Authors: A. C. Greyling, P. S. J. van der Spuy
Year: 2025
Industry: Gas Turbines
Keywords: Use FSE, Dynamic, HTTU, Micro Gas Turbine
ABSTRACT
A power turbine for the CAT250TJ micro gas turbine engine was manufactured and tested. The turbine rotor was made from 21CrMoV5-7 steel. A centrifugal compressor was used as the load for the power turbine. Cold air tests were conducted at speeds of up to 60000rpm, during which a maximum power output of 12kW was measured. Additional tests were performed with the power turbine connected to a CAT250TJ engine, achieving a maximum speed of 55000rpm and a maximum power output of 4.5kW. Performance maps of the micro gas turbine compressor and turbine and the power turbine were generated using computational fluid dynamics (CFD), while the load compressor map was obtained experimentally. A CFD simulation at the design speed indicated that the manufactured design was choked at 95% of the baseline design’s choked mass flow rate. The maps were used in a one-dimensional simulation in the Flownex® Simulation Environment and the experimental results were replicated successfully. The Flownex® power turbine model showed that the modifications made to the manufactured power turbine resulted in a change in the operating point of the micro gas turbine: the CAT250TJ will operate at 103.9% of the design speed, 93.6% of the design mass flowrate, andat97.2%ofthedesignfuelconsumptionwhile powering the manufactured power turbine. The model also indicated that the manufactured turbine will be able to reach the required speed and power output values of the baseline design (60000rpm and 37.8kW). By scaling the load compressor geometry within the same model, it was predicted that the optimal load compressor for the experimental set-up would have an outlet diameter of 160mm.