Numerical and experimental investigation of a radially reduced diffuser design concept for a centrifugal compressor performance at design point

Large scale, high pressure ratio (PR) centrifugal compressors are commonly made up of a radial impeller with a vaned diffuser. In research to date, the majority of research and design has focused on extending the operating range or improving the compressor efficiency. However, a cost and weight saving can be achieved by reducing the compressor dimensions. This is a study of a vaned diffuser design concept aiming to reduce the overall radial dimensions of the compressor without any sacrifice of compressor performance at design point (DP). The study parameterized a diverging endwall diffuser concept and optimized it to achieve a similar performance within a reduced radial outlet dimension. A metamodel assisted Multi Objective Genetic Algorithm (MOGA) method has been used. A numerical approach has been used to investigate how the flow physics within the diffuser passage changed with the new geometry and detailed experimental measurements have been used to validate the numerical approach. The result of this study is a summary of the impact of vane geometry defining parameters within a diverging endwall concept which offers design guidance for application of the concept. The measured performance showed that the same efficiency performance was achieved within a 15% radially reduced diffuser passage using the diverging endwall concept.