By combining together these two devices: by delivering the
acetylene to the injector jet at a pressure sufficient to drive the
mixture of gas and air forward rapidly enough, and by narrowing the
leading tube either wholly or at one spot to a diameter small enough, it
is easy to make an atmospheric burner for acetylene which behaves
perfectly as long as it is fairly alight, and the supply of gas is not
checked; but further difficulties still remain, because at the instant of
lighting and extinguishing, i.e., while the tap is being turned on or
off, the pressure of the gas is too small to determine a flow of
acetylene and air within the tube at a speed exceeding that of the
explosive wave; and therefore the act of lighting or extinguishing is
very likely to be accompanied by a smart explosion severe enough to split
the mantle, or at least to cause the burner to fire back. Nevertheless,
after several early attempts, which were comparative failures,
atmospheric acetylene burners have been constructed that work quite
satisfactorily, so that the gas has become readily available for use
under the mantle, or in heating stoves. Sometimes success has been
obtained by the employment of more than one small tube leading to a
common place of ignition, sometimes by the use of two or more fine wire-
gauze screens in the tube, sometimes by the addition of an enlarged head
to the burner in which head alone thorough mixing of the gas and air
occurs, and sometimes by the employment of a travelling sleeve which
serves more or less completely to block the air inlets.
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