Study on Liquid Volume in a Tank under micro-gravity space

点击翻译按钮获取中文摘要

The space project are important for human beings and the space station projects are on schedule in many countries.Modules in the the space stations are under the micro-gravity condition. Measurement methods worked well under the earth gravity condition does not always work in such the micro-gravity conditions. The level meters employed widely to measure the liquid quantity in the tank under the earth gravity is one of such the examples. Methods other than level meters are required to measure the liquid content in the tank under the micro-gravity.This paper treats the problems occurred when the pneumatic method is applied to measure the liquid content in a closed tank under the micro-gravity condition.The pneumatic method measures the periodic change in the pressure in the tank which is subjected to the periodic small displacement of the volume. The method (1) first estimates the volume of the ullage gas in the tank from the measured pressure and the volume displacement by applying the relation of ideal gas law, and (2) calculates the liquid content by subtracting the ullage gas from the tank capacity. This method is different from the level meters and thus can measure the liquid content in the micro-gravity conditions. However the following essential problems for the measurement of the pressure change were not investigated when applied under the micro-gravity condition.(1) What happen when many bubbles exist in the liquid?(2) What happen when pressure sensor immerses in the liquid?(3) How does the vaporized liquid influence to the pressure?(4) How does the thermal time constant of the tank influence to the measurement?We investigated these problems theoretically. The validity of the pneui-natic method was examined by experiments under the micro-gravity conditions realized by tlie parabolic flight of an airplane.