In this case the production of light is chiefly due to the fact that
calorific condensation, caused by the use of the helicoidal coil
surrounding the curved wire, prevents loss of heat in this conductor.
In these forms of high-power burner, in which the gas is used directly
for the production of light, the difficulty generally encountered of
heating the air (present in a larger volume than the gas) has been
successfully overcome.
Fig. 3 shows the straight and outspread flame burner with a special
heater. In this arrangement the gas and air are heated before
combustion, in the compartment, G, directly exposed to the action of a
small Bunsen burner, R, which is placed (in an opaque glass) in the
middle of a lyre-shaped figure formed by the two gas-pipes, AA. The
burner proper consists of two fine annular passages meeting above, and
emitting a thin annular sheet of gas over the guide, T, made of a
white refractory substance placed between the two annular jets. The
object of this guide is to stretch the incandescent sheet of flame,
composed of several jets, and interpose friction, so as to prevent a
too rapid ascent of hot gases.
[Illustration: FIG. 3 and FIG. 4 REGENERATIVE BURNERS WITH INVERTED
FLAMES.]
The luminous focus is placed within a glass globe, C, mounted on the
bell, B, of the heater; and the external air enters this bell,
mingling with the products of combustion of the heating burner, R.
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