Combustion theory applied to jet piercing flames is propounded. This is followed by a description of techniques used in measuring the temperature of flames and an account of experiments undertaken on the jet piercing flame.
It was found that the maximum flame temperature recorded was of the order of 2000°C for a flame using 95% stoichiometric oxygen, i.e., 950 cubic feet per hour for combustion with 44 pints per hour of kerosene. The maximum temperature for other flames is much lower.
Velocity of the exhaust gases was also measured and found to vary between 6,750 and 7,240 feet per second with varying fuel-oxygen ratios. The velocity associated with the hottest flame is 6,800 f.p.s.
Investigations were carried out into the piercing rates of various Australian rocks. Jaspilite, granite, tuff and quartzite pierced at rates up to 60 feet per hour. Hornfels and iron ores proved less susceptible to the process, while marble cannot be pierced at all.
It is concluded that the commercial jet piercing units with their large diameter holes would definitely be and economical proposition in Australian granites, quartsites and jaspilites, provided a cheap source of bulk oxygen is available.
Finally, probable causes of rock breakdown are discussed and suggested avenues of future research outlined.