Bellmouth design

Question

Bellmouth design

AleksS (Mechanical)

(OP)

5 Apr 03 16:29

Does anyone know of any methods for designing a bellmouth? Are there certain design constraints? ie. the radius is equal to half the radius of the inlet tube. Thanks for the help.

JeanAlesi (Aeronautics) · Answer 1 · 2003-04-06 13:45:41

RE: Bellmouth design

JeanAlesi (Aeronautics) 6 Apr 03 13:45

What is a bellmouth?

AleksS (Mechanical) · Answer 2 · 2003-04-06 14:28:40

Sorry, I was a little unlcear. Its the top part of a velocity stack on the intake. Here is a pic http://www.todaracing.com/images/engine_toyota_4ag_b.jpg
Its meant to smoothen out the airflow into the engine. Its also known as a trumpet (for obvious reasons). Hope this makes things a little clearer.

sciguyjim (Chemical) · Answer 3 · 2003-04-11 10:17:27

I remember reading once that, ideally, the "bell" should do more than just curve away from the mouth of the intake, as seen in the photo you referenced.  I read that the optimal shape is for the edge of the "bell" to curl back on itself rather than simply stop in mid air.  I'll try a (greatly simplified) drawing...

    __       __           _        _
   /  \     /  \           \      /
   |   \   /   |   vs       \    /
    \__|   |__/             |    |
       |   |                |    |
       |   |                |    |

chasbo (Chemical) · Answer 4 · 2003-08-31 23:35:21

The design of the bellmouth affects its design parameters. One for a jet engine intake is designed differently than one for a ducted fan. There is an inlet section, but ducts with bellmouth entrances also can either have a straight discharge, or can taper inward or outwardly.

What do you plan to use it for?

Chasbo

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Bellmouth design