离心叶轮气动声场的数值计算与分析

采用SIMPLEC算法对Ghost叶轮的三维非定常流场进行了数值模拟。利用计算所得流场结果并结合Lighthill和Lowson声学方程计算了由叶片表面非定常脉动力产生的气动噪声。计算结果表明:气动噪声的峰值主要集中在基频及其谐波附近;与静止的点声源相比,运动的点声源不仅使声场存在明显的多普勒效应,还会使声场的强度产生较大的变化;但对转速恒定的旋转点声源,加速度的变化对声场的影响可以忽略;从声场的分布来看,整个旋转叶轮可以看成是一个按简谐变化的偶极子源,数值计算结果与理论分析的结果吻合良好。

Numerical Analysis to Centrifugal Impeller Aeroacoustics

The prediction method for identifying the acoustic source generated from a centrifugal impeller is developed.To predict the acoustic field,the three-dimensional unsteady flow fields and unsteady forces fluctuations are calculated by solving Navier-Stokes equations with SIMPLEC algorithm.The results show that the aeroacoustics is dominated by tones at blade passage frequency and the higher harmonics in a centrifual impeller with vaned deffuser.To reveal the effects of the moving sound source,three acoustic formulas are applied to calculate the acoustic pressure.It is indicated that the moved acoustic source remarkably disturbs the intensity of acoustic field with obvious Doppler effect,the variation of acceleration can be neglected,the whole rotating impeller is reasonably regarded as a dipole source with simple harmonic motion.