Whole Engine Design

Research Theme: Process Management

The complexity of aero engines has led to their design by decomposition and thus the establishment of a design specification and constraints for each module. To better understand the implications of these constraints, the Integrated Engine Design (IED) model uses an integrated multidisciplinary multi-component approach that incorporates real-time visualization to overcome organizational boundaries and maximise multidisciplinary trade-offs at the preliminary design stage.

Motivation

Typical integration of the aero engine design process involves the automatic integration of existing design-by-analysis and optimization tools. Although suited to scaling existing detailed designs, this approach requires complete geometry and as such is not used early in the design process where there are many unknowns and significant risk yet the most freedom for design improvement.

True multidisciplinary optimisation should not be solely an automation of the existing manual design process, but should provide new avenues of exploring and visualising the preliminary design trade-offs.

Objectives

  • Increase understanding of multidisciplinary trade-offs during the preliminarydesign process through visualisation and integration.
  • Identify limiting design constraints and investigate the implications of "softening" thoseconstraints.
  • Explore feasible design space by decoupling design tasks and investigatingnew design process pathways.

Method

An integrated design and visualization tool (IED) for multidisciplinary preliminary design is being developed with proprietary and custom modules including aerodynamics, thermodynamics, mechanics, noise, emissions, weight, costs, business modeling, performance retention, product life management, uncertainty/risk analysis and optimisation tools.

Findings

The IED currently includes 1D and 2D aerothermal, weight and emissions models and a materials database. It has been used for: studies of the trade-offs between weight, fuel consumption and nitrogen oxide emissions; hierarchical weight minimizations; constraint visualization and multi-component design space exploration.

Details

An integrated design model (IED) that encompasses all relevant engineering disciplines, uncertainty/risk analysis and economic modeling is being developed with multiple fidelity levels. The IED uses a hierarchical database structure which maintains design integrity throughout the engine hierarchy and manages the confidences associated with the results of each calculation.

Combining integration and visualization with optimization will enable a visual exploration of the multidisciplinary design space. Although visualizing the multi-dimensional design space in real-time is challenging, it can provide valuable understanding of the complex trade-offs being made and the effects of constraints on the process outcome. The constraints that drive and limit the design process can be identified and implications of “softening”, or modifying, these constraints can be investigated.

The IED was used for a spool weight minimization study and the five performance constraints were visualized throughout the optimization as shown in Figure 2. This visualization indicates that the number of compressor blades (Comp. NOB) is limiting the optimization, as it is the only constraint that does not re-enter the constraint envelope of ±1%. By relaxing the Comp. NOB constraint to ±10%, valid solutions are achieved towards the end of the optimization as the other constraints are satisfied and lower weight designs are found. This study provides an example of how visualizing and understanding constraints enables "softening" of the limiting constraint, which introduces flexibility into the design process and results in better designs. The IED offers an opportunity to understand and explore the effects of changing the constraint boundaries, which is important for maximizing the performance of a mature and complex design.

Acknowledgements

Proprietary modules provided by:

Support for this project was provided by the J. Armand Bombardier Fellowship, the Cambridge Commonwealth Trusts and the EPSRC.

Selected Publications

  • BELL, T.A., JARRETT, J.P. and CLARKSON, P.J. (2006) 'Exploringmultidisciplinary trade-offs in turbomachinery design' in ASME InternationalGas Turbine Institute TURBO EXPO 2006, Barcelona, Spain, American Societyof Mechanical Engineers, Barcelona, 2006.
  • BELL, T.A., JARRETT, J.P. and CLARKSON, P.J. (2006) 'Supportfor the preliminary design of aero engines' in 2nd AIAA MultidisciplinaryDesign Optimization Specialist Conference, Newport, Rhode Island, U.S.A.,American Institute of Aeronautics and Astronautics, Rhode Island, USA, 2006.
  • BELL, T.A. and JARRETT, J.P. (2005) 'An integrated approachto the conceptual design of aeroengines' in CAID & CD 2005, The 6thInternational Conference on Computer-Aided Industrial Design & ConceptualDesign, Delft, The Netherlands, 2005.