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MapleSim Hydraulics Library from Modelon

Chamber  Oil-filled chamber with a moveable piston and pressure-dependent compressibility

The Chamber component describes an oil-filled chamber that has a moveable, frictionless, and massless piston. The volume is given by

Veff=Vdead+sbsarodApiston

There is a check whether

stroke=sbsarod

is greater than zero during the simulation.

To compute the pressure in the chamber, an equation for the bulk modulus is needed. It uses the oil model defined on the system level. The bulk modulus is given by

β=βpA

The calculated pressure is not limited to the vapor pressure but can reach unlimited negative values. A limitation is done for the computed force where the relevant pressure is limited by the vapor pressure. Another limitation is implemented in TwoPortComp where all pressures used to compute the differential pressure between the ports are limited to the vapor pressure. Detailed information about the bulk modulus of the oil is given in the documentation for OilVolume. Use the modifier

port_A(p(start=2e6,fixed=true))

to set the initial condition for the pressure in the chamber in Pa.

 

Equations

Variables

Connections

Parameters

Equations

msim/FORmsim/INi#1,1..nports,p=port_A[i#1].p

β=βoilp=pabs,T=T,vair=vgasoil,psat=psat

ρ=ρoilp=pabs,T=T,vair=vgasoil,psat=psat

T=T0oil+ΔTsystem

f=maxp,pvapouroilpatmoilApiston

stroke=srelrod

Veff=strokeApiston+Vdead

pabs=p+patmoil

qcham=vrelApiston

srel=switchflange_b.sflange_a.s

vrel=tsrel

flange_a.fswitch=f

flange_a.f+flange_b.f=0

tp=βmflowAρ+qchamVeff

Variables

Name

Value

Units

Description

Modelica ID

srel

 

m

Relative position

s_rel

f

 

N

Force between flanges

f

vrel

 

ms

Relative velocity between flange flange_a and flange_b

v_rel

stroke

 

m

Stroke of chamber

stroke

Veff

 

m3

Effective volume = dead volume + stroke  piston_area

EffVolume

qcham

 

m3s

Induced flowrate because of piston movement

qcham

pabs

 

Pa

Absolute pressure, used for all property calls

p_abs

p

 

Pa

Pressure in Chamber

p

β

 

Pa

Bulk modulus

beta

T

 

K

Local temperature

T

ρ

 

kgm3

Density

rho

psat

[1]

Pa

Gas saturation pressure

p_sat

oilWarnings

 

 

 

oilWarnings

pressureSensor

 

 

 

pressureSensor

pAsummary

p

Pa

Pressure at port A

summary_pA

Tsummary

T

K

Local temperature

summary_T

βsummary

β

Pa

Bulk modulus of oil

summary_beta

ρsummary

ρ

kgm3

Density

summary_rho

Phydsummary

pvrelApiston

W

Hydraulic power

summary_HP

[1] oil.gasSaturationPressureT=T,vgas=oil.vgas

Connections

Name

Description

Modelica ID

oil

 

oil

flangea

 

flange_a

flangeb

 

flange_b

portA

Port A, where oil flows into the component (0<q, pB<pA means 0<&Delta;p)

port_A

Parameters

General Parameters

Name

Default

Units

Description

Modelica ID

reverse

false

 

Reverse the sign convention, see documentation for details

reverse

nports

0

 

Number of ports

nPorts

Apiston

0.01

m2

Piston area

piston_area

rod

0.005

m

Rod length

RodLength

Vdead

10-6

m3

Dead volume for stroke = 0

dead_volume

&Delta;Tsystem

0

K

Temperature offset from system temperature

dT_system

See Also

OilVolume

Volumes

MapleSim Hydraulics Library from Modelon Overview

 


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