From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparison of benzol and petrol distillation curves, and an analysis of alcohol as a potential substitute fuel.
| Identifier | ExFiles\Box 32\1\ Scan021 | |
| Date | 22th March 1913 | |
| THE AUTO - MOTOR JOURNAL. MARCH 22, 1913. exhaust round it. In any case I have little doubt that sooting troubles and the like are entirely caused by the charge delivered to the cylinders being of a non-homogeneous character.” One of the most interesting distinctions between benzol and petrol may be illustrated by a comparison of their distillation curves as shown in the accompanying diagram. DIAGRAM TEXT: - Y-axis: PERCENTAGE (DRY, 90, 80, 70, 60, 50, 40, 30, 20, 10) - X-axis: CENTIGRADE (40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°) - Curves: BENZOL, PETROL Petrol ordinarily commences to distil at or about 45° C., and 25 per cent. of it is gassified at a temperature of 80° C. 60 per cent. or so passes over at 100° C., and 90 per cent. at 130° C. All the liquid must have been distilled to dryness below a 150° C., if the petrol in question is to be properly regarded as a benzine. Benzol, on the other hand, commences to distil only when the temperature is 80° C., and it is this lack of more volatile fractions that causes it to be liable to give trouble when engines are started from the cold. Compared with petrol it is, however, a strikingly homogeneous spirit ; the distillation curve rises almost vertically, 85 per cent. of the liquid distilling over at 90° C., while the entire quantity is gassified under 120° C. A consideration of thermal values assumes considerable importance when the attention is transferred from benzol to alcohol as a possible substitute for petrol. So far from being an improvement on the motor spirit now employed, alcohol would only provide about half the heat for the same quantity of liquid. This would immediately reduce the power output of modern engines for the same consumption unless means were taken to raise the standard of thermal efficiency of the engine itself. The direct road to this end is to increase the compression, but one must bear in mind that motor car engines are designed for other things than mere thermal efficiency, and that high compression cannot be indefinitely exaggerated in motor cars employed for pleasure purposes. Were it possible to do so with advantage, compressions higher than those that now obtain might long since have come into operation, and it is therefore somewhat questionable whether, from a motorist's standpoint, a higher compression would be of direct assistance in popularising the alcohol engine. The strongest argument in favour of alcohol as a petrol substitute is that which draws attention to the broad principle of its unlimited supply. Alcohol, as produced, say, from maize, is a ready means of converting the sun's energy, year by year, into a convenient form for man's use. On the assumption, which is undoubtedly correct, that the earth's contents of coal and petroleum is limited —being a creation of prehistoric times, which we are now using up at an immense rate—the general idea of encouraging the use of alcohol for industrial purposes presents itself for study as an economic question. To England, which is so much isolated from her sources of liquid fuel supply, the problem might be supposed to appeal with great force, but no very satisfactory evidence has yet been adduced to show that we could grow cheap alcohol within our own shores in sufficient quantities to satisfy the demand at a reasonable price. The climate does not suit the growing of grain on the necessary scale, and agricultural considerations render it very unlikely that potatoes would be grown for sale at a price that would make their conversion into alcohol a commercial proposition. If one obtained 20 gallons of alcohol from a ton of potatoes, the spirit would still cost 1s. a gallon if the farmer were paid only £1 a ton for his potatoes and the conversion process cost nothing. If potatoes were worth growing at all in this country, or even in Ireland, they should surely be worth more than £1 per ton, and, as we have seen, any spirit that is likely to cost 1s. per gallon at the factory is most unlikely to reach the motorist's petrol tank at much below the present price of petrol. The problem of introducing alcohol as a petrol substitute is in any case one that presents particular difficulties in England owing to the legal position. Thus, the law demands that alcohol must be denatured, that is to say rendered undrinkable, by a process that is not only comparatively costly in respect to the materials employed, but is also expensive in the manner of its operation under Government supervision. The present price of methylated spirit is a sufficient indication of the nature of those charges. Pure alcohol is, of course, subjected to an enormous tax. Thus, even assuming the suitability of the material, it would still be unavailable for use unless very radical changes of a legislative order were brought about. Until the fuel problem becomes more than ordinarily acute, therefore, it is not to be expected that any serious move will be made in the direction of cultivating industrial alcohol. Industrial alcohol is cultivated in Germany for reasons best known to the German Government. The situation in that country is very different from what it is in England. Great tracts of land exist in Germany, which are usefully turned to account for this purpose, but even so it does not appear as if the industrial alcohol were made at a profit. Industrial alcohol is used for many purposes in Germany, and its use is encouraged by the State. It seems somewhat significant, however, that among the purposes for which it is applied, the driving of motor cars does not figure pre-eminently. Peat has often been suggested as a source of alcohol, and also for that matter as a source of synthetic petrol, but it is doubtful whether this substance could be handled economically for either purpose. If alcohol is grown in tropical climates in the form of maize, or were produced from the refuse of the lumber yards in the great timber regions, it might be written down at an apparently enticing price per gallon, but then we are again in the unfortunate predicament of having to superimpose freight charges which, under similar circumstances, would not be less than at present obtain for petrol. The freight question is, indeed, a governing factor in the fuel problem to-day, for the construction of tank steamers and the organisation of an adequate cargo 343 D 2 | ||