Effect of Taper and Twisted Blade in Steam Turbines.

Abstract

Turbo machinery is critical to various processes and their application range from steam turbines to aircraft turbines. Turbo machinery bladed disks are subjected to severe centrifugal loads. The centrifugal force is one of the problems that face the designers of blades especially the long ones. The severe loading leads to large peak stresses. One way to tackle this is by using twisted blades or using variable cross-section area blades. Rotating structures having the shape of pre-twisted blades commonly affect the modal characteristics. In order to design the rotating structures properly, their modal characteristics must be estimated accurately. The modal characteristics of rotating structures often vary significantly due to the effect of the centrifugal inertia force induced by the rotation motion. For this reason, the modal characteristics of rotating structures have to be investigated. In this paper effect of taper and twist in steam turbine blade is analyzed using ANSYS. Blades are idealized as tapered cantilever beams that are fixed to a rotating disc. The results obtained are then utilized in the design of the constant stress blade