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Title: Multidisciplinary optimisation of radial and mixed-inflow turbines for turbochargers
Author: Zhang, Jiangnan
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2018
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The radial and mixed-inflow turbines have been widely used for the turbocharger application. The design of a turbocharger turbine with good performance still presents a lot of challenges. Apart from the traditional requirements such as high efficiency and low stress, the turbine blade is also required to achieve certain performance targets at multiple operating points, high unsteady efficiency under pulsating flow condition, reduced moment of inertia (MOI) and high vibration characteristic. To meet these challenges it is important to optimise the radial and mixed-inflow turbines for the aerodynamic performance at multiple operating points and the structural performance subject to MOI, stress and vibration constraints. In this thesis we propose an approach based on 3D inverse design method that makes such a design optimisation strategy possible under industrial timescales. Using the inverse design method, the turbine blade geometry is computed iteratively based on the prescribed blade loading distribution. The turbine’s aerodynamic and mechanical performance is evaluated using CFD and Finite Element Analysis (FEA). A linear regression is performed based on the results of a linear DOE study. The number of design parameters is reduced based on a sensitivity analysis of the linear polynomial coefficients. A more detailed DOE with around 60 designs is generated and Kriging is used to construct a response surface model (RSM). Multi-objective genetic algorithm (MOGA) is then used to search the optimal designs which meet multiple constraints and objectives on the Kriging response surface. The radial filament blading is always applied by the conventional design method to reduce the stress, while the inverse designed blade is three-dimensional (3D). Two radial filament modification (RFM) methods are proposed to control the stress level of 3D blades. Radial turbines with a backswept leading edge (LE) designed using the inverse design method show improved cycle-averaged efficiency. An optimal design is obtained through the second optimisation. Its performance is evaluated in both the aerodynamic and mechanical aspects based on CFD and FEA simulations. The CFD model is validated against the experimental results of the baseline design. The numerical results show that the optimal design leads to better performance in almost all aspects including improved efficiency in the low U/Cis (velocity ratio), reduced maximum stress, reduced MOI, and increased vibration frequencies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available