Читать книгу Gas and Petroleum Engines - H. de Graffigny - Страница 5

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The history of gas engines may be said to date from a time when coal gas and petroleum were unknown. This statement appears at first somewhat paradoxical, but it arises from the fact that the first gas engine, invented by the Abbé de Hautefeuille in 1678, used the explosive force of gunpowder as a motive power. The principle of this early gas engine, however, is exactly the same as that of its more modern brothers; that is, the work is done by the expansion and cooling of a volume of heated gas, the only difference being that gunpowder contains within its grains the oxygen necessary for its combustion, while coal gas or petroleum require admixture with the oxygen of the air before they can be made to explode.

Two years after the Abbé de Hautefeuille had made public his idea, in a memoir entitled A Method of Raising Water by means of Gunpowder, the Dutch savant Huyghens published a similar work, describing an apparatus consisting of a cylinder with two leather exhaust pipes, forming valves; to the bottom of the cylinder was screwed a small box in which gunpowder was to be ignited. The effect of the explosion was to drive out a large quantity of heated gas through the valves, which closed again when it had passed. The gas remaining in the cylinder soon cooled down, so that the pressure within it fell below that of the surrounding atmosphere, and caused the piston to be forced down by the excess of atmospheric pressure.

This operation was certainly very crude, and, as might have been expected, scarcely came up to the expectations of its inventor. The idea was, however, not allowed to rest here, and Papin set himself to find out some better agent to replace the gunpowder, whose action was uncertain and, to say the least of it, brutal. The result of his experiments pointed clearly to the condensation of steam as being the most suitable method of producing a space filled with a gas at a lower pressure than that of the atmosphere, and many inventors, following in his footsteps, adopted this process for working pumping engines. In consequence of the great success of the steam engine, which was due to the genius of Watt and his successors, the idea of using combustion to act directly as a motive power was lost sight of for a great number of years, and it was not till the year 1791 that any suggestion was made which was an improvement on the engines of De Hautefeuille and Huyghens. The inventor, this time an Englishman, by name John Barber, specified in his patent, in somewhat laconic language, the use of a mixture of a hydrocarbon gas and air, and its explosion in a vessel which he termed an exploder. Several years later, in 1794, Robert Street, also an Englishman, took out a patent for the production of an explosive vapour by means of a liquid and air, ignited by a flame in a suitable cylinder so as to drive machinery and pumping engines. Petroleum or any other inflammable liquid was allowed to drip on to the heated bottom of a cylinder so as to be vaporized and drive up the piston.

Philip Lebon, of Brachay, the creator of the coal gas industry in France, took out a patent in 1799, setting forth very clearly the principle and construction of an engine using the explosion of coal gas as its motive power. Lebon, in fact, devised his gas-producing plant with the intention of only using the coal gas in his gas engine, lighting by its means being quite an afterthought. In a second patent two years afterwards he describes a more perfect apparatus, in which a pump is provided for compressing the mixture of coal gas air, and also an electric machine worked by the engine itself for igniting the compressed mixture. Unfortunately, the career of this fertile inventor came to an abrupt end by his assassination in 1804. It is highly probable, that if he had lived gas engines would have come into general use at the beginning of the century instead of nearly sixty years later.

From 1799 up till the year 1860, in which the first really practical gas engine made its appearance, several schemes were put forward, some of them not lacking in ingenuity, of which the most interesting were due to Welman, Wright, Johnston, and Barnett. Wright’s machine was particularly well thought out and constructed. The double-acting cylinder was placed in a vertical position and the gases were ignited by a gas-jet. A centrifugal governor regulated the pumps which compressed the explosive mixture in the cylinder, and at the same time varied the composition of the explosive mixture so as to always be proportional to the work which was required to be done. When we come to consider that this engine was brought out in the year 1833, it is wonderful that it did not meet with greater success, but this was probably due to the fact that the steam engine was at that period coming greatly into favour, and for the time being completely eclipsed all other forms of motive power.

About this time a double-acting gas engine was devised by Johnston, using pure hydrogen and oxygen as the explosive mixture, in the proportion of two volumes of hydrogen to one of oxygen. After the explosion and driving forward of the piston, the combined gases being cooled were precipitated as water, and a partial vacuum obtained which was used during the return stroke. This idea was a highly ingenious one, but failed owing to the high price of hydrogen and oxygen, but perhaps some day, when these obstacles have been removed, this idea may once more be taken up.

