US1896139A - Coal dust furnace - Google Patents

Description

Feb. 7, 1933. G. HAYN GOAL DUST FURNACE Filed Dec. 25, 1928 Patented Feb. `7, 1933 PATENT foi-FICE GEORG HAYN, or KASSEL, eiiainaivvl i GOAL DUST TURNVACE V yApplication,ineapimenter 2s, i928, serial No.` 328,586, mid incermanyianuary' 31, 192g',

The invention relates to coal dust furnaces `more particularly those'intended for loco- 'motivesand having a burner that'has the A shape of la spray nozzle.

One of the most difficult problemsin apj plying coal dust furnaces to locomotives is the realization of a complete combustion under the peculiar conditions existing in locomotives, that is, the adaptation, as far aspossible, of the furnace to the usual design of the locomotive combustion chamber. In comparison with 4'stationary furnaces the main difficulty with locomotives resides in the fact that in the latter theJ combustion chamber is very small, whilst on 'the other hand the coal dust particles for their complete combustion' require a certain minimum time, minimum path, and a minimum volume ofl the combustion chamber. These conditions can be vcombined to a minimum value lthat must not be reduced, only if the other conditions are the most favorable* for ycombustion. f i

To this end it is necessary that the coal dust particles are mixed With a sufiicient y quantity of air previous to leaving the burn-f er, in order that theoxygen required forfthe combustion may be immediately at the disposal of every coal dust particle. Conven- '30 -iently a portion ofthe combustion air, in the mostfofcases the greater part thereof;` this 4depending upon the desired division ofthis air,-is added to the c oal dust before the latter entersy the combustion chamber. f Further# 5 more, a rapid pre-heating of the coal dust-air mixturel after its entrance in the combustion chamber has to be providedfor, by radiation, best from the hot brickwork, in order to have the coal dust ignited as soon as possible after mhaving .entered the combustion chamber, to fully utilize the latter. This requirement may be met .by a suitable distribution of the mixture in the combustion chamber, by em ploying one or more burners that are so constructed that they subdivide the mixture into a great number of partial jets `and thus in-v crease its surface. With this arrangement individual short thin flames are formed that unite into a round flame and completely fill the combustion chamber Without sharply striking ther Walls, a premature'destruction of the latter thus being avoided. `Finally,

the determinationoffthe average `temperatureof the fire box is ofV importance, as due l, to `the small sizeof thisv chainberinlocomo- 55 tives only afdetermined gasvolume can be f lodged therein, which however increases with increasing temperature. A lowering fof' the temperature in the lire box andthus a reduction of the gas volume therein however re- "6 sults in an increase of thespeciiic load of the iire box, that is an increase of the quantity of heat supplied inthe time unitand space unit of the combustion chamber.

If all these favorable conditions are to be fulfilled, it is necessary to have the igniting zone of the coal dust situated close to the burner head Whichythereby in a Very high degreeis exposed to the action of the heat radiated. by the flame. To prevent therefore '7 premature destruction of the burner, a water cooling arangementfhasnbeen provided with knownsfurnaces of this type.V This provi# sionA however involves both a very complicated construction and an undesirable in- 275 crease of Weight, so that With other designs this Water cooling has been replaced by an air cooling arrangement. To this end 'a portion of the Vcombustion air is 'supplied to the y combustion chamberas so-called additional '80 air through passagesthat surround the coal dust supplying` tube, this cold additional air causing the temperature atthe burner head tok be held within admissible limits. I 7 The known lconstructions'hereinbefore de- 85 scribed however do notconstitute the simple solution of the problem to be aimed at. Now the object .of my presentinvention is a coal dust burner that to the largest possible extent fulfills the required conditions as to simple'construc'tion, sufficient cooling effect and other requirements. This object is obtained by constructing a burner which has a front plate comprising a large number ofy closely spaced small nozzle-shaped holes; The burner body proper therebylies entirely outside the-combustion chamber and beingy thus cooled by thev outer air remains comparatively 'c old even with the highest effect of the n burner, While thenozzle plate whichl is exosed to the radiation of the flame is cooled y the air that conveys the cold coal dust-air mixture entering the combustion chamber.

