LECTURE XXIII. CONTENTS. Governing of Engines Watt's Governor Action of Watt's Governor-Theory of Watt's Governor-Conical PendulumExample I.-Common Pendulum Governor-Crossed-Arm GovernorParabolic Governors-Galloway's Parabolic Governor-Porter's loaded Governor-Theory of Porter's Governor - Example II.-Spring loaded Governors-Proell's and Hartnell's Spring Governors -Macfarlane's Safety Governor-Willans' Spring Governor-Pickering GovernorGoverning by Throttling and Variable Expansion-Shaft Governors -Relays-Knowles' Supplemental Governor-Inertia Governors Flywheels-Balancing Machinery-Weston Self-balancing Centrifugal Machine-Questions. Governing of Engines.*-For many purposes to which engines are applied, it is necessary that they should maintain a uniform speed. Owing to variations of load and of pressure on the piston, they must have some regulating device, in order to accomplish this object. Fluctuations of the speed of a steam engine are of two kinds. (1) Those which occur during the time of a revolution, and are periodic, being caused by the varying pressure on the piston, and obliquity of the connecting rod. (2) Those which are due to change of load, or boiler pressure, and are not periodic. To control the first of these as far as possible, an engine is fitted with a Flywheel, and for the second a Governor is also required. *The following is a list of books and papers treating of governors and governing : : Paper on "The Electrical Regulation of the Speed of Steam Engines," by P. W. Willans. Proc. Inst. C.E., 1885, vol. lxxxi., p. 166. Paper on "A New Method of Investigation applied to the Action of Steam Engine Governors," by Prof. Dwelshauvers-Dery of Liége, translated by Michael Longridge. Proc. Inst. C. E., 1888, vol. xciv., p. 210. Paper on The Cyclical Velocity-Variations of Steam and other Engines," by H. B. Ransom. Proc. Inst. C.E., 1889, vol. xcviii., p. 357. Paper on "The Application of Governors and Flywheels to Steam Engines," by Prof. Dwelshauvers-Dery, translated by Bryan Donkin. Proc. Inst. C.E., 1891, vol. civ., p 196. 66 Paper on Flywheels and Governors," by H. B. Ransom. Proc. Inst. C. E., 1892, vol. cix., p. 330. Paper on "Steam Engine Governors and their Insufficient Regulating Action with Extreme Variations of Load," by Prof. Dwelshauvers-Dery, translated by Bryan Donkin. Proc. Inst. C. E., 1892, vol. ex., p. 276. Paper on "A Method of Testing Engine Governors," by H. B. Ransom. Proc. Inst. C. E., 1893, vol. cxiii., p. 194. A governor is a piece of mechanism which regulates the amount of steam supplied to the engine, to suit the work it is doing, whereas, as explained in the previous Lecture, a flywheel acts in virtue of its inertia, so as to distribute throughout a whole revolution the energy developed in the cylinder. The governor can have no effect whatever on the periodic variations of speed, since it can only act during the time that steam is being admitted to the cylinder. With regard to the irregular fluctuations of speed, due to a change of load, the flywheel makes them more gradual and thus gives the governor time to act. A great many varieties of governors have been invented since the introduction of the steam engine, such as hydraulic, centrifugal, inertia, and electrical governors. By far the greatest number, however, depend for their action on centrifugal force and inertia, and since these form useful examples of the practical application of the principles enunciated in the previous Lectures, we shall now confine our remarks to such governors. Watt's Governor.-One of Watt's important inventions was his conical pendulum governor, as applied to his double-acting engine.* This governor consists of two arms, A A, carrying heavy balls, BB, and pivoted on a pin, P, passing through the centre of the vertical spindle, V S. The upper ends of these arms are bent, as shown on the figure, and are connected by short links, LL, to the sleeve, S. This sleeve is free to move vertically on the spindle, V S, but is made to rotate with it by a feather, F, and corresponding keyway. This sleeve acts on one end of the bell crank, BC, and thus moves the rod con Paper on "The Mechanical and Electrical Regulation of Steam Engines," by John Richardson. Proc. Inst. C. E., 1895, vol. cxx., p. 211. Paper on "Governing of Steam Engines by Throttling and by Variable Expansion," by Capt. H. R. Sankey. Proc. Inst. M.E., 1895, p. 154. Paper on Steam-Engine Governors," read before the Manchester Association of Engineers, by C. F. Budenberg, M.Sc. See The Practical Engineer, 17th April, 1891, vol. v., p. 258. A series of articles on 66 Engine Governors," by R. G. Blaine, M. E., in The Practical Engineer, beginning 13th June, 1890, vol. iv., p. 386, and ending 24th April, 1891, vol. v., p. 277. Article on "A New Shaft Governor," by E. J. Armstrong, in The Practical Engineer, 26th July, 1895, vol. xii., p. 71. Article on "Shaft Governors," by E. T. Adams, in the Electrical World of New York. July, 1896. See Index for Governors in Gas, Oil, and Air Engines, by Bryan Donkin, published by Charles Griffin & Co. The Steam Engine, by D. K. Clark (Blackie & Son), chap. v., on Steam and Steam Engines, Lecture II., nected to the throttle valve of the engine. The vertical spindle may be driven by the engine by means of a belt or rope passing round a pulley keyed on it, or by bevel wheels, as shown at BW. In order to relieve the pin, P, the arms are driven by the guides, G G, which are fixed to the vertical spindle. Action of Watt's Governor. The governor is so adjusted, that when the engine is working at its normal speed, the balls rotate at a certain distance from the vertical spindle, and thus the throttle valve is kept sufficiently open to maintain that speed. Should the load be decreased, the speed of the engine, and therefore that of the governor balls, naturally becomes greater. This causes an increase of the centrifugal force of the balls, and therefore they diverge further, thereby pulling down the sleeve, and partially closing the throttle valve, which diminishes the supply of steam and the power developed by the engine. On the other hand, should the load be increased the reverse action takes place, the balls come closer together, the sleeve is raised, the throttle valve opened wider, and more steam admitted to the engine. It will thus be seen that a change of speed must take place before the governor begins to act; further, that for any permanent change in the work to be done, there is a permanent alteration of speed. For each particular load on the engine, the throttle valve will be opened by a definite amount, which will be different for different loads, and each position of the valve has a corresponding position of the governor balls. But, as will be shown further on, each position of the balls corresponds to a definite speed, so that there will be a particular speed for each different load. Theory of Watt's Governor-Conical Pendulum.-Let the balls be rotating about the vertical spindle with a uniform velocity. Then the several forces acting on the different parts of the instrument are in equilibrium with each other. The arms, A, will describe the surface of a cone, BP B, whose height is PC, and for a given velocity of the balls there will be a definite |