Abstract
Development of silent air-conditioners is one of the most important tasks in recent changes to life-styles, such as demands of silent office and home. Aerodynamic noise from fans contributes to a large percentage of the overall noise from air-conditioners. Therefore, the development of silent fans would contribute to reducing the noise levels of air-conditioners. In this study, flow fields in multiblade fan for the indoor units of air-conditioners were calculated with large eddy simulation (LES). The computational fluid dynamics (CFD) code employed throughout the LES was called FrontFlow/blue (FFB). The numbers of grid elements were approximately 80 million. In the computational aero-acoustics (CAA), the sound propagation equation of Lighthill was solved in the frequency domain. The number of mesh elements is approximately 12 million. We compared calculated and experimental results for validation. We confirmed that the static pressure rise and the shaft power reasonably agreed with the experimental results. The predicted sound pressure level agreed reasonably well with the experimental data in the frequency range from 1000 Hz to 2500 Hz. The tendencies of acoustic effects were captured near 1200 Hz and 2000 Hz. As a result, we confirmed that the calculated results captured main flow field structures and acoustic field, which played dominant roles with aerodynamic noise. Moreover, we confirmed that CFD and CAA in this study were useful tools for predicting the aerodynamic noise of multiblade fan.