As in this manner the quantity of air passing 5 through the nozzle plate is very abundant, this air conveniently being not only coal dust conveying air but also in part combustion air, the temperature of the nozzle plate is held Within such limits that this sensitive burner part is not endangered.

Furthermore, the Haring shape of the nozzles or openings of said burner plate has a particularly favorable influence upon the cooling of this plate. For, by the high speed of the cooling means, that is of the conveying and combustion air, at the narrowest or most constricted place of the nozzle plate not only the necessary reduction of the temperature of this plate is obtained, but also the iame is prevented from striking back into the burner body, since it is possible to determine by suitably shaping the nozzles the speed of the coal dust'air mixture so as to always be higher than the speed of ignition ofthe mixture. By conically enlarging the nozzles toward the combustion chamber, whereby the speed of the mixture is reduced, the condition is fulfilled which is in opposition to the aboveindicated requirement, that the speed of thel constituents of the mixture should be as low as possible to obtain a short length of iame.

In order to allow my invention to be more easily understood, a preferred embodiment of the same is illustrated by way of example in the drawing which accompanies and forms part of this specification. In this drawing VFigure l is a longitudinal section through the combustion chamber of a coal dust fired locomotive. Y

.Figure 2 is the section on line I--I of Figure l, seen in the direction of the arrows and on an enlarged scale.

The combustion chamber of the coal dust furnace illustrated consists of a fire box a of usual description and a bottom box b fitted with suitable brickwork. In the rear, vertical wall of box b are arranged symmetrically to the longitudinal middle plane of the engine two burners c1 and c2. Each of these burners substantially consists of a hollow truncated conical portion, the smaller rear face of which is connected to a suitable mixer f for the coal dust-air mixture. These burners are designed as spray nozzles, that is their heads are formed by a rose plate d, this plate simultaneously forming a portion of the wall of box b. In the plates d are provided close together nozzle-shaped holes e which may be circular, 'slotted o-r of any other suitable shape and through which the coal dust-air mixture is blown into the combustion chamber. For the sake of clearness in Figure 2 these holes e are shown somewhat greater than they really are. As already mentioned the intimate mixing ofthe two mixture constituents taking part in the combustion takes place before the burner proper within the mixer f separately provided for each burner and not shown in detail.

The function of the burner and the manner in which it is cooled will be understood from the foregoing without further explanation. Owing to the brickwork being restricted to a minimum extent, the temperature of the iire box can be lowered as mentioned above, because a good heat transmission is obtained by the non-lined water-cooled walls of the lire box. To inspect or repair the burners, they need only be disconnected from the wall of the box and can then be removed from their seats. To this end they are fixed on the wall from outside.

Instead of being arranged on the wall of said lower box, as in the embodiment illustrated, the burners may be disposed at any other place of the lower box or iire box, according to special constructive points of view or conditions of service. Besides as a Inatter of course more or less individual burners may be provided for instead of the two burn- "l ers illustrated, as circumstances may require, without deviating from the scope of the invention.

What I claim and desire to secure by Letters Patent, is :-u

1. In a coal dust firing installation, a common coal dust and air supply conduit, a burner in which said conduit terminates, said burner having a face plate provided with a large number of small flaring discharge openings adapted to discharge the mixture of coal dust and air, said openings being closely spaced with their axes parallel to the axis of the burner.

2. In a coal dust ring installation, a common coal dust and air supply conduit, a burner in which said conduit terminates, said burner having a face plate provided with a large number of small discharge openings adapted to discharge the mixture of coal dust and air, said openings being closely spaced with their axes parallel to the axis of the burner, and said openings Haring in the direction of flow, thereby permitting expansion of the mixture and consequent reduction in velocity as it iows through the plate.

The foregoing specification signed at Frankfort-on-the-Main, Germany, this 12th day of December, 1928.

GEORG HAYN.

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