EXPERIMENTAL INVESTIGATION OF A COOK-OFF TEMPERATURE IN A HOT BARREL

摘要

There are a number of current cook-off (self-ignition) tests including the UNseries: small-scale cook-off bomb (SCB), slow cook-off, fast cook-off,electrically heated tube test; and one-dimensional time to explosion (ODTX) [1].Safety under storage and decomposition parameters are the primary focus ofthese tests. As such the tests use either constant or increasing temperature profilesand, typically, are conducted on the composition or item packaged for transportand storage. The output of these tests is a determination of reaction type andviolence as well as the thermal stability and decomposition rate of the material.In 2012 Pitcher [2] experimented with the study of cook-off in gun barrels withparticular emphasis of the temperature behaviours of the powder (Bulls Eye )prior to cook-off. This work was presented as a poster exhibit at the InternationalBallistic Symposium in 2013 and recommended a number of further studies toobtain enhanced data. One suggestion was to conduct a number of experiments tointroduce the 7.62mm cartridge case, modified with Bulls Eye propellant, into a‘hot’ chamber rather than heating the simulated breech from room temperatureuntil cook-off.Azavedo [3] locally designed and produced an experimental rig to replicate a‘hot’ gun chamber scenario. An MSc project was carried out in 2013 at CranfieldUniversity to conduct these experiments and compare/contrast results to theprevious project [2] with the aim of elucidating the effects of this modification.In essence, what this paper seeks to do differently from previous studies is tosimulate and extrapolate characteristics and behaviour of cook-off during anoperational weapons firing situation with a view to establishing atime/temperature profile of the cook-off risk. For these experiments it was foundthat the cook-off temperature of Bulls Eye propellant in an instrumented 7.62mmcartridge case having the same heat transfer profile as that of the simulated barrelis between 151.4 and 153.4°C, with the reaction occurring less than 300s afterround chambering. A time-temperature profile was developed, indicating theconditions in which 99.99% of cook-off reactions are predicted to occur.