In-engine performance evaluation of a mixed-flow impeller with a crossover diffuser compressor stage

Abstract This study evaluates the in-engine performance of a mixed-flow impeller with crossover diffuser compressor stage designed for the CAT250TJ micro gas turbine engine. The upgraded compressor configuration was analysed using CFD simulations in Ansys ® Fluent ® and thermodynamic cycle modelling in Flownex ® SE, then manufactured and experimentally tested. CFD predictions showed the mixed-flow crossover compressor achieved a 14.10 % increase in pressure ratio at the design point compared to the baseline GEN1 configuration, though with reduced operating margins. Experimental validation at 115,000 RPM demonstrated a 12.21 % increase in static thrust (246.65 N vs. 219.82 N) and a 9.61 % reduction in thrust-specific fuel consumption (46.31 g/s/kN vs. 51.24 g/s/kN) relative to the baseline GEN1 compressor engine. The mixed-flow impeller required approximately 7 % less shaft power across the operating range, necessitating a 15 % reduction in engine outlet area to achieve optimal compressor-turbine matching. The CFD model showed good agreement with experimental measurements at lower speeds but overpredicted pressure ratios at higher speeds, while the Flownex ® cycle model predicted thrust within 6 % and accurately captured exhaust gas temperature trends. These results validate the complete design methodology and demonstrate significant performance improvements through advanced compressor stage design for micro gas turbine applications.