坂本 勇樹

<p>A capacitance sensor for void fraction adopting asymmetric helical electrodes is proposed to avoid adverse effects of gas-liquid two phase flow distribution on measurement accuracy. In this research, in addition to verification in the Stratified flow already performed, the accuracy in the Dispersed flow was confirmed using an Electric Field Analysis (EFA). The analysis was performed for the proposed three types of models (Helical type, Square type, Hexagonal type). In order to simulate the Dispersed flow, the fluid element was divided into 325 parts and the gas - liquid distribution was randomly assigned. In the result of the electric field analysis, the maximum EFA error was 7.07% in the case of Helical type, and the standard deviation was 1.62% even in the model with the lowest precision. Therefore, it was confirmed that the capacitance sensor for void fraction adopting asymmetric helical electrodes can maintain accuracy and precision even in the Distributed flow.</p>

平成26年度宇宙輸送シンポジウム（2015年1月15日-16日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000036020レポート番号: STCP-2014-020

Capacitance type void fraction sensors for cryogenic fluid has been developed by our research group. The sensors are roughly categorized into three types; arc type, small-sized arc type, and asymmetric type. In this paper, the three type sensors are compared, and each sensor's merits and demerits are indicated. The arc type sensor was first developed. The sensor is simple, but S/N ration is low and influence of "temperature drift" is large. The small-sized arc type sensor was developed for the sounding rocket S310 test No.43, so the sensor was needed to make as small as possible. The sensor succeeded to measure the void fraction of the liquid nitrogen flow even under microgravity. The asymmetric type sensor was deviced to improve the measurement accuracy. Inaccuracy of the sensor between true void fraction and measured void fraction was only 3% for stratified flow, whereas that of the arc type sensor 30%.