节气门急速开启过程流动噪声数值分析与研究

研究了节气门运动对流动噪声的影响。采用计算流体力学与计算声学耦合方法,并结合运动网格技术,实现对节气门由关闭向全开位置急速转动过程时空气瞬态流动引起噪声形成的三维数值模拟,分析了节气门处于不同转角时刻,空气流场与流动噪声的变化规律。在节气门转动初期,节气门后侧流动区域有涡流形成,节气门前后两侧的压力发生陡降,在节气门上边缘和下边缘附近产生两个流动噪声区,随后在节气门下游逐渐合并。流动噪声声功率级先增加然后逐渐减小,并接近稳定,节气门开度在40°附近时,声功率级达到最大。随着节气门开度的继续增加,节气门后侧的涡流逐渐减弱,节气门前后两侧的压力降逐渐减小。噪声场时域-频域计算结果发现,节气门噪声属于中低频段宽频噪声,其中大约100Hz以下的低频噪声占主要贡献量,声压级较高,并且声压没有随着测点与节气门的距离增加而明显衰减。控制节气门流动噪声的重点在于减少低频噪声。

Numerical Simulation and Study on Flow-Induced Noise During-Automotive Throttle Quick-Opening Process

The influence of the throttle motion on the air flow-induced noise process is studied. By applying the computational fluid dynamics (CFD) and computational aeroacoustics (CAA) coupling approach and the moving mesh technique, a 3-dimensional air transient flow and flow-induced noise process is simulated to realize the throttle quick-opening from the closed position to the fully open position. The principle of the air flow and flow-induced noise is analyzed when the throttle is opening at different rotation angle. At the beginning period of the throttle rotation, the vortex appears in the flow field behind the throttle, the pressure drops distinctly between the front and the back of the throttle, two flow-induced noise fields appear near the top and bottom position of the throttle and move towards the downstream and then merge gradually, the maximum value of the acoustic power level appears when the throttle rotation angle is opening near 40 degree, the flow-induced noise acoustic power level firstly increases and then decreases. With the opening angle increasing, the vortex is weaken and the value of pressure drop decreases between the two sides of the throttle. The time-frequency domain numerical simulation results fo the flow-induced noise show that during the throttle quick-opening process the flow-induced noise is mainly a kind of middle and low frequency broadband noise, the main part of the noise is frequency noise below about 100 Hz, the acoustic pressure is higher and does not reduce significantly with the increase of the distance between the measurement point and the throttle center. Reducing the low frequency noise plays a key role in the flow-induced noise control of the throttle.