A NEW PARAFFIN CARBURETTER.
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A Multi-jet Carburetter with 300 jets Using Paraffin Fuel. By Henry Stetriney.
ibxNYTHING WHICH will reduce the cost of operation of commercial
motors is important, and few directions in which running costs can be reduced are so important, or so promising as a field for investigation, as the paraffin carburetter,
Many attempts have been made to produce a successful device of this character, and some have arrived at partial success. In all of them, hitherto, the problem has been tackled by arranging special methods fonheating up the carburetter, or the mixture by means of heat from the exhaust, and, hence, it is more than interesting to find an investigator breaking away from preoedent and attacking the problem upon altogether new lines, which the Cammen laboratories of New York do in the new Jet-a-jet paraffinpetrol carburetter which they are now producing. This carburetter, beyond drawing its air supply from around the hot exhaust pipe, does not depend on heat at all for its efficiency, which, from all accounts, would apear to be good.
Instead of endeavouring, as other inventors have done, to vaporize the fuel in or near the carburetter and so to pass it into the engine, as with petrol, as a completed mixture, they make no effort to produce a vapour external to the cylinders, but to pass the fuel into the cylinders broken up into exceedingly minute drops depending upon the minuteness of these drops for the efficiency of the results. Their investigations showed them that, whereas, when paraffin entered the engine in the form of spray of not very minute particles—say, 1-50th of an inch in diameter—the evaporation caused by the heat inside the cylinder, whilst vaporizing the outer surface of the drops caused a cooling, or freezing, effect on the centre of the drops, which adhere to the cylinder walls and get past the rings, upsetting the lubrication, an effect which is well known. This, because the time— about 1-20 sec.—available in a motorcar
engine for the operation, is insufficient to allow of further _continued 'heat vaporizing the whole of the drop. On the other hand, complete vaporization can be obtained if the size of the drop is reduced to, say, 1-500th of a inch in diameter, and the design of their carburetter has the obtaining of this result as its, object.,
In the course of their investigations, they further found that the mere passing of paraffin through fine holes in a, containing surface was not sufficient to secure the results desired, as the "skin " of the liquid prevented the break-up of the fluid into its particles, but it was necessary, in order to secure this effect, that the passage through svhich the liquid was forced should be of some length in relation to its diameter, which would have the effect of breaking up this "skin," or surface tension, and allowing particles to separate themselves from the mass.
Accordingly, the plan of their operations is to pass the liquid through as many and as fine channels as possible, and, to this end, they use six groups of jets, which are opened up consecutively to the suction of the engine by a, taper slot in a barrel-shaped throttle. Each of these sixgroups contains no less than 50 jets, or fuel passages, so that in all there are 300 of these, which are all in operation when the throttle is wide open, although only a portion of those in the first group are in work when the engine is throttled down to the "just ticking round " point.
Each of these jet groups is controlled by an adjustable needle valve, as shown in the annexed illustration, and, as it would, of course, he impossible to drill such fine holes, the fuel passages are closed by circular pings just fitting them and held down by a central screw. Each plug lies ruled on its circumference by a special ruling machine 50 lines, or semicircular grooves, some 4-1000 in. diameter and -kk in. long, so that, when the plugs .arein situ, they form as many fine passages through which the fuel is caused to pass, the •particles forced through such tiny apertures being, as may be snrmised, very minute.
This, then, is the special feature of the whole device, which coimsista of a longitudinal central block containing these six jet groups and the throttle, and, as the engine has to be started on petrol in order to secure the initial heat for vaporization within the cylinder, two float feeds are provided, one for each fuel ; the paraffin one feeding the six multi-jets-above described, and the other feeding a series of six single jetscontrolled by their own needle valves, as shown in the illustrations appended: Each jet is separately adjusted by its own particular needle valve, and it is claimed that the carburetter may, thus, be very accurately and easily adjusted to the needs of any particular engine, and that the adjusting, once effected, is pen: manent.
Another novel feature about this very interestinA device may be noted here, and that is that trial and error are not depended on for the adjustment, but the carburetter is provided with a screw' attachment for the purpose of connecting it up with a vacuum gauge, and the valves are then set in such a manlier that, at full throttle, the gauge shows not more than 8' ins, of mercuryvacuum.
A shut-off, or turn-over valve, is provided, so that, when the engine has been heated up by running for a few minutes on petrol, it can be turned on to the paraffin; hut as each side of the carburetter, petrol or paraffin, is efficient in itself, either fuel can continue to be used, so that the driver has, in effect, two carburetters in one, and can run on either fuel according to the availability of his supplies. • The Jet-a-jet hi-fuel carburetter is claimed, to be fully efficient and quite satisfactory in working with paraffin fuel under the usual conditions of operation.