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Investigation and Validation of Combined Turbine and Nozzle Design Changes on performances

Asgarshamsi, Abolhassan | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47103 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Hajilouy Benisi, Ali; Pourfarzaneh, Hossein
  7. Abstract:
  8. In this thesis, the rear part of a turbo-jet engine consisting of a one stage axial turbine and its exhaust nozzle are optimized numerically and experimentally. The decrease of total pressure loss of the flow in the stator and rotor blade cascades is investigated by change of two-dimensional profiles. The three-dimensional blade shape optimization is employed to study the effects of the axial turbine stator and rotor lean and sweep angles as well as radial distributions of stagger angle on the turbine performance. In adition, the effect of the turbo-jet engine exhaust nozzle on its performance is explored. Geometry candidates for the three-dimensional optimization algorithm of the axial turbine are generated by re-stacking of the two-dimensional airfoil sections. Therefore, modifications of 2D airfoils are carried out at blade cascade and then in three-dimensional space, the positions of 2D airfoils in radial direction are investigated. In each case, appropriate objective functions, optimization parameters and their constraints are presented. By coupling of verified CFD simulation software with a Genetic Algorithm, an automated design procedure is prepared. In this thesis, single-point optimization is performed in cascade space. In addition, single-point and two-point optimization are executed for the axial turbine modifications. The developed method results in improvements in new turbine stage efficiency in design and off-design speeds and the increase in mass parameter at choke condition. The changes in lean and sweep angles successfully improve the turbine stage total-to-total efficiency 1.3% and 1.17%, while the decrease in the stage pressure ratio is 1.47% and 1.12% in its design and ideal speeds, respectively. The change in radial distribution of stagger angles results in an improvement of 1.06% in the turbine stage efficiency with a decrease of 0.82% in stage pressure ratio. The optimization of 2D airfoil profiles resulted in a reduction of 1.5% in the rotor total pressure loss and 3.0% in stator one, for a prescribed incidence angle. In experimental investigations, the equipment of Gas Turbine Laboratory of Sharif University of Technology is developed. At different conditions, the turbo-jet engine is investigated and the performance of each component obtained on operation line of the engine. The experimental results are used for specifying the boundary conditions and validation of the simulation results. The outer wall of the exhausts nozzle is changed. A new nozzle is designed and manufactured. In ideal speed, the maximum increase in the turbojet engine is 28.5% while the decrease of the turbine pressure ratio is measured which is 2.47% in comparison with the initial engine
  9. Keywords:
  10. Stator ; ROTOR ; Axial Flow Turbine ; Nozzles ; Optimization

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