TURBINE NAVIGATION. The applica tion of steam-turbines (see TURBINE) to tor pedo boats, destroyers and cruisers is to be an ticipated from their unique capacity for develop ing great power and high speed with light and compact machinery. The conditions in a fast passenger steamer are favorable to the economi cal application of steam-turbines, and in such steamers the smoothness of their running will be a strong recommendation. C. A. Parsons, who has made remarkable developments in the steam-turbine, claims many advantages for the marine turbine engine. Among these many ad vantages he gives the following: (1) increased speed; (2) increased economy of steam; (3) increased carrying power of vessel; (4) in creased facilities for navigating shallow waters; (5) increased stability of vessel ; (6) increased safety of machinery for war purposes; (7) re duced weight of machinery; (8) reduced space occupied by machinery; (9) reduced initial cost ; (10) reduced cost of attendance on machinery; (11) diminished cost of upkeep of machinery ; (12) largely reduced vibration; (13) reduced size and weight of screw propellers and shaft ing. It may be said, generally speaking, that the larger scale on which the engines are made, the simpler is the construction, the higher the steam efficiency and the lower the speed of rotation.
The Turbinia In 1894 the steam-turbine had developed to such an extent that a syndicate was formed to apply the turbine to marine work, and a vessel, appropriately named the Turbinia, was built to develop high speed and to secure determinative measures of the value of steam-turbines in driving the screw-propeller. The first outcome of the ex periment on the Turbinia was the discovery of a previously unsuspected cause of inefficiency at high speeds of rotation of the screw such as were adopted in this construction-- acavitationx' by centrifugal action about the screw, which worked in a self-created cave in the midst of the water, throwing out the water faster than it could flow into the space by the action of gravity, even reinforced by the often still more active tendency to fill the vacuum thus caused.
It was only when the speed of rotations of the screws had been reduced to 2,000 revolu tions per minute, and after they were set in series of three on the same shaft, that the little boat made her famous run and attained a speed of 3234 knots an hour, and later of The trials of the Turbinia were reported as follows: tThe mechanical friction of the turbines is particularly small, and the work spent on fric tion is not materially increased by increasing the range of expansion. This allows the steam to be profitably expanded much farther than would be useful or even practical in an engine of an ordinary kind. Apart from questions of friction the addition of weight and bulk to al low for this extended expansion would be enor mous in the ordinary engine; in the turbine it is very moderate. Steam is expanded nearly 200 fold in the Turbinia and this is accomplished with engines which are much lighter than re ciprocating engines of the same power, although in these the expansion would be much less complete. Rough weather was met with in some of the trials, but the 7'urbinia proved to be a good sea boat. The machinery worked witIrperfect smoothness, the screws did not race and the bearings remained perfectly cool throughout. From first to last during the whole of the trials, there was no hitch whatever or difficulty of any kind in the action of the tur bine. Some 20 were made under various condi tions as to speed, the range of speeds tested extending from 04 knots to 32g knots. Two successive runs on the measured mile in oppo site directions in smooth water and at the slack of the tide gave the following data: