design issues

[K-Star Automotive]

WOW, I did the string deal.

I am not sure what a normal bench looks like but on mine, with the 300 calibration plate on and about 2 inches into the bore adapter that string went nuts.

At one point i swear that it actually come back towards the opening instead of towards the vacuum source.

Keith

[jfholm]

Keith,
GREAT Looking bench.

I will try the string on my bench and see what happens.

John

[jfholm]

Here is what I found when I used a string to check the flow on my bench. First let me tell you what it is. It is basically the chamber side with orifice plate from Bruce's plans. Instead of having a motor side I plumbed in two shop vacuums as that is what I had when I was using the Flowquik.

It will pull 10"+ H2O through a SBC head flowing 263 cfm.

When I let the string go into the center of the hole it wiggles a little but not bad and will go straight down almost to the baffle plate above the orifice. When I hold it to the north side of the hole it will go in fairly smoothly and go around the baffle plate. If I do the east side of hole smooth and around the east side of the plate. South side also smooth and goes around the south side of baffle plate and west goes around west and smooth.

In this design I see a fairly smooth air flow through the hole and around the baffle. It seems to be working as designed.

John

[larrycavan]

Well....how are you making out Keith?

[K-Star Automotive]

I am so busy with customer engines i don't have alot of extra time to work on it right now.

I did fab up a elbow out of pvc today. I installed it with the opening facing the vacuum source. It totally took the noise away, but it messed the bench up. My 300 plate calibrated at 315. I re adjusted the bench and set it to 300 then my 150 plate was 135.

I think at this point i found the problem. Now it's just what to do to fix it.

One other thing with that elbow installed i can't get over 28" with the 300 plate on it. I think it's because my pick up is in the far corner of the chamber. I think facing that elbow toward the vacuum source cut off about half the chamber, probably rendering that corner dead.

I have a few weeks of work to get caught up on. I'll check back in once i get it apart and decide on how to increase that chamber size.

Keith

[thomasvaught-1]

I have flowed several orifice plates on the "Ford bench" and have found that a long section of pipe (even a 4" pipe) will restrict flow if using a large orifice (pipe wall effect) and then the elbow in the system. The air all flows on one side of the elbow and the total flow changes with the elbow vs a straight "Stack" into a large plenum. Smaller orifices seem to work better in the 4" pipe. We need to do a "beta ratio" sweep in our benches and find the best ratio for the "pipe" type benches.

Quote:

"Per ASME estimates the pressure drop that is permanently lost with a sharp edged orifice plate varies from about 45% to nearly 100% of the sensed DP based principally on the Beta ratio (d/D). The smaller the Beta ratio the higher the drop. A properly sized orifice plate will typically lose 40% of the sensed DP to permanent pressure loss. This loss is from the turbulence being converted to heat energy. The main consequence of the loss is the required pressure energy to maintain a certain system pressure. In some cases where a a loss is required anyway, this isn't a problem but a welcomed attribute. In other systems such as a low pressure fan driven system even very small losses will require a bigger and hence more expensive fan. There are other more subtle consequences that may also affect a process system.

Sincerely,
John Catch
[url=http://www.inflowinc.com"]http://www.inflowinc.com"[/url]

The link with more info:



Quote:

"A good reference book on this and other metering subjects is R.W. Miller's "Flow Measurement Engineering Handbook" available through McGraw-Hill."

Agree.

Tom Vaught

[johno]

Hi there mate, i too went for an AUDIE pitot bench but my bench set-up is completely different to yours. I mounted mine into an MDF rolling tool cabinet REPCO are selling here in Australia but im having the exact opposite problem your having! When i test-flow some test orifices i made on my friends SF-110, the readings from the larger orifices are slightly lower on my pitot bench than the super-flow readings, but when i flow-test cylinder heads, that have also been tested on the same super-flow bench, the readings are within 2-3 cfm!! I too have a shallow plenum/settling chamber but have my vacuum/pressure applied directly below and in line with the test hole! I'm thinking maybe the differences in our readings are from the different 'CRASH' effect of air-flow created by an 'open' orifice operating over our differing test-plenums?! I too am re-designing my test plenum (See site; FLOW PERFORMANCE- 'PREFERRED SETTLING CHAMBER DESIGN'). It may be the answer to both our problems! ???

[johno]

Can someone point me in the direction of some temp. correction figures and how to apply them (ie; as if i was using a SF-110)? ???

[slracer]

John O, This should help! Look it over and see if your questions are answered. -- Doug

[johno]

Thanks heaps for that extremely usefull information Doug, champion!! :;):

[Eagle Eye]

Bruce, I have some questions about your digital manometer setup. It has been talked about highly on the forum. I have the Quadrant Scientific bench which there are pictures of in the forum. A pitot setup(from the darkside). I'm wondering if your setup would function on my bench? I understand that the pressure taps into the settling chamber (no problem). The external pitot hooks up to your setup(no problem), but where would I sense the airflow? There is a tunnel in the machine that the existing flow sensing probe pokes into. I don't know how your unit senses the airflow. Much appreciate your answer and anyone else that wants to chime in. Jim

[bruce]

Jim, The PTS DM is currently only setup to use on an orifice style flowbench using a 16" differential pressure across the orifice plate, preferably a PTS style Flowbench built from my plans as we already know it's capabilities/capacities. The PTS DM was designed to support this product.

Rick has talked about setting up FlowSoft Basic (which is the software package used to read the DM output) to work with a pitot style flowbench but, that is a back-burner project right now.

[Eagle Eye]

Thanks for the info. I assume that the depression could be sensed and the external pitot for probing could be used without sensing the airflow. Or not? Let me know. Thanks