Up and Running.

[1960FL]

As a note so you do not get to far off base here, your plates sharp edge ID measured to +/- .002, if a true sharp edge and 45° angle should be assumed as .62 CD perform the calculated flow (Eds spreadsheet) at what ever test pressure you plan to use ??/ 24" stated above this is your bases.

For now lets use your 1.20" orifice at 24" it should flow 95.65CFM call it 96CFM what you now need to do is test this plate in the intake mode sharp edge up at 24" and take your reading. You will now adjust your calculations for flow such that at the measured DP you math works out to be 96CFM by adjusting your internal orifice CD up or down should fall between .58 and .64 or so.

Now you will test the other plates with the correct .62 math applied to them I/E .838 @24 with .62CD = 46.65 call it 47. now test this on top of the bench sharp edge up at 24" do the floe math using the same CD you used on the first test right down your results. May be high or low it does not matter yet.

Now test the 1.49 plate at 24 same as above it should be like 147 to 148 at 24" do the math using the same CD as test 1 and 2. This test may be higher or lower right it down.


Now you have two major points of adjustment here #1! is incline angle this fine adjustment will help with gross offsets in linearity I/E error getting larger or smaller as orifice size goes up, The second is the CD you use for your internal flow calculations this is the CD of the internal plate if you made this plate the same as the rest it should be close to .60 - .62 but you will see.

You need to perform the above for all plates and determine your internal plate CD and adjustments to the incline angle that provides the most consistent results in both linearity and error. You will most likely end up with the smaller plated reading 1 to 2 CFM high and the larger ones 1 to 2 cfm low but this will all depend on what internal plate you are using.

Please post your results as most of the senior guys here will know where i am going with you getting a true calibration.

Good luck

Rick

[Ravoll]

Because of having the fluid density for water set at 1,9 g/cm³,the calculations were showing me a 24" Delta P.
At 1 g/cm³ I have a 12" delta P, but my plates were tested for 24" Delta P.
I'm gonna send the largest plate off again,and have it flowed at 12". Will use it in the bench as a starting point and work down from there.
It may be a week or two before I can post any results.

[1960FL]

What are you using for your test Pressure it is my mistake as in reading your posts it appears you are using 24" not 28" ???, you do not need to send you plates to be flowed yet, if you can just post the internal dimensions and design we can give you the expected flow. This will move your calibration along faster, then if you are trying to be in the same calibration as another bench you are often compared to you can adjust your CD accordingly.

I cannot state this enough a proper calibration is the the most important foundation you can build into your bench once the construction is completed. Understanding the flow, CD and when and where numbers go wonky is far more important than having your numbers match someone else's. A properly calibrated bench produces factual data, not faux data.

Rick

[Ravoll]

O.K.,I'm back,
I never sent anything orifices off to be tested.The people where I sent before have no time and the other 4 or 5 companies with Flow benches all want astronomical sums to test one Orifice.120 Euros to build an adapter and then 98 euros an hour for testing,upwards.

So I bought myself an Anemometer to play with,and this is what I did.

By the way I do use a Delta P of 12". Scale length 24" with a 12" rise.

First I calculated my orifices using the spreadsheet.I mounted them into the bench, ran the delta P up to 100% (12"),and used the anemometer as a test piece. This is what I came up with.

orifice calculation Test.JPG

Afterwards I tested them against one another, using the smaller ones as test piece (intake Mode),and the larger ones in the bench.I used both the Anemometer and the bench readings during this test.
Recorded were delta s in mm,Percent of flow,and cfm (mm/%/cfm). Looks like a mathematical equation but it's not.

orifice test2.JPG

The last test was the same as test 2 but only with bench results.

Orifice test 2 no ane.JPG

Since my orifices were calculated for a 12" delta P, I also used 12" as my test pressure. What I'm seeing is that with increasing orifice diameters used in the bench,the CFM flow of the test pieces are also increasing although the 12" test pressure remains constant.

I did a quick test .I mounted a cylinder head to the bench,and and set the valve lift to 0,200".I started with the 1,2" orifice,working up to the 2,1" while maintaining a 12" drop across the head.Even though the lift and pressure drop never changed,the head flow increased with each increase in orifice diameter.

What's causing this?

[Brucepts]

Since my orifices were calculated for a 12" delta P, I also used 12" as my test pressure. What I'm seeing is that with increasing orifice diameters used in the bench,the CFM flow of the test pieces are also increasing although the 12" test pressure remains constant.

I did a quick test .I mounted a cylinder head to the bench,and and set the valve lift to 0,200".I started with the 1,2" orifice,working up to the 2,1" while maintaining a 12" drop across the head.Even though the lift and pressure drop never changed,the head flow increased with each increase in orifice diameter.

What's causing this?

My quick reply to this question . . . airflow "presentation" to the orifice hole is not allowing it to maintain a consistent Cd for the orifice plates? From my testing I have found you want the orifice plate to "see" the flow coming from all sides and dropping over the edge of the plate not direct at the hole. Think of a waterfall where the water is running down stream and then just drops over the edge, this is what you want the airflow to your orifice inside the flowbench to do.

[Ravoll]

Actually that's almost what I was thinking.As airflow demand rises,the air stream isn't spread out far enough for the delta P to be correctly balanced? Or is it a velocity problem?

If I think about it,a test pressure of 12",and a 12" Delta P across the orifice gives 24" combined (36" at the motors).And that'll always be the same for all my 12" delta P orifices , at 12" test pressure. As the Orifice diameter goes up,the only way to reach the 12" test P is with a higher velocity across the orifice.
Is this why my Smaller orifices are almost spot on while the larger ones are all over the place.

Is really all I can come up with I don't think the air is streaming directly into the orifice,because my inbound air stream is not even close to being in line with the orifice.Nor is the outgoing air stream.

rough sketch flowbench.JPG

I will mess around on the weekend lowering the Delta P and Test P to see if things settle down.Iz could be that my box is just to small for the velocity involved.

[Ravoll]

But wait,
By studying the drawings of my bench,and using what i know about port velocities and short side turns in an intake port,I see the problem, I think.To many turns in my box? With larger orifices I have 12" above the orifice,but the velocity is maybe so high that the airflows not making the turns.To produce the 12" depression above the orifice is taking more pressure than normal below the orifice,causing an artificially high Delta P.?????
Just thinking.
If this is the problem,I could probably find the point where the velocity gets to high by recalculating my plates to a lower Delta P and lowering my test pressure to match.Say 6",8",10".and somewhere it should even out.If this solves things then my bench is to small volume wise to support higher depressions

On a side note : I tried to send an email from the PTS parts page,but it tried to direct me to my gmail account when I clicked send.I have some questions on the PTS bench plans, and the digital manometer.

[Brucepts]

Your bench design in the orifice area is creating a velocity effect on your plate as the plate diameter gets larger the "beta ratio" gets smaller above the hole.

When you send from the parts page on my website it opens up the email server you have linked to your web browser to "send mail" most people do not set this up within their browser software.

Just click below on PM or Email and you can get me that way

[Ravoll]

Your bench design in the orifice area is creating a velocity effect on your plate as the plate diameter gets larger the "beta ratio" gets smaller above the hole.

" Beta ratio" is the relationship of the orifice area to the chamber area before it? Does the same apply to the chamber area after the orifice?

[Brucepts]

I'll say, yes it does, my bench design allows the airflow to come at the orifice from the bottom for exhaust testing so that chamber also needs to worry about the beta ratio.