Hi,
I`ve had past experiences with pressure switches giving "strange" (pulsed) signals due to nearby discharge valves closing or opening. Looking a little into it I run into reading about compressibility theory and "shock tubes".
Just for info, a "shock tube" is a tube with 2 zones, "driver" with high pressure gas, and "driven" with low pressure. Separating them there is a "valve" that is suddenly opened.
The shock tube model explains the steep pressure change evolution, and the different "zones" after the "valve" is opened.
After the valve is opened there are two zones, start and end of the tube where the pressure is yet the initial and an "intermediate" zone where the pressure is a constant value between both.
It appears a "shockwave" as a steep change in pressure, that is the limit between the "intermediante" and end zone, progressing towards the end of the tube, and a "rarefaction wave" limit zone progressing to the init of the tube.
With values of (10 bar driver, and atmospheric output) in this link
http://www.aero.iisc.ernet.in/~lhsr/web/stc.php
can be calculated that the "shock" front (intermediate zone) is 2.85bar and the speed Mach 1.61.
Thinking about it I see that in a simple pneumatic model (i.e. reservoir, valve and pipe to atmospheric output) the main difference with the shock tube is that the "driver" section is actually a source of pressure, only limited by the flow resistance.
The question (sorry for the long explanation) is if the shocktube results are really related to the "shock" case in a reservoir+valve opening+tube to atmosphere system and how the "rarefaction" wave would behave upstream towards the reservoir in the real pneumatic system
Regards and thanks for your comments
I`ve had past experiences with pressure switches giving "strange" (pulsed) signals due to nearby discharge valves closing or opening. Looking a little into it I run into reading about compressibility theory and "shock tubes".
Just for info, a "shock tube" is a tube with 2 zones, "driver" with high pressure gas, and "driven" with low pressure. Separating them there is a "valve" that is suddenly opened.
The shock tube model explains the steep pressure change evolution, and the different "zones" after the "valve" is opened.
After the valve is opened there are two zones, start and end of the tube where the pressure is yet the initial and an "intermediate" zone where the pressure is a constant value between both.
It appears a "shockwave" as a steep change in pressure, that is the limit between the "intermediante" and end zone, progressing towards the end of the tube, and a "rarefaction wave" limit zone progressing to the init of the tube.
With values of (10 bar driver, and atmospheric output) in this link
http://www.aero.iisc.ernet.in/~lhsr/web/stc.php
can be calculated that the "shock" front (intermediate zone) is 2.85bar and the speed Mach 1.61.
Thinking about it I see that in a simple pneumatic model (i.e. reservoir, valve and pipe to atmospheric output) the main difference with the shock tube is that the "driver" section is actually a source of pressure, only limited by the flow resistance.
The question (sorry for the long explanation) is if the shocktube results are really related to the "shock" case in a reservoir+valve opening+tube to atmosphere system and how the "rarefaction" wave would behave upstream towards the reservoir in the real pneumatic system
Regards and thanks for your comments
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