Abstract:
The profile shapes of axial turbine blades need to fulfil the requirements of not only aerodynamics but also mechanical criteria. A design requires aerodynamically favorable velocity distribution as well as mechanically favorable geometry that can withstand the dynamic forces. So, several constraints from Aerodynamic, mechanical perspective are generally imposed while optimizing blade profile that fulfills all engineering restriction. But in this work, only mechanical aspect of design is investigated ignoring aerodynamics, to provide a better insight on effect of different blade profiles on Modal & fatigue behavior of the blade. As Previous works includes fatigue analysis on case-by-case basis. No one worked on comparative analysis on fatigue and modes with blade profile with varying angle of twists. First several NACA-4 series profiles were selected and the coordinates of selected profiles were generated with python programming language. The equations for NACA four series profile were used to calculate the coordinates of profile. Using the generated coordinate files, The CAD models were generated using Visual Basic programming language in Visual Studio 2015 with the help of SolidWorks 2021 API. The CAD models were created from the combinations of selected NACA profiles and selected twist angles. The CAD models were imported into ANSYS Workbench using scripting language to perform Modal and Fatigue analysis using Finite Element Method (FEM). The mesh settings were chosen such that the results converge to a satisfactory degree. The results were then exported to Excel file to comparative analysis and graph generation. The simulation results showed interesting trend with blade profiles. The change of natural frequencies with respect to increasing degree of twist is observed to have a downward trend for 1st and 2nd modes. But an opposite trend is found for 4th, 5th and 6th modes. A correlation between Fatigue life cycle with respect to degree of twist is also discovered. The fatigue life is found to be increased with increasing angle of twist. A similarity is found in the results for different NACA profiles.
Description:
Supervised by
Dr. Md. Zahid Hossain,
Professor,
Department of Mechanical and Production Engineering (MPE),
Islamic University of Technology(IUT),
Board Bazar, Gazipur-1704. Bangladesh.
This thesis is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Mechanical and Production Engineering, 2022.
