Research On Submarine Gas Hydrate Jet Breaking Experiment And Engineering Application

Natural gas hydrate,also known as "combustible ice",is a new type of energy that is highly efficient and clean.The effective exploitation and utilization of natural gas hydrates is a primary problem.In order to solve the shortcomings of traditional hydrate mining,the characteristics of natural gas hydrates in China's South China Sea are uncovered,non-compact,and weakly cemented.Zhou Shouwei first proposed the solid-state fluidized mining technology for submarine in-situ mechanical crushing and mining.On this basis,considering the scope and limitations of mechanical crushing,this paper proposes the mining method of water jet crushing hydrate ore body mining,and the mining tools and influences of water jet crushing based on the South China Sea seabed hydrate.The performance parameters of water jet crushing were studied.The parameters of the relevant engineering applications were obtained by single nozzle jet flow field simulation,jet crushing numerical simulation and water jet crushing hydrate simulation sample experiment.The main research work of this paper is as follows:(1)Based on the influence factors of single nozzle crushing performance,the FLUENT flow field simulation method was used to analyze the flow velocity of the flow field under different single nozzle flow path structure and size conditions.With the jet velocity as the main reference,the nozzle with diffusion angle was determined.structure.On this basis,the key parameters such as single nozzle shrinkage angle,nozzle cylinder length to diameter ratio,nozzle diffusion angle and total length are optimized.(2)Based on the ALE algorithm,combined with the LS-DYNA display dynamics analysis program,the numerical simulation of water jet breaking hydrate is carried out to analyze the influence of jet velocity and jetting distance on the crushing effect in the process of hydrate water jet crushing.The jet velocity is the key factor affecting the depth of jet fracture.When the spray distance is 5mm,the jet velocity increases from 50m/s to 150m/s,and the jet fracture depth and crush volume increase by 3 times.(3)Based on the theory of high-pressure water jet rock-soil breaking,a high-pressure water jet experimental device was used to carry out a single-nozzle water jet crushing hydrate simulation sample experiment.The experimental results verify the validity of the numerical simulation.At the same time,the jet breaking depth,the crushing volume and the jet breaking time under different single nozzle diameter and jet pressure conditions and the specific influence law and curve of each parameter on the jet crushing effect are obtained.At the same time,the shape and variation of the jet crushing pit are observed through experiments.(4)Based on the optimization of single nozzle structure,a combined nozzle tool was designed through reasonable arrangement.Combined with the actual engineering application needs,the jet rupture experiment of the hydrate sample of the combined nozzle was carried out.The important working condition parameters affecting the jet crushing efficiency under the action of the combined nozzle tool are studied.The experimental data affecting the mining efficiency and the diameter of the crushing hole under different parameters including speed,jet pressure and displacement are obtained,which is the future hydrate.The test production parameters provide a certain experimental reference.In this paper,through the theoretical and experimental research on the hydrate jet fracture,the design idea and experimental method of a set of water jet crushing hydrate ore bodies are preliminarily established.It provides a certain reference and experimental data for the working parameters of water jet breaking seabed hydrate ore body under actual working conditions.Therefore,the research in this paper is of great significance to the hydrate jet bursting in practical engineering applications,and provides a reference for the process parameters related to hydrate jet crushing.