2}\right)\\ A_{max}=\frac{\pi d_s^2}{4}\end{array}$$

The maximum metering area occurs when the valve lift is greater than or equal to

$$x_{max}=\frac{d_p}{2\sin \frac{\gamma }{2}}\left(-1+\sqrt{1+{\left(\frac{d_s}{d_p}\right)}^2\frac{1}{\cos \frac{\gamma }{2}}}\right)$$

The jet angle is ɑ = γ/2.

If $$r_p\cos \frac{\gamma }{2}<r_s,$$ the metering area and maximum metering area are

$$\begin{array}{l}A=\{\begin{array}{ll}\pi r_s\sqrt{{\left(x+G\right)}^2+r_s^2}\left(1-\frac{r_p^2}{{\left(x+G\right)}^2+r_s^2}\right),\hfill & x<x_{switch}\hfill \\ \frac{\pi }{2}\sin \gamma \left(d_p{x}_2+x_2^2\sin \frac{\gamma }{2}\right),\hfill & x\ge x_{switch}\hfill \end{array}\\ A_{max}=\frac{\pi d_s^2}{4}\end{array}$$

where

$$\begin{array}{l}{x}_2=x-x_{switch}+x_{2_{switch}} \\ x_{switch}=r_s\tan \frac{\gamma }{2}-G\\ x_{2_{switch}}=\frac{2r_s}{\sin \gamma }-\frac{r_p}{\sin \frac{\gamma }{2}}\end{array}$$

The jet angle is

$$\alpha =\{\begin{array}{ll}\arctan \frac{x+G}{r_s},\hfill & x<x_{switch}\hfill \\ \frac{\gamma }{2},\hfill & x\ge x_{switch}\hfill \end{array}$$

Block Sub-Components

The Poppet with Seat at B (IL-PB) block is equivalent to a composite component that comprises these Simscape Foundation and Fluids library blocks:

• Hydromechanical Valve Interface (IL-PB)

• Local Restriction (IL)

• Pressure Sensor (IL)

• Ideal Translational Motion Sensor

• Mass (PB), if you select Enable poppet mass.

• Force Actuator (PB)

• Translational Hard Stop (PB)

• Translational Spacer (PB)

This image shows the equivalent diagram when you select Liquid flows around poppet to port F:

This image shows the equivalent diagram when you clear Liquid flows around poppet to port F:

Variables

To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.

Examples

New

Hydromechanical Poppet Check Valve

Build a check valve with a poppet design using components from the Hydromechanical Valves library and compares it to the behavioral Check Valve (IL) block.

• Since R2026b
• Open Live Script

Ports

Conserving

B — Valve seat, poppet, and fluid

hydromechanical valve composite

Hydromechanical valve composite port that comprises three nodes:

• B.valve_body — Position-based translational node along the valve body. This node represents the valve seat.

• B.spool — Position-based translational node that moves along the valve element. This node represents the front of the poppet, which contacts the valve seat.

• B.fluid — Isothermal liquid node associated with the flow path inside the valve. This node represents liquid flow to and from the adjacent component through the valve seat.

Programmatic Use

Port: B

F — Valve seat, poppet, and fluid

hydromechanical valve composite

Hydromechanical valve composite port that comprises three nodes:

• F.valve_body — Position-based translational node along the valve body. This node represents the valve seat.

• F.spool — Position-based translational node that moves along the valve element. This node represents the back of the poppet.

• F.fluid — Isothermal liquid node associated with the flow path inside the valve. If you select Liquid flows around poppet to port F, this node represents the fluid of the adjacent valve component behind the poppet. Otherwise, this node is unused and the adjacent valve component on this side cannot contain liquid.

Programmatic Use

Port: F

Af — Liquid entry or exit

isothermal liquid

Isothermal liquid conserving port associated with the liquid flow around the side of the poppet.

Programmatic Use

Port: Af

Parameters

Flow Metering

Poppet geometry — Type of poppet

Conical (default) | Cylindrical | Spherical

Shape of the poppet.