In 1838 William Barnett took out a patent for an engine based on the same principle as that of Lebon. Two pumps compressed separately the combustible gas and the air and forced the mixture under pressure into the cylinder. The explosion was caused by a small gas-jet, communication between it and the cylinder being set up at the right moment by a revolving valve. The gas-jet was situated in the valve itself, and was so arranged that during half a revolution it was turned towards the outside, and was then lighted by a second jet, and during the remainder of the revolution it communicated with the interior of the cylinder and ignited the explosive mixture. This was the first gas motor in which the ignition was from the outside, and in which the explosive gases were at the same time under pressure. In most modern gases the same result is obtained, but the original and rather crude method of obtaining it has of course been much modified and improved. During the next few years several patents were taken out relating to the same subject. In 1844 John Reynolds suggested using a battery which should white-heat a platinum wire in order to ignite the gases, the ignition taking place at the required moment by means of an automatic switch closing the battery circuit.

In 1850 Stéphard recommended a magneto-electric machine driven by the engine itself instead of the primary battery.

Barsanti and Matteucci described in 1857 an atmospheric motor, their arrangement of the parts being afterwards adopted by Otto and Langen. A Bunsen cell supplied current to a De la Rive multiplier, causing a stream of sparks to pass between two fine points situated within the combustible mixture. In 1858 and 1859 Degrand explained in two patents a gas engine in which the gases were compressed in the cylinder itself. Owing to mechanical difficulties his machine was impracticable, but the idea forms an important step in the history of gas engines.

In 1860, when the Lenoir motor appeared, no other existed which was capable of regular and comparatively efficient work.

This machine, devised by Lenoir and constructed by Marinoni, had the appearance of a double-acting horizontal steam engine. The explosive mixture was ignited by an electric spark produced by a Ruhmkorff coil and a primary battery. The machine ran smoothly and regularly and its cost was moderate: among the advantages which it possessed at that time over other forms of motive power, were the absence of a cumbrous boiler and costly foundations, and the little care and attention necessary to keep it in working order. So great was its success at the time, that many people prophesied that the steam engine would soon become extinct.

In spite of this the Lenoir motor possessed many defects which engineers were not slow to recognize. The enthusiasm which it had aroused soon cooled down when it became known that for steam and gas engines of equivalent power, the steam engine was considerably cheaper. It required in fact 3000 litres of gas to produce one horse-power hour, and to cool the cylinder of such a motor a volume of water was necessary four times as great as that required to produce the steam of a steam engine of equal power. Besides this, the machine had to be kept flooded with lubricating oil. In consequence of these various defects the Lenoir motor disappeared almost as rapidly as it had arisen. In spite, however, of this apparent failure, it did some good, for it once more directed the attention of inventors to the problem of a practical gas engine.

Among the numerous patents taken out in consequence of this reaction, the most important, filed in 1860 by M. Hugon, related to a gas motor with a flame ignition, and in which the cylinder was cooled by injecting into it a very fine spray of cold water. Experiments were made upon it in 1876 by M. Tresca, and it was found that the motor consumed 2445 litres of gas per horse-power hour. The temperature of the exhaust gases was 180° C., while in the Lenoir motor they were about 280° C. The diminution in temperature was probably due to the better method of cooling the cylinder, and was found to be a great improvement, the cylinder requiring much less lubrication. In 1861 Kinder and Kinsey somewhat modified the existing arrangements of the parts, but otherwise their motor embodied no new ideas. Another motor was devised about this time by Millon, once more bringing forward Lebon’s idea of compressing the gases in the cylinder itself.

We have now reached the year 1862, which may be considered a memorable one in the history of the gas engine, for it was in this year that a patent was taken out by M. Beau de Rochas, setting forth from a theoretical point of view the best working conditions for a gas engine. During the forward stroke of the piston the explosive mixture was to be drawn into the cylinder, during the return stroke this volume of gas being compressed; at the dead point at the beginning of the second forward stroke the explosion was to take place, driving the piston forward, the gases being expelled during the second return stroke. The whole principle will be seen to consist of four distinct operations, forming what is known as the Otto cycle, for reasons which we will presently explain.

The peculiar part of the patent was its purely theoretical explanation. Whilst giving all the honour due to the inventor, and recognizing that he fully understood what he was talking about, we must not forget that there was nothing whatever in the patent indicating how the ideas embodied therein might be carried into practice. No drawings were appended to the text, explaining how the gases were to be ignited, or how the exhausted gases were to escape; it contained nothing, in fact, but the plain statement of the most efficient cycle of operations.

M. de Rochas did not construct a machine on this principle, and as he omitted to pay his patent fee for the second year, the idea became public property. For these reasons no attention was drawn to it until ten years afterwards, when it came to light during some patent litigation undertaken by Dr. Otto in 1878.

