Marine engine

“ Those modern marine engines use about the same steam pressure and expand about in the same proportion. With the direct action from the piston-rod to the crank-shaft, the multitubular boiler and screw-propeller, and the surface condenser perfected in 1831 and 1832, at which time his construction of a marine steam-engine would have been just what it now is forty years later. ”

“ The reciprocating marine engine, however, had been steadily improved, until it was a marvel in efficiency. Quadruple expansion engines driving twin-screws of a size and shape known to develop the greatest efficiency, for several years offered invincible competition to the new type of engine. ”

“ While the marine steam-engine has been perfected in Europe, it is worth noting by the way that the producer-gas engine, though yet in the experimental stage for ship use, has been brought to a higher state of perfection for land use in America than in Europe. Magazine articles by marine engineers have been published, urging American ship-owners to adopt this new method of propulsion, because it is to make a revolution almost as far-reaching as the iron screw steamer made in 1855. ”

“ The nature of the work which the marine engine has to perform, is such, that great regularity of action is neither necessary nor possible. The agitation of the surface of the sea will cause the immersion of the paddle-wheels to vary very much, and the resistance to the engine will undergo a corresponding change: the governor, and other parts of the apparatus already described, contrived for imparting to the engine that extreme regularity which is indispensable in its application to manufactures, are therefore here omitted ”

“ Number two served, the steam does duty a third time in number three, and perhaps yet a fourth time before it reaches the condensers, where its sudden conversion into water by cold produces a vacuum suction in the last cylinder of the series. The secret of a marine engine’s strength and economy lies then in its treatment of the steam, which, like clothes in a numerous family, is not thought to have served its purpose till it has been used over and over again. ”

“ Each engine is given an extended run with propeller load. After giving the required standing thrust at the proper speed, the engine is completely torn down for inspection and carbon removed. After assembling, it is given a second test on a water dynamometer, which gives the horse-power developed.
Miscellaneous:
Few people realise that the aeronautical motor is subjected to usage equalled by few internal combustion engines. The average car engine is seldom run on full throttle for extended periods. The marine engine is ordinarily a very heavy, slow speed machine. ”

“ Most other engines, however, travel at about the speed of 128 times the cube root of the stroke in feet; but some marine condensing engines of recent construction travel at as high a rate as 700 feet per minute. To mitigate the shock of the air pump valves in cases in which a high speed has been desirable, as in the case of marine engines employed to drive the screw propeller without intermediate gearing, India rubber discs, resting on a perforated metal plate, are now generally adopted ”

“ It is but rudely finished, but the very fact that its great inventor’s eye dwelt upon it with pride and triumph invests it with a poetry all its own. Another beam engine, once belonging to Watt, with parallel motion attached to the piston-rod, is a better example of mechanical skill. We have not far to look for the first germ of steam navigation. That huge model which appears to be a combination of two funnels and a number of chains working over wheels is the parent marine engine. ”

“ By the [Pg 575] reciprocating movements of a steam impelled piston within a closed cylinder, the motive power of the modern steam-ship is obtained, as in the Comet; yet, probably, on no other subject has more mechanical ingenuity been lavished than on the marine engine. Twenty years ago, almost every engineer had his own peculiar type, comprising the “side lever,” the “steeple engine,” the “grasshopper,” the “trunk,” the “oscillating,” and the “direct acting engine,” with an endless variety of sub-combinations ”

“ One of the greatest reasons for the increased speed of these new ships was the introduction of the compound engine. It was in 1854 that John Elder, a Briton, adapted the compound engine to marine uses. This improvement, by utilizing more thoroughly the expansive power of steam, increased at one stroke the power developed by engines without increasing [Pg 90] the supply of steam. The principle of the compound engine is simple. Steam escaping from the single cylinder of a simple steam engine still retains a part of its pressure—that is, a part of its power to expand. ”

“ It is well known that engineers can only become acquainted with the true capacity of machinery by long and careful study. Statistics have proved that marine engines in the navy under the direction of good men have been run with less coal, less oil and greater working power year by year when the same man has had control of the engine-room. ”

“ The extraordinary increase in the speed of steamships that has been effected within the last few years depends mainly upon the improvements that have latterly been made in the marine engine—a machine of which we have been unable to give an account, because its details are too numerous and complicated to be followed out by the general reader. ”

“ During the last twenty years marine engines have been enormously improved. But the advance of auxiliary [205] appliances has been even more marked. In earlier times the matter considered of primary importance was the propulsion of the vessel; and engineers turned their attention to the problem of crowding the greatest possible amount of power into the least possible amount of space. This was effected mainly by the "compounding" of engines—using the steam over and over again in cylinders of increasing size—and by improving the design of boilers. ”

“ In the meantime, science is seeking to surpass all its present achievements. The marine steam engine, of whatever type, will give way to the internal combustion engine of a type which will surpass all the existing machinery as surely as the best turbines are ahead of the old compound engines. The battleship of the future will have an armament surpassing in effective range and penetrative power anything at present afloat, and an armour as far in advance of the present steel armour as that is ahead of the compound armour it but lately supplanted. ”

“ Another very important advance in marine engines has been gained by the used of toothed gearing. This gear enabling the high number of revolutions in turbines to be reduced, so that large slow-running propellers can be used in conjunction with very quick-running efficient turbines, a much higher efficiency has been secured and increased speed of ship and economy of working has resulted. ”

