Rig Testing of the Operability of a Transonic Compressor Blade of an Industrial Gas Turbine
Abstract This paper describes the flow and vibrations measured in a 1.5-stage transonic research compressor tested at the Notre Dame Turbomachinery Laboratory. The compressor is a sub-scale version of a large-scale industrial gas turbine. The experiment measured the compressor performance and investigated the operability issues of stall and flow-induced blade vibrations due to buffet and flutter. The buffet was investigated at full-speed with fully-closed inlet guide vanes; the full-speed, no-load condition of gas turbines used for power generation. The flutter was investigated at part-speed conditions with partially closed guide vanes; the part-power condition where stall flutter typically occurs for aero-engines. At both of these conditions the blades operate with high incidence and moderate velocity, which can result in flow-induced vibrations. Aero-elastic simulations were performed to predict the flutter boundary. The flutter analysis predicted positive aerodynamic damping near the operating line, and a decrease in aerodynamic damping as the stall boundary was approached. No flutter was observed in the stable operating range of the compressor. The experimental campaign used blade tip timing to measure the vibrations and unsteady pressure transducers above the compressor blade. These two types of data were correlated to better understand the drivers of vibration. The paper describes the behavior of the aerodynamic drivers of buffet and flutter and the resulting vibration.