Learning Forum

[javat33489]

Hi all.

I am interested in the calculation of a centrifugal pump in fluent.

Ansys has a video on this topic:

The video sets the inlet pressure to 0, which means atmospheric pressure, and the outlet flow. Fine. In real life, a centrifugal pump does not work like that, it needs to gain pressure, it is first launched onto a closed valve and then it is slowly opened to equalize the pressure, so the outlet pressure can be, for example, 10 MPa.

So how can I carry out such a trick? My pump produces a nominal output of 500 m3/day. Can I set the inlet flow and mute the outlet? Then I will look at the graph of the pressure in the pump cavity, when the pressure increases, I will stop the calculation and increase the outlet diameter each time, for example 0, 10, 50 and 100 mm - this is the desired diameter. Will the pump reach the required pressure?

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I calculated the pump as an ansis video, the inlet pressure is 0 and the outlet flow rate is 500 m3/day. But with this condition, I have a lot of negative pressure. Why?

[javat33489]

HELP please

[C N]

Hello Javat,

To avoid getting negative pressure , you must set the appropriate operating pressure.

The operating pressure mainly depends on 

Density of the fluid and mach number . 

I am attaching the Various recommendation settings on how to accurately set the operating pressure.

For more information kindly refer the attached user guide link

8.14. Operating Pressure (ansys.com)- Detailed information about pressure is mentioned.

I hope this helps you.

Thanks,

 

[javat33489]

Thanks for the answer. Yes, of course I use operating pressure.

[javat33489]

Fine. Another question about the graphs. In the video from ANSYS I use the expression “head”:

Why are they used in this production?

I also need to calculate the efficiency and output push of the pump:

output push:

efficiency:

(If the mass flow of water is indicated at the inlet, I set it, if there is pressure at the inlet and flow at the outlet, I put the outlet mass flow of water)

Am I calculating them correctly???