Traub P., Gründel H., Gautier S.

The growth in demand for aviation means that further improvements are required so that aviation can meet the ambitious customers’ requirements within environmental limits. The aero engine manufacturers are setting themselves challenging projects and research programs to decrease significantly the most important measurable indicators for environmental issues, exhaust and noise emissions. MTU Aero Engines is playing its part in more than 40 projects. In this presentation some insights are given related to the aero-acoustical design process in the frame work of a technology program. Challenged by the objective to get a significantly quieter design than earlier LPT variants, up-graded prediction methods and a state-of-the art 3D-CFD modelling approach have been successfully applied to perform and evaluate low noise design features. In a first step the key parameters especially for tonal noise generated by viscous wake interaction between blades and vanes have been identified. According to this design variants and their influence on noise have been investigated numerically whereas the parametric study focus on the effects of rotor/vane numbers and 3D-design features (e.g. lean, sweep, bow) of the last turbine stage with exit guide vanes. Each cascade is computed separately accounting for the sound propagation downstream; the result is presented in sound power level scale related to the turbine exit plane. Concluding from that a favourable choice of rotor/vane numbers (apart from cut-off design) combined with 3D-airfoile design can significant reduce the turbine noise by 2-7 dB. Finally the potential of noise reduction have been balanced with performance and costs. The developed low noise design measures, now ‘technological ready’, can be incorporated into new products and are applicable to optimize both existing and future turbine designs.