The Design And Experimental Study Of Gas-tight Water Sampler Based On Pressure Self-adaptive Volume Compensation

Gas-tight water sampler is one of the instruments used to collect sea water directly, which can not only be used to obtain liquid samples, but can also reserve the gas composition completely, offering precise raw data for the research of deep-sea water. It provides valuable information for tracing sources of the physical, chemical and biological changes in the ocean, and predicting the global climate as well as environment changes. Furthermore it provides important clues for finding hydrothermal sulfide and gas hydrate.The primary work of this dissertation focused on the design and experimental study of gas-tight water sampler based on the theories of pressure self-adaptive volume compensation. Firstly, identified a gas-tight method without pressure-keeping means to realize gas-tight sampling, compared with the ones with pressure-keeping means, the design, usage and maintenance of the overall system is much more simple and convenient whereas we have no need to take into account the design of pressure hull and high pressure sealing. Secondly, selected floating piston-type pressure compensator which is stable in structure and has large compensated volume, after comparing all kinds of compensators which can meet the need of gas-tight without pressure-keeping. Thirdly, calculated the cubage of the compensator in precise, according to the property of sea water and the variation about the volume of gas and liquid along with pressure and temperature. Subsequently, built up the mathematical model of the static and dynamic characteristics based on the Newtonian second law and Boyle law. Meanwhile carried out the study by means of simulation under the circumstance of MATLAB, getting the result of pressure difference between two sides of piston when the piston starts to move, as well as the compensated capacity of the compensator along with the lifting speed throughout the overall process. Finally, carried out a series of experiments on the static working characteristics of compensator, obtaining the actual pressure difference between two sides of piston when the pressure compensator starts to move critically. Ensured the gas tightness through the gas tight experiments of water sampler. And carried the sea trial to ensure the feasibility and reliability of system.The study of this dissertation is fundamental and explorative for the whole deep-sea water sampler system, which paves the way for the improvement and exploration of the more complex and perfect sampling systems.