Mechanism of Generation of High Speed Liquid Jet Driven by High Pressure due to Underwater Shock Wave Focusing and Its Application

对水下冲击波聚焦过程中产生的超高压驱动的脉冲高速液体射流进行了实验研究，并进行了详细的数值模拟，以了解相关的流场，特别是高压的产生过程。为了利用微型炸药产生理想的球形水下冲击波，已经做了很多努力。结果，我们用10 mg叠氮银引爆100 mg的PETN，成功地获得了高于8000bar的最高压力。根据初步实验获得的数据，我们试制了一种由大约2100bar的高压驱动的高速液体射流。高压发生在长短轴为212 mm×150 mm的椭球形腔的第二焦点处，这是由于水下冲击波的聚焦，该冲击波是由放置在第一焦点处的10 mg叠氮银引燃而产生的。如果在第二焦点处设置一个带有喷嘴的圆管，在椭球腔的外侧设置一个喷嘴，就可以得到高速的脉冲液体射流。我们用自制的PVDF压力计测量了射流冲击产生的滞止压力，得到了最大值约为90bar，脉冲宽度为2µs。液体射流的冲击速度约为130m/s。脉冲液体射流具有工作空间小、时间短(2-3微秒)的优良特性，应在不久的将来推广其在医学等科学领域的应用。

An experimental attemp was made to produce a pulsed high-speed liquid jet driven by ultra high pressure generated during underwater shock wave focusing.A numerical simulation was also carried out to know the flow field concerned in detail, especially to make clear the process of high pressure generation. Much efforts had been performed in order to produce an ideally spherical underwater shock wave by using a microexplosive. As a result, we succeeded in getting a maximum pressure higher than 8,000bar with 100mg PETN ignited by 10mg silver azide.Based on the data obtained from a preliminary experiment, we tritato produce a high-speed liquid jet, driven by a high pressure of about 2,100bar. The high pressure occurred at the second focal point of an ellipsoidal cavity with the major and minor axes of 212mm X 150mm, due to focusing of an underwater shock wave, which was generated by igniting 10mg silver azide placed at the first focal point of the cavity. If a circular pipe with a nozzle, provided at an outer side of the ellipsoidal cavity, is set at the second focal point, we can obtain a high-speed, pulsed, liquid jet through this nozzle.We measured stagnation pressure due to impact of the jet by means of a home -made PVDF pressure gauge, and obtained it as the maximum value of about 90bar and pulse width of 2mus. The corresponding impact velocity of a liquid jet can be estimated as about 130m/s.A pulsed liquid jet has such excellent feature that working space and time are extremely small and short (2-3mus), so that its application to medical and other scientific fields should be promoted in the near future.