Delta P over orifice

[jdvaughn]

I was wondering about the topic of delta P across an orifice. Is there a method to choosing what delta P would work best or be best for your flow bench? Reason I ask is because all of the orifice size calculation sheets have a spot for orifice delta P and I am not sure what delta P to enter for my orifice. Do i want a larger delta P to give me more resolution and measurment depth? or do I want a smaller delta P because the relationship of delta P to CFM is not linear? I realize they may be a basic question, but if someone could clear this up that would be great! ???

[49-1183904562]

[jdvaughn]

I am going to be using a digital measurment system. I am using a National Instruments DAQ setup with the sensors that can be found at the following link:



I am using a +/- 1psid sensor from my CFM sensor which will allow for delta P's of up to 27.7" of exhaust and intake without switching connections.

I am using a +/- 5psid sensor for my test pressure measurement which will allow plenty of room for test pressures.

These sensors output from .25V to 4.25V and read zero at 2.25V for the bi-directional sensors.

I will most likely run 28" of test pressure for most of my testing but may need to get higher pressures to test for "choking" of our intake design since we have a 20mm resrictor for competion. We want to try and find the best design to avoid choking our engine, so we may need high test pressures then.

so if I understand correctly, I can pick some delta P for the orifice that works for my sensors bandwidth correct? so for these sensors I will probably go with about 15"-20" of water delta P so I can get decent resolution from the sensor. am I on the right track with my thought process now? I think I am.... ???

[bruce]

Yes, you are on the right track . . .