Explosion Pressure from a gas-air mixture in a closed vessel
Explosion Pressure from a gas-air mixture in a closed vessel
(OP)
I am designing a hazardous gas sensor housing that must be explosion-proof and follow CSA standard C22.2 No. 30. One test that is used in testing of the standard is a gas-air mixture is flowed into the housing through the stainless steel flame arrester. Once inside, the gas is ignited. I would like to know what pressure that would produce? I have found a value of 21 bar (305 psi). The gas mixture is 17% acetylene, 22% oxygen, 61% air. Once I have a pressure value, I am modeling the housing as a thick-walled cylinder with closed-ends.
Thanks
Thanks
RE: Explosion Pressure from a gas-air mixture in a closed vessel
RE: Explosion Pressure from a gas-air mixture in a closed vessel
HAZOP at www.curryhydrocarbons.ca
RE: Explosion Pressure from a gas-air mixture in a closed vessel
I have gotten CANMET in Ottawa Canada to do the necessary tests. For the gas mixture is 17% acetylene, 22% oxygen, 61% air, the maximum experimental pressure was 130 psi. I used 305 psi is the design. I also design the sensor housing to UL 1203 and that standard said the min wall thickness is 1/8" which produces a very large safety factor with the type of aluminum alloy I used. The sensor housing has now pass all the necessary tests.
Thanks again for your guys help,
GasSensor
RE: Explosion Pressure from a gas-air mixture in a closed vessel
HAZOP at www.curryhydrocarbons.ca
RE: Explosion Pressure from a gas-air mixture in a closed vessel
Just like an automotive engineer saying petrol is 43MJ/kg and knowing the heat released by multiplying mass of fuel by 43MJ, you could find the heat released by burning the acetylene and work out the pressure when the heat is applied to the gas in its container.
Correct?
RE: Explosion Pressure from a gas-air mixture in a closed vessel
I did a quick constant volume, constant internal energy calculation using EQUIL (part of Chemkin) and it predicted P_final = 13.2 atm
Here are the initial conditions that I used:
P = 1 atm
T = 300 K
17 % C2H2
34.8 % O2
rest is N2
j2bprometheus
RE: Explosion Pressure from a gas-air mixture in a closed vessel
HAZOP at www.curryhydrocarbons.ca
RE: Explosion Pressure from a gas-air mixture in a closed vessel
I may be wrong, but it appears to me there isn't sufficient oxygen for complete combustion, when considering that the oxygen volume should be 2.5 times that of acetylene from a stoichiometric viewpoint.
I agree with owg in that in a matter of a fraction of a millisecond pressures may peak and then stabilize at lower values. Although the resulting pressures may not be excessively high, the rate of pressure rise in a confined detonation may be some hundreds of bar/s, and the maximum rate may not necessarily appear at the maximum pressure. The rate also appears to be a function of the vessel volume.
RE: Explosion Pressure from a gas-air mixture in a closed vessel
"Exhaust Explosion" is not a controlled event like this one.
The question I have is what parameters are involved?
In Q=m*c*(Delta T), Q is heat of explosion of m lbs of un burnt methane & air mixture that didn't ignite in ignition chamber (mis fire?) and c at almost constant volume is approx. that of air & CH4, and then, one may find T2 and therefore P2. Am I right? Or am I making a lot of wrong assumptions considering thermodynamics & fluid dynamics?
Thanks
RE: Explosion Pressure from a gas-air mixture in a closed vessel
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RE: Explosion Pressure from a gas-air mixture in a closed vessel
Maximum and minimum pressures from the instantaneous ignition of the mixture is obtainable from solution of
"Chapman-Jouguet detonation and deflagration waves"
Regards
RE: Explosion Pressure from a gas-air mixture in a closed vessel
GasSensor