Two-fuel Carburetters and Fittings.—VI.
Page 12
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A Paraffin Vaporizer as Fitted by the Albion Motor Car Co., Ltd., to Certain of its Well-known Commercial Vehicles.
it is necessary, before one can thoroughly understand the working of the Albibn vaporizer, to consider carefully the operation of the company's unique and efficient carburetter, in conjunction with which the vaporizer works. The carburetter as fitted for using petrol is also utilized where it is intended to use the heavier fuel, but with the addition of a special and
• well-designed exhaust-gas-heated vaporizer. As usual, of course, two tanks are necessary—a standard • tank for paraffin and an auxiliary or supplementary one for petrol ; these, together with the two-way cock, which is arranged to couple either tank with the carburetter float-chamber at will, complete the device. The carburetter is shown in section in one of th% accompanying illustrations. The throttle and mixture-controlling portion of it is entirely separate from that containing the fioat-chamber and the jet. This arrangement of the Albion fitting is common to the company's petrol-driven chassis and those in which paraffin is used.
The Albion Carburetter.
We first refer to the petrol carburetter, per se. Warm air is drawn from the region of the exhaust pipe, across a simple jet of such a size, and situated in a choke tube so proportioned that the mixture provided at this point is a rich one. This mixture is car.riedthrough a pipe, which is water-jacketed for a
• portion of its length, and conveyed to the branch of the throttle valve which is shown on the left of our • illustration of that fitting. When starting, or when running the engine very slowly, this rich mixture passes through the small openings in the main doublebeat throttle valve, and enters the induction pipe past the small centrally-placed pilot valve, which valve is opened for the purpose. In this manner the rich mixture suitable for starting and slow running is taken direct to the cylinder. Further movement of the hand control lever or accelerator pedal opens the main double-beat throttle valve'; this, in addition to providing means of ingress for more of the rich mixture from the carburetter, also allows a certain amount of cool, pure air to enter by the pipe which is shown on the right of our drawing of the carburetter, thus providing a mixture which is slightly less rich and suitable for hard pulling at moderate engine speeds. As the throttle is still further opened, and the speed of the engine increases, the diluting valve is also opened, thus allowing an even greater proportion of air to enter, with the effect of weakening the mixture still further.
Points to be noticed are that both pilot and doublebeat valves. are held on their seats by means of coil spriugs The diluting valve is fixed so that it cannot be closed entirely ; hence, it is always possible for air to enter as soon. as the double-beat valve is open, and before the increased speed of the engine renders it desirable for the opening of the speed-air or diluting valve to be increased.
For Paraffin.
The same arranKement, in general, holds good for both fuels, with-this difference: in the case of paraffin, rich mixture as it leaves the jet is drawn through a vaporizer of special form, and it thereby acquires sufficient heat thoroughly to vaporize the paraffin.
The vaporizer used has been designed both with an eye to its efficiency as an imparter of heat and also with a view to accessibility for cleaning purposes. As our drawing shows, it consists, in general, of a box with a vertical partition dividing it into two approximately-equal parts. The hot exhaust gases pass Irani the cylinder through the rear half of this box on their way to the silencer. The ether half is provided with a number of radiating fins ; it is open in front, and covered when in use by an air-tight lid. The fins, in addition to serving as a means of radiating the maximum amount of heat front the exhaust gases to the paraffin mixture, are also of use in that they tend to break the mixture up and to effect more thorough intermingling of its constituents.