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Registered Member #3040
Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237
I do quite a lot of work with large gas flame systems and have become quite interested in the deceptively simple looking design of gas burner nozzles (e.g. as on a blowtorch) Normally I buy in existing commercial stuff and modify it to my needs but it would be good to be able to design my own. The basic requirements are :-
Jet orifice : A small hole that the gas squirts through forming a jet.
Air intake : Hole(s) through which air is sucked in (venturi effect) to provide the correct gas air mix for combustion.
Nozzle/combustion chamber : Where the gas and air is mixed in various ways to provide the combustible mixture for the flame.
Sometimes the gas/air mix is such that it starts burning inside the combustion chamber, other times there's not quite enough air sucked in via the venturi and the mix only burns once it leaves the nozzle and is able to get some extra air from the atmosphere (this helps keep the nozzle cooler).
So now for the questions. Basically where do I start looking for the various equations required for :-
Gas flow through the orifice (depends on orifice size, pressure and gas density) from experience the diameter appears to be VERY critical, a tiny change can make a big difference in performance.
Volume of air sucked in via venturi (depends on the velocity of the jet, diameter of the nozzle, size of the air holes (and maybe other factors?)
and anything else I need to consider?
Anyone got experience of this sort of thing? Is the best way to do it experimentally rather than trying to calculate it? Also any ideas for Free/cheap fluid dynamics software that can simulate this sort of thing?
Registered Member #3263
Joined: Sat Oct 02 2010, 04:43AM
Location: Sydney, Australia
Posts: 34
It's been a long time since I did any fluid mechanics (and I didn't much like it), but what you've described sounds like "Compressible flows through an orifice plate"
This:
provides equations for the mass flow rate for a given set of conditions, the rest however, I'm stumped on -- It is a complex problem.
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Burner design
