diy flow bench

[George Gorman]

To do it with the minimum of electronics-

I would use an AC blower. The air would flow through the fan, the port on
the bench, through a sharp edged circular orifice in the line, and through
a variable flow restriction. (some sort of valve for varying the overall
head- A speed control on the fan or a blow off valve will solve the same
problem)

Explanation-
The fan provides the head.

Put a manometer across the flow bench. This tells you when you have got to
your desired pressure drop.(10'' or whatever) You adjust this with your
variable air flow restriction.

Put a manometer (a plastic tube full of water?)across the sharp edged
orifice. A mech eng textbook will give you the empirical relationship
between head loss and volume flow rate for a sharp edged orifice of
diameter D, say. This is quite accurate - much better than measuring dodgy
variables like motor current.

the procedure then is - 

move poppet valve to new setting

start motor

play with restriction until desired head across flow bench

measure head across orifice and use this to calculate airflow, using
textbook relationship.











At 09:56 24/03/99 +1000, you wrote:
>Does anybody know if anybody has built a diy flowbench ? I had an idea
>that you could use an electric motor with an air pump on it and measure
>the current drawn by the motor. You could use it uncalibrated in just a
>good, better mode or maybe you could calibrate it by flowing known
>items. It would be easy to hook up a PC and have a proffesional looking
>display. The bench part would be easy to build and you could mount the
>motor/pump underneath. Any thoughts?
>
>--
>
>Matt Boland                                     m.boland at cat.csiro.au
>CSIRO Division of Exploration and Mining        Phone: +61 7 3212-4482
>PO Box 883  Kenmore                             Fax:   +61 7 3212-4455
>QLD 4069 Australia
>
>
>
>
>

George Patrick Gorman

Mechanical Engineer
Australian Arrow P/L  Ph (03) 9785 0853  Fax (03) 9775 0477
65 Lathams Rd, Carrum Downs 
Victoria, Australia 3201
george_gorman at aapl.com.au