Hollow design of engine turbine disk to minimize stress at blade fir tree

• Main Author: Lee, Jian Ming
• Other Authors: Chow Wai Tuck
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Aeronautical engineering::Jet propulsion
• Online Access: https://hdl.handle.net/10356/140483
• Institution: Nanyang Technological University

This report presents the study of the effects of a hollow design of the engine turbine disk to minimise stress at the disk-blade fir tree design. The study was first conducted using script programming with Mechanical ANSYS Parametric Design Language (MAPDL), to perform a gradient descent study and to obtain a 2-D topology optimisation for a fir-tree external geometry design. The effects of certain variables were also studied from initial simulations using 2-D analysis on ANSYS Static Structural. These included the length of the fir-tree blade, the angle between the fir-tree blades and the effect of hollowing certain parts of the turbine disk. The 2-D design process consists of 2 different methods to improve the 2-D extrusion of the fir-tree design. The first method was a gradient descent to optimise the external geometry of the fir-tree design. The second method was a topology optimisation for hollowing the internal geometry. After obtaining an optimised 2-D design, it was extruded to form a 3-D design. Material was then removed at certain portions of the teeth to redistribute the stresses away from high concentration areas more evenly to the lower concentration areas on ANSYS Static Structural. The variables adjusted for 3-D design include the angle of the cut, the distance of the cut from the centre and the material removed on different teeth. Hollowing certain portions of the turbine disk were not successful in reducing the maximum principal stress of the entire system but managed to reduce the stresses on the turbine disk root. The effects of material removal on the 3-D designs have managed to successfully reduce the maximum principal stress on the turbine disk and blade attachment by 13.3%, in the Triangular Cut design 7. Furthermore, these designs have also reduced the weight of the turbine by removing material on the fir-tree teeth.