双腔室自振脉冲喷嘴空化射流数值模拟

以风琴管喷嘴为基础，串联一个谐振腔形成双腔室自激振荡脉冲喷嘴，利用Fluent对其流场进行数值模拟，分析射流靶距、二级谐振腔腔长比、腔径比的变化对空化射流流场的影响。结果表明：谐振腔尺寸过大或过小均会影响涡环结构的形成，进而影响空化效果。当谐振腔腔长比为0.77、腔径比为2.6时，谐振腔内涡环结构对称性好，轴向含气率高，射流速度较高，该结构利于清洗效率的提高。靶面滞止压力可对空化效果产生影响。当射流靶距较小时，在滞止压力的作用下二级谐振腔无涡环结构产生，轴向含气率较低。当靶距增加到18 mm时滞止压力产生的影响减小，轴向含气率明显提高，因此清洗靶距应至少为18 mm。但靶距的增加会降低射流到达靶面的动能，因此最佳靶距应取18 mm。

Study on Numerical Simulation of Cavitation Jet Flow for Two-chamber Self-vibrating Pulse Nozzles

On the basis of the nozzle of organ pipe, a resonant cavity was connected in series to form a double-chamber self-excited oscillating pulse nozzle. The flow field was numerically simulated by Fluent, and the effects of jet target distance, cavity length ratio and cavity diameter ratio on the flow field of cavitation jet were analyzed. The results show that either the cavity length ratio is too large or too small will affect the formation of vortex ring structure, and then affect the cavitation effect. When the cavity length ratio is 0.77 and the cavity diameter ratio is 2.6, the vortex ring structure in the resonator has good symmetry, high axial gas holding ratio and high jet velocity, and the structure is conducive to improving the cleaning efficiency. The stagnation pressure of the target surface can also affect the cavitation effect. When the jet target distance is small, no vortex ring structure is generated in the secondary resonator under the action of stagnation pressure, and the axial gas holdup is low. When the target distance is increased to 18 mm, the influence of the time delay pressure is reduced and the axial gas holdup is significantly increased. Therefore, the cleaning target distance should be at least 18 mm. However, the increase of target distance will reduce the kinetic energy of jet reaching the target surface in turn, so the optimal target distance should be 18 mm.