Programmatic Use

Parameter:	poppet_geometry
Values:	"fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.PoppetGeometry.Conical" | "fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.PoppetGeometry.Cylindrical" | "fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.PoppetGeometry.Spherical"

Seat geometry — Type of seat

Conical (default) | Sharp-edged

Shape of the valve seat.

Programmatic Use

Parameter:	seat_geometry
Values:	"fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.SeatGeometry.Conical" | "fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.SeatGeometry.SharpEdged"

Poppet cone angle — Angle of cone for conical stem

120 deg (default) | positive scalar

Cone angle for the conical poppet stem.

Dependencies

To enable this parameter, set Poppet geometry to Conical.

Programmatic Use

Parameter: poppet_cone_angle

Poppet diameter — Diameter of poppet

0.1 m (default) | positive scalar

Diameter of the poppet.

Dependencies

To enable this parameter, set Poppet geometry to Spherical or set Poppet geometry to Cylindrical and Seat geometry to Conical.

Programmatic Use

Parameter: poppet_diameter

Seat cone angle — Angle of seat opening

120 deg (default) | positive scalar

Angle of the seat opening.

Dependencies

To enable this parameter, set Poppet geometry to Cylindrical or Spherical and Seat geometry to Conical.

Programmatic Use

Parameter: seat_cone_angle

Seat hole diameter — Diameter of seat hole

0.07 m (default) | positive scalar

Diameter of the opening in the seat.

Programmatic Use

Parameter: seat_diameter

Fraction of minimum to maximum metering area — Ratio of minimum to maximum metering area

1e-6 (default) | positive scalar

Ratio of the minimum metering area to the maximum metering area. The block uses this parameter to calculate the minimum metering area.

Programmatic Use

Parameter: min_area_fraction

Area of connecting fluid channel at valve seat — Cross-sectional area of fluid channel

0.01 m^2 (default) | positive scalar

Cross-sectional area of the fluid channel at the location of the valve seat.

Programmatic Use

Parameter: connecting_area

Discharge coefficient — Discharge coefficient

0.64 (default) | positive scalar in the range of [0,1]

Correction factor that accounts for discharge losses in theoretical flows.

Programmatic Use

Parameter: Cd

Critical Reynolds number — Upper Reynolds number limit for laminar flow

150 (default) | positive scalar

Upper Reynolds number limit for laminar flow through the component.

Programmatic Use

Parameter: Re_c

Poppet

Poppet length along valve axis — Length of poppet

0.05 m (default) | positive scalar

Length of the poppet along the valve axis.

Programmatic Use

Parameter: poppet_length

Enable poppet mass — Option to model poppet mass

off (default) | on

Option to model the mass of the poppet.

Programmatic Use

Parameter:	enable_poppet_mass
Values:	"true" | "false"

Poppet mass — Mass of poppet

0.5 kg (default) | positive scalar

Mass of the poppet.

Dependencies

To enable this parameter, select Enable poppet mass.

Programmatic Use

Parameter: poppet_mass

Liquid flows around poppet to port F — Option to model liquid flow to port F

on (default) | off

Option to model liquid flow to port F. If you select this parameter, the block models flow around the poppet and to the adjacent valve component behind the poppet. Otherwise, fluid does not flow to port F and the adjacent valve component on this side cannot contain liquid.

Select this parameter if the poppet position depends on the pressure difference across the front and back of the poppet. Clear this parameter if the poppet position depends on the gauge pressure in front of the poppet.

Programmatic Use

Parameter:	contains_liquid_F
Values:	"true" | "false"

Flow Effects

Flow momentum force model — Method for modeling flow momentum force

None (default) | Based on poppet and seat geometry | Based on tabulated jet angle

Method for modeling flow momentum force on the poppet. If you select None, the block does not model flow momentum force on the poppet.

Programmatic Use

Parameter:	flow_force_model
Values:	"fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.PoppetFlowForceModel.None" | "fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.PoppetFlowForceModel.PoppetSeatGeometry" | "fluids.isothermal_liquid.valves_orifices.hydromechanical_valves.enum.PoppetFlowForceModel.TabulatedJetAngle"

Poppet lift vector for jet angle — Poppet lift vector

0 : 0.002 : 0.01 m (default) | vector

Poppet lift values that correspond to the jet angle values for inflow and outflow through the seat.

