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Stress Analysis and Optimum Profile Shape Design in Gas Turbine Engine Disk

Armaghan, Delavar | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45375 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Kouchakzadeh, Mohammad Ali
  7. Abstract:
  8. In this thesis, turbine disk thermo elastic and creep stresses has been extracted and the turbine disk cross-section is optimized. Gas turbine disks are used at high temperature and high rotational speed. Due to high temperatures gradients, the mechanical properties vary along the radius of the disk. Most of the stresses in the gas turbine are exerted by centrifugal force and thermal strains. At first, thermo elastic and creep equations for these disks are derived, assuming plane stress and axisymmetry. The resulting differential equations are nonlinear and can not be solved using analytical solutions. Two methods are used to solve the equations which finally are verified employing the finite element method (FEM). Using the first method, disc is divided into rings having constant thickness and properties. By applying the boundary conditions and the continuity of displacement and radial stress, stress distribution at the boundary of each ring is obtained. This technique can be used for determining the creep strain rate. Then general differential equation for disk is solved using the Generalized Differential Quadrature (GDQ) method and the stresses distribution is obtained. In GDQ method, the Chebyshev polynomials are modified, and used to discritize disks and the order of the differential equation of nodes is reduced to zero. Displacement of each node is described using displacements of other nodes. By applying the boundary conditions and solving the system of equations and unknowns, the displacement field is obtained. In the next step, objective functions and constraints are examined to propose a new objective function for disk optimization. This objective function is a weighted function of the weight and stress distribution and, results in more uniform stress distribution with reduced weight. Due to great number of design parameters and complexity of objective function, Genetics Algorithm is used the optimization process. Finally, disks are optimized with different objective functions and the results are compared
  9. Keywords:
  10. Creep Analysis ; Optimization ; Thermoelastic ; Generalized Diffrential Quadrature ; Gas Turbine Engine Disks

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