CONTACT STRESS EVALUATION OF SHROUD CONFIGURATIONS IN AERO ENGINE HP ROTOR BLADES

The blades in Aero Engine are exposed to peak centrifugal stresses, thermal stresses, gas bending loads and excitations from various engine elements at high rotary speeds. Hence, blades need to be interconnected using machine elements to avoid blade failure due to cyclic load conditions. Which may otherwise results in blade bending, vibratory stresses, cracks developing at blade roots and finally blade may lift from the rotor. In this research shrouds are introduced as blade interconnecting elements in the HP Compressor rotor. Shrouds provide better structural integrity when compared to free standing blades. During high cyclic operating conditions, frictional forces get coupled with variable normal loads. A shroud resist these external forces and keeps the blade intact by locking with the shrouds of neighboring rotor blades. Shrouds are exposed to both static and dynamic contact in operating conditions, which leads to computations involving Elastic to Elasto-Plastic conditions, as high contact stress act perpendicular to contact surfaces and the frictional stresses act tangentially between the surfaces. Hertzian contact stresses is defined for localized stresses, which develops when two curved surface come in contact and deform slightly under the imposed loading conditions. In which the study of corresponding stress distributions at the contact interface and the interfacial separation between the two solids in the non-contact regions are studied in detail. Similar study is carried out here at the interface between the talking adjacent shroud faces. Hence, calling for the better shroud configuration to be chosen at desired ¾th position along blade height. Shrouds chosen for this study are of Flat, Airfoil and Zig-Zag cross-section configurations. In this paper modeling is performed for chosen configurations and analyzed using ANSYS package to determine the better shroud configuration, which provides greater structural stiffness along with least deformation to power the Aero Engine.