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Published on Aug 22, 2010
Hydrogen Oxygen has an adiabatic flame temperature of about 3000 degrees kelvin, thats about half the temperature of the surface of the Sun. Question is... just for fun, can you put that into a pop bottle!
Previously I've shown other fuel air burns, one similar to that used in most internal combustion engines (butane air), and the other as one of the more common rocket fuels (hydrogen oxygen). Both release lots of energy when they burn, which is of course what makes them suitable as fuels.
The hydrogen oxygen burn though is particularly fascinating as it only produces water as an 'exhaust', further it produces very little water! Indeed to fill a bottle with hydrogen and oxygen you only need to turn about 0.5g of water into H2 and O2, and of course when you burn it you only recreate that half gram of water.
To make life even more interesting, to actually do the electrolysis I use a 12 volt Li-ion polymer battery, very similar to those used in most laptops today, simply so folk can visualise in a very simple way the energy content in these everyday objects. Indeed the energy content is significantly higher as only a fraction of the energy I draw from this battery actually goes into creating the H2 and O2, while probably the majority goes into heating up the electrolysis solution.
Now when H2 and O2 burn, there is actually a reduction in the number of molecules of gas, which would, if all other conditions were the same actually produce a reduction in pressure, however the temperature of the exhaust gas is not the same, it goes from about 300K to 3000K which in a confined system would increase the pressure from about 1 to 10 atmospheres. This is getting close to the failure threshold of these bottles, and also represents a significant rate of release of energy.- caution is required, and this really isn't something you should be trying unless you really know what you are doing.
High speed camera used was a casio exilm EX-FC100. On paper it can do 1000fps, but with lousy resolution. The video here is about 240fps, thats about 1/10th speed, but seeing as the cameras costs about the same as a regular mini digital camera (~200bucks) it not so bad.