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Author: Subject: Measuring the pressure of an explosion
low.safety.standards
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[*] posted on 21-9-2018 at 13:35
Measuring the pressure of an explosion


Hello People,

Does anyone know what kind of device was historically used to measure pressure in rocket combustion chambers? I've thought of having some sort of "oil trap" in a long copper tubing where the oil does the interface between the hot gases from the combustion chamber and a simple pressure gauge, any ideas on a diy scheme that uses a common pressure gauge?

[Edited on 21-9-2018 by low.safety.standards]
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DubaiAmateurRocketry
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[*] posted on 21-9-2018 at 14:56


an actual detonation will probably shatter a "combustion chamber", also what you're talking about is probably combustion pressure of a rocket combustion chamber, if you were to measure detonation in that way, im not sure how the shock wave will interact with the pressure gauge.

Theoretically, it should read an extremely lower number than the actual detonation because the moment of detonation is when the pressure is the highest, and as it expands inside a chamber that will drop significantly. I am not sure though, user dornier will probably give a better answer.
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low.safety.standards
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[*] posted on 21-9-2018 at 15:20


Quote: Originally posted by DubaiAmateurRocketry  
an actual detonation will probably shatter a "combustion chamber", also what you're talking about is probably combustion pressure of a rocket combustion chamber, if you were to measure detonation in that way, im not sure how the shock wave will interact with the pressure gauge.

Theoretically, it should read an extremely lower number than the actual detonation because the moment of detonation is when the pressure is the highest, and as it expands inside a chamber that will drop significantly. I am not sure though, user dornier will probably give a better answer.


"Measuring the pressure of an explosion" was just a way to phrase it, I'm not looking for instantaneous readings but the overall mean pressure as measured by a common pressure gauge
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JJay
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[*] posted on 21-9-2018 at 17:02


I'm guessing you could use something like compressible brass tubes of different thicknesses requiring different amounts of pressure to deform.



I'm no longer involved in this forum.
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markx
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[*] posted on 21-9-2018 at 17:33


Well...one could also use just a suitable pressure gauge/sensor separated by a "reasonable" amount of metal tubing to take care of the heat transfer. Since there is very little actual transmisson of gas flow into the gauge, the "reasonable amount" really becomes resonable in the sence of the meaning. Sure, the reading shall be somewhat biased, but repetitive comparable results should at least indicate the trends: pressure falling or pressure rising vs. altered parameters in the propulsion system. Just to point it out....most if not all of the other pressure measurement methods shall also produce a more or less biased result in such a highly dynamic system.



Exact science is a figment of imagination.......
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bobm4360
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[*] posted on 21-9-2018 at 21:41


Solid motor and uncooled liquid motor pressures were often measured with strain gauges on the chamber wall. Real-time and recordable.
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[*] posted on 21-9-2018 at 21:52


Quote: Originally posted by bobm4360  
Solid motor and uncooled liquid motor pressures were often measured with strain gauges on the chamber wall. Real-time and recordable.


My motor has a jacket! :/
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