Improved Compressor Exit Diffuser for an Industrial Gas Turbine

Cycle studies carried out for the medium pressure ratio gas turbine THM 1304 of 10 MW power output manufactured by MAN Turbomaschinen AG GHH BORSIG predicted that the overall efficiency of the multistage compressor, composed of a ten-stage axial and a single-stage centrifugal compressor, would improve by 0.8 percent if the efficiency of the back stage centrifugal unit could be raised by 4 percent. It was expected that this would result in a noticeable improvement of the thermal gas turbine efficiency. The paper describes the aerodynamic design process used for the stage optimization, applying today’s advanced design tools for blade generation and three-dimensional aerodynamic calculation methods. Additionally, it describes the manufacturing procedure for the resulting three-dimensional blades and the experimental verification of the design approach.