An Experimental Evaluation of the Local Effects of a Water Microjet on the Cavitation Erosion

1. 为了精确区分微射流和冲击波的脉冲压力，研制了几种局部压力传感器。每个传感器元件都有一个1mmX1mm的敏感区域，与微射流的主截面几乎相同。利用空化泡的传感器和闪光照片，精确地计算了微射流和激波的脉冲压力，揭示了空化泡在第一和第二坍缩和膨胀阶段的侵蚀机理。制作了一种方便的仪器来观察瞬态空化气泡运动。利用4 MHz的高采样频率驱动CCD线性图像传感器对气泡运动进行政治观测。CCD传感器的输出数据由A/D转换器和缓冲存储系统直接采样并传输到微型计算机。该装置对一维数据的采样速度约为37微秒，相当于一张约27000帧/秒的高速照片。将该装置应用于固体边界附近空化泡运动的观测，证实了该装置对观察瞬态空化泡运动和微射流的产生是非常有用的。

1. In order to distinguish the impulsive pressures of a microjet and a shock wave precisely, several local pressure sensors are manufactured. Each sensor element has its sensitive area of 1mmX1mm, which is almost the same as the main cross section of the microjet. By the sensor and flash photographs of the cavitation bubble, the impulsive pressures of the microjet and shock wave are precisely evaluated and the erosion mechanism by cavitation bubbles is revealed at the first and second collapsereexpansion stages of the cavitation bubble.2. A handy apparatus is made to observe the transient cavitation bubble motion. The bubble motion is potically observed by a CCD linear image sensor, which is driven by high sampling frequency of 4 MHz. The output data of the CCD sensor are directly sampled by an A/D converter and buffer memory system and transferred to a microcomputer. The sampling speed of the apparatus for one-dimensional data is about 37 microseconds, which corresponds to a high-speed photograph of about 27000 frames/s. The apparatus is applied to observe the cavitation bubble motion near solid boundary and it is confirmed that the apparatus is very useful to observe the transient cavitation bubble motion and the microjet generation.