Otimização aeroacústica de ventiladores centrífugos com pás auxiliares

Abstract

Given the current demand for increasingly quieter fans, in order to comply with industrial and/or domestic noise level standards, the importance of introducing innovative concepts in the design of low-noise centrifugal fans becomes evident. This can be achieved through numerical analyses using Computational Fluid Dynamics (CFD). In this work, an initial approach was developed to determine the main aerodynamic performance characteristics of centrifugal fans with and without splitter blades, considering the rotor-volute interaction. At this stage, steady-state simulations were employed to identify and quantify noise sources through acoustic source prediction. The simulation methodology used to obtain aerodynamic quantities was validated using results from experimental tests conducted on a fan test bench at the LabVent laboratory, IEM/UNIFEI. In a second approach, transient simulations were carried out to analyze sound pressure levels over a wide frequency range, aiming to consistently characterize the aeroacoustic behavior and noise sources of the fans. From the solution of the flow and acoustic fields in configurations with and without auxiliary blades, the following geometric variables were considered: i) inlet angle, ii) outlet angle, iii) curvature radius relative to the main blade, and iv) circumferential position and shape of the tongue. These variables were optimized based on a factorial design of experiments, from which a metamodel was generated using radial basis functions, aiming to achieve maximum efficiency while maintaining acceptable sound pressure levels. The results showed that as the length of the splitter blades increases and they are positioned closer to the suction side of the main blades, the flow conditions within the fan improve, leading to satisfactory aerodynamic behavior in terms of effective efficiency and total pressure. Additionally, a reduction in tonal noise was observed, as the peak sound pressure levels at the blade-passing frequency decreased in comparison to the baseline fan geometry. This work presents technological contributions based on scientific methodologies, integrating aeroacoustic field analyses with multi-objective optimization techniques to maintain fan performance characterized by high efficiency and low noise levels. These findings contribute to the development of new design concepts for centrifugal fans intended for industrial applications.