several of the turbine propelled vessels recently built. One high-pressure turbine, H, is arranged on the centre line of the vessel. This exhausts by the pipes P, P into the low-pressure turbines L, L. These exhaust by the large passages E, E into the condensers C, C. The air-pumps are shown at A, A, and the hot wells at W, W. F, F indicate the feed-tanks, G, G the hot-well pumps, B, B the bilge pumps, and U, U the circulating pumps. X, X are the auxiliary cruising turbines which are of greatest use on war-ships, but may with advantage be placed on very high-speed steam yachts intended to cruise extensively at much reduced powers. (The Tarantula is provided with a cruising turbine to increase the economy at speeds up to 15 knots.) S, S are the steam supply pipes to these cruising turbines. When these auxiliary engines are omitted, the airpumps are sometimes placed forward of the high-pressure turbine. The reversing turbines are placed inside the casings of the low-pressure turbines, and exhaust into the condensers by the same passages E, E. The pipes conducting live steam to the reversing turbines are omitted from the drawing for the sake of clearness. The steam turbine possesses several advantages over the reciprocating engine for marine propulsion. In the first place, there is the absence of vibration-an important point, both as regards comfort in passenger steamers and as regards accuracy of gun-fire in naval vessels. Then there is a distinct saving in weight. This is not so marked in vessels of the destroyer type, where the engine-room weights are cut down to an abnormally small amount, as in larger vessels, and especially in the mercantile marine. This saving in weight can, of course, be used either in increasing the engine power, and consequently the speed, of the vessel, or in adding to its carrying capacity. The low situation of the engine-room weights in a turbine-propelled vessel also tends to improve the stability, and, in the case of a war-vessel, places the engines in a more protected position. Turbines require less attention than reciprocating engines, and are easier kept clean and bright. |