In the framework of this project the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology has been building a Subsonic Test Turbine Facility (STTF) for experimental investigations of sound generation and propagation of low pressure turbines. This test rig was was designed in cooperation with MTU Aero Engines Munich. The aerodynamic and the acoustical design of the test rig is representative for the last stage of a modern commercial aeroengine LP turbine. The measurement section is equipped with microphones flush mounted on both inner and outer duct walls in the cylindrical duct of the turbine exit. This setup enables the decomposition of the sound field into azimuthal and radial duct modes up to a frequency of 17 kHz. Thus the dominant sound generation mechanisms, caused by the aerodynamic interaction of rotor blades with the fixed blade rows could be identified and the amount of sound power, transported in and against the flow direction, evaluated. Beyond the scope to deepen the physical understanding of noise generation in LP turbines, the test data is used for validation of numerical methods.
Properties of the test faciliy: