Research On The Key Technologies Of Hydrothermal Fluid Pressure-retaining Sampler At Deep-sea

The analysis and measurement on physical and chemical properties of hydrothermal fluid at deep-sea is one of the main tasks for ocean resources exploration, and it is also the basic means for oceanography. Sampling study is a common exploration method, but the most extreme environments of hydrothermal vents pose considerable engineering challenges for sampling hydrothermal fluids. In addition, decompression changes of samples will cause the gas phase dissipation, the decomposition of organic matter and the death of microorganism. So, it is very necessary to study the pressure-retaining sampling technology for the deep-sea hydrothermal fluid sampler.A novel manipulator triggered, accumulator pressure-retaining hydrothermal fluid sampler is put forward. To address the issue that pressure of fluid samples is changed for changes of seawater's temperature and pressure, the working principle of a pressure compensator was studied by theories of thermodynamic and heat transfer. Based on Finite Element Analysis (FEA), structural parameters of the pressure case were optimized; thus its' mass and strength are compromised. A new high pressure-resistant and zero-leakage sample valve with a new mate type is presented. The poppet return spring influence on the seal property of sample valve was studied by experiments. Based on the finite element model, simulated results on stress distribution of the poppet with different structure parameters and preload spring force were discussed, and the static axial deformations on top of the poppet were experimented. The results show that the sampling valve could withstand high pressure of 70 MPa. To assure sampling the designed volume of samples, it is necessary to control sampling rate of the sampler for making the nitrogen gas in the pressure compensator changing as an approximate isothermal process when sampling. Based on AMESim, dynamic model of the sampler was built and then the relation between the sampling rate and the influential factors were discussed. The mathematic model was validated by the experiments. The main contents of this thesis could fall into six chapters, as followings:In chapter 1, the formation process of hydrothermal fluid and its distribution at the whole world are introduced. The present statuses of hydrothermal fluid sampler are summarized from power source, pressure-retaining method and trigger mechanism of sampling valve etc. Thus, the main research contents are proposed.In chapter 2, the principle of pressure-retaining sampling based on the pressure compensator is analysed. The state change of gas in the pressure compensator was studied by theories of thermodynamics and heat transfer. The factors that affect final pressure of the fluid samples were evaluated. Then the changing trend of the state of gas was found. The analyses show that it is feasible to retain the pressure of the fluid samples by the pressure compensator.In chapter 3, the design of the key components in sampler system is studied. Based on finite element analysis, the design criterion was gained for structure parameters influence on mass and maximum stress of the pressure case. In addition, based on the finite element model, simulated results on stress distribution of the poppet with different structure parameters and preload spring force were obtained.In chapter 4, the dynamic mathematic model of the sampler was built by the theory of hydrodynamics. Based on dynamic soft AMESim, the dynamic characteristic of the sampler were analyzed. The dimension of orifice was determined for assuring sampling the designed volumn of samples.In chapter 5, the integrated assembly of the sampler is introduced. The performances of the sampler were experimented in Lab environment. In addition, the minitype sampler was successfully tested by sea trial. The results show that the principle and structure design of the sampler system is reasonable and feasible.In chapter 6, the main contents of this thesis are summarized and then future research is put forward.