BRÖNNER'S BURNERS.
The credit of having produced the first flat-flame burners designed upon scientifically correct principles belongs undoubtedly to Herr Julius Brönner, of Frankfort-on-the-Maine. Long before the date of his invention, efforts had been made to reduce the pressure of the gas within the burner. But these endeavours were carried out in so hap-hazard a fashion as to lead to the belief that no definite conception was entertained as to what was really required. As we have seen, layers of wool had been employed; but the area of the interstices, or the gas-way through the material, was a matter of the merest accident. And there was not the slightest guarantee that the same conditions should prevail in any two burners. Herr Brönner shrewdly detected the cause of former failures, as he clearly perceived the end which it was requisite to attain, and towards which previous inventors had been but blindly groping. Having formed a right estimate of the requirements to be fulfilled, and the difficulties to be surmounted, he set about accomplishing the desired result by other means. There were two causes which had chiefly contributed to the unsuccessful issues of previous attempts. One was the uncertain and indefinite operation of the means employed for diminishing the pressure; the other was the inadequate provision for enabling the gas to lose the current, or swirl, acquired in passing the diminishing arrangement, and come to a state of comparative rest before issuing into the atmosphere. Both these errors were successfully avoided in Brönner's invention—the former by making the inlet to the burner of restricted and definite dimensions, and of less area than the outlet, or slit; the latter by enlarging the chamber, or place of expansion within the burner, as well as by the different arrangement adopted for diminishing the pressure.
A Top. B Top.
Fig. 8.—Brönner's Burners.
The general appearance of Brönner's burner is pear-shaped; and in size it is considerably larger than an ordinary burner designed to pass an equal quantity of gas. It consists of a cylindrical brass body surmounted by a steatite top, and tapering to a very small diameter at Construction of Brönner's burners. its lower end, or inlet; the latter being closed by a plug of steatite, in which is a rectangular slot, or aperture, of accurately defined dimensions. The size of this aperture determines the quantity of gas which, at any particular pressure, is admitted to the burner; and the slit, or outlet of the burner, being of greater area than the inlet, ensures the gas being delivered from the burner at a lower pressure than that at which it enters it. By varying the respective dimensions of these two openings, and their relation to each other, the burner may be regulated to deliver its gas at any required pressure short of the initial pressure at the entrance to the burner. The enlargement of the cylindrical body provides an expansion chamber, wherein the velocity of the stream of gas which rushes through the narrow opening at the inlet of the burner is checked, and any agitation or unsteadiness which may have been imparted to it is subdued before the gas issues into the atmosphere and is consumed. There are two kinds of tops for the burners, which are distinguished by the letters A and B. The B top is of the ordinary semi-spherical type, giving a true batswing-shaped flame; the A top is flatter, almost square in form, and yields a flame taller than, but not so broad as the former. In consequence of this difference in the shape of its flame, the latter burner is better adapted for use in globes. The general appearance of the burners, and their distinguishing peculiarities, will be clearly understood from the illustrations.
Properties of steatite. The material of which the more important parts of the burner are constructed is eminently adapted for the purpose. Steatite is a mineral which, as found in nature, is so soft as to be readily turned in a lathe, and shaped to any design; but when heated up to about 2000° Fahr. it becomes almost as hard and durable as flint, while perfectly retaining its form and colour. These properties peculiarly qualify it for receiving a slit or orifice, which, though of minute proportions, must be accurately formed to precise dimensions. Besides which, like "adamas," its capacity for conducting heat away from the flame is so limited that, in this respect, it has a considerable advantage over metal for the purpose of being formed into gas-burners.
The following tables, which are extracted from the report of the Committee of the British Association appointed to investigate the means for the development of light from coal gas of different qualities,[ [8] exhibit the very satisfactory results obtained by the use of these burners. In Table I., the gas operated upon was cannel gas (such as is generally supplied in Scotland), and possessed an illuminating power, when employed in the standard burner, of 26 candles per 5 cubic feet. Table II. contains the results of determinations with common gas (such as is used in London, and generally throughout the greater part of England); 5 cubic feet of which, in the standard burner, gave an illuminating power of 16 candles. The first and second columns of the Varied adaptability of the Brönner burner. tables refer to the different sizes of the tops and bottoms of the particular burners employed; there being in all some 16 sizes of the one, and 11 sizes of the other. These, being interchangeable, permit of a great variety of combinations; and enable a burner to be selected suited to any particular quality or pressure of gas. For as with pressure, so with illuminating power: In order to obtain the utmost lighting efficiency, different burners are required for gases differing in quality or their degree of richness. A burner which, with gas of one quality, will yield excellent results, may, under the same conditions of pressure and supply, be totally unsuited to gas of another quality. That this should be so will be evident from a consideration of what has been said as to the theory of burning gas to the best advantage; and, in brief, results from the richer gas containing in its composition a greater proportion of carbon, and so requiring an increased supply of air for its thorough combustion. This increased supply of air can only be obtained (with flat-flame burners) by causing the gas to issue into the atmosphere at a higher pressure; and so it comes about that, compared with the quantity of gas to be delivered through them, the slits of batswing and the orifices of union-jet burners must be considerably narrower when intended for cannel gas than when common gas is to be consumed. In other words, in order to develop its full illuminating power, it is essential that the pressure at which the gas issues from the burner should be proportioned to its quality. The gist of the matter is set forth in the general statement that "the poorer the quality of the gas, the lower must be the pressure at which it is consumed; and vice versâ."
