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The diameter of the jet orifice is 1 to 3mm., and in later forms there is a crown or disc set round the nozzle and pierced with holes of 1.25 mm: diameter, through which air is intrained. The output under a pressure of six kilos =84.4 pounds, was as follows when tried at Cherbourg

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Tried on the locomotives of the Vladi-Kavkaz Railway these atomizers with double jets sprayed 230 kilos=506 lb. per hour under a pressure of only 4·2k=59·8 lb. From the trials made by the French Navy it appears that these mechanical atomizers work very regularly and, moreover, silently, if the oil is first filtered and heated to 80°C. 176°F. They are recommended for getting up steam, the force pump being hand worked until such time as steam is produced sufficiently to work the pulverisers.

M. Bertin lays stress on the benefit of supplying oil to a burner at a considerable pressure and at a high velocity, for even with air or steam atomizers the fine jet will atomize more easily, for an oil pressure of three kilos, for example, permits of a velocity four times as much as is given by a head of 2 metres.

The Howden System.

In the Howden system, a general arrangement of which is given in fig. 20, for combined coal and oil firing, a modified Körting jet is employed. The closed ashpit system is employed for the forced draught of the boilers according to the well-known Howden system, and this of course provides an ample air supply to enter the furnace around the oil nozzle. When solid fuel is to be used alone and the sprayers are removed, this air opening is closed by a plug, as shown in the figure at the lower right hand of fig. 20. The use of solid fuel in combination with oil appears to afford

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bustible bed on which any unduly large globules of oil may fall. In fig. 20 the grate is shown covered with fire-bricks for use with liquid fuel alone.

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a favourable opportunity for sprayers of the Körting type, because there is a com

Plug
inserted
when burning
Coal

Fig. 20.

LIQUID FUEL BURNING, COMBINED SYSTEM. HOWDEN'S SYSTEM OF FORCED DRAUGHT WITH CLOSED ASHPITS

I

Chapter XVI

LIQUID FUEL APPLICATIONS TO LOCOMOTIVE BOILERS

The Holden System

N this system, which was the first to come into extensive use in Great Britain. the object has been to combine liquid and solid fuels so that either or both can be used indifferently without a moment's notice of the change.

Mr. Holden, of the Great Eastern Railway of England, was troubled to dispose of the tars produced by oil gas apparatus, and primarily devised his system for getting rid of this; but he has used many liquids for fuel, including coal tar, blast furnace tar and oil, shale oil, creosote and green oils, astatki and crude petroleum. Locomotives thus fitted are very clean to work, make no dust, smoke or sparks, have little wear of tubes or fireboxes and have little ash and clinker to remove. Steam can be raised rapidly, adjusted at an even pressure, and waste at the safety valve is prevented. Any boiler can be fitted for liquid fuel without alteration of furnace, though it is desirable in the locomotive to add a fire-brick lining on the tube plate below the arch.

The fire is made up thin with coal and about 120 pounds of broken chalk, a commodity cheap enough in South England or East Anglia. The ashpit damper is kept sufficiently open to maintain the fire bright.

There is nothing striking to be seen from the footplate, with the exception of an extra fitting on the firebox casing, carrying four steam cocks and two small wheel valves about the firedoor level on each side thereof. Looking into the firebox there is seen, however, only a light fire of coal upon the grate, and yet this engine is to run the down train in a few minutes' time and has yet to get up full steam pressure. A hinged plate appears under the fire door, and on lifting this there are visible two holes through the firebox outer casing leading into the firebox. They are disposed equidistant on each side of the centre line 21 inches apart, and they are 5 inches diameter and 10 inches above the grate surface. In each hole is a ring of pipe perforated on the front side so as to direct numerous jets of steam forward into the firebox. These cause an induced current of air. In the centre of each of the rings there is the nozzle of an injector. These are steam worked and inject oil into the firebox, mixed with air, which enters at the rear of the injectors by an indiarubber hose connexion from the vacuum brake if this is used.

The steam inlet to each injector is on the inside, steam coming by a single pipe, which branches off by square turns right and left to the injectors. Oil enters by separate pipes worked by the two independent regulating wheel valves, which stand above the footplate at the fire door level. Each valve is thus independently ad

justable, but both can be worked together by a special gear, instantly to open and Otherwise the oil apparatus is conOne of these turns steam on to the

close, if necessary, at stations and other stops. trolled from the four cocks mentioned above.

injector supply; another, by similarly arranged right and left branch pipes, turns on steam to the air injecting rings first named; and a third admits steam into a warming coil in the oil tank for the purpose of bringing the oil to a state sufficiently liquid to flow freely to the injectors, and also to destroy its viscidity to enable it to be sprayed sufficiently fine by the action of the steam and the air injected with it. The fourth serves as an oil pipe clearer, and can be used to blow back steam through the oil fuel pipes to the tank to clear any obstruction or to blow back oil which has cooled in the pipe or to warm the pipe, and to blow through the oil passages of the injectors as shown.

The Great Eastern Railway favours the Westinghouse brake, but has a number of engines fitted with the automatic vacuum brake in order to be able to run the cars of other companies. This fills a Board of Trade requirement.

