ARGAND BURNERS.
[Sidenote: The premier gas-burner.]
The premier position among gas-burners undoubtedly belongs to the
Argand; and it is from no unwillingness to recognize its claims, much
less from ignorance of its merits, that I have left the consideration
of this burner until now. It occupies this honourable position as much
by virtue of the importance it has acquired through being accepted by
Parliament as the test burner, and the peculiar relation in which it
consequently stands to other burners, as for any marked superiority in
operation. For while, in general, the Argand gives superior results to
other burners, this is not always the case. There are circumstances
and conditions to which the Argand is quite inapplicable, and where a
simpler and less pretentious burner will give excellent results.
Indeed, some of the simple flat-flame burners which we have had under
notice have now been brought to such a stage of perfection, that, when
intelligently used, they not unsuccessfully rival the Argand. But it
has been in the direction of demonstrating the illuminating power
which it was possible to obtain from gas, and stimulating to the
attainment, by other and simpler burners, of the same level of
excellence, that the influence of the Argand has been most beneficial.
For, by reason of its peculiar construction, and more especially its
mode of obtaining the air necessary for combustion, the Argand lends
itself, more readily than any other burner, to the work of
investigating and experimenting upon the conditions necessary for
economical combustion, and the development of the highest illuminating
power from the gas consumed. In this burner, the air supply to the
flame is under complete control; and thus one of the chief elements of
uncertainty and difficulty which are experienced in dealing with other
burners is eliminated. The delivery of gas to different parts of the
flame is also more susceptible of variation; and the results of such
variation more fully exposed to observation. The consequence has been
that the most remarkable advances in developing improved illuminating
power from coal gas have been made with this burner. But after the
possibility of obtaining an improved duty from the gas has been
demonstrated by means of the Argand, and the conditions necessary for
its attainment determined, equally good results have been achieved by
other burners.
[Illustration: PLAN OF GLASS-HOLDER AND BURNER TOP.
SECTION OF BURNER.
FIG. 13.--ARGAND BURNER.]
In thus showing the benefits to be derived from a more scientific mode
of combustion, and leading the way to the fuller attainment, by other
burners, of the illuminating power obtainable from the gas, the Argand
burner has acted as a pioneer in the development of gas lighting. For,
on account of its complexity, and its delicacy of construction, this
burner has never been, nor, indeed, can ever hope to be generally
employed. Besides the inconvenience and expense entailed by the
cleaning and renewal, when broken, of the glass chimney which is
indispensable to this burner, its very perfection as a burner
precludes its being adopted under the conditions which appertain to
the great majority of situations in which gaslight is required. For
while, under the particular conditions as to pressure of gas, &c., for
which it has been constructed, the Argand may give results surpassing
any other burner, a very slight divergence from these conditions is
productive of far more damaging results to the illuminating power of
the flame than is the case with other and less efficient burners. The
cause of this seeming anomaly will be apparent when we come to
consider in detail the construction of the Argand, and the conditions
which must be observed to ensure its satisfactory operation. For the
present it will suffice merely to make mention of what appear to be
well-established facts--viz., that the most perfect burners are the
least adapted for use under uncertain and varying conditions; and that
in proportion to the efficiency of a burner, under the conditions for
which it has been constructed, is the injury to the illuminating power
of its flame which is experienced when these conditions are departed
from.
[Sidenote: What is an Argand burner?]
Resolved into its simplest form, the Argand burner may be said to
consist of a hollow ring of metal, or other suitable material,
provided with the necessary tubes or connections for communicating
between its interior and the gas supply, and perforated on its upper
surface with a number of holes for the emission of the gas. Through
these holes the gas issues in a series of jets, which immediately
coalesce to form one cylindrical sheet of flame. The burner is
surmounted, and the flame enclosed, by a glass chimney, which is
supported on a light gallery connected with the burner; the chimney
serving the double purpose of shielding the flame from draughts, or
currents of air (thus enabling the gas to burn uniformly and
steadily), and of drawing upon the surface of the flame the supply of
air necessary for its proper and complete combustion. For in the
Argand the air supply is produced under conditions totally different
from those which govern its production in all the other burners we
have had under consideration. In flat-flame burners, the quantity of
air supplied to the flame is determined by the pressure of the gas;
or, in other words, the velocity with which it issues from the burner.
In Argand burners, on the contrary, the air supply is obtained quite
independently of the pressure at which the gas issues; and the
conditions most effective for the economical combustion of the gas,
and the development from it of the highest illuminating power
attainable, are only secured when the pressure of gas is reduced to a
minimum.
It has been shown, in speaking of flat-flame burners, how the
illuminating power of the flames yielded by such burners is
injuriously affected by an excess of pressure in the gas, as it issues
into the atmosphere, causing a too great intermingling of gas and air.
