Steam turbines; a practical and theoretical treatise for engineers and students, including a discussion of the gas turbine . earing, for driving machines the speed of which approximatesthat of the turbine, such as large alternators, centrifugal aircompressors, and high head centrifugal pumps. For any given capacity and steam condition there is, for eachtype of turbine, a speed which will give the highest efficiency,.and it is a problem for the designer to make the proper arrange-ment of blade lengths, blade angles, disk diameters, etc., so asto secure the ratio of steam velocity to blade speed
Steam turbines; a practical and theoretical treatise for engineers and students, including a discussion of the gas turbine . earing, for driving machines the speed of which approximatesthat of the turbine, such as large alternators, centrifugal aircompressors, and high head centrifugal pumps. For any given capacity and steam condition there is, for eachtype of turbine, a speed which will give the highest efficiency,.and it is a problem for the designer to make the proper arrange-ment of blade lengths, blade angles, disk diameters, etc., so asto secure the ratio of steam velocity to blade speed that willsecure the best efficiency. In medium sizes, that is, up toabout 3000 kilowatts, the multi-stage impulse turbine, in somecases fitted with velocity stages in the first pressure stage, is themost efficient by quite an appreciable margin. Comparing themulti-stage turbine with the reaction turbine in small sizesunder these conditions, the high pressure blades of the reactionturbine become very short in proportion to the leakage paththrough the clearance at the ends of the blades. Due to the 188 THE STEAM TURBINE. COMMERCIAL TYPES 189 fact that the leakage takes place over the ends of the movingblades and under the ends of the stationary blades of reactionturbines, it is not feasible to use types of packing which is ap-plied so effectively for packing the joints between the shaftsand diaphragms of multi-stage turbines. A sectional drawing of a typical De Laval multi-stage steamturbine is shown in Fig. 87. The rotating part of the turbineconsists of a heavy shaft upon which is mounted a series of disksfor carrying the blades. The shaft and the blade disks are shownin Fig. 88. Each blade disk revolves in an independent cham-
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