Engineering Wonders of the World
Volume I

THE PROPELLING MACHINERY OF A SHIP. 37 which proved the superiority in many respects of the turbine. On the Atlantic mail and pas- senger service the turbine was adopted first for the Allan liners Victorian and Virginian, and afterwards in the Cunard Company’s in- termediate vessel Carmania, and their express mail steamships Lusitania and Mauretania, the two latter, with their enormous powers, representing the latest word in turbine pro- pulsion in the mercantile marine. All the warships now under construction for the Brit- ish Admiralty are being fitted with Parsons turbines, which have also been adopted by the Austrian, French, German, Italian, Japan- ese, and United States Navies. The following description of the Parsons turbine, by th© inventor himself, is perhaps the most lucid Principle of the Parsons Turbine. that can be given :—“ It con- sists of a cylindrical case with numerous rings of inwardly- projecting blades. Within this cylinder, which is of variable internal diameter, is a shaft or spindle, and on this spindle are mounted blades, projecting outwardly, by means of which, the shaft is rotated. The former are called fixed or guide blades, and the latter revolving or moving blades. The diameter of the spindle is less than the internal diameter of the cylinder, ring of fixed guide blades, which deflects it so that it strikes the adjoining ring of moving blades at such an angle that it exerts on them a rotary impulse. When the steam leaves these blades it has naturally been deflected. The second ring of fixed blades is therefore interposed, and these direct the steam on to the second ring of rotating blades. The same thing occurs with succeeding rings of guide and moving blades until the steam escapes at the exhaust passage.” (Fig. 10.) The spindle or rotor is directly coupled to a line of shafting, on the end of which is fitted a screw propeller, and as the rotor is caused to revolve rapidly the motion is communicated to the screw. Steam is admitted from the boilers first to the high-pressure turbine, and as it passes along between the blades it loses pressure and expands, necessitating an increase in tho diameter of the Expansion . ,, of Steam. cylinder or casing and m the size of the blades as the distance from the point of entry of the steam increases. From the high-pressure turbine the steam passes to the low-pressure turbines, which, of course, are larger in diameter than the high-pressure, and thence into the condenser. Most turbine-driven war and merchant ves- Casing a, Entrance port for steam, d1, n2, x>3, Rotor drums of increasing diam- eter. m m, Blades attached to rotor. ff, Blades attached to casing, p1, p2, Balance pistons to counteract longitudinal thrust of rotor blades, b, Exhaust port, s, Shaft, c and e, Ports leading to balance piston. Fig. 10.—SECTION OF A PARSONS STEAM TURBINE; and thus an annular space is left between the two. This space is occupied by the blades, and it is through these the steam flows. The steam enters the cylinder by means of an annular port at the forward end ; it meets a seis are fitted with three screws, each con- nected to a separate shaf t. The usual arrange- ment of turbines in triple-screw merchant steamers is for the central shaft to be worked by the high-pressure turbine, while the two