With such burners, however, some degree of pressure is needed, in
order, by bringing the flame into contact with sufficient of the
oxygen of the air, to promote the requisite intensity of combustion;
whereas with the Argand the draught that is produced through the
agency of the glass chimney enables the necessary supply of air to be
obtained for the support of the flame without adventitious aid from
the pressure of the gas. Consequently, one of the chief objects to be
aimed at in the construction of the latter burner is to so reduce the
pressure of the gas within the burner that it may issue with little or
no greater velocity than that due to its own specific lightness. In
some of the best Argands this object is attained very successfully;
and the ingenious devices which have been made use of to gain this end
will be duly described in the sequel. But, in addition to causing the
gas to issue from the burner at the minimum of pressure, it must be
delivered evenly and equally at all parts of the ring of holes; so
that there shall not be an excess of gas supplied to one portion of
the flame, and an insufficiency to others. Then the area of the
opening in the centre of the ring, through which the air supply is
obtained to the inner surface of the flame, as well as the length and
diameter of the glass chimney, must be so proportioned that the exact
quantity of air needed to enable the flame to yield its maximum
results shall be drawn upon it. These, and other equally essential
requirements, have to be taken into consideration, and provided for,
in constructing an efficient Argand burner. It is no wonder,
therefore, that the development of the powers of this burner has taken
up so much time and labour and inventive skill; and the remarkable
degree of efficiency to which it has now been brought testifies to the
thought and the accurate knowledge of the principles of combustion
which have been brought to bear upon it.
[Sidenote: The earliest Argands.]
It is, however, only within comparatively recent years that its true
principles of construction have been at all fully recognized, as
evinced by the burners which have been produced. For a long period,
Argand burners were made upon wholly empirical and arbitrary rules.
During the early years of gas lighting, the makers of gas apparatus,
and such persons as professed to have a special knowledge of the
production and utilization of the new illuminant, appear to have been
ignorant of even the most obvious of the conditions required for the
successful working of the burner. In one of the earliest works which
appeared relating to gas lighting,[11] we find the Argand burner
described as consisting of "two concentric tubes closed at the top
with a ring having small perforations, out of which the gas can issue;
thus forming small distinct streams of light." According to this
description, the burner referred to cannot have been an Argand in the
strictest sense of the word; but, in reality, must have consisted
chiefly of a series of single jets placed in a circle, and surrounded
by a glass chimney. But the great improvement in the amount of light
developed, which resulted from bringing the jets of flame closer
together, so as to cause them to coalesce and produce one homogeneous
mass of flame, could not long escape notice; and accordingly we find
that in "Clegg's Treatise," which appeared twenty-five years later,
the proper disposition of the holes in the ring, necessary for the
successful operation of the burner, is clearly recognized. In this
work, speaking of the Argand burner, it is remarked (p. 193) that "the
distance between the holes in the drilled ring should be so much that
the jet of gas issuing from each shall, when ignited, just unite with
its neighbour."
[11] Accum's "Treatise on Gas-Lights."
Before a really efficient burner could be produced, there were,
however, to be successfully encountered other problems, the precise
nature of which was not so clearly apparent as that of the one above
referred to; otherwise their solution would not have been so long
delayed. Of these, the most important, and at the same time the most
difficult, were two--namely, the right adjustment of the air supply,
and the most advantageous pressure at which to consume the gas. In the
earliest Argands, not the slightest provision was made for diminishing
the pressure of the gas before it was consumed. It was thought that
everything had been accomplished that was necessary if the holes for
its emission were sufficiently minute to allow of no more than the
required quantity of gas passing through them at the extreme pressure
at which it was supplied to the burner. The consequence was that the
gas, issuing from the burner at a very high velocity, became so
intermingled with air before it was consumed, that its flame was
excessively cooled; and only a small fraction of the illuminating
power available was developed. Then as to the air supply. In nearly
every burner produced prior to Mr. W. Sugg's invention of the "London"
Argand in 1868, this was greatly in excess of the requirements; nor is
it to be wondered at. Had the supply of air been delicately adjusted,
while yet there was no provision for diminishing the pressure of gas
at the burner, the flame would have been liable to smoke on any sudden
increase in the pressure of gas in the mains; and the annoyance and
inconvenience occasioned by a smoking flame were greater drawbacks
than the loss of light experienced through having the air supply
greatly in excess. Thus, although during this period there were many
so-called "improved" burners brought into notice, in none of them were
these two cardinal requirements in the production of an efficient
burner clearly recognized and seriously grappled with; and,
consequently, the high level of excellence to which the Argand is
capable of being brought was not attained.
SUGG'S ARGANDS.
[Sidenote: The 'London' Argand.]
