Research On Propellant Mass Dynamic Measurement Technology In Engine Operating Condition

Accurate measurement of the remaining propellant mass will help enhance the rocket carrying capacity. Rocket propellant mass accounted for 85%～90% of the total mass of the rocket, because in the rocket engine operating process, oxidizer and fuel mass gauging and flow control imprecise, rocket stages have a certain percentage of redundancy propellant, redundancy propellant cannot be effectively used, causing huge waste. If we can accurately measure the remaining mass of each tank in the engine operating condition, then can adjust the oxidizer and fuel mass flow, ultimately significantly reduce redundant propellant and improve the overall performance of the rocket. At the same time, the residual propellant mass measurement data can help to optimize the combustion mixture ratio and the propellant loading mass in the subsequent launch task, that can enhance the rocket carrying capacity, has great economic value. During the flight, affected by the rocket body attitude, the liquid is inclined respect to the tank, so level sensing commonly used in the rocket cannot measure accurately.On-orbit spacecraft refueling can prolong the life and increase mobility, is the basis for efficient and cheap application of space. Remaining propellant mass gauging is a key technology, it can determine the refueling time and refueling mass. Mostly of the gauging methods have one or more aspects of the defect, and cannot apply to the engine operating condition measurements.Therefore, we propose a volume excitation technique, it has many advantages, such as high accuracy, easy operation and wide application. This technique can be used for mass gauging in engine operating condition of high thrust rocket or micro-propulsion system.Firstly, pressurization feed system and remaining propellant mass gauging methods are discussed, against the gauging requirements for engine operating condition, we conduct a feasibility analysis of existing methods, then we propose volume excitation technique, the basic idea is brief stop pressurization for the tank, then gas volume changes caused by the outflow of propellant.Secondly, deduced the ideal measurement equation and the correction equation considering the heat transfer effect, and discussed other factors. For small mass-flow micro-propulsion system, gas pressure changes caused by the outflow of propellant are too small to be measured accurately, so we need to add activation device. With the tank system simulation model established, we simulate the temperature and pressure changes. The analysis focused on the impact of heat transfer. The results show that the impact of heat transfer cannot be ignored, we should select the appropriate thermodynamic model to calculate.Finally, the ground test system for high mass-flow and small mass-flow are set up, including the tank, the compression system (only used for small mass-flow), the measuring system and the data process system. Using experimental means deduced the process coefficient; the test results meet the simulation results. Tests showed, two kinds of conditions can reach 1% measurement accuracy of tank volume, so volume excitation technique is feasible.To sum up, volume excitation technique used for the remaining propellant mass measurement in engine operating condition is studied by theoretical and experimental methods, both showed that this technique is feasible and with high accuracy, and all these work will provide reference for further improvement.