Hydrogen-oxygen explosions in exhaust ducting

Paul M. Ordin
naca-tn-3935
Apr 1957


The ignition of hydrogen-oxygen gas mixtures at a pressure of 1 atmosphere in a 2-foot-diameter duct resulted in detonation combustion. The detonation static pressure at an oxidant-fuel mole ratio of 0.82 was about 315 lb/sq in. abs (pressure-rise ratio of 21). The use of water curtain sprays distributed through a substantial section of the duct did not prevent a detonation but did reduce the peak pressure to 200 lb/sq in. abs. The detonation could be prevented by adding sufficient carbon dioxide to place the gas mixture out of the flammable range. The use of smaller quantities of carbon dioxide resulted in a reduction in the peak detonation pressures. The total pressures exerted on various designs of 90 degree steel elbows by the detonation were about 900 lb/sq in. abs (pressure-rise ratio of 60). A design stress of 38,400 psi and suitable supporting members for the exhaust duct elbow contained the detonation without any damage to the structure.

An Adobe Acrobat (PDF) file of the entire report:
http://naca.central.cranfield.ac.uk/reports/1957/naca-tn-3935.pdf