Development of Cavitation Nuclei Distribution Measuring Equipment

研制了具有高迁移率的空化核分布测量装置。用光散射法测量空化核。该设备具有以下特点：(1)能够将液体中的微气泡与固体颗粒区分开来。(2)在液体中直接测量空化核。(3)实时测量和数据处理。在此之前，散射光强度是用米氏理论计算的。在不同的光学元件排列方式下，估计了散射光的收集效率和控制体积内检测到的光强。根据这些计算，从两个方向(<theta>, <phi>)=(90, <-！+ > 15)。激光从(<theta>, <phi>)=(0,90)方向射入控制容积，气流从(<theta>, <phi>)=(90,0)方向进入控制容积。由于光强的不均匀性和微泡在孔径上的畸变，导致了对微泡散射光的检测不准确。为了估计系统的精度，采用蒙特卡罗模拟，其中核的大小和控制体积内的位置是随机确定的。仿真结果表明，需要5000个数据才能获得可靠的数据。该设备分为光源、安装在空化隧道内的探头部分、光电探测器和数据处理器四个部分。光源、探头和光电探测器之间通过光纤连接，提高了迁移率。当两个信号同时被观测时，从微泡中收集到两个被探测到的光。将采集到的两个信号进行对比，只有当两个信号在200% ~ 50%范围内重合时，才可识别为微泡散射光。在某空化隧道中进行了测试，验证了该测量系统的可靠性。少

The cavitation nuclei distribution measuring equipment which has a high mobility has been developed. Cavitation nuclei are measured by a light scattering method. This equipment has the following feature: (1) Microbubbles are able to be distinguished from solid particles in the liquid. (2) Cavitation nuclei are measured directly in the liquid. (3) Measurement and data treatment can be done in real time.Preceding the development, the scattered light intensities are calculated using the Mie's theory. The collecting efficiency of the scattered light and the detected light intensity in the control volume are estimated in various alignments of optical parts. According to these calculations, the scattered light is detected from two directions ( <theta> , <phi> )=(90, <-!+> 15). The laser light incidents into the control volume from the direction of ( <theta> , <phi> )=(0,90), and the flow enters into the control volume from the direction of ( <theta> , <phi> )=(90,0). The light scattered from … More a microbubble is not detected correctly due to not only the nonuniformity of the light intensity but also the distorted image of the microbubble on the aperture. In order to estimate the accuracy of the system, a Monte Carlo simulation is employed, where the size of nuclei and the location within the control volume are determined randomly. This simulation reveals that 5000 data are required to obtain reliable data.The equipment is divided into four parts, i.e. light source, probe part which is installed in a cavitation tunnel, photo detector and data processor. The light source, the probe and the photo detector are connected by the optical fibers, which improved the mobility. The two detected lights from the microbubble are collected when the two signals observed at the same time. The collected two signals are compared each other and the signals are recognized as the scattered light from a microbubble only when the signals coincide within from 200% to 50%.The measuring system is tested in a cavitation tunnel and the reliability of the system is confirmed. Less