Turbine tonal noise prediction using an improved quasi-3D linear model

This study presented a fast tonal noise prediction method for the turbine. The improved quasi-3D linear model was developed based on Hanson's coupled 2D cascade theory of blade row and Goldstein's duct aeroacoustics equation. The improved model can take into the influence of the radial modes account by applying the strip theory. Furthermore, a two-flat-plates assumption was used for the first time to account for the large turning angle of the turbine blade, and different wake velocity defect models with coefficient correction have been developed for each of the two-flat-plates. Briefly, firstly applying extended Hanson's theory to predict the unsteady load on blade surface and then using Goldstein equation to calculate cut-on modes and sound power level of interested frequencies. The present model was validated by URANS/Goldstein hybrid model by comparing the tonal noise radiation generated by the final stage of the GE E3 low pressure turbine at different rotational speeds and various stator-rotor spacings. The results showed that the present model generally agreed well with the hybrid model and can correctly capture the variations of the sound power level with the operating conditions, which indicated that the present model might be applied as an effective tool for turbine tonal noise prediction with less cost in early design phase of turbine blade.