The mode of working the oil burning apparatus is as follows: the engine comes up from the shed with the light coal fire with which steam has been made. It is clear and red and the firebrick arch is well heated, and the fire made up with chalk lumps as usual. When desired to burn oil, the steam is first set blowing through the injector. The delivery of the injectors is directly forwards and sideways, the nozzle having two orifices. No oil is therefore sent against the firebox sides, but only towards the brick arch and towards the middle of the box, the two inclined jets approaching each other. After the steam is turned on, the oil admission valves are slowly opened and the oil is sprayed and ignites apparently at once, the whole firebox being filled with a dazzling white flame as seen through the sighthole in the door.

If this alone is done, there is smoke at the funnel from insufficient air supply. This is instantly checked by turning steam into the ring jets which draw in a further large quantity of air through the five inch openings, and smoke can be reduced to any desired extent down to total disappearance. This is a specially valuable feature in economy, for while it is so desirable to prevent smoke, it is equally undesirable to admit too much air, and this can be regulated to a nicety, merely enough air to stop the smoke being injected, or even only enough to reduce the smoke to an occasional suspicion of it. There need be no waste due to excess of cold air unnecessarily introduced.

As now set going, there is rapid steam production, and nothing further is necessary to be done, but the engine will continue to produce steam as long as the oil is supplied. The light coal fire is kept going by an occasional shovel of coal, or a little chalk is added, as required.

Though the whole apparatus is thus exceedingly simple, if it were possible for it to be put out of order in the middle of a trip, the fireman would commence to shovel coal upon the existing bed of fire which has been, as usual, started with the customary care as to using lumps of chalk on the grate, and the engine would run on as an ordinary coal burner without a hitch or stoppage.

When on a trip, if steam is high, the injectors can be instantly stopped on arriving at a station, or, if the steam is low, continued at full blast as when running, and the fire kept up to a maximum efficiency and steam got up during the wait. There is less dependence on the blast pipe, and a variable blast nozzle is used, the simple movement of a lever in the cab swinging a hinged cap over the pipe top and

reducing the nozzle from 5 inches to 5 inches diameter when necessary for coal burning.

Should any oil by chance be unburned and travel so far as the brick arch, and even run down it, it cannot live and travel over the firebrick protection of the lower tube plate without vaporization and combustion, hence this protection, which is the one slight difference observable from common practice, a difference, however, of no importance or injury to the engine's coal burning properties.

There is no projection of any oil upon the firebox sides, neither is there any local intense combustion as exists in such systems as vaporize the oil before igniting, and thereby produce local plate wasting. On the contrary, the whole interior of the firebox is filled with flame, and no special ignition point, or rather, combustion area, is apparent. Heating is therefore general, and temperature even.

Though nominally a pound of oil has not the steam making power of two pounds of coal, nor perhaps could it be shown to have, in a prolonged test; yet in practice, one pound of oil is found to be equal to double the quantity of coal, owing to the facility of regulation and the saving at the safety valve and of the back pressure from reduced blast pipe resistance. All these points are favourable to the oil, which has the further advantage of cleanliness and greatly reduced labour all round, for it makes no unconsumable refuse, requires no stoking beyond the keeping up of the small bed of coal fire, which seems to have such an advantage, where liquid fuel supplies are doubtful in quantity and uncertain in price, over any system of oil burning which rejects coal entirely.

In the ordinary work of the Great Eastern Railway the run between London and Cambridge about 56 miles-will be made with one firebox full of fuel made up ready for the run and untouched. This will bring the train to its destination, and if it were known that the engine would be shedded at once the steam might be pretty well reduced and the fire left to finish nearly dead. Here comes in the advantage of liquid fuel. Even if steam be down and the fire nearly out, the turning of a handle or two will put the engine in readiness to take out any train in five minutes after notice, and thus an engine may be worked to the economy it would be if about to be shedded, and yet be ready for a full-power run almost instantly. As the fireman remarked, "She will keep steam as far as Doncaster without an effort, and then be just as fit to run a further 200 miles as when she started."

On the occasion of the author's run to Cambridge on No. 760, the Doncaster Express started out from Liverpool Street with a train of seventeen vehicles, weighing, exclusive of engine and tender, 537,600 pounds, or 240 English tons (269 American tons).

The total train weight was thus 704,508 pounds, but six vehicles were slipped at Broxbourne, and the remainder of the journey made with 11 only. The run to Cambridge was made in 75 minutes, including the slow-up for Broxbourne slip and several signal blocks, none of which, however, involved actual stoppage.

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The fireman's work consisted in a very little use of the shovel to keep up thin fuel bed on the grate, and in attention to the oil apparatus at the slow-ups to prevent the waste of steam at the safety valve.

About 120 pounds of chalk is put upon the grate for lighting up, and it would seem that this quantity could be increased and the firebed worked to a very considerable degree of what would be called dirtiness if not for the daily lighting up, that is, the engine could be run night and day until the grate was almost completely impervious to air, only enough air being needed to keep the thin fire reasonably

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