The invention by Mr. W. Sugg, in 1868, of the famous "London" Argand
constitutes an important epoch in the history of gas lighting. Prior
to that time, the construction of this class of burners had been
carried out in a wholly empirical manner; and such improvements as had
been effected must be looked upon as being rather the fortuitous
issues of hap-hazard endeavours, than as resulting from the
acquirement of clearer views as to the conditions to be complied with
in order to ensure the successful operation of the burners. The
invention of the "London" Argand was the first earnest attempt to
abandon the former chance methods, and to proceed upon more scientific
lines. Its construction shows that its inventor possessed a thorough
acquaintance with the principles of combustion; while, in many
particulars, it exhibits an intelligent discernment, and a successful
application of the precise means required to attain a desired end. In
this burner, the extreme importance of causing the gas to issue at a
low pressure is for the first time clearly recognized; and the manner
in which this object is so successfully attained is as simple as it is
ingenious. At the entrance to the burner the gas is divided among
three narrow tubes, the combined capacity of which is much smaller
than that of the pipe supplying the burner. Through these tubes the
gas is conducted into a concentric cylindrical chamber (forming the
main body of the burner), where its rapid flow is checked; the
current, or swirl, which it may have acquired, is subdued; and the gas
comes to a state of comparative rest before it issues into the
atmosphere and is consumed. The top rim of this concentric cylinder is
pierced with 24 holes, the aggregate area of which is considerably
greater than that of the three supply-tubes; thus ensuring that the
gas shall be delivered at a much lower pressure than that at which it
enters the burner. By dividing the gas into three streams, which enter
the cylindrical chamber at equidistant points in its circumference,
the supply is equally distributed throughout the entire ring of holes;
and a flame of even and regular shape is the result.
The arrangement by which, in this burner, the air supply is obtained
and regulated is as noteworthy as are the means adopted for
controlling the pressure of the gas. The opening within the circular
ring of holes is much smaller than in previous Argands; thereby
proportionately reducing the quantity of air supplied to the inner
surface of the flame. The space between the cylindrical body of the
burner and the glass chimney is occupied by a truncated cone of thin
metal, the upper edge of which is on a level with, and reaches to
within a very short distance of the rim of the burner; while its base
rests upon the gallery supporting the chimney. By means of this cone,
all the air entering between the burner and the chimney is directed
upon the immediate surface of the flame; thereby promoting intensity
of combustion, and a higher illuminating power of the flame. Then the
chimney itself is of such dimensions that, with the quantity of gas
for which the burner has been constructed, just sufficient air is
drawn upon the flame to completely consume the gas by the time the top
of the chimney is reached; a flame of such length as to nearly reach
to the top of the chimney, without smoking, being the most effective
and economical for the quantity of gas consumed.
[Illustration: FIG. 14.--SUGG'S "LONDON" ARGAND.
(_Full Size._)]
Another matter which tended not a little to enhance the results
yielded by this burner was an alteration in the material of which the
body of the burner was constructed. In previous Argands, this had, in
almost every instance, been metal; whereas in the "London" burner
steatite was employed. How the illuminating power of the flame is
affected by the material of which the burner is constructed has been
gone into so fully before (in relation to flat-flame burners), that it
is unnecessary to dwell upon the matter here; only remarking that as
in Argands the contact surface between the burner and the flame is
relatively so much greater than in flat-flame burners, the cooling of
the flame due to this cause is proportionately increased.
[Sidenote: The standard test burner.]
[Sidenote: The improved "London" Argand.]
So great was the improvement effected by this burner in the
illuminating power developed from the gas consumed, so obvious its
superiority to every previous Argand, that it was immediately adopted
by the Metropolitan Gas Referees as the standard burner for testing
ordinary coal gas within the area of their jurisdiction; and from that
time down to the present it has continued to be prescribed in Acts of
Parliament as the burner to be employed in testing ordinary coal gas,
not only in the Metropolis, but generally throughout the United
Kingdom. But although, as the standard test-burner, the original
"London" Argand can still be obtained, it has been far surpassed, in
the results yielded, by a new series of Argands, in which the same
ingenious inventor has still further applied the principles first put
into practice in the former burner. In this newer series of burners,
the details of construction before adopted are modified in two or
three particulars; but without departing from the general principles
embodied in the arrangement of the earlier burner. Thus the holes in
the ring are considerably larger, while the three supply-tubes remain
of exactly the same capacity as before; by which means the gas is
delivered at a much lower pressure. As the increased size of holes
necessitates that the cylindrical body of the burner should be of
enlarged diameter, the opening in the centre becomes of greater area
than before. Were it to remain so, it would permit too large a
quantity of air to be drawn upon the inner surface of the flame; to
obviate which result a metal spike rises in the centre, reducing the
area of the opening, and proportionately diminishing the quantity of
air which would otherwise be admitted at this part of the burner. The
arrangement for regulating the air supply to the outer surface of the
flame is likewise modified, but in a different direction. The upper
edge of the cone is brought nearer to the rim of the burner, and
slightly curved, so as to direct the air more completely upon the
flame; while the base of the cone, instead of extending to the glass
chimney in an unbroken surface, is pierced by a number of holes, which
admit air between the cone and the chimney. The action of this third
current of air is to keep the chimney cool, and to steady the flame;
and, in addition, it may be that it provides a supply of air to
support and intensify combustion at the upper extremity of the flame.
