Gas System with Vacuum Pump

I am trying to model a vacuum pump in Simscape. The Volumetric Flow Rate Source (G) is exactly what I need, however, instead of keeping the outlet flow rate constant at e.g. 0.1 m^3/s I need it to keep the inlet flow rate constant. Is there an easy way to achieve this or do I have to code a custom simscape block?

[Andreas]

Could you add your model here?

Do you face problems crossing boundaries (pressure)?

[Dan]

Thanks for your comment.

I do not have a model for this as this was just a general question. However, you could just imagine a constant volume chamber connected to a constand flow rate source. I now want a constant volume flow rate at the inlet (chamber facing side) of the flow rate source, which doesn't seem to be achievable without programming a new custom block.

I do not face problems crossing boundaries.

Answer 1

[Juan Sagarduy]

Hi Dan

I believe it is better to use a pressure source than a volumetric flow rate source. In the inlet, you have the chamber where vacuum is created. Then, the diff pressure in the Pressource source shall make gas leave the chamber until absolute pressure is zero.

But Simscape will complain when pressure is below zero. Finding that level just above zero atm is what you need through an adequate value of pressure in the source.

Hope that helps Juan

[Andreas]

Hi Juan,

I attached two models.

vacuum_chamber_ps uses a pressure source and won't work the way expected:

vacuum_chamber_cfrs uses a constant flow rate source and empties the chamber till zero (end with exception).

How to do it right?

[Juan Sagarduy]

Hello Andreas

I managed to make the model with a variable pressure source work. However, I need to insert a flow resistance element between pressure source and the vacuum chamber.

With an increasing rate of (0.1/3) bar/s the vacuum is created in 30 seconds.I guess that in reality one shoud then limit the pressure (or compressor speed) once vaccum is created.

Cheers

Juan