喷气涡流纺喷嘴流场的粒子图像测速法测试及分析

Measurement and analysis of the flow field in the vortex spinning nozzle using particle image velocimetry

为对喷气涡流纺喷嘴中气流流动特性的数值模拟结果进行验证,为喷嘴的设计提供指导,采用粒子图像测速(particle image velocimetry,PIV)技术,对喷气涡流纺喷嘴内的高速旋转流场进行了实验测试。考虑到流场速度高且分布不均匀,采用马赫数相似准则进行测试的难度较大,实验中以水为流动介质,对喷嘴原型和模型采用了雷诺数相似准则,测试了喷嘴模型中不同截面内的旋流的分布特性与流动速度,并与数值模拟结果进行了对比。研究发现:在喷射孔出口截面附近,旋流存在较高的强度,切向速度在近管轴附近的区域内具有较小的数值,且变化幅度很小;随着径向位置向涡流管壁面靠近,切向速度迅速增大并达到最大值,但旋流速度沿轴向向下游逐渐减小;尽管由于实验中未考虑流动的可压缩性,使得实验与数值模拟获得的速度存在一定的差异,但两者所获得的喷嘴内的流动特性与速度分布规律是一致的。结果表明粒子图像测速技术可以用来定性研究喷气涡流纺纱喷嘴中的流场特性。

In order to verify the numerical results of the airflow characteristics in the vortex spinning nozzle and to provide guidance for the nozzle design, particle image velocimetry （PIV） technique was adopted to experimentally investigate the high-speed swirling flow field in the vortex spinning nozzle. Considering high and unevenly distributed flow velocities which lead to the diffi- culty in matching the Mach numbers between the nozzle prototype and model, a duplication of Reynolds number was adopted u- sing water as the flow medium in the experiment. Flow pattern and flow velocities at several cross sections in the nozzle model were measured and compared with the results obtained by numerical simulation conducted previously. It was found that the swirl intensity in the vicinity of the iniectors is high. The tangential velocity has a low value and unohvious variation in the region near the nozzle axis. With the radial position approaching to the nozzle wall, the tangential velocity shows a sharp increase to its maximum but decays axially downstream. Although a discrepancy between the velocity values obtained by the experiment and numerical study was observed due to the compressibility effects not being reproduced in the PIV experiment, qualitatively matched results of the flow characteristics and distribution rules of the flow velocities can be found. The results show that the flow characteristics in the vortex spinning nozzle can be qualitatively investigated using PIV technique.