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MapleSim Hydraulics Library from Modelon

Accu2  Hydro-pneumatic accumulator (refined gas model)

The Accu2 component describes a hydro-pneumatic accumulator. The model of the charge gas is more refined than in the Accu1 component. There is a valve at the inlet port. Oil flows into the accumulator if the pressure at port_A is higher than the gas pressure, pgas. A lower limit is given for the gas pressure, pgas, by the precharge pressure. This is calculated from the volume of the accumulator, the temperature of the environment and the gas mass. The gas volume at t = 0 must be less than or equal to the volume of the accumulator. There is a check whether this condition is met. The model uses the Beattie-Bridgeman-equation to calculate the behavior of nitrogen as the charge gas. The following m-files calculate parameters for model Accu2. They can help with the numerical analysis of an accumulator and are to be used with MATLAB(R), not Dymola(R). This model will be replaced by a new model next release.

Name

Description

bbp.m

Calculates the pressure for given temperature and specific volume.

bbvs.m

Calculates the specific volume for given temperature and pressure.

cvp.m

Calculates the specific capacity for constant volume.

Related Components

Name

Description

Accu1

Hydro-pneumatic accumulator with a simple model of the charge gas.

 

Variables

Connections

Parameters

Constants

Variables

Name

Value

Units

Description

Modelica ID

GasVolBB

 

 

 

GasVolBB

TWV

 

 

 

TWV

PMeas1

 

 

 

PMeas1

PMeas2

 

 

 

PMeas2

ValveLog

 

 

 

ValveLog

pAsummary

pA

Pa

Pressure at port A

summary_pA

Connections

Name

Description

Modelica ID

oil

 

oil

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

Vacc

0.001

m3

Volume of accumulator

AccVol

VgasT0

0.001

m3

Gas volume at t = 0

GasVol_T0

Θ

300

K

Temperature of environment

Theta

Temp0

300

K

Temperature of charge gas at t = 0

Temp_0

mgas

0.0394

kg

Gas mass (default is for 1e-3 m3 und 3.5 MPa)

gm

Τ

5

s

Thermal time constant

Tau

cv¯

750

 

Mean value of cv

CvBar

Oil Parameters

Name

Default

Units

Description

Modelica ID

VA

10-6

m3

Geometric volume at port A of TwoWayValve

volumeA

VB

10-6

m3

Geometric volume at port B of TwoWayValve

volumeB

Valve Parameters

Name

Default

Units

Description

Modelica ID

overlap

0.02

 

Overlap of valve relative to max. displacement = 1

overlap

qnom

8.33·10-4

m3s

Nominal flow rate of valve

qnom

&Delta;pnom

3.5·106

Pa

Pressure drop at qnom of valve

dpnom

dleak

0

m

Diameter of equivalent orifice to model leakage of closed valve

dleak

k1

10

 

Laminar part of orifice model

k1

k2

2

 

Turbulent part, k2&equals;1Cd2

k2

ω0

500

rads

Natural frequency of spool

omega0

damp

1

 

Damping coefficient of spool

damp

Constant Parameters

Name

Default

Units

Description

Modelica ID

spezVol

Vaccmgas

 

computed

spezVol

pprecharge

[1]

Pa

Gas pre-charge pressure, computed

pprecharge

[1] 100000RΘ1CΘ3spezVolspezVol&plus;B01BspezVolspezVol2100000A01AAspezVolspezVol2

Constants

Name

Value

Units

Description

Modelica ID

R

0.00297

 

 

R

A0

0.00174

 

 

A0

B0

0.0018

 

 

B0

AA

9.34·10-4

 

 

AA

B

-2.47·10-4

 

 

B

C

5.09·10-8

 

 

C

See Also

Accu1

Volumes

MapleSim Hydraulics Library from Modelon Overview

 


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