And then there's this response to WokMon. I find it rather convincing.

Geo

http://stroupaloop.com/blog/diy-wok-converter/

From the reference,
“On the way there, my housemate asked why this design would work. Engineering!!! In simple terms, if you think of the flame consisting of very small, vibrating balls (gas molecules), they become compressed as the area becomes smaller moving towards the end of the nozzle. Those balls now occupy less space which means they’re hitting each other and the wall more frequently creating friction (HEAT). This leads to a hotter flame, which achieves the goal for wok cooking.”

Think Blow Torch.
While the above is true, the simple fact is that the BTU’s available do not change and using a blow torch on a Wok drastically reduces the area for high heat cooking.-Richard

Totally correct, Richard. (Hmmm, and if I correctly remember, there's going to be some incidental inverse changes in velocity/pressure in that flame stream, too. Which is unimportant, actually, but it shows that maybe, just maybe, at one time I might have known something about this kind of stuff! : )

However, I think that the lessening area/increasing temperature isn't such a bad result: in a wok the differential temp zones are what allows it to cook the style it does. The problem IMHO is that on a standard stove burner NO zone gets hot enough. With this contraption, it might be the case that at least *one* zone--small as it might be--gets hot enough to do the 'frying' that makes stir-frying such a desirable method.

Hypothesizing here, but maybe it's right...

Geo