Diffusion Of Natural Gas Concentration Field Under Humidity Gradient

With the Rapid development of city gas in China, That on the one hand, stimulating the rapid economic growth, improve the quality of people’s life and reduce the pollution of the environment, On the other hand, more and more gas accidents to the lives and property of the residents also bring huge losses, which has become the focus.The meteorological factors that affect gas leakage diffusion mainly includes: temperature humidity, wind speed, etc. Due to the use of the gas for a short time, the related research started relatively late too, Directly to the influence factor of gas leakage diffusion research seldom reported at home and abroad, there are many factors affecting the leakage and diffusion,the basic theory and derivation process is more complicated At the same time.Through reasonable hypothesis and simplify the analysis of natural gas pipeline and leakage process, based on the three-dimensional torrent model, This paper adopts CFD software to simulation on the concentration field of gas diffusion in a building group external space, and analyzes the effects of the temperature and humidity to gas diffusion and the changeable law of the concentration field. Analysis results show that: with the increase of ambient temperature the diffusion rate of natural gas leak also increases vertically and horizontally; with the increase of environment relative humidity, the diffusion rate of natural gas gradually slows down in the vertical direction, but in the horizontal direction the diffusion rate increases gradually, therefore the diffusion area decreased in the vertical plane, and increased in the horizontal plane.Most studies have focused on wind speed, obstacles and the effect of the temperature on the diffusion of the pollutants, tend to ignore the influence of atmospheric humidity change for diffusion. And actual observations can reflect atmospheric humidity change for gas pollution and particle pollution diffusion effect, but without the support of theoretical model. In order to analyze the influence of humidity of gas diffusion, this paper analysis the natural convection mechanism of the temperature gradient, density gradient, humidity gradient from the macroscopic angle, gradient of the physical fields will cause the material flow, is bound to cause component gas diffusion. Again, from the perspective of the fick’s law, the introduction of three equation and state equation of ideal gas, without temperature gradient, the action of forces can be divided into the concentration gradient of concentration gradient force and buoyancy lift caused by density difference, Derivation of the concentration gradient of the diffusion theory, the theoretical formulas split into several parts, detailed analysis the internal mechanism of the concentration gradient force (pressure gradient) term impact on gas diffusion; Combining with the physical knowledge, launched in different relative humidity conditions, Get the formula Density buoyancy of polluting gases. Finally, the fifth chapter simplified simulation, only highlight the humidity factor, through the Fluent, simulation of gas diffusion of water vapor content in the air in different. Cross-sectional analysis of the simulation results verify the theoretical analysis.Structure of this paper is to propose questions, theoretical problem solving, simulation and verification conclusion of a process, starting from the basic Fick’s law, analyzes the moisture diffusion factors on the role of a gas leak, the analysis obtained under the laws of natural gas in complex weather conditions leakage and diffusion provide a theoretical basis and reference.