Source: The Railway Review - Vol XXVI, N°23, p 279
Date: June 5th, 1886
Title: Substitute for Steam
Abstract of paper read by Geo. H. Babcock before the American Society of Mechanical Engineer, (May meeting)
Babcock tries to show why the failure of the engines other than steam.
First he describe the various air engine technologies that attempted to supersede the steam engine. And he comes to the conclusion that, most, if not all, these attempts have been based upon the erroneous supposition that latent heat is necessarily wasted heat.
This conclusion is then demonstrated with a theoretical explanation.
Having been called upon a number of times within a few years past, and twice quite recently, to witness and report upon the working of engines using other fluid than steam, I have thought it worth the while to give a brief history of such attempts in the past, discuss their possible advantages, and their evident disadvantages, and inquire what can be hoped for in that line.
The steam engine had scarcely left the hand of Watt and demonstrated its practical usefulness, before efforts began to be made to supersede it by engines driven by some other fluid, having fancied elements of economy.
Such efforts have not always been made intelligently, and up to the present time have not met with any marked success, excepting, perhaps, in air and gas engines for lighter powers.
The first use of other vapors than that of water for producing power may be traced to Rev. Dr. Edmund Cartwright, the ingenious inventor of power looms, who patented, in 1717, an engine in which he proposed to use "ardent spirits or ether, or any other spirits more volatile than water".
Mr. Thomas Howard, of London, patented, in 1825, and made between that and 1830, an engine in which the vapor of alcohol was used, condensed und returned to the boiler.
In 1824 Du Tremblay patented, In France, an engine in which ether was substituted for water. Some five years later he brought out his "binary engine" in which he used steam in an ordinary engine, the exhaust from which was employed to evaporate ether, which vapor was used to develop power in another cylinder and was itself condensed at as low a temperature as possible. This was claimed to double the power with no additional expense, and was put to use on no less than eight steamships between that and 1859. One of Du Tremblay's engines was brought to this country in 1851 and erected at the Novelty Works, New York, but was not successfully operated.
A bi-sulphide of carbon engine, built by one Hughes, of Rochester, was running in New York in 1857, and another one by Prof. Salomons, In Baltimore, which was tested by a commission of naval engineers.
The Ellis Vapor Engine Company was formed in Boston in 1872, their engine being substantially the same as the Du Tremblay, substituting bi-sulphide of carbon in place of ether. Notwithstanding it claimed 166 per cent. gain of power with the same fuel, it, like its predecessor, soon disappeared.
The scheme for using alcohol in place of water was revived some three or four years ago, and at the present time there are one or two parties attempting to form large stock companies upon claims of gain by the use of bi-sulphide vapor. The fallacy of all these schemes has been frequently pointed out.
Soon after carbonic acid gas had been liquefied by Faraday in 1823, numerous inventors attempted to develop power from its use in engines, among which was the well-known engineer, Sir M. Isambard Brunel. Ammonia gas has also been extensively experimented with by M. Tellier, in 1860; M. Frot, 1867, and was the basis of Dr. Gamgee's zero motor of a few years ago, which promised to cross the ocean with no expenditure of heat save what was drawn from tho surrounding water.
About 1851 the "cloud engine" made considerable stir in New York by its promise or economy through the mixture of air with steam, forming "visicular vapor".
In 1857 the steamboat "John Farron" was run upon the North river for a time, and in 1867, George Warsop, of England, built a locomotive which was run for three years upon the Lancashire & Yorkshire railway, each using products of combustion mixed with steam. The Idea, however, was much older, having been suggested by Richard Trevithick as early as 1811, and patented by William Wilmot Hall, of Baltimore. in 1830. The economy gained by this means was slight, if any.
The use of heated air for motive power dates from the last century, while the gas engine may be said to have originated with M. Lebon in 1801. An early as 1826 Samuel Morey had an engine at work in New York or Philadelphia by the explosion of a mixture of atmospheric air and vapor from proof spirits and turpentine, of which great expectations were entertained. About the same time a boat built by the Canal Gas Engine Company, and propelled by gas, was tested upon the Thames.
