Jim,

You're trying to defeat one of the laws of physics, I think. Not sure just which one, or maybe more than one, since I'm no physicist, but I do know that the gas/air mix must be mixed before it will burn properly. To obtain maximum heat from the fuel, the mix must be stoichiometric, that is, it must be the optimum in terms of molecules of fuel combining with molecules of oxygen from the air so that all the carbon and hydrogen in the fuel will be consumed. If using pure oxygen, or a mix of air and oxygen, the same still applies - to get a hot, neutral flame the mix must be stoichiometric or near that. Any deviation results in either a reducing flame (too much fuel) or an oxidizing flame (too much oxygen) - either deviation results in a flame that is cooler than a neutral flame.

When building an atmospheric burner (venturi mix type) to use propane and air, there must be a sufficient length of pipe between the venturi and the flame front to allow complete mixing of the air/fuel mix. For a 3/4" pipe burner this works out empirically to be a minimum of 9" of burner tube. For a blown burner, i.e. one using forced air rather than induced air, the fuel and air must still mix adequately but some of that can happen early n the game, so to speak, if the fuel is delivered into the intake side of the blower itself. This results in significant mixing in the blower volute and the burner tube can be somewhat shorter as a result.

The there is the issue of "burn-back", that is, having the velocity of the fuel/air mix too slow so that the flame front travels back up the burner tube instead of staying at the end of the tube. There are various ways to deal with this such as flares, flame holders, accelerators, etc. Generally, with blown burners this is not a problem but it can happen if the blower is undersized.

All of the above, while I speak of air/fuel mix, still applies if the mix is fuel/air/oxygen. With the addition of the oxygen things change, but the principles are the same. You still have to mix the fuel with the oxidizer. And this is where I'm predicting that you're going to have problems, if I understand correctly what you're thinking of doing. I don't see how it will work trying to inject the oxy/air directly into the burning fuel. You won't get proper mixing that way and things will be too random. Without a mixing area prior to combustion you just can't develop a consistent ratio of fuel to oxidizer.

For some good reading on the topic of naturally-aspirated burners for propane and air, I suggest Micheal Potter's book, "Gas Burners for Forges, Furnaces and Kilns." I haven't found any books that cover the topic of forced-air burners well, nor have do I know of any on the topic of air/oxy/fuel burners. Many people have fooled around with the notion of using an oxygen-enriched air/fuel system, but I don't know of anyone who has really made it work well. I have seen one YouTube video of a guy's forge using oxygen enrichment, but it was not too informative and I don't have a URL for it. You might search it out on YouTube.

Is this the sort of information you were looking for? If you have further questions I'll try to help. I've built a fair number of forges, furnaces and kiln using many different types of burners, and I'm happy to share whatever information I can if you give me specific questions.

Rich