旋进射流喷嘴的频率及流场特性研究

在圆筒套管内设置一块孔板构成旋进射流喷嘴，由此获得持续稳定的旋进射流，研究了喷嘴最优的结构参数。用热线风速仪测量出口射流的速度并进行功率谱分析，得到旋进射流的频率及流场特性。研究表明，旋进射流具有较高的紊流强度，速度场沿径向的分布趋向平缓，其进动频率随流量增大而加快，喷嘴的尺寸和结构对射流进动有影响。

Frequency and Flow Field Characteristics for the Fluid from a Precessing Jet Nozzle

A self-sustained uninterrupted precession motion is generated in a precessing jet nozzle consisting of a cylindrical tube added to an orifice and the optimal configuration parameters for the nozzle are presented. The flow field of the precessing jet is obtained by a hot wire anemometer at the nozzle exit and the precession frequency is identified from a power spectrum density analysis to the velocity signal. It is shown that the precession frequency increases with the increment of flow rate (Reynolds number). The exit profile of mean velocity in the precessing jet is far wider spread and the turbulence intensity is much higher compared to that of the in-line jet. It is also indicated that the size and configuration of the nozzle also have a significant influence on the precession motion of the exit jet.