SPRAY BURNERS In spray burners the oil is atomized by a blast of steam or compressed air. The most efficient burner for any purpose is the simplest possible piece of mechanism using the least possible amount of steam or air for atomizing purposes. An analysis of the various types of spray burners made by the U. S. N. "Liquid Fuel Board" shows that five general classes will cover practically all the main features of construction. These five classes of oil burners may be thus grouped : 1. Drooling burner.
2. 'Atomizer burner.
3. Chamber burner. • 4. Injector burner.
5. Projector burner.
These five classes are shown by fig. 53, in Which each burner is pared down to its very simplest elements of construction, leav ing out all unnecessary features of manufacture or detail which might be regarded as merely accessory.
1. Drooling burner.--iThe name selected for this burner, while perhaps unusual, best expresses its function as seen from the diagram ; the oil simply oozes out, or properly "drools" out, at the orifice over and on to the steam jet. In this case the drool ing oil is simply carried away on a jet of flaring steam. The action is supposed to be as follows : As the steam issues forth it expands within the layer or film of oil which is being carried into the air by the fire box. It may be thought that this rather rough method of effecting vaporization would hardly be possible or satisfactory ; yet as large numbers of these burners have been and are in actual use, they can not be regarded as crude or unsat isfactory.
2. The Atomizer burner.—In this burner the oil is brought through an orifice from which it is swept off by a brush of steam or air. It is, in short, a principle made use of in an ordinary cologne sprayer. This form of spraying or atomizing is a very old invention, and its capabilities for spraying into a fine mist have long been appreciated.
3. Chamber burner.—In this burner the oil and steam are more or less mingled within the body of the burner and pass out from the tip or nozzle as a mixture, and then, owing to the ex pansion of the steam, the oil is rapidly broken into minute particles. Burners of this type are simple in construction and have been carried through a large range of design.
4. Injector burner.—Burners of this type are analogous to the injector often used for boiler feeding and similar purposes. Here the steam and oil rising, each through its own passage, mingle within cone-shaped passages, and as a mixture passes through a contracted nozzle, and then outward through a reversed flaring cone. Burners designed on these lines have the principle common to injectors in general, that they can draw or suck the oil to them and force the mixture of and oil outward at considerable velocity. Burners of this type have been in use for forty years or more on the railroads of Russia and have be come with that nation what might be regarded as a standard type.
5. Projector burners.—In burners of this type the oil is pumped to the oil orifice and from there is caught by a passing gust of steam and blown off. This might be regarded as a sub classification of No. 2, the atomizer burner, except for the fact that the brush of steam is located some distance from the oil orifice, and this sweeping brush of steam, as usually constructed, is arranged to entrain a certain amount of air further to aid in spraying and in combustion.
By changing the pressure on the atomizing medium or by some slight variation of construction a long or short flame of special advantage for some particular purpose, may be pfoduced in the first four of the types described above. As an example,
the possible modifications of the drooling burner are shown in fig. 54. In this illustration the first sketch shows the basic form of the drooling burner. This subdivides into four special classes designated as A, B, C, and D. In form A is shown the drooling burner made in its simplest possible form, the upper view show ing simply two drilled holes, the larger for oil and the Smaller for steam, while the lower view shows two pipes in a double T-elbow, the larger pipe being for oil and the smaller for steam. Burners have often been made in this exceedingly elementary form, and will give results without any further recourse to mech anism. For convenience, this subdivision A is termed as "straight shot burners," due to the fact that the flame formed will have considerable length. In form B the basic section of the drooling burner is developed into a class which gives two long slots. In this form a large number of burners have been con structed, and in another part of this report results of tests are given on the Santa Fe burner, which has been largely used on a railroad of That name. In this simple form of a box-shaped cast ing these burners have gained a wide use, especially for railroad work. The construction is of course crude, but the results from a practical standpoint have been quite satisfactory, due to the fact that there are no complicated parts, and it is almost impossible to choke up any of the openings even with quite a dirty oil. Where burners are required to use a very heavy oil or residuum, or even a tar, these burners will always operate. This form B, which, for convenience, has been termed the long-slot burner, can be developed into the additional form C, or a fan-tailed burner. In form C there are two burners which can be devised. The first form, in which the fan-tailed effect spreads through but a small arc of a circle, and the second form, in which the fan-tailed effect is extended so as to cover the arc of the entire circle. The first form will cover a large amount of surface in a wide or square firebox, while with the second farm the burner can be placed in the center of a grate and the flame will extend outward in the form of a continuous sheet and cover the entire firebox or grate area, such uses being desirable, for example, in the fire box of vertical boilers, such as fire engines, etc. The last form or modification, form D, can be developed from the basic section of this drooling burner by conceiving that the section is revolved around an axis parallel with the burner axis. By revolving the section around an axis on the steam side there will be derived a burner of the style shown in the upper part of the pair of form D, or by revolving the basic section around an axis near the oil side we get a form of burner shown as the lower one. Either of these two burners, while apparently very different in form from the basic section, yet are nothing more or less than a devel opment of the original type. Burners of this style should prob ably only be used where very heavy consumption of oil is required. In heavy metallurgical operations, brick kilns, and where a large volume of flame is desired such burners have a wide field of usefulness.