Numerous other experiments were tried. Lenoir, in Paris, 1867, was the first to make a business in gas engines, a large number of his being sold and put into use, and since the later well known invention of Otto gas engines have come into very extensive use, and in many cases have superseded steam for small powers.
The first practical engine in which liquid fuel (as petroleum) was used was made in 1860, by Stephen Wilcox, a member ot this society. George B. Brayton patented one in 1874, many of which have been built with varying success. If petroleum could be substituted for gas in a modern gas engine, with equal efficiency, it would give 10 horse-power for each gallon used per hour, and might compete with steam on equal footing, at present market rates.
The use of the products of combustion from coal within an engine cylinder was first suggested by Sir George Cayley in 1807. Successful engines of this character have been built by Stephen Wilcox, S. H. Roper and Philander Shaw. One of Shaw's engines, exhibited at the Paris exhibition in 1867, ran an average of over 20 horse power on a consumption of 1-4 pounds of coal per hourly horse power, equal to the best result obtained by steam.
Among air engines, as distinct from those using the products of combustion within the cylinder itself, that made by Robert Stirling, from 1816 to 1841, was one of the best. One of those for three years drove a foundry in Dundee, with good economy.
The stupendous failure of the Ericsson air ship in 1852 will be remembered by many.
The "compression engine" in which a given quantity of air is constantly changed in volume, being compressed while cold and expanded while hot (first patented in 1853 by Franchot), offers many advantages and promises to become the air engine of the future.
Most, if not all, these attempts have been based upon the erroneous supposition that latent heat is necessarily wasted heat. So far from this being the case, however, it may be shown that it is the form of heat convertible Into power, and that if there was no latent heat there could bo no available energy.
Sadi Carnot, In 1821, seems to have been the first to enunciate the principle, now universally recognized, that the ratio of the maximum mechanical effect in a perfect heat engine to that total heat expended upon it, is a function solely of the two constant temperatures, at which respectively heat is received and rejected, and is independent of the nature of the intermediate agent or working fluid.
There are, however, practical limits to those values;
(a.) The temperature of rejection cannot be carried below that of the substance into which it is rejeted, and is independent of the fluid employed.
(b.) The temperature of reception cannot be greater that the highest temperature of combustion, nor greater than the surfaces of the piston and cylinder will stand; nor greater than will produce in a given fluid the highest allowable pressure.
(c.) The highest pressure is limited by the strength of the mechanism and the safely of its operation, and is also independent of the fluid. As all fluids except mercury attain this limit of pressure before the limit of temperature, the pressure is the practical limit in this direction.
Obviously, then, as the limits of lowest available temperature and of highest practical pressure are the same for all vapors, it becomes evident that the fluid having the highest temperature at the limit of pressure, other things being equal, has the advantage, theoretically, in possible economy. Of all available liquids water fulfills this condition best. It becomes evident, therefore, that a successlul substitute for steam in motive power cannot be found among vapors, and most probably, if found at all, it must be found among permanent gases.
Atmospheric air has several elements of value in the problem, and gives the best promise for an economical substitute for steam in pressure engines. The prospect of much further economy in steam engines is not bright. There are good reasons, however, for believing that the efficiency of air or gas engines may yet be increased to 50 per cent., in which case, if coal can be utilized directly for fuel, a horse power may be obtained for an hour for 1/3 pound of coal, a saving of 78 per cent. upon the best results yet attained with steam.
Are there still further possibilities of economical development of power? Probably not, in the line of pressure engines. But science already points to the possible conversion of heat directly into electricity, and if that can bo done without too great a loss, the electrical engine may yet become a prominent rival of the steam or air engine.
With these possibilities before us, and the still further possibility of the direct conversion of heat into available power, with not over 10 per cent, loss — by some means yet to bo discovered - who shall say there is not ample scope for invention and experimental research?
Is steam, therefore, doomed to be superseded? By no means. Even if robbed of its position on the throne of power, it must ever remain one of the most useful servants of men, as it is the best attainable medium of transferring heat within a certain range of temperature, from the furnace to the place where it may be wanted for various processes. So far as now appears, it need fear no successful substitute in that field.