The feature-based computational geometry and secondary air system modelling for virtual gas turbines

Abstract

This dissertation presents a novel method for generating the computational geometry of three spool aero engine for the Virtual Engine (VE) design environment, which is capable of carrying out full integration of preliminary and detailed design and analysis activities. The multi-fidelity and multi-disciplinary analysis of complex gas-turbine assemblies is the prime requirement of industrial design. The present challenges for gas-turbine industry, namely excessive design times, lack of decisive information till the late design stages, mismatching of databases and high costs associated with testing etc. necessitate creation of an integrated design framework such as VE. This thesis presents the work on selected parts of VE design environment. The present work initially focuses on the development of an integrated geometry modelling system for VE. The architecture of geometry module is derived from the requirements of VE design environment and Computer Aided Design (CAD) geometry systems. A dedicated geometry modeller is developed to represent gas turbine components. The building blocks of this modeller, known as features, are constructed as object-oriented data structures. A taxonomy of turbomachinery design features is defined to generate 2D axisymmetric geometry model of three-spool aero-engine. Such system supports intra-analysis information augmentation, data updating and automated data transformation for any kind of analysis. In the next phase, the Computer Aided Engineering (CAE) capabilities of VE are demonstrated by carrying out flow network analysis of Secondary Air System (SAS). Particular attention is devoted to the automated extraction of SAS network from the geometry. The generation of SAS network involves interrogation of component models, automatic identification of flow links and pre-processing of network elements. A library of physics-based linearized pressure loss models is prepared, validated and incorporated in VE. A new loss model for straight-through labyrinth seal is developed from numerical experiments and it is validated against those in the literature. A linearized flow solver for the whole engine SAS network model is also developed. Finally, low fidelity steady-state flow analysis is demonstrated on a limited domain of SAS network model. This work meets its objectives by showing a way of constructing important modules of VE design framework. It bridges the gap in current features technology by creating the design features that represent turbomachinery components. The work demonstrates quick generation of low-fidelity geometry model for whole aero-engine assembly, thus endorsing its utility for the analysis in early stages of design. A methodology for performing automated CAE analysis of secondary air system (SAS) of aero engine has also been developed. The development of new loss model for labyrinth seal and the demonstration of low-fidelity steady-state SAS analysis confirm the successful implementation of selected part of VE project.