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Then I invite you very strongly to repeat on a larger scale this interesting experiment ; because when people see that with a low oil consumption we can get enormous flame puffs people will be astonished and will admit the real importance of our discovery.“ White oil of petroleum is akin to kerosene. From July 8th 1817, Claude’s tests are getting more defined, according to Nicephore : “As a matter of fact if you succeed in injecting white oil of petroleum with enough energy to get instant vaporisation,it is sure, my dear friend, that you should obtain the most satisfying result.“ It was indeed ,as we know now in today’s engines,fuel injection that Claude was inventing and fine-tuning.As a matter of fact the Niépce brothers are today credited as the inventors of the fuel injection principle. • Discovery of fuel injection. The tests were promising. On July 16th,Nicephore wrote : “You just proved again that Lycopodium,the most flammable solid substance, produces less flame, however, than a given amount of vaporized oil of petroleum.“ Nicephore made many tries.He vaporized the fuel by heating to red hot the end of the pipe through which the oil was running, but the results were less than constant.He then tried a new technique to have the oil sprayed like the lycopod powder at the time of ignition.First, he equipped himself with a pipe about 20 cm long (8 inches) and a diameter of 7 mm (1/4 of an inch).He filled it with water on a length of 3 cm and then blew in it violently.The water was expelled as a jet composed of tiny droplets, spread as well as a powder.He improved this result by flattening the exhaust end in a rather short bevel reminding him of an “ oboe reed .“ He repeated the experiment replacing water with alcohol and setting a lighted wick at the exhaust orifice with the purpose of igniting the liquid droplets.It was a success : “the alcohol detonated in burning like the lycopod “, he said. Nicephore had just discovered that the fuel must be ignited when it is cold and as a vapor, as was the case with the kinds of heated pipes he used formerly.The mixture of air and of minuscule droplets of flammable liquid would then become explosive. The next step was to test white oil of petroleum.Nicephore had a 9 mm diameter pipe made and bent at a 90°angle, so that he would no longer have to use his tongue as a valve.The part through which he had to blow was about 66 cm long and the one through which the oil would flow was about 33 cm.The exhaust was beveled as in the preceding experiment. This was completely successful :“The flame, compared to the small amount of oil used ,was enormous ; it was intense,instantaneous, and detonated like lycopod“ Nicephore said, and added : “the results that I just got have rekindled my courage and fully satisfy me.“ The smaller the amount of oil used the bigger the explosion. It was complete : efficiency and economy.Convinced by the performances of this fuel,he stopped testing completely. • Sadi Carnot’s comments. A few years later, in 1824, Sadi Carnot (1796-1832), Lazare Carnot’s son (1753-1823), wrote a book titled :“Reflections on the driving force of fire and the machines proper to develop this force “, in which he made a commentary about the Niépce brothers’engine : "Among the first attempts made to develop the driving force of fire through atmospheric air,we must point out those of M.M.Niépce that took place in France ,many years ago, by the mean of a device called pyreolophore by the inventors.This device consisted of a cylinder ,with a piston, where atmospheric air was admitted at normal density.A highly flammable substance was projected at a very high level of fineness, and that remained a little while in suspension in the air,then it was ignited. The ignition caused an effect almost as if the elastic fluid had been a mixture of air and a flammable gas,like air and carbonaceous hydrogen ; there was a sort of explosion and a sudden dilatation of the elastic fluid,dilatation that used to act entirely on the piston.This one would be set in a motion of a certain amplitude,and the driving force was thus created. The operation could be restarted by renewing the air and going through the cycle again. This very ingenious and interesting machine, especially by the novelty of its principle,had a capital defect. The material that was used as fuel (it was lycopodium dust,used to produce flames in our theaters)was so expensive that any advantage of its use would have vanished : and unhappily enough it was very difficult to use a cheaper fuel, because a body in very fine powder was necessary, the ignition of which was fast,easy to propagate,and left few or no ashes.“ Sadi Carnot dealt only with the first patent and seemed to have ignored the Niépce brothers’ later works with white oil of petroleum |
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