表面楔形结构对发动机冷却风扇性能影响研究

摘要

To study the influence of the wedge structural design on the aerodynamic and aeroacoustic performance of engine cooling fans,a series of numerical simulations are carried out with CFD (Computational Fluid Dynamics)/CAA (Computational Aerodynamic Acoustic) distributed coupling method.The flow field and acoustic field of two cooling fans without and with wedge structures on its suction surfaces are analyzed under the rated condition.The results show that the aerodynamic performance of cooling fans is vulnerable to the wedge structures.But noise performance is obviously influenced.The noise values at the inlet and outlet of the cooling fan with wedge structures are decreased by 8.8％ and 8.9％ respectively while the volume flow increases slightly.Through specific analyses of flow field and acoustic field of two cooling fans,it can be concluded that the wedge structures act as "vortex flow generators" on the suction surfaces.They advance the transition from laminar flow to turbulent.Thus the vortex noise induced by premature airflow separation around the blade surface is reduced obviously,which lead to a definite decline in the overall noise.%采用CFD/CAA分布耦合仿真方法,在额定工况下对发动机冷却风扇叶片吸力面是否设置凸起楔形结构的两种方案的流场与声场进行三维数值模拟,研究了楔形结构对冷却风扇气动性能和噪声性能的影响.结果表明,该楔形结构对冷却风扇气动性能影响较小,而对其噪声性能影响显著;设置了楔形结构后冷却风扇进出风口噪声值分别下降8.8％和8.9％,风量略有增加.通过分析冷却风扇流场及声场的分布情况,可知楔形结构在叶片吸力面起到了“涡流发生器”的作用,促进边界层提前转捩,进而大大降低了叶片表面气流过早分离引起的涡流噪声,因此总声压级也明显下降.