Steam turbines; a practical and theoretical treatise for engineers and students, including a discussion of the gas turbine . ss can be calculated for enough pointsto determine the profile. The section shown in Fig. 213 is a * Jude, The Theory of the Steam Turbine, page 200. 424 THE STEAM TURBINE typical flat disk. To facilitate the forging of such disks theprofile is not made exactly as calculated but is gradually taperingfrom the smallest section to the center. The increase in thethickness from the rim to the center is very small compared withmany designs, approximating a concavo-convex form
Steam turbines; a practical and theoretical treatise for engineers and students, including a discussion of the gas turbine . ss can be calculated for enough pointsto determine the profile. The section shown in Fig. 213 is a * Jude, The Theory of the Steam Turbine, page 200. 424 THE STEAM TURBINE typical flat disk. To facilitate the forging of such disks theprofile is not made exactly as calculated but is gradually taperingfrom the smallest section to the center. The increase in thethickness from the rim to the center is very small compared withmany designs, approximating a concavo-convex form (). It is argued by some designers that the treatment of the concavo-convex forms is entirely wrong and that most prob-ably it is not possible for the stresses all along the central planeto be either equal to or less than those at the rim by merely satis-fying equation (38), and that the metal in the bulging part of suchdisks has little influence in modifying the stresses in the centralplane. Some of the best authorities agree that it seems reason-able that whatever the form of the profile of a disk the stresses. 1 Fig. 214. Typical Solid Disk without a Hole at the Center. in and about the central plane do not differ greatly from thosein a1 flat disk running at the same speed.* A typical solid disk without a hole for bolts or for the passage ofa shaft through it is shown in Fig. 214. It was designed for avery much higher speed than the one in Fig. 213, so that it hasa bulging from near the center. This design shows an ingeniousmethod for the attachment of the body of the disk to the will be observed that the disk is made with a very small sec-tion near the rim; so that the stress there far exceeds that any-where else. If the wheel breaks it will rupture first at thissmallest section and the rim and blades will be torn off. Whenthese parts are gone the centrifugal force will be so much reducedon the part of the wheel remaining that there can be still a very * Jud
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