AnsweredAssumed Answered

How do you simulate a pressure build up?

Question asked by Goncalo Costa Martins on Jun 20, 2019
Latest reply on Jul 11, 2019 by Peter Francis

Hi everyone,

 

I am trying to run a simulation wherein a radial blower is used to produce an airflow into a container. The air then escapes to atmospheric pressure (output) through two holes which are smaller than the inlet.

 

The blower has a volume flowrate of 260 m3/h with no overpressure and can operate up to a maximum overpressure of 0.4 bar with a volume flowrate of 170 m3/h. I don't know how much pressure build up there will be, so I simulated with 260 m3/h (input). My goals were set to use bulk average velocity at the outlet for convergence. Aside from that and gravity, there are no special settings to the simulation preferences.

 

In the final results I got a really high pressure at the inlet of 120 bar, but given the maximum operating pressure of the blower of 1.4 bar, this seems rather unrealistic. The velocity also increases from 25 m/s to around 330 m/s.

 

These are results from a simulation of a simplified model, but when I did this with the actual model, I also got the following errors:

 

  • Maximum Mach number exceeded
  • Inlet boundary condition may conflict with supersonic flow regions
  • Achieved Pressure ratio exceeds possible limit, solution cannot be obtained

 

The errors in the real model and the high pressures in the simplified model indicate that the simulation isn't right, so what could be going wrong?

 

Edit: These results were obtained with an undeveloped flow. I then checked the developed flow box and got a maximum pressure of 7300 bar and velocity of 320 m/s. Something's definitely not right...

Outcomes