One of the components of turbofan noise is the tone noise arising due to inter-row interactions in the booster stages. Though the booster stages are significantly less powerful source of noise than the fan, their noise can be noticeable at some operational conditions. Also its relative contribution to the engine noise can become a concern for future engines as the fan noise is further reduced.   

In the work the results of the numerical investigation of the tone noise of the three booster stages designed for a high bypass ratio turbofan are presented. The model under investigation includes high bypass pressure fan and three booster stages. Calculation was performed at the approach working conditions using CIAM (Central Institute of Aviation Motors) in-house 3DAS (3 Dimensional Acoustics Solver) solver. The results of the computation were compared with the experimental data obtained in the CIAM C-3A acoustic test facility.

The method of tone noise calculation used in the 3DAS solver is based on the solution of linear or nonlinear Euler equations for disturbances over viscous steady mean flow field in the reference frames of blade rows. The calculations can be performed either in the time domain or in the frequency domain. For the spatial approximation the fourth order DRP (Dispersion Relation Preserving) scheme, rewritten for the finite volume method is used. For the time derivative approximation the fourth order Runge–Kutta scheme of HALE-RK (High-Accuracy Large-step Explicit Runge–Kutta) type is implemented.

The method of a multistage turbomachine tone noise calculation implemented in 3DAS solver is based on the notion of harmonic fragment - component of flow which has definite frequency and phase lag between boundaries of blade passage. According to the method, the flow field in the blade passage of a single row is approximated by the finite set of fields of harmonic fragments, belonging to the specified set of tones. Harmonic fragments calculated in the rows are determined by the choice of interactions, which should be considered in the calculation.

The investigations of the tone noise of the first booster stage have been carried out in CIAM during last several years. The noise of the first booster stage was calculated at two operational conditions using the previously mentioned frequency domain method. For both conditions the satisfactory correspondence between calculation and experiment were obtained. Also the comparison between calculations in the time and in the frequency domains showed close coincidence between them. 

In the work the extension of the previous work approach on the case of three booster stages is presented. The sensitivity of the results to the number of harmonic fragments included in the investigation is studied. In general satisfactory correspondence between the results of the calculation and the experiment is obtained. The results can be treated as a significant argument for the validity of the frequency domain method of the multistage turbomachinery tone noise calculations.


Numerical Investigation of the Low Pressure Compressor Tone Noise of a High Bypass Ratio Turbofan

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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