Gas Burners Old and New / A historical and descriptive treatise on the progress of invention in gas lighting, embracing an account of the theory of luminous combustion

by Owen Merriman

But there is yet another direction in which the prior heating of the air supply contributes to the development of improved illuminating power. Being heated, its density is lowered; so that in any given volume of air there is less weight of oxygen than when cold. The consequence is that as less oxygen is presented to a given surface area of flame, the separated particles of carbon remain for a longer period of time in the incandescent condition before being entirely consumed. Thus there are three distinct results produced by heating the gas and air before combustion—namely, first, the particles of carbon are liberated earlier in the flame; second, they are raised to a more exalted temperature; and, third, they remain for a longer time in the incandescent condition. The combined effect of all three is the improved illuminating power developed from the gas consumed.

Fig. 19.—Bowditch's Regenerative Gas-Burner.

So far back as the year 1854, the principle of heating the air supply to an Argand burner, by means of waste heat from the flame, was partially applied, with some success, by the Rev. W. R. Bowditch, Bowditch's regenerative burner. M.A., of Wakefield. Mr. Bowditch's burner, which is shown in the accompanying diagram, contained, in addition to the ordinary chimney, an outer glass chimney, which extended for some distance below the inner one, and was closed at the bottom; so that all the air needed to support the combustion of the gas was required to pass down the annular space between the chimneys, and in its passage became intensely heated by contact with the hot surface of the inner chimney, as well as by radiation from the flame itself. This burner contained many defects. Amongst others, the inner chimney could not long withstand the intense heat to which it was subjected, and, in consequence, had to be frequently renewed; the heating of the air was not effected solely by the products of combustion, but, perhaps in a greater degree, by the abstraction of heat from the flame itself; while, at best, this heating was but partial. Yet, these defects notwithstanding, the burner showed very clearly the beneficial results attending even a partial application of the principle; as, in the illuminating power it developed from the gas consumed, a clear gain of 67 per cent. over the ordinary Argand burner was obtained. Although the drawbacks connected with the construction of Mr. Bowditch's burner prevented its ever receiving general, or even extensive adoption, its simplicity has gained for it the distinction of being freely copied by so-called inventors of a later day.

It was left to Herr Friedrich Siemens, of Dresden, to produce a burner which, while applying the principle of regenerative heating in the most scientific and complete manner, should also be adapted to the ordinary conditions of gas lighting. After much experimenting on the Invention of the Siemens regenerative burner. subject, a burner embodying the essential features of the regenerative system was invented by this gentleman in 1879; and so great was the advance which its performances manifested over anything previously attained, so wide the prospect of further achievements which was opened out, that it may fairly be said to have inaugurated a new era in gas illumination. In this burner the products of combustion were made to give up a considerable portion of their heat to the gas and air, as the latter passed to the point of ignition; the flame itself not being called upon to contribute in any degree to this result. Although, as was but natural, the first attempts towards the construction of such a burner were very crude, and but partially successful in their results, the inventor persevered in his endeavours to work out his ideas into practical and thoroughly satisfactory shape. It was not until after it had gone through many modifications that the burner acquired the peculiar form which now distinguishes it, and attained to its present stage of perfection. Before proceeding to describe an example of the burner as now constructed, it is necessary to state that the principles embodied in Herr Siemens's invention are equally well adapted—and, indeed, are applied with equal success—to the construction of flat-flame and Argand burners; but as the distinctive features of the invention are common to both classes of burners, it will be quite sufficient to describe in detail one of the latter type.

A prominent feature in the appearance of the Siemens burner, as will be seen from the annexed illustration, is a large metal chimney, for creating a draught to carry away the products of combustion. The entrance to this chimney is situated a little above the apex of the flame; but there is a branch flue connecting the main chimney with the interior of the burner. The body of the burner is of metal, and its interior is divided into three concentric chambers. Of these, the innermost is open at the top, and is surmounted by a porcelain cylinder, which, when the gas is lighted, is surrounded by the flame. This chamber is closed at the bottom, but communicates at the side with the before-mentioned branch tube, or flue, leading to the main chimney. The intermediate chamber communicates, at its lower extremity, with the gas supply; and terminates, a short distance from the top of the burner, in a number of small metal tubes, which convey the gas to the point of ignition. The outer chamber is open both at top and bottom, and is for conveying air to support the combustion of the gas. In order to promote greater intensity of combustion, there is a notched deflector at the summit of the latter chamber, and another on the lower part of the porcelain cylinder, which cause the air to impinge more directly upon both sides of the flame. There is also an arrangement for introducing air between the outer casing of the air chamber and the glass chimney which encloses the flame; its object being to keep the chimney cool.

Elevation. —Enlarged Section of Combustion Chambers.
Fig. 20.—Siemens's Regenerative Gas-Burner.

Action of the Siemens burner. The action of the burner is as follows:—When the gas is ignited at the ring of tubes, the heated air and products of combustion, which rise from the flame, create a draught in the main chimney. Through the communication established by means of the lateral flue, a partial vacuum, or area of low pressure, is induced in the innermost chamber of the burner, and within the porcelain cylinder which surmounts it. As the flame terminates close to the mouth of the latter, the greater portion of the products of combustion, instead of going into the main chimney, are sucked into the porcelain cylinder; and thus a current is set up through the interior of the burner, and by the lateral flue, to the main chimney. The heat carried away by the products of combustion is communicated, through the walls of the chambers, to the entering gas and air; and by this means the latter are heated to a very high temperature before they issue from the burner and are consumed. The consequence is that a much greater intensity of combustion is maintained; the carbon particles are separated earlier in the flame, and are raised to a more exalted temperature; and the ultimate effect is a higher yield in illuminating power per cubic foot of gas consumed. Independent tests by various experienced photometrists have conclusively shown that a light equivalent to that from 5 to 6 candles is obtained per cubic foot, from gas which, in the standard "London" Argand, yields a light of only from 3 to 3½ candles.

While the advantages of the Siemens burner are many and obvious, it is not without its disadvantages. These partly arise from causes connected with the very observance of the conditions necessary to Defects of the Siemens burner. secure the efficiency of the burner. With every advance in the more efficient operation of gas-burners, increased care and attention are demanded in their employment, in order to obtain the benefits they are calculated to yield. Indeed, it would almost appear that the nearer the approach to perfection which is made in the construction of a burner, the greater must be the drawbacks to its general adoption. Thus, in the burner under notice, if the gas supply is allowed to become in excess, the tail of the flame enters the porcelain cylinder, and soot is deposited in the interior of the burner; obstructing the passages, and impairing the burner's action. Then, to cause the burner to yield its highest results, it is necessary that the air supply be accurately adjusted to the quantity of gas being consumed. To this end the entrance to the air chamber, at the bottom of the burner, is covered by a perforated semi-circular cup, by turning which the quantity of air entering the burner can be increased or diminished as required. Moreover, the bulky construction of the burner, with its accompaniment of chimney and flue, and its complicated arrangement of tubes and chambers, imparts to it a somewhat clumsy and inelegant appearance, which is calculated to impair the favour with which its remarkable performances cause it to be regarded. But these drawbacks are far outweighed by the undoubted advantages conferred by the burner—in improved illumination combined with economy of combustion, and the facilities it affords for securing perfect ventilation.