The Numerical Study On Diffusion Of Gases In Limited Space

The accidental release of vast flammable,explosive or toxic materials produced and used in modern industries would bring about a great disaster to the society and what happened has left a deep lesson to the person.Since 1970 the United States Bureau of Mines published the report of"hazardous of LNG Spillage on Marine Transportation",which mad international researchers to pay attention to the study of diffusion and then the numerical simulation of diffusion of gases become the rapid development and advanced research field.Recently with the rapid development of computer technology,a variety of excellent numerical simulation code was developed in numerical calculation field including FLUENT which has been widely used in the field of fluid flow and heat transfer.The thesis simulated the transportation and diffusion of gases accidentally released in limited space with FLUENT code and showed the concentration contour maps of gases with time and space and the velocity vector distribution, and then studied deep into the influence of different influencing factors to the diffusion of gases and gave the related conclusions.It has a big significance both in accident prevention such as fire alarm and the development of emergency rescue measures after it happened and in safety assessment.The main work and conclusions in this paper are as follows:1) A mathematical model was created to simulate the diffusion of gases in limited space and illustrate the numerical methods being used,the RNG k-εturbulence model was used to describe the turbulence of air in the space and species transport model was activated and SIMPLE algorithm was utilized to calculate the flow of the fluid.2) Based on the mathematical model of gases in limited space,the transportation and diffusion of hydrogen was simulated using the FLUENT code and the calculated results was compared with the experimental data in related reference and it was proved that the mathematical model of diffusion of hydrogen in the ventilated room is right and the algorithm with the FLUENT code being chose is accurate and feasible.3) According to the calculated results of the hydrogen diffusion in the ventilated room, the characteristics of concentration distribution of hydrogen is discussed and study deep into the influence of change of location of vent and the existence of barrier to the concentration distribution of hydrogen and velocity vector distribution.4) Based on the precedent numerical simulation example,the diffusion model of methane in the simplified coal mine tunnel was created and added the consideration of wind velocity outside.The concentration distribution of methane in the simplified coal mine tunnel with the barrier existed was discussed and study deep into the concentration contour maps and velocity vector distribution on different conditions such as:the different velocity of release,the different size of barrier(width and height of barrier),the unequal distance between the leakage source and the barrier,the relative location between leakage source and the barrier and the different density of the gases.And then the related conclusion was given and based on that some suggestion was given to the fixing of the combustible gas alarm.