Axial turbine wheel design for mini trubojet engine

• Main Author: Koh, Yiyuan.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Aeronautical engineering
• Online Access: http://hdl.handle.net/10356/50300
• Institution: Nanyang Technological University

In the operation of a mini-jet engine, the turbine plays a critical role of driving the compressor. Without the turbine, the compressor will not turn and the engine cannot function. Thus, it is crucial that the turbine is properly designed to meet the power demand of the compressor. In order to increase the thrust of the SR-30 mini-jet engine, the compressor has been re-designed to improve the compression pressure ratio from 2.5 to 3 at 80,000 rpm. The power requirement of the compressor has increased to 47,183 W. At this new design point, the original SR-30 turbine is only capable of producing 21,799 W with an isentropic efficiency of 66.59%. Thus, a new turbine wheel has to be design to meet the higher power requirement. This report covers the steps to create a new single stage axial turbine wheel design. Firstly, the fundamental working principles of the axial turbine are studied. Cycle analysis is then performed to obtain the boundary conditions at the turbine inlet. Next, design software from CONCEPTS NREC is used to generate a preliminary design based on the boundary conditions and power requirement. The computational fluid dynamic (CFD) stimulation shows that the preliminary design (P_design_2) is able to output 47,457 W with an isentropic efficiency of 73.96% at 80,000 rpm. The blade geometric parameters, i.e. inlet and exit blade angles, stagger, unguided turning, TE passage width/pitch and blade counts, are then modified. CFD stimulations are performed to investigate the effects of each parameter on the power output and isentropic efficiency. Using the results from the parametric study, the preliminary design is modified to optimize the efficiency while still meeting the power requirement of 47,183 W. The final optimized design (Opt_design_2) has a power output of 47,209 W and an isentropic efficiency of 75.00%. Comparing with the preliminary design and the original SR-30 turbine, the isentropic efficiency has been improved by 1.41% and 12.63% respectively. Both preliminary and optimized designs are then fabricated using a CNC milling machine in Nanyang Polytechnic. The material, Inconel-718 is being used. The future work will focus on the testing of the new turbine and using the experimental data to validate the flow stimulation. After validation, other methods of reducing aerodynamics losses, such as blade leaning and variable stagger along blade span, can also be explored. Commercial optimizer, such as TurboOpt II and IOSO can be used to facilitate the optimization process and yield better results.