Posted:
Wed Apr 07, 2004 5:21 pmby 84-1074663779
Yes Jamie, because the pressure drop will be in the opposite direction.
Or you can make it easy on yourself and keep the flow direction through your whole bench in the same direction. Why not have two test holes in your bench top ? One hole sucks and the other blows. I have this on my bench and it simplifies a whole lot of things in the design of the bench.
If you reverse the flow, how do you know your orifice flows the same in both directions ? The internal flow dynamics inside the bench are going to be totally different when you reverse the flow.
I can shift the whole head from one hole to the other in about ten seconds on my bench, and there is absolutely no need to change anything else.
Posted:
Thu Apr 08, 2004 9:15 amby 102-1081363915
Very good points Tony. I had not thought of that. Do you have any pics of your bench? I have a good idea how I want to do what you are describing, but you know how it is if someone else has already did the "test run" on it.
Posted:
Thu Apr 08, 2004 7:54 pmby 84-1074663779
I do not have a camera, so no pictures yet unfortunately. If I win the lottery I will definitely buy a camera.
My bench is about the size of a kitchen table and is just a large box made from one inch MDF bolted to a welded heavy steel angle frame. It is divided by an internal partition into a right hand chamber (1/3) and a left hand chamber (2/3).
The centre partition has a two foot diameter round turret, fitted with eight individually removable pressed in plastic orifice plates. There is a shaft, an indexing system, and a car steering wheel on the right hand end of the bench, to position the turret. The suction test hole is in the top of the bench which leads into the right hand chamber. This right hand plenum chamber is just a large volume to allow the air to recover and slow down before it flows through the measurement orifice.
The left hand chamber contains the blower, which is a two foot diameter centrifugal forge blower with a cast iron scroll, driven at up to 6,000 RPM by a 7.5 Bhp three phase motor. The blower intake is open to the inside of the enclosure, but the blower exhaust goes through some plastic pipe to the blow test hole on the left hand top of the flow bench.
It is very simple construction compared to what some other people have built. It has only two controls, blower speed knob, and orifice selection wheel.
The whole blower module is spring mounted and is driven from a variable frequency drive. Motor speed controls flow. There are two large removable panels in the front of the bench to give access to the inlet plenum and turret on the right, and the blower plenum on the left. Both front panels are bolted and gasketed, and operate under high negative pressure, so are very easy to seal.
It is totally unlike anyone else's bench, it is my third effort so far, and a lot of thought has gone into it. The whole blower module is removable within a couple of minutes and just lifts out (it weighs 350Kg). I could easily upgrade or replace this blower in the future with something even more powerful if need be.
Posted:
Sat Jan 01, 2005 2:55 pmby DaveMcLain
That makes your flow bench a "blower center" setup which works like a Superflow 110 in that you've got to do a correction for the change in air temp introduced by the blower, but that would only happen in the exhaust direction if I'm reading your post correctly.