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).
Article from 'The Autocar' magazine discussing the possibilities of alcohol as an automotive fuel, comparing it to petrol and benzole, and detailing horsepower tests.
| Identifier | ExFiles\Box 32\1\ Scan027 | |
| Date | 8th November 1913 | |
| THE AUTOCAR, November 8th, 1913. 901 The Possibilities of Alcohol Fuel. though obviously alterable, are often spoken of as though they had a foundation so deep in the moral view of humanity that they must for ever remain as they are. The restrictions upon the sale of alcohol have no moral foundation whatever. They are merely convenient means of supporting an ordinance which certainly has a foundation in morality, that drinkable and intoxicating spirit must not be obtainable cheaply. Other means, almost equally convenient, of maintaining the price of such drink without indirectly handling fuel alcohol can probably be found quite well, and consequently the price to the motorist of fuel alcohol need not be in excess of its cost of production and distribution, plus a reasonable profit to those concerned. This, on a reasonable estimate, would give us fuel alcohol, suitably and even advantageously denatured, at a competitive price per gallon. It is for the automobile manufacturer to show that he wants such alcohol, and can use it in quantities when the Government makes him free of it. And it is at this point that Dr. Ormandy takes up the subject in his paper. Fuel Values. Alcohol has a very low calorific value. That is to say, on burning a given quantity of it with air, relatively little heat is given out as compared with the amount given out by petrol or benzole. The figures in fact are approximately as follows in British thermal units per pound of fuel burnt. Paraffin ... 21,000 B.T.U. Petrol ... 20,500 " Benzole ... 18,200 " Ethyl alcohol ... 12,700 " Methylated spirit (alchool) ... 11,600 " Now heat and work are convertible at a known rate of exchange. This rate is about 775 units of work to one unit of heat; and as it is, of course, an absolutely unalterable rate it follows that a given weight of alcohol is only going to do something like two-thirds the amount of work in an engine as the same weight of petrol will do. From this arises the great stock objection to alcohol, that, all questions of price economy apart, a given engine at a given speed cannot develop on alcohol more than about two-thirds of its power on petrol. Yet this assumption, based on a little learning, is simply erroneous. The engine will give theoretically almost exactly the same power on the poorer fuel as with the richer. This is so because alcohol happens to require much less air for its combustion than the richer fuel, in practically inverse ratio to their respective fuel values. And since less air is taken into the given space of the cylinder, more fuel can be taken in; and more fuel means more heat units and more work. Dr. Ormandy gives a table of all these fuels, their constituents, chemical formula, molecular weight, and the consequent proportions of mixture for perfect combustion. From this table it directly appears that whichever of these fuels you take, a cylinder full of it and its correct amount of air will always contain almost exactly the same amount of potential heat. That is a very important point to have before us so definitely. It means that an alcohol engine at a given speed can be, so far as these primary considerations are concerned, as powerful as a petrol engine of the same dimension. The Horse-power Tests for "The Autocar." It is here that we had better turn to the experiments themselves, and afterwards consider engine efficiency with alcohol under various degrees of compression and at various piston speeds. The experiments were conducted with the sole object of proving the relative values of petrol, benzole, and mixtures of benzole and alcohol (methylated spirit) in terms of brake-horse-power and fuel consumption. The brake-horse-powers were determined by means of a rope dynamometer. In order to obtain steady readings, the two spring balances were used instead of the upper spring balance and a dead weight on the foot of the rope; the lever, spring, and adjusting screws, were used towards the same end, and to get "dead beat" readings the needles of the spring balances had small rubber friction pads attached to them. The rope drum or flywheel was water-cooled, and the rope was continuously lubricated with oil from a tank. The engine used was a standard four-cylinder 17 h.p. Maudslay of 90 mm. bore and 130 mm. stroke with overhead valves. The ignition was by high-tension magneto with variable timing. The cooling water for the engine was supplied directly from a water main, and the temperature was regulated by means of a stop cock on the outlet pipe. The carburetter used was a standard White and Poppe. This type was adopted on account of the simplicity with which it allows the proportions of the mixture to be varied whilst running, and special handles were fitted to the carburetter to add further to the facility with which this could be done. The inlet pipe above the carburetter was water jacketed, the water supply being taken from the top of the outlet pipe of the engine circulation and the temperature regulated, as in the other case, by means of a stop cock on the outlet. Thermometers were placed in the water inlet pipes, outlet pipes, and in the water jacket round the induction pipe, and readings were taken on each test. The fuel was contained in a tank situated high above the engine, and pipes were so arranged that the fuel could be led either direct to the engine without measurement, or to a measuring glass, and thence to the engine. The method, when a measurement was wanted, was to note the time taken to use half a pint of fuel. To make the readings more accurate, tubes of about 3/16 in. bore were fitted as extensions to the body of the measuring glass, and the time taken as the liquid passed calibrated points on the top and bottom tube respectively. The fuels employed in the tests were: Petrol, Pratt's A, having a specific gravity of .710 at 60° F Benzole 90's " " " " " .885 " " Benzole 50/90's " " " " " .875 " " Methylated spirit " " " " " .815 " " Here, perhaps, we had better have some description of two of these fuels. Benzole 90's is, of course, that grade of coal-produced spirit of which 90 cubic centimetres out of a total 100 cubic centimetres will have been boiled away when the temperature of the liquid has been raised to 100° Centigrade. The denomination of a commercial benzole will depend on the proportion in which its constituents, toluol, xylol, and benzole, are present. 90's benzole is that most suitable for and most sold to motorists. 50-90's benzole is a mixture of benzole and toluol chiefly, 50% of which will boil away at 100° Centigrade and 90% at 120° Centigrade. With regard to the alcohol used, it should be observed that this is called methylated spirit. It is worth while showing where this product comes in, in the group of industrial alcohols. Commercially pure ethyl alcohol costs about 25s. per gallon, but even apart from the question of cost, there is no advantage in working with the pure product. In any circumstances our alcohol will have to be denatured to make it nauseating to drink. As denatured at present, with | ||