Alcohol as Fuel Discussed.
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Dr. W. Watson Talks of "Engine Knocking and Pinking."
At the ordinary general meeting of the Institute of Automobile Engineers, which was held on the premises of the Institution of Mechanical Engineers, on Wednesday, the 12th inst., the President, Mr. J. S. Critchley, presided at the reading of the paper by Dr. W. A. Ormandy, entitled, " Some Experiments on Mixed Fuels with Special Reference to Alcohol Mixtures." In the course of the discussion which followed, some of the speakers made interesting statements. Mr. H. W. STANER agreed that there exists great need at the present time for further experimental work in connection with the liquid fuel question. He did not consider that benzole could alone solve the situation, and pleaded for the further investigation of the claims of alcohol. In his opinion alcohol and benzole mixtures are likely to prove practicable.
Mr. W. A. HALL was of opinion that these tests which have been made with alcohol, that is to say "ordinary running tests in motorcars, without changing the compression or makeup of the engine material, have not met with any degree of success at all." He wished to know why the price of alcohol has not come down, in view of the great demand which has been voiced for it. He is not hopeful of the production of a cheaper fuel by the mixture of alcohol and benzoic
Dr. WATSON pointed out that, in respect of the use of petrol, the thermal efficiency in a good engine can be changed from 17 per cent. to 28 per cent, without either smoke pouring from the exhaust or, as far as can be ascertained, any change taking place in the chemical composition of the exhaust. This speaker was unable to agree with Dr. Ormandy's suggestion that the reason the horse-power obtained with methylated alcohol mixture was loss than with other fuels was because of slow combustion. He did not think that at speeds of as much as 700 r.p.m. a large decrease in the rate of the burning of the fuel would affect the results.
Dr. Watson found fault with the lecturer's use of the terms "tremendous rapidity" in respect of the rate of burning. "The maximum rapidity in the case of petrol air is 7 ft. per second." The reason why petrol fires so much more quickly in an engine is not because it burns more quickly, but because "
turbulence" exists, that is to say, the charge in the cylinder of the engine is swirling about. The rate of burning in practice in a petrol engine depends particularly upon the shape of the combustion chambers, that is to say, upon the extent to which convection currents of the mixture persist. He had much of interest to say with regard to what is known as the knocking of an engine. This, he went on, "is simply the charge from the slow propagation of flame to the case where extra pressure due to the spark makes it flash right across." The fact that you can prevent knocking by the retarding of the spark is evidence of the correctness of this surmise. "True pre-ignition is an unstable condition; it advances more and more every time the engine fires. It preignites earlier and earlier, and true pre-ignition eventually pulls the engine up.' With regard to what Dr. Watson called "pinking," that is to say, a detonation "like a little hammer being struck on the side of the cylinder casing, it means generally that you have got a combustion chamber of that kind which is so shaped that you get resonance in the acoustical sense between these two chambers, and if you spark there you get a true detonation wave set up. This can be, as a rule, entirely cured by moving the sparking plug to another point or by slightly altering the relative volumes. The actual difference in the speed of propagation in alcohol mixtures and petrol is infinitesimal."
Dr. Watson then went on to criticise Dr. Ormandy's claims for the advantages of slow burning of alcohol mixture. He had stated that this gave small pressures, "but if you consider the indicator diagram, slow horning insane that you will get a range diagram of a different nature to the ordinary peak diagram. In another part of his lecture he recommended the high-compression pressures. " If :yon have high-compression pressures, you simply build the peak up again, so that he (the lecturer) is going to cure one of his recommendations by doctoring the other up. With high compression you get high temperatures corresponding to the advanced spark. The specific heat of gas increases rapidly in temperature when employed in internal-combustion engines, so that the specific heat of your working fluid goes up as the temperature rises. Therefore, a given amount of heat imparted to the fuel raises the pressure less and less, because there is more heat required, and it is with this kind of specific heat that these weak mixtures are an advantage."
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Mr. A. E. VON GROELING, in speaking of the benzoic question, said: "I think if we here in the United Kingdom would pay more attention to by-product recoveries, and not grizzle so much about what to do with the coke, we might possibly succeed in having a greater output of benzoic" He thought the railways might make more use of coke, as they were doing in Germany. The Prussian railways have been more than satisfied with their experiments, particularly in regard to the stopping of spark-flying. It is a fuel which does not deteriorate, it is easy to store, and it is lighter. This speaker said that he was particularly anxious to impress the fact that "it is not necessary to have a sort of record in coal export." It is better to keep the coal in our own country and make the best of it than to export it all over the world. He thought there was room for all kinds of fuels, whether they be alcohol-benzole or chemically-treated para'
lin if they be cheap enough. "There is also room for the cracked products. The petrol in crude oil used to be rather a nuisance; everybody tried to get rid of it, and everybody tried to get as much kerosene as possible, because it was as material. Now there is an endeavour to get as much petrol from the crude oil as possible. The result is that the cracking process is worked on a different method altogether." He thought that various cracking processes have a very great future if they deal particularly with cheap oils and waste fuels.
Lord MONTAGU referred to the fact that a great deal was heard of the possibility of the use of industrial alcohol in the years 1903-4. Since then, nearly 10 years ago, nothing has happened in this country of any importance in respect to its development for use in the automobile world. He saw it in use in France in 1901. A very serious drawback to the use of it in those days was its overpowering exhaust odour. He drew attention also the fact that, "notwithstanding a very comfortable bonus which was given by the German Government for the production of alcohol from potatoes, the use of alcohol for internal-combustion engines in Germany has not progressed to any considerable extent. In France, equally, all the manufacturers of alcohol of different kinds, and there are many, naturally tried to get this fuel accepted as a home-produced fuel. In France also it did not prove very successful. I do not think you can find a single motorcar in France in ordinary use running on alcohol. MT. HORACE Wy.arr referred to the fact that at the Imperial Motor Transport Conference, which, we may recall, was held during the Olympia Heavy Vehicle Show week, a desire was expressed that the claims of alcohol should be investigated. Mr. Wyatt gave some information with regard to the continuation of his permanent Imperial Motor Transport Council, of which an alcohol motor fuel committee was in course of formation. He asked that the Institute of Automobile Engineers might seriously consider the question of pecuniary assistance for the investigations which this committee will have to carry out, and he warned his audience of the grave necessity for this pecuniary assistance at some length, and urged this aspect of the subject of the lecture.
Dr. Ormandy briefly replied on the discussion.