New Axial Compressor Cascade Aerodynamic Interference Noise

The noise reduction is now a leading priority in the further development of aircraft engine. The basic method to reduce noise is reasonable aerodynamic design which has great denoise potentialities.The concept of uneven blade spacing is firstly introduced into the compressor denoise studies. Considering the aerodynamic performance and acoustic properties during the design of the compressor, the feasibility of uneven blade spacing in discrete noise reduction is investigated. Theoretical calculation and analysis show:The numerical simulations of unsteady flow were carried out for compressor with equally spaced rotor blades and unequally spaced IGV and stator blades. The effects of different uneven blade spacing configurations on stator blade aerodynamic force are presented. The calculations predict that the characteristics of stator blade force frequency chart are discrete for all configurations.The effects of unequally spaced IGV and stator blades on the sound generated by IGV wake-rotor interactions are analyzed by solving the generated Lighthill equations. The comparison of results shows the sound pressure level(SPL) radiated by a rotor decreases for one of these configurations without influencing the aerodynamic performance, but it is different in the upstream of the rotor from the downstream.The main effort was focused on the sound generated by rotor-stator interaction in an axial compressor with equally spaced rotor and unequally spaced IGV and stator blades. The noise radiation formula of unequally spaced stator blades is derived in terms of the generated Lighthill theory. It is found that the stator sound propagating modes of uneven configurations are changed and the SPL at the blade passing frequency radiated by a stator decreases for one of these configurations without influencing the aerodynamic performance.Based on above schemes, the uneven blade spacing has certain effects on reducing interaction noise with on influence on the compressor aerodynamic performance.