A Case Study to Illuminate the Concepts of Design Expertise and Designer Flair in Engineering Design

The paper addresses the issue of design expertise and designer flair in the context of the conceptual phase of the engineering design process as it is here that key design skills in idea generation and disciplined creativity are displayed. The investigation to be reported in this paper is based on a problem which frequently arises in the design of axial flow turbomachinery where rotating arrays of blades impart energy to a stream of fluid in an adverse pressure gradient. In axial flow compressors, for example, it is often necessary to change blade angle settings in the early stages of a multi-stage compressor in order to accommodate changes in flow rate, this to prevent premature separation and stalling of the flow over the blade surfaces and thus avoid compressor surge. To achieve this outcome a mechanism has to be designed to transfer motion (in three dimensions) from an input controller or actuator to the axes of the designated set(s) of blades. The opportunity to undertake this investigation arose from an industry/university liaison between the authors and a senior design engineer in an aero-engine manufacturer. With the Company's permission the design engineer briefed the authors on a problem of the type described in the preceding paragraph, a problem in compressor design which the Company had faced and a solution found and implemented, hereafter referred to as the case problem. The design brief was adapted to form the basis of an undergraduate project and presented to (a) undergraduate students of engineering design at the University of Melbourne, and in a follow up study to (b) three mechanical engineers with extensive experience in engineering design. Sets of sketches of alternative mechanisms - ideas generated by both student and experienced designers - were recorded and provided the experimental evidence for the analysis and interpretation of the designers' performance.