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Development of a Probe-Type Freezing Method for Droplet-Size Measurement

开发用于液滴尺寸测量的探针式冷冻方法

基本信息

批准号：
21560200
负责人：
SHIGA Seiichi
金额：
$ 3.16万
依托单位：
Gunma University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2009
资助国家：
日本
起止时间：
2009 至 2011
项目状态：
已结题

项目摘要

A so-called probe-type freezing method was invented, and applied to sprays with smaller size droplets produced from a humidifier (ultrasonic vibrator type) and a nebulizer (tens of thousands micro-holes combined with ultrasonic vibrator, used for medical sucking). Followings were revealed.(1) With the probe-type freezing method, sphere shaped frozen particles could successfully be produced, and it is useful to be applied for droplet-size measurement.(2) With the probe-type freezing method, it is useful to measure droplet size measurement under the condition that the effect of evaporation and coalescence could be minimized, and thus several physical phenomena were clarified related to them.(3) The probe-type freezing method has an advantage in the measurement of droplets less than 10 micro-meter comparing with a conventional phase Doppler anemometry and a narrow-angle forward scattering technique, since the droplet diameter distribution in smaller range for the freezing method is more t … More han those obtained with a phase Doppler and a scattering technique.However, in the probe-type freezing method, when the frozen droplets were observed directly during their falling process with a digital microscope, the enlargement rate greater than 1000 caused seriously narrower focusing depth, and the average measurable number of droplets captured on one photograph was only five. Thus, there appeared a problem of less data rate. In order to solve this problem, a direct freezing sampling method was developed. This method introduced spray directly into a sampling dish in a thermally insulated vessel. Especially, since a modern phase Doppler anemometry system was available in the last year, followings were revealed.(1) For smaller droplets less than 10 micro-meter of the Sauter mean diameter (SMD) produced by a humidifier and a nebulizer, the newest phase Doppler anemometer gives more droplets less than 2 micro-meter than the direct freezing sampling method. This must be due to the improvement or the progress of the phase Doppler anemometer system. However, there was pretty well consistency of droplet size distribution for droplets greater than 2 micro-meter between this simple direct freezing sampling method and the newest phase Doppler anemometer. This verifies the practical validity of this simple freezing method.(2) For larger droplets more than 50 micro-meter of SMD for a hollow cone spray produced by a swirl nozzle, the droplet size distribution of the direct-freezing sampling method shifted to greater size than that of the newest phase Doppler anemometer. It would be due to the limited dynamic range for the newest phase Doppler anemometer, which must be a great advantage of this freezing method.(3) Thus, this direct-freezing sampling method has better performance of smaller droplet measurement than a conventional phase Doppler anemometer but has inferior than a newest one. It has better dynamic range than both phase Doppler anemometers. Less

发明了一种所谓的探针式冷冻方法，适用于由加湿器(超声波振荡器类型)和雾化器(数万个微孔与超声波振荡器组合而成，用于医用吸吮)产生的液滴尺寸较小的喷雾。结果表明：(1)探针式冷冻法可以成功地制备出球形冷冻粒子，可用于液滴尺寸测量。(2)探针式冷冻法可以在最大限度地减小蒸发和聚结影响的情况下测量液滴尺寸，从而澄清了与之相关的几个物理现象。(3)与传统的相位多普勒风速仪和窄角前向散射技术相比，探针式冷冻法在测量小于10微米的液滴方面具有优势。由于冻结法在较小范围内的液滴直径分布更多的是t…然而，在探针式冻结法中，当用数字显微镜直接观测冻结液滴的下落过程时，放大速率大于1000会导致聚焦深度严重变窄，一张照片上捕获的平均可测液滴数量仅为5个。因此，出现了数据速率较低的问题。为解决这一问题，提出了一种直接冷冻取样法。这种方法将喷雾直接引入绝热容器中的取样盘中。特别是在过去的一年里，由于现代的相位多普勒测速系统的问世，发现：(1)对于由加湿器和雾化器产生的索特平均直径(SMD)小于10微米的小液滴，最新的相位多普勒测速仪比直接冷冻取样法得到更多小于2微米的液滴。这必须归功于相位多普勒风速计系统的改进或进步。然而，对于大于2微米的液滴，这种简单的直接冷冻采样法与最新的相位多普勒风速仪之间的液滴尺寸分布具有很好的一致性。对于旋转喷嘴产生的中空锥体喷雾，对于大于50微米的较大液滴，直接冷冻采样法的液滴尺寸分布比最新的相位多普勒风速仪的液滴尺寸分布更大。这是因为最新的相位多普勒风速仪的动态范围有限，这肯定是这种冻结法的一大优势。(3)因此，这种直接冷冻采样法在测量小液滴方面优于传统的相位多普勒风速仪，但不如最新的。它比两种相位多普勒风速计都有更好的动态范围。较少