APRIL 23, 1914] 
convinced me some years ago that if an explosive 
gaseous mixture be either injected on to or forced 
through the interstices of a porous refractory incan- 
descent solid under certain conditions, which will be 
hereafter explained, a greatly accelerated combustion 
would take place within the interstices or pores, or, 
in other words, within the boundary layers between 
the gaseous and solid phases wherever these may be 
in contact—and the heat developed by this intensified 
combustion would maintain the surface in a state of 
incandescence without any development of flame, thus 
realising the conception of flameless incandescent sur- 
face combustion, as a means of greatly increasing the 
general efficiency of heating operations wherever it 
can be conveniently applied. 
There are critics who, whilst admitting the accelerat- 
ing influence of an incandescent surface upon gaseous 
combustion, are sceptical about the process being really 
flameless. The force of such objections largely dis- 
appear when we get into close quarters with the 
phenomenon, and realise how extremely slow a trans- 
action flame combustion really is when considered in 
terms of molecular time. Take, for example, the case 
of such a quick-burning mixture as electrolytic gas 
(2H,+0O.,). When this is ignited at atmospheric pres- 
sure, the flame is initially propagated by conduction 
with a uniform slow velocity of 20 metres a second, 
and during this initial period of ‘‘inflammation,” the 
total duration of chemical change in each successive 
layer is something like the order of 1/50 second, an 
interval of at least one hundred million times as long 
as the average interval between successive molecular 
collisions in the gas. Even after ‘‘detonation’’ has 
been set up in the mixture, when the combustion is 
propagated from layer to layer as a wave of adiabatic 
compression, at a velocity of 2820 metres a second, 
the total duration of chemical change is still of the 
order of 1/5000 or 1/10,000 second, or about a million 
times as long as the interval between successive mole- 
cular collisions. 
The New Processes of Incandescent Surface Com- 
bustion. 
Leaving the theoretical aspects of the subject, I will 
now describe some of the more important features of 
two processes of incandescent surface combustion 
evolved at the works of Messrs. Wilsons and Mathie- 
sons, Ltd., in Leeds, under my direction, with the 
assistance of Mr. C. D. McCourt, in which a homo- 
geneous explosive mixture of gas and air, in the proper 
proportions for complete combustion (or with air in 
slight excess thereof), is caused to burn without flame 
in contact with a granular incandescent solid, whereby 
a large proportion of the potential energy of the gas 
is immediately converted into radiant form. The ad- 
vantages claimed for the new system, now known as 
the ‘‘ Bonecourt ’’ system, are :—(1) The combustion 
is greatly accelerated by the incandescent surface, 
and, if so desired, may be concentrated just where the 
heat is required; (2) the combustion is perfect with a 
minimum excess of air; (3) the attainment of very 
high temperatures is possible without the aid of 
elaborate regenerative devices; and (4) owing to the 
large amount of radiant energy developed, trans- 
mission of heat from the seat of combustion to the 
object to be heated is very rapid. These advantages 
are (as I believe) so uniquely combined in the new 
system that the resultant heating effect is, for many 
important purposes not only pre-eminently economical, 
but also easy of control. ; 
Diaphragm Heating and its Applications. 
In the first process the homogeneous mixture of gas 
and air is allowed to. flow under slight pressure 
through a porous diaphragm of refractory material 
NG..2321, VOL. ea] 
NATURE 
203 
and is caused 
surface of exit, 
from a suitable feeding chamber, 
to burn without flame at the 
which is thereby maintained in a state of red-hot 
incandescence. The diaphragm is composed of 
granules of firebrick, or other material, bound to- 
gether into a coherent block by suitable means; the 
porosity of the diaphragm is graded to suit the par- 
ticular kind of gas for which it is to be used. The 
diaphragm is mounted in a suitable casing, the space 
enclosed between the back of the casing and the dia- 
phragm constituting a convenient feeding-chamber 
for the gaseous mixture which is introduced at the 
back. Such a mixture may be obtained in either of 
two ways, namely, (1) by means of suitable connec- 
tions through a Y-piece with separate supplies of low 
pressure gas and air (2 or 3 in. W.G. is sufficient), 
or (2) by means of an ‘‘injector’’ arrangement con- 
nected with a supply of gas at a pressure of 1 to 2 lb. 
per sq. in.; the gas in this case draws in its own air 
from the atmosphere in sufficient quantity for com- 
Dees 
Fini — a8 
poet 
Fic. 1.—Diaphragm, 
plete combustion, the proportions of gas and air being 
easily regulated by a simple device. 
We will now start up a diaphragm (Fig. 1). Gas is 
first of all turned on and ignited as it issues at the sur- 
face; air is then gradually added until a fully aerated 
mixture is ohtained. The fiame soon becomes non- 
luminous, and diminishes in size; a moment later, it 
retreats on to the surface of the diaphragm, which at 
once assumes a bluish appearance; soon, however, 
the granules at the surface attain an incipient red heat, 
producing a curious mottled effect; finally, the whole 
of the surface layer of granules becomes red-hot, and 
an accelerated ‘‘ surface combustion ’’ comes into play. 
All signs of flame disappear, and there remains an 
intensely glowing surface throwing out a_ genial 
radiant heat which can be steadiiy maintained for as 
long as required. 
Whilst the diaphragm is in operation before you, I 
may point out some of the more striking features of 
the phenomenon which it presents. First, the actual 
combustion is confined within a very thin layer—j to 