Dependencies

To enable this parameter, set Flow momentum force model to Based on tabulated jet angle.

Programmatic Use

Parameter: lift_jet_TLU

Jet angle vector for inflow through seat — Jet angle values for inflow

60 * ones(1, 6) deg (default) | vector

Jet angle values for inflow through the seat. These values correspond to the values in the Poppet lift vector for jet angle parameter.

Dependencies

To enable this parameter, set Flow momentum force model to Based on tabulated jet angle.

Programmatic Use

Parameter: jet_angle_inflow_TLU

Jet angle vector for outflow through seat — Jet angle values for outflow

60 * ones(1, 6) deg (default) | vector

Jet angle values for outflow through the seat. These values correspond to the values in the Poppet lift vector for jet angle parameter.

Dependencies

To enable this parameter, set Flow momentum force model to Based on tabulated jet angle.

Programmatic Use

Parameter: jet_angle_outflow_TLU

Hard Stop

Hard stop model between poppet and seat — Hard stop model

Stiffness and damping applied smoothly through transition region, damped rebound (default) | Full stiffness and damping applied at bounds, undamped rebound | Full stiffness and damping applied at bounds, damped rebound

Method to use to model the hard stop:

• Stiffness and damping applied smoothly through transition region, damped rebound — Specify the transition region in which the force ramps up from zero. At the end of the transition region, the block applies the full stiffness and damping. This option applies damping on the rebound, but limits it to the value of the stiffness force. Therefore, damping can reduce or eliminate the force provided by the stiffness, but never exceed it. All equations are smooth and produce no zero crossings.

• Full stiffness and damping applied at bounds, undamped rebound — This option applies full stiffness and damping with impact, and applies no damping on the rebound. The equations produce no zero crossings when velocity changes sign, but there are position-based zero crossings. This option uses nonlinear equations.

• Full stiffness and damping applied at bounds, damped rebound — This model has full stiffness and damping applied with impact, with damping applied on the rebound as well. The equations are switched linear, but produce position-based zero crossings. Use this option if the simscape.findNonlinearBlocks function indicates that this block prevents the network from being switched linear.

Programmatic Use

Parameter:	hardstop_model
Values:	"foundation.enum.HardStopStiffness.Smooth" | "foundation.enum.HardStopStiffness.FullUndamped" | "foundation.enum.HardStopStiffness.FullDamped"

Contact stiffness — Elasticity of collision

1e6 N/m (default) | positive scalar

Elastic property of the colliding bodies. The greater the value of this parameter, the less the bodies penetrate into each other and the more rigid the impact becomes. Setting this parameter to lesser values makes contact softer, but improves convergence and computational efficiency.

Programmatic Use

Parameter: hardstop_stiffness

Contact damping — Dissipating property during collision

150 N*s/m (default) | positive scalar

Dissipating property of the colliding bodies. The greater the value of this parameter, the more energy dissipates during impact.

Programmatic Use

Parameter: hardstop_damping

Transition region — Region where force ramps up

0.1 mm (default) | positive scalar

Region where the force ramps up from zero to the full value. At the end of the transition region, the block applies full stiffness and damping.

Dependencies

To enable this parameter, set Hard stop model between poppet and seat to Stiffness and damping applied smoothly through transition region, damped rebound.

Programmatic Use

Parameter: hardstop_transition

Plots

Metering area — Generate metering area plot

button

Use the Plot button to generate the metering area plot.

Jet angle — Generate jet angle plot

button

Use the Plot button to generate the jet angle plot. To generate a plot, you must set Flow momentum force model to Based on poppet and seat geometry or Based on tabulated jet angle.

References

[1] Manring, Noah D. Hydraulic Control Systems. John Wiley & Sons, 2005.

[2] Merritt, Herbert E. Hydraulic Control Systems. John Wiley & Sons, 1967.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2026b