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Essentially a jet engine consists of a compression system, a combustion chamber and a directed outlet to create a reaction force to propel a vehicle. The combustion chamber is a semi-sequestered volume to add energy to the isolated gases contained within. An oxy-hydrogen or oxy-acetelene torch is merely an open combustion jet with the force of the flame acquired through the pre-pressurized gases fed to the burner but there is not much force involved and most of the work is done by the heat alone. If the burning were done in a semi-enclosed chamber similar to that of a mimiature rocket engine the energy of the combustion could add a force component to the flame which might accomplish flame cutting with greater efficiency and speed and accuracy.
sand, Jun 25 2006
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Actually, an oxy acetylene cutter does shoot a jet of oxygen to blow molten metal out of the way.
The above comment is correct.
Both the oxygen and the acetylene are already coming out at a very good clip. These have no problems blowing metal out of the way, because blowing it out of the kerf is only a secondary cutting element. Metal cutting works primarily by oxidixing the material. You can demonstrate this yourself by attempting to cut aluminum with an oxyacetylene torch. Molten slag goes everywhere and is very dangerous. Compare that to steel or iron, which burns clean through and begins to consume itself,. The work catches fire, and burns over 8000 degrees Celcius. Burning steel/iron is also used in another cutting tool, the thermic lance, used to cut concrete on demolition jobs.
When accuracy and speed are real concerns, they use CNC plasma torches. These burn at several million degrees kelvin (depending on the eV's of the plasma) and have a ion velocity of over 8000/ms.
Compare that to oxyacetylene, which has a maximum flame tip temperature of ~6570 in ideal lab conditions.
Actually, aluminum burns much more easily than iron/steel. The spattering is likely due to the aluminum burning excessively. Not only does an oxy-acetylene torch have high pressure gas to start with, but the burning and consequential expansion does in fact act like a rocket motor, increasing the velocity and pressure of the stream. When you light one, you can feel the thrust.
Have you ever used an oxy-acetylene cutting torch, sand? Probably not. There are multiple tips for an oxy-torch, and that's one of the reasons why it's so popular. As well as not having to wear near as much protective equipment, fully portable, no electricity needed, and you can swamp tips to create a welding tip. An oxy-acetylene torch cuts through 1/4 inch thick I-beams like it was butter.
See this clip, about 26 seconds in, he starts hitting the oxygen and you can see the difference. You also see the difference when he lays the flame down on the metal and then hits the oxygen in order to cut it effectively.http://youtube.com/watch?v=BWBxBrvXkVI
I have used an oxy-acetylene torch quite a lot but mostly for brazing and I have not had much experience in cutting steel nor had any instruction in the use of various tips.
I don't think this idea would work since you would need a huge amount of combustion energy to move the vehicle forward. Jet engines work by sucking huge volumes of air through a turbine which "pulls" the aircraft forward.
Rockets use explosive power to push vehicles against the earth's mass. The smaller mass of the rocket will move it upwards and not affect the mass of the earth.