MOTORING NOTES
ALTERNATIVE FUELS
Tim internal-Conabustion engine has been vastly improved during the last decade and the power delivered in proportion to weight in the present-day motor-car engine is very greatly in advance of what it was even a few year ago. It is strange, therefore, that little or no improvement has been effected in the method of carburation. The carburettor is practically the same as it was when the motor-ear was in its infancy. At the best, it is a somewhat primitive-instruments depending as it does upon the suction of the piston on the induction stroke when the inlet valve is open. This suction causes a stream of air to rush past a jet leading from the fuel tank, thus drawing the fuel in the form of spray into the induction tube, where it mingles with the air and forms the mixture. The volume of air and the quantity of fuel absorbed in this way arc variable and are influenced by numerous factors.
As an indication of the primitive method of carburation employed it may be stated that, even with the best designed carburettors, something like 25 per cent. of the fuel is wasted, the greater part of this passing out into the air through the exhaust. The whole problem of carbitration is a very difficult one. It is extremely important that the fuel should be converted into a stable and permanent gas, so that it is proof against those influences which tend to condense it, but to design an instrument that delivers the air and fuel vapour in the exact proportions - required under varying conditions, and with varying -agents at work against it, means excessive complication and intricate adjustment. In order that simplicity may be secured it is essential to sacrifice a certain amount of engine efficiency. Petrol is the fuel mainly employed at. the present time, and nothing is more suitable. But its supply is not inex- haustible, and a time will assuredly come, perhaps sooner than some of us imagine, when other fuels will have to be employed. The price of petrol, too, warrants experiments with a view to discovering alternative fuels. The great advantage of petrol is that it is a very volatile liquid and becomes gaseous at fairly low temperatures. The objection to the majority of the suggested alternative fuels is that they arc lest volatile ; consequently some means of heating them must be adopted before a suitable combustion mixture can be made. This involves a modification in the carburettor.
The most successful alternative fuel is benzole. This is a by-product in the distillation of coal and it can, therefore, be produced in enormous quantities in this country. The chief advantage of benzole is that it can be used in its pure state —it is a standardized liquid to-day—with very little alteration to the adjustment of the carburettor. Another advantage that it possesses is that it can be mixed in any proportion with petrol, the resulting liquid giving excellent results. A mixture of equal parts of benzole and petrol does not call for any alteration in carburettor adjustment.
Paraffin oil may be used for motor-ears, but in this case the hemineSS of the liquid necessitates heating either the* fuel itielf',the Mixture of fuel and air, so that the former
may be _properly -.vaporized. In all cases, however, it is essential tirintert-up petrol ; thus a small petrol tank must be fitted in. addition to the main fuel tank. The paraffin is heated by the exhaust gases and has to pass through a vaporizer and, unless thii be well designed, very heavy deposits of carbon will form on the piston head, cylinder head and ports.
A considerable amount of attention has been and is being devoted to another fOrm of fuel, shale oil. In composition shale oil is something like benzole, and is _obtained by the distillation of shale. As yet, howeVer, this fuel cannot be recommended for motor-car use.
The alternative fuel that holds out the greatest possi- bilities is industrial alcohol. This could be produced in vast quantities in this country and at a very low cost. The use of alcohol, however, would necessitate a considerable degree of modification in present design, not only of carburettor, but also of the engine itself. The best compression for the average car is from 70 to 80 lb. per square inch. When alcohol is employed it is necessary to have a compression ratio of about 200 lb. to the square inch if the full value of
the spirit is to be realized. But the question of modified engine design is one that can safely be left to motor engineers if a :sufficient . supply of alcohol be available. The chief question at the moment is whethea supplies will be forth. coming. That is really the crux of,,the;Whole matter.- There are' three ways in which alcohol coidd be provided, by extracting it from home-grown materials, by importing the raw materials, and by importing the finished product. It is difficult to see how the first is possible. One suggestion is that potatoes should be employed, but this would mean that the price of the resulting liquid would be prohibitive. The plan of extracting the spirit from raw materials, such .as molasses, is being closely investigated, but it does not appear to offer a good solution of the problem. But there are certain parts of the world where supplies of raw materials could be obtained very cheaply. Scientists are now trying to find a suitable material from which to extract alcohol and are searching in out-of-the-way corners of the Empire. Much attention has. of late been given to the mowra flowers which grow in such profusion in India. These flowers are very rich in sugar and a single tree will produce as much as 200 lb. to 300 lb. in a season. It is said that 20 gallons of 95 per cent. alcohol can be secured from one ton of the dried' flowers. It is estimated that Hyderabad State alone posseises enough of these trees to render it possible to produee 700,000 gallons of proof spirit yearly.
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