Analysis Of Leakage And Diffusion Law Of Submarine Natural Gas Pipeline

In recent years,due to the increase in demand for natural gas.China has increased the exploitation of natural gas resources under the sea.Pipeline as a major means of transporting natural gas is also developing rapidly.The current seabed leakage simulation mainly studied steady-state leakage,ignoring that the leakage velocity changed over time.Moreover,the impact of sea surface waves on diffusion has not been considered.The studied of the leakage and diffusion of submarine natural gas pipelines provided a theoretical basis for the safe operation of pipelines.First,established a physical model of the leak process.Simulated the effects of water depth,leaking pore size and pressure inside the pipelines on the leak.The relationship between the mass flow rate from the start of the valve closing time to the time when the leak does not occur is obtained.Then,used the function fitting method,the variation of the boundary conditions at the leak was obtained with time.It is concluded that as the leak progresses,the leaking pipe section is filled with water.As the water depth increases,the leak rate decreases and the leak time increases.The larger the leak aperture,the larger the leak rate,the larger the mass flow rate of the effluent gas,and the shorter the leak time;the larger the pressure inside the tube,the shorter the leak time.Secondly,for the studied of natural gas diffusion distribution,different influencing factors were setted for diffusion simulation,and the influence of different factors on diffusion was obtained.Considered that the water flow velocity was changed with the change of water depth,used a custom function,It was obtained that the greater the velocity of the water,the stronger the impact on the natural gas close to the surface,and the longer the leakage ofnatural gas in the water,the greater the horizontal width of the leaked gas;the increase of water depth leads to an increase in the pressure gradient of the seabed,which reduces the upward movement of the leaking gas,increases the movement time of the gas in the water,and increases the radius of the gas surface;as the leakage aperture becomes larger,the higher the leakage rate and the increased leakage,the time of motion is shortened in the water,and the diffusion radius of the leaking gas reaches the water surface is larger;the longer the wavelength of the sea wave,the longer the gas moves in the water,and the larger the radius of the gas surface.Finally,the horizontal diffusion width and vertical height were introduced in this paper to studied the spatial variation law of seafloor leakage natural gas diffusion process,studied the relationship between vertical height and horizontal diffusion width and time,by comparing the water depth in vertical heigh.The range of horizontal diffusion width.It has important guiding significance for the development of emergency measures after the occurrence of a submarine gas pipeline leakage accident.