Optimizing OGV Lean to Reduce Tonal Fan Noise

Kurzfassung

Leaning the outlet guide vanes (OGVs) is a well-known measure to reduce fan tonal interaction noise. In conventional designs, the lean angle is typically constant along the span. In the present study, the OGV lean distribution is optimized with respect to tonal interaction noise using unsteady flow simulations, allowing for a spanwise-varying lean configuration. The optimization contains two steps. At first, the lean distribution is optimized exclusively for tonal interaction noise reduction. Then, in a second step, a multi-objective optimization is performed that maintains aerodynamic efficiency and broadband interaction noise at the level of the non-leaned reference configuration, while also ensuring mechanical feasibility and sufficient stall margin. Broadband interaction noise is assessed using an analytical fan noise prediction model. The same analytical framework is further employed to analyze the underlying mechanisms responsible for tonal noise reduction due to blade lean. The resulting design features a partial lean concentrated in the tip region and achieves a significant reduction in tonal interaction noise with negligible penalties in efficiency, broadband interaction noise, and stall margin compared to the baseline configuration.