A Large Design Space Multidisciplinary Optimization of a Mixed Flow Micro Gas Turbine Compressor Stage

Abstract

A parametrization method for the simultaneous optimization of the impeller and diffuser of a mixed flow compressor stage across a wide geometrical diversity is presented. The optimization focused on determining the optimal mixed flow (meridional) angle for a predefined set of constraints. The number of parameters required to achieve the large geometric diversity associated with a variable mixed flow angle was greatly reduced by coupling the endwall and camber Bézier control points with user-defined functions. The influence of geometric features on design performance was assessed using a Pearson correlation coefficient map. It was observed that stage total-to-static pressure ratio, and efficiency, were strongly influenced by diffuser outlet passage height and diffuser vane wrap angle. This was due to these parameters’ control of flow separation magnitude at the diffuser hub in the radial-to-axial bend. The method improved design point efficiency by 4.24 percentage points (to 86.24%) and increased the operating range by 6.7% at the cost of a decreased design point pressure rise, when compared to the baseline design.