The combined effect of these alterations is to cause the burner to
develop from 7 to 12 per cent. more light from the gas consumed, than
is yielded by the original "London" Argand.
[Sidenote: Silber's Argand burner.]
The Silber Argand, which is a remarkably efficient burner, in the main
features of its construction is very closely related to Mr. Sugg's
later Argands just described. The air is directed on to the outer
surface of the flame, as in those burners, by a curved deflector, of
which the upper edge is, however, at a higher level than in Mr. Sugg's
burners. Air is also admitted between the deflector and the glass
chimney. The most striking divergence in its construction from that of
Mr. Sugg's burners is contained within the opening in the centre of
the burner. Instead of a solid metal spike, there is a brass tube,
through which, as well as between its circumference and the
cylindrical body of the burner, air can enter to feed the inner
surface of the flame. In addition to promoting the steadiness of the
flame, it would appear that the air entering through this inner tube
supports the combustion of the gas at the tail of the flame. The
arrangements for diminishing the pressure of the gas within the
burner, and for ensuring its equable distribution to all parts of the
ring of holes, though quite different, seem to be scarcely less
complete than those employed in the "London" burner. From the nipple
which connects the burner to the gas supply, the gas enters (by four
minute perforations) into a horizontal chamber, where its velocity is
checked, and whence it is conveyed into the cylindrical chamber
forming the main body of the burner. The very satisfactory
performances of the burner (which are in advance of those of the
standard Argand) sufficiently attest the correctness of its
construction.
[Sidenote: Multiple Argands.]
For consuming large quantities of gas, double or treble Argands are
constructed. These consist, in effect, of two or three Argand burners
placed concentrically to each other within one chimney. Mr. Sugg
has produced a series of burners of this class, designed to pass
quantities of gas ranging from 15 to 55 cubic feet per hour; and, in
some instances, exceeding even the latter figure. These burners, with
ordinary (16-candle) coal gas, give a light equal to 4 candles per
cubic foot of gas consumed; which is a considerably better result than
is afforded by the standard burner. The cause of their yielding
results so superior to the ordinary Argand is found in the
circumstance that their flames present a much smaller surface area to
the cooling action of the air, in proportion to the quantity of gas
consumed. The arrangement of these burners differs from that of the
improved single Argands, which have been described, only in that there
are two or more steatite cylinders, each fed by its own supply-tubes,
and having its own distinct ring of holes; while the space between the
cylinders is so proportioned as to admit no more than the quantity of
air required to produce the necessary intensity of combustion.
[Illustration: FIG. 15.--THE DOUGLASS ARGAND.
(_A A, Focal Plane, or Belt of Strongest Light._)]
THE DOUGLASS BURNER.
The multiple or concentric Argand invented by Mr. (now Sir) J. N.
Douglass, the Engineer to the Trinity House, may be mentioned here.
This burner is of the type of those last noticed, but possesses
certain peculiar features which give it a distinct claim to novelty.
As will be seen by the accompanying illustration, the concentric
cylinders of which the burner is composed terminate at different
heights; their tops forming a regular gradation of steps, of which the
innermost is the highest. These cylinders are of considerable depth,
permitting the gas and air to be heated by contact with their surfaces
before the point of ignition is reached. The essential feature of the
invention, however, is a series of deflectors of peculiar shape,
which, in addition to directing air on to the surfaces of the flames,
are so formed "as to force the outer flame or flames on to the inner
flame or flames in the manner illustrated." By this means the flames
are concentrated and united into one, and combustion is quickened;
and, a greater intensity of heat being thus attained, the illuminating
power is much augmented. When this burner was first brought into
notice, in 1881, high hopes were entertained as to its future. The
results which it was said to afford, being far in advance of anything
previously obtained from a simple Argand, seemed to promise for the
burner a speedy and unequivocal success. At the North-East Coast
Marine Exhibition, held in 1882, a burner with ten rings was
exhibited, which was reported to develop, from 16-candle gas, 6
candles per cubic foot--a truly remarkable result to be given by so
simple a burner. But, notwithstanding its apparently successful
introduction, the burner has made little or no headway in the
direction of its practical application. Indeed, it may almost be said
to have faded altogether out of public view. This would seem to imply
that there are difficulties in the way of its successful working, when
brought under ordinary conditions, which were not foreseen at the time
of its invention.