7 The Limitations of the Steam Engine. By William Dennis Marks, Ph.B., C.E. Economical Cut-Off in Steam Engines. By S. W. Robinson.... Progress of the Dephosphorization of Iron (continued). By F. Gautier.................... The Russian Imperial Yacht "Livadia." By E. E. Goulaeff, Captain of the Corps of Naval Architects, Russian Imperial Navy, Ad.C., F.R.S.N.A., M.I.N.A..... 94 The Involute of the Circumference of a Circle. By J. J. Skinner, Ph.D... ............ The Summation of Series without the Calculus............ The Beaumont Compressed Air Engine........... New Applications of the Dynamo-Electric Current....... On a Fourth Stato of Matter. By W. Crookes, F.R.S... ...... 107 109 112 117 121 On the Artificial Formation of the Diamond. By J. B. Hannay, F.R.S.E., F.C.S. 123 136 Lighting Rooms......... 138 A New Developer in Photography. By Capt. W. de W. Abney, R.E., F.R.S., etc....... 139 141 Communications............ ITEMS. Influence of Winds on the Barometer, 84. French Railway Union, 86. Laws regulating the Spheroi dal State of Matter, 93. Variations of Temperature at Different Altitudes, 93. Dust Showers, 106. Treatment of Frosted Potatoes, 111. Electric Synchronism of Motors and Receivers, 116. Aerial Photographs, 110. Volatile Power of Liquids, 137. Roof Varnish, 140. Crystalline Form of Magnesium, 141. Earthen Filtering Plates, 142. Electric Sun, 142. Dissociation of Metalloids, 142. An Intensified Electro-Magnet...... ......... 142 Philadelphia: FRANKLIN INSTITUTE, 15 South. Seventh St. ESTABLISHED 1853. HOWSON & SON'S OFFICES FOR PROCURING United States and Foreign Patents AND PROSECUTING PATENT CAUSES. HENRY HOWSON, Engineer and Solicitor of Patents. CHARLES HOWSON, Attorney-at-Law and Counsel in Patent Cases, Principal Office, 119 South Fourth Street, Philadelphia. Branch Office, 605 Seventh St., Washington, D.C. Authors of "The American Patent System," "Our Country's. Debt to Patents," "Answers to Questions of the State Department Relating to Patents." Also, of a "Brief Treatise on Patents," published by Porter & Coates. Jan. '80, 1 yr. RUDOLPH M. HUNTER, M.E., C.E., £3 CONSULTING ENGINEER & SOLICITOR OF United States & Foreign Expert in the Trial of Patent Causes. Examinations in regard to the Validity and Infringement of Patents. Offices, Rejected Cases a Specialty, 901 Walnut St., Dec., '79 1 yr PHILADELPHIA. THE Franklin Institute is not responsible for the statements and opinions advanced by contributors to the JOURNAL. THE LIMITATIONS OF THE STEAM ENGINE. BY WILLIAM DENNIS MARKS, Ph.B., C.E., Whitney Professor of Dynamical Engineering, University of Pennsylvania. Perhaps there is no more unsafe proceeding in science than to attempt to predict the limitation of the development of any of its results. Yet the theory of the steam engine has so far been developed as to seem to permit us to mark out the boundaries of its progress with tolerable accuracy. At least, we trust that a full criticism of its present deficiencies, and a deduction of its limitations from known laws, will interest such of our readers as are engaged in the improvement of this machine, to which our civilization is more indebted for its advancement than to any other one thing. In this article we will consider the steam engine alone, as it is in no wise responsible for the economy of the boiler which supplies the steam, or for the losses incurred in conveying the steam from the boiler to the engine. The boiler should be considered apart from the engine, and it is well to incidentally remark here that the performances of the best types of boiler leave but little room for improvement so far as evaporation is concerned. WHOLE N. VOL. CX.-(THIRD SERIES, Vol. lxxx.) 6 It is rather in the utilization of the steam after it reaches the engine that we must look for progress, and in this point, we take it, lies the value of a thorough investigation of the machine itself. The well-known formula for the horse-power of a steam engine* contains three factors, which can be varied at will: the mean effective pressure, the volume of the cylinder, and the number of strokes per minute. Concentration of power in a small space is the greatest attribute of the steam engine; it is its power to concentrate the strength of thousands of horses in the space of an ordinary room that renders the steam engine so useful and indispensable to us. For this reason we cannot go on increasing the volume of the steam cylinder indefinitely without a proportionate increase in power, and it is only necessary to remark to mathematicians, with regard to the proproportions of the cylinder, that that cylinder whose stroke equals its diameter contains the maximum of volume with the minimum of condensation surface. The importance of reducing condensation surface is becoming more and more appreciated among engineers, and shortening the stroke will prove less of a bugbear when the laws of inertia, as applied to the reciprocating parts of a steam engine, are better understood. Shortening the stroke has the further advantages of shortening the space passed over by the piston head during a given number of strokes, and consequently of reducing the wear on the piston head, as well as of rendering the engine more compact for a given power. The following formula gives for any assumed horse-power, mean effective pressure, and number of strokes per minute, the required common diameter and stroke of cylinder, in inches: Concentration being attained, the next important consideration that arises is economy of steam, and this is the battle ground upon which the struggle for supremacy among our engine builders is to-day PLAN (HP). In which P mean effective pressure per square inch, L length of stroke in feet, A area of piston in square inches, N number of strokes per minute, (HP) : indicated horse-powers, AL The Relative Proportions of the Steam Engine, p. 16. Marks. volume of cylinder. being practically fought out, while the physicists are quite as hotly engaged in a dispute as to the relative theoretical merits of steam, hot air, and electric engines, into which we will not enter. Practically, we think that, as far as the steam engine is concerned, the impossibility of supplying to the steam in the cylinder any appreciable amount of heat by means of steam or hot air jackets is acknowledged by all, and the jacket is only expected to keep the cylinder warm, and prevent it from abstracting heat from the steam inside the cylinder. The jacket proving imperfect, we must find other means for preventing condensation by cooling, and they are these: Diminution of condensation surface, as already stated above, and shortening of the duration of the time for condensation, which means an increase in the number of strokes of the piston. The effect upon the structure of the engine of increased rotative speed is not injurious to the engine, as so positively stated by many engineers; but, if attempted, rapid speed requires a far greater knowledge of the dynamics of the steam engine than has as yet been applied to it by many constructors, and will almost inevitably shake to pieces a faultily designed structure. . The length of the crank pin and shaft bearings must also increase directly with the number of revolutions made, while their diameter, within ordinary limits as to pressure and speed, has no appreciable effect upon the heating of the bearing; but when we consider the practical fact, that the eccentrics, possibly because of greater speed of rubbing surfaces, are always sources of large frictional losses, it would seem best to make the diameters of all bearing journals just as small as the pressures allowable upon the surfaces of contact will permit. Much yet remains to be determined with regard to the laws controlling bearings. A very interesting work has been published on Friction and Lubrication, by Professor Thurston, but it is to be regretted that he has formulated the results of his experiments with so much positiveness, as other and careful experimenters have found it difficult to obtain results which clearly verify each other. He has shown conclusively that the coefficient of friction is much affected and reduced by the state of the rubbing surfaces, by the method of lubrication, and by the quality of the lubricant. Perfect, almost mirror-like, surfaces reduce the coefficient of friction far below the 3 to 5 per cent. formerly stated by Morin as a minimum, provided a continuous lubricating apparatus is used with good |