OIL AS A FUEL FOR STEAM WAGON BOILERS.
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A Cheap and Effective Oil Burner for Steam Wagons, which is Easily Made and which Renders the User Independent of Coal.
MO those owners of steam wagons who have urgent haulage work in hand and are finding themselves short of their usual fuel the following description and the accompanying sketches of an efficient, practically automatic and economical oil burner may be welcome. In the system in question a tnbe of large bore (it has no fine holes to become choked) is supplied through a float chamber with oil at a constant level about in. to # in. below its top lip. A steam jet directed at right angles across the 'mouth of this tube picks tip the oil and delivers it in a sprayed condition in the form of a cone in front of the tube.
The steam jet at the same time induces the flow of air through the venturi-shaped throat-of the body, the air combining with the sprayed oil to form a perfectly combusted flame with a heat of no particular intensity, as in many oil burners ; the heat can, therefore, impinge on boiler plates and other parts without detriment.The steam supply can be controlled by hand and the size of the flame can be regulated when the wagon is standing. The firebox is closed, except for certain extra-air inlets, which are adjusted once and for all.
On starting the engine, and when under running conditions, the blast from the exhaust causes a partial vacuum in the firebox (as with coal firing). The effect of this vacuum is to raise the level of the oil in the tube, so that the amount sprayed by the steam jet is increased, because it is then easier for the oil to be picked up ; simultaneously more air is drawn in through the throat and the extra-air inlets. As a consequence a larger flame is automatically produced as the tax on the boiler is increased.
In the first burners of this type to be tried successfully the throat or body consisted of a plain piece of 4-in. steam pipe and the steam jet was placed about 1 in. behind the oil tube. .
It is essential that the latter be adjustable, so that the correct position in the steam jet can be found by experiment ; after it has been found no further adjustment is required, about in. below the level of the steam being about the best for a maximum oil pick-up, which is what is required. This position is shown in the side view of the burner proper (Fig. C).
A single burner of 4-in, throat diameter will generally be found sufficiently large to supply the needs of an ordinary ti-ton steam wagon, and, although two burners of a smaller size have been used sucecssf ally, the adjustment was found to he more difficult than when a single burner was employed.
The adjustable oil tube can -readily be made from a i-in. valve, the spindle being withdrawn and a special hollow one made, the adjustment-being effected by a handle so that the mouth thereof may be correctly positioned in the steam stream.
Fig. A shows the general arrangement as adapted to an overtype steam boiler, the firebrick or clay lining to the ashpan being used to deflect the horizontal flame upwards into the firebox and thence to the tubes.
For lighting up, wood can be used through the usual fire door. Old road blocks are useful for this purpose and they
are also handy for leaving in the firebox when the wagon has to be left standing at any time, the burner being then completely closed off.
Fig. B shows the arrangement for Sentinel and other boilers of a similar type, the bottom of the shoot being protected by a cast-iton baffle supported on a rod, the baffle serving to deflect the flame on to the tubes. The baffle may be let down into the-burner to protect it when it is required to stoke wood for lighting up.
Lighting up, however, is not required if steam can be obtained from another source, such as another wagon or a stationary boiler, the oil burner then being used. straight away. Fig. C shows the body of the burner, which can be adapted to steam wagons or bolted to a plate, which can take the place of the fire door in a horizontal boiler of any kind. The angle of the burner does not influence its functioning so long as the float chamber is able to maintain a supply o oil close to the top of the tube for the steam jet to pick up easily.
Fig. D shows a simple form of float chamber used very successfully. It has a strainer on the top, but, for experimental purposes, one tin floating in another was quite effective as a temporary arrangement. This float chamber should be attached close to the boiler in order that it may become warmed, as this ensures a ready supply to the tube when the consumption is at a maximum, the heat keeping the oil thin and fluid.
If a burner is made according to the sketches no difficulty will be experienced in obtaining satisfactory combustion.
The size of the steam jet and the oil tube may have to be modified to suit different pressures and conditions and the exhaust blast in most cases must be reduced. This gives greater freedom to the engine, as less draught is required than with a coal fire.
The size of the extra inlets to suit each condition can easily be found by
experiment and, if the combustion be so arranged that there is no black smoke at the funnel or yellowish red flames in the firebox, it can be assumed that the combustion is quite good. Usually the flame, when correct, is of a light yellowish blue and should not pop out when the steam jet is turned on or the blast is operating from the engine. Should it do so it may be assumed that the mixture is too weak and that either the oil level is being maintained, too low or the air inlets are too large.
A word of warning when experimenting is desirable. If the burner should go out through a rush of water in the steam jet, as may sometimes happen, the burner should nbt be looked into in order to ascertain the reason, as it might relight itself with a considerable " pop " to the detriment of the observer's eyebrows.
A piece or two of wood should be left burning in the firebox until the surroundings are nicely warmed up, when nothing disconcerting will occur.
MAE:ETTA. •