In 1867 at the International Exhibition at Paris a vertical atmospheric motor was to be seen working, based on the primitive principle of the gunpowder pump of De Hautefeuille. This machine was constructed by two German engineers, Otto, and Langen of Deutz near Cologne, and was a perfected form of the Barsanti and Matteucci motor invented ten years previously. The explosion of the gases in the cylinder only served to obtain a partial vacuum underneath the piston, which was therefore forced down by the excess of atmospheric pressure above it. This arrangement had one great advantage over the Lenoir and Hugon motors, it only burnt 1350 litres of gas against their 2500 or 3000 per horse-power hour, and consequently it rapidly came into favour, and the lucky inventors were able to sell no less than 5000 motors in a few years.

The motor itself was very rough and had many defects: the gear-wheels rattled and made a furious noise, the igniting flame kept up a continuous roar, and above the noise of clanking machinery the explosion of the gases could be heard like a cannon going off; in fact, no one could say that the ideal of domestic motors had been attained; but as the motors constructed in 1872 only consumed 800 litres of gas per horse-power hour, rendering power produced by this means cheaper than steam, its success was assured in spite of the defects.

The success of these early attempts stimulated Dr. Otto to further efforts, and in 1878 he brought out his famous gas engine, which has earned a world-wide reputation by reason of its incontestable merits. It was based on the principle explained in the De Rochas patent which we have spoken of, but Otto undoubtedly knew nothing of this patent, and his invention was perfectly independent and fresh as far as the world was concerned. The enormous success to which the new motor attained naturally led to many unscrupulous imitations, and legal proceedings were instituted in England and France. In this country the validity of Otto’s patents were upheld, but in France the De Rochas patent was for the first time brought to light, and the verdict went against him. This verdict has been attributed to malice on the part of the French judges, for at that time the French nation would have probably conceded as little as possible to a German; but whether that be so or not, we are indebted to Dr. Otto for having made the gas motor a really practical engine after many years of patient experiment and study. At the same time as the Otto engine three other motors appeared at the Exhibition of 1878: the Bisschop gas engine constructed by Mignon and Rouart, and two others by Simon and Ravel. The Simon motor, of which only a very small number were constructed, was very interesting from the economy point of view. The explosion of the mixed gas was not allowed to take place suddenly, but proceeded gradually as the piston moved forward, and the heat which in the Otto engine is carried off by the water jacket, was made use of, as in the old Hugon motor, to vaporize a spray of cold water, and thus adding to the total force behind the piston. This process was so effective, that on shutting off the supply of gas the motor continued to revolve for a considerable period by means of the vaporized water. About 800 litres of gas were consumed and four litres of water per horse-power hour, a very good result. The Ravel motor used even less, about 500 or 600 litres only, but owing to the bad arrangement of the parts the mechanical efficiency was very low.

Such was the position of the gas engine in 1878. A standard type had been adopted and worked excellently. It merely required to be perfected in detail and simplified in order to make it still more economic, and capable of holding its own against its powerful rival the steam engine.

Many modifications of the Otto gas engine have appeared since that date, among the most important being those by—Dugald-Clerk, in 1879, a motor which compressed and exploded the gases once in every revolution; Lenoir, in 1833, the cylinder being cooled by currents of air; and in the same year appeared the Griffin gas engine, with a complete cycle of operations every three revolutions.

At the Antwerp Exhibition of 1884 several new types appeared, among them the Stockport engine by Andrews, and others by Koerting, Bénier, and Benz. In the same year a very good motor appeared, called the Simplex, constructed by Powell of Rouen (now Matter et Cie.), according to the plans of MM. Delamare-Deboutteville and L. Malandin. This engine was the subject of some litigation, the Otto people considering it an infringement of their patents, but the improvements in the design of the working part and the novelty of several details being apparent, the Simplex gas engine gained the day. In 1885, after the appearance of the Simplex and the new Lenoir motors, most makers made use of the Otto cycle, and about this time appeared the first carburetted gas motors, that is to say, using volatile spirits and products of petroleum for their source of energy. Such motors have been devised by Tenting, Koerting-Boulet, Diedrichs, Gotendorf, Noël, Forest, Ragot, Rollason, Atkinson, etc.

At the International Exhibition in 1889 there were thirty-one exhibitors and fifty-three machines, with a total power of 1000 horse-power. All except four used the Otto cycle, and for the first time a motor was to be seen using a gas other than coal gas, namely a poor gas produced at a very low cost in a special gas-producing plant. The motor itself was of the single-cylinder Simplex type of 100 horse-power, opening up a new horizon to inventors, and demonstrating the possibility of using large gas engines supplied with poor gas.

This short history of the gas engine will be seen to consist of three distinct periods—firstly, from 1700 up to 1860, during which time many inventors tried and failed to produce anything practical; secondly, from 1860 to 1889, during which the gas engine became something really practical; thirdly, from 1889 up to the present date. In this period gas engines have grown in size, and large units of 200 to 400 horse-power are now constructed, worked by poor gas produced from special gas plants, and enabling the gas engine to successfully hold its own against the steam engine, which it may one day entirely supplant.