Table I.
| At 1·0-Inch Pressure. | At 1·5-Inch Pressure. | ||||||||
| No. of Burner. | No. of Top. | Cubic Feet per Hour. | Illumi- nating Power. | Illumi- nating Power per Five Cub. Ft. | No. of Burner. | No. of Top. | Cubic Feet per Hour. | Illumi- nating Power. | Illumi- nating Power per Five Cub. Ft. |
| 2 | 2 | 1·20 | 5·07 | 24·13 | 2 | 2 | 1·40 | 5·25 | 18·75 |
| 2 | 3 | 1·40 | 6·64 | 23·71 | 2 | 3 | 1·95 | 7·37 | 18·90 |
| 2 | 4 | — | Smokes | — | 2 | 4 | 2·30 | 10·33 | 22·46 |
| 2 | 5 | — | " | — | 2 | 5 | 2·40 | 11·24 | 23·42 |
| 2 | 6 | — | " | — | 2 | 6 | — | Smokes | — |
| 2½ | 2 | 1·40 | 5·53 | 19·75 | 2½ | 2 | 1·90 | 8·30 | 21·84 |
| 2½ | 3 | 1·70 | 8·48 | 24·94 | 2½ | 3 | 2·30 | 10·14 | 22·04 |
| 2½ | 4 | 2·03 | 10·33 | 25·49 | 2½ | 4 | 2·70 | 12·08 | 22·37 |
| 2½ | 5 | — | Smokes | — | 2½ | 5 | 2·85 | 14·29 | 25·07 |
| 2½ | 6 | — | " | — | 2½ | 6 | 3·00 | 15·21 | 25·35 |
| 3 | 2 | 1·45 | 6·27 | 21·62 | 3 | 2 | 2·00 | 8·48 | 21·20 |
| 3 | 3 | 1·90 | 8·66 | 22·79 | 3 | 3 | 2·40 | 11·34 | 23·63 |
| 3 | 4 | 2·13 | 11·24 | 26·39 | 3 | 4 | 2·80 | 14·84 | 26·50 |
| 3 | 5 | — | Smokes | — | 3 | 5 | 3·15 | 17·04 | 27·20 |
| 3 | 6 | — | " | — | 3 | 6 | 3·25 | 18·07 | 27·80 |
| 3½ | 2 | 1·50 | 5·81 | 19·36 | 3½ | 2 | 2·12 | 8·85 | 20·87 |
| 3½ | 3 | 1·95 | 8·30 | 21·28 | 3½ | 3 | 2·55 | 12·63 | 24·76 |
| 3½ | 4 | 2·55 | 12·08 | 23·68 | 3½ | 4 | 3·00 | 14·47 | 26·12 |
| 3½ | 5 | 2·80 | 14·38 | 25·68 | 3½ | 5 | 3·50 | 18·07 | 25·81 |
| 3½ | 6 | 3·00 | 15·58 | 25·97 | 3½ | 6 | 3·60 | 19·45 | 27·01 |
| 4 | 2 | 1·60 | 6·36 | 19·87 | 4 | 2 | 2·30 | 9·77 | 21·24 |
| 4 | 3 | 2·10 | 10·69 | 25·45 | 4 | 3 | 2·90 | 13·83 | 23·84 |
| 4 | 4 | 2·65 | 13·37 | 25·23 | 4 | 4 | 3·30 | 17·06 | 25·85 |
| 4 | 5 | 3·45 | 17·61 | 25·52 | 4 | 5 | 4·10 | 21·57 | 26·30 |
| 4 | 6 | 3·55 | 18·07 | 25·45 | 4 | 6 | 4·20 | 22·40 | 26·66 |
| 5 | 2 | 1·77 | 7·38 | 20·85 | 5 | 2 | 2·60 | 9·68 | 18·81 |
| 5 | 3 | 2·30 | 11·90 | 25·87 | 5 | 3 | 3·30 | 13·64 | 20·67 |
| 5 | 4 | 3·30 | 15·40 | 23·33 | 5 | 4 | 4·00 | 19·91 | 24·14 |
| 5 | 5 | 4·10 | 20·74 | 25·29 | 5 | 5 | 5·00 | 25·36 | 25·36 |
| 5 | 6 | 4·30 | 22·68 | 26·37 | 5 | 6 | 5·30 | 27·66 | 26·10 |
Table II.