Application of multi-objective optimization to axial compressor preliminary design

Abstract

The axial compressor is one of the most challenging components for aero engine design. 
The highly complex and multi-disciplinary design process is built up from several 
separate design phases differing with respect to the number of details. Typically, meanline 
prediction is the first step of the aerodynamic design process where the goal is to 
provide a first guess and proper choice of basic design parameters. As a preliminary 
design procedure it is one of the most important parts of the compressor design process 
since a poor design decision on these parameters cannot be corrected by subsequent 
development efforts. The design of a compressor is always a compromise between contradicting 
requirements like high efficiency, low number of stages and high surge margin. This is 
typical for multi-criterion optimization problems requiring a high number of design 
analyses and a well-designed procedure for finding trade-off solutions. The paper will 
show how to automate a given Rolls-Royce preliminary design process in order to find 
Pareto-optimal trade-off solutions for design conditions. The aspect of process acceleration 
is also an important goal to release the design engineer from time-consuming parameter 
studies. Essential elements for speeding up the design process are the use of modern 
process integration tools, multi-criterion decision concepts, and nonlinear programming 
algorithms. Results will be shown based on a given Rolls-Royce compressor design for 
multi-objective optimization with respect to maximum efficiency, maximum surge margin, and 
maximum overall pressure ratio, where different deterministic and stochastic algorithms are used.