“ Between the years 1860 and 1870 great improvements were made in marine engines, and screw-steamers very generally replaced side-wheel boats for ocean traffic. The improvements in the engines consisted largely in the use of higher pressures, surface condensation, and compounding of the cylinders, which resulted in a saving80 of about half the amount of fuel over engines of the older type. As a result steamers were able to compete successfully with the sailing ships, even as freighters for long voyages, such as those between Europe and Australia. ”

“ But in the side-lever engine lightness and compactness were sacrificed to solidity and length of connecting-rod, and as the use of steam gradually spread in the navy, and it became apparent that for every ton saved in the weight of and space occupied by the machinery valuable increase could be effected in the armament and coal capacity of the ship, it was inevitable that the ingenuity of the first engineering country in the world should be directed to the necessity for improvement in marine motive power. ”

“ She is most closely and firmly trussed with iron and wooden diagonals and shelf-pieces, which with the whole of her upper works are fastened with screws and nuts to a much greater extent than has hitherto been put in practice. Her engines are the largest marine engines yet made. The boilers are constructed with several adaptations for the economy of steam and fuel on an entirely new principle. ”

“ The usual kind of gasoline engine is known as the four cycle type and has from 12 to 16 cylinders, the pistons of each of which are connected to one crankshaft, and together they form a power unit, as the complete engine is sometimes called.
A submarine engine of this kind can develop upwards of 5,000 horsepower and the large units weigh close to 100 tons. Except that it is larger and is built especially to meet the needs of the submarine it is exactly like a motor car or an airplane engine which is shown in Fig. ”

“ The weight of the turbine engines of this vessel is only 3 tons, 13 cwts., and the whole weight of the machinery, including boilers and condensers, is only 22 tons, with an indicated H.P. of 1576, and a steam consumption of but 16 lbs. per hour. The weight of the turbine is only one-fifth of that of marine engines of equal power; the space occupied is smaller; the initial cost is less; not so much superintendence is required; the charges of maintenance are diminished; reduced dimensions of propeller and shaft suffice; vibration is eliminated; speed is increased ”

“ We must pass hastily over the other inventions, rapidly following each other, and all designed to make ocean travel more swift, more safe, and more comfortable, and to increase the profit of the shipowner. The compound engine, which has been so developed that in place of Fulton's seven miles an hour, our ocean steamships are driven now at a speed sometimes closely approaching twenty-five miles an hour, seems already destined to give way to the turbine form of engine which, applied thus far to torpedo-boats only, has made a record of forty-four miles an hour. ”

“ Indeed the perils and discomforts of ocean voyages are now largely reminiscent, thanks to the rapid succession of scientific discoveries and their practical application during the last half century. The size of modern vessels minimizes rolling and pitching. Turbine engines practically eliminate engine vibrations. The danger from fires was practically eliminated by the introduction of iron and steel as building material; the danger of sinking after collisions is now guarded against by the division of the ship's hull into water-tight compartments ”

“ A strong purpose is to a man what an engine is to a ship. Suppose a hull lies in the water, stanchly built, graceful in lines of strength and speed, nosing at the wharf or tugging back on the mooring line, it may be a fine piece of building but it cannot be much admired. But place an engine in the hull and add to those fine lines the purr of a motor—there is a sight which brings a smile to the lips and a light in the eyes. Anthony had been like the unengined hulk, moored in gentle waters with never the hope of a voyage to rough seas. ”

“ In the awash condition, when the boat is otherwise air- and water-tight, communication is kept up with the outer air by means of ducts and a smoke-pipe, the former bringing in air for combustion and respiration, and the latter carrying off deleterious products of all kinds. For submergence special fittings are used to close these ducts and pipes, and to stop the gasolene generator. The main engine is then no longer available, and for propulsion power is drawn from the accumulators, the dynamo thus becoming a motor which derives current from the accumulators and itself drives the screw-shaft. ”

“ A somewhat larger vessel from the same makers is 100 feet in length, with a beam of 13 feet 6 inches, and her internal combustion engines give her a speed of 231⁄2 knots. The advantages, and they are very great, claimed for all boats propelled by powerful engines of this type over those propelled by steam engines, are that as the vessels have no funnels there can be no flaming from funnels, with its risk of betrayal of the vessel’s whereabouts; that only half the engine-room staff is required, and that the range of action is three times what it would be under steam. ”

“ Owing to the great range of an airship a thoroughly reliable engine is a paramount necessity. The main requirements are--firstly, that it must be capable of running for long periods without a breakdown; secondly, that it must be so arranged that minor repairs can be effected in the air; and thirdly, that economy of oil and fuel is of far greater importance to an airship than the initial weight of the engine itself. ”

“ When the boat is running on the surface of the water, with full steam power, and it becomes necessary to dive quickly, the pilot gives the order, 'Prepare to dive.' The oil fuel is instantly shut off from the furnace, the valves are opened to admit water to the water-ballast tanks, an electric engine draws down the smokestack and air-shaft into the superstructure, and moves a large, massive sliding valve over the aperture on the turret through which the smokestack passes. ”

“ Of course oxygen can be manufactured aboard a submarine, but you can’t breathe artificial air forever—you’ve got to have fresh air, especially if they run gasoline engines, as they probably do, though the main ones may be operated by electricity from a storage battery.”
“Why do they need so much air for gasoline engines?” asked Bob.
“Because gasoline won’t explode unless it’s mixed with air. The engine simply must have it. So that’s why they’re probably staying on the surface [121] so long—to renew the air in the compression tanks to feed to the motors.” ”