Research On Autonomous Liquid Propellant Mass Gauging Technology With Micro-gravity

The accurate propellant mass in tank is very important to the life of spacecraft. It will affect the mission of spacecraft. Besides, it will determine the refill time for propellant refilling project. But for the micro-gravity condition, it is rough to gauge the propellant with high accuracy. The Compression Mass Gauging of the propellant is mainly discussed in this thesis. Its managing principle and the effect factors are analyzed. The ground test system of this method is studied preparatorily.Firstly, Most of the methods in this field are discussed with their measuring principle and advantages and disadvantages. The measuring principle of the Compression Mass Gauging is studied in detail. Besides, the effect factors such as the non-adiabatic process, the tank compressibility, the composition variation in ullage bubbles and ect. The mathematics models of these error factors are derived and their modification to the ideal compute equation is done. With the modern technology, the error of each parameter is given and the total accuracy is estimated.Secondly, the compression process is simulated and the variation of thermodynamic variables in ullage bubbles is illustrated. It is can be seen from the result that the non-adiabatic process can not be neglected. the ground test system is preparatorily studied with the follow subsystem: the tank, the compression system, the measuring system and data process system. The measuring and date process are introduced respectively.Thirdly, the effect of resonance is discussed, including the tank structure, liquid surface waves, the pressure transducer and oscillation of the ullage bubbles. Each source of resonance may have a series of resonances. The lowest resonance that can be excited directly by the compressor is almost always the cooperative oscillation of the bubbles. Surface waves only occur when thy have a resonance coupled to the cooperative oscillations. Resonant frequencies of the tank structure and the pressure transducer are higher than that of the cooperative resonance if the hardware is designed properly.Finally, in order to find a method with high accuracy, good applicability and proper operation, several improvements of the measuring method are proposed. The managing principles are demonstrated and further work is needed to be done for the applicability.To sum up, the Compression Mass Gauging theory is discussed systemically in this thesis, the ground test project is researched. It is clear that this gauging method can be easily operated with high accuracy. All these work will be the solid reference and definitely guidance for the next ground experiment.