Studies Of Bus Active Protection Based On The "Air-Rain" Theory

The bus is the subject of the public transportation,it has a significant role in the economic development of urban,which equal to the flow of “public architecture”;However,the security issues are highlighted,when the bus car arson terrorist attack or chemicals with its small space and passengers in and out of traffic,which will pose a threat to the life safety of the passengers.Now,There is no more definite way for passengers to stop the spread of terrorism hazardous chemicals and control the spread of the fire in bus,therefor,So the author of this paper is combined previous research that the harmful chemicals can be resisted their spread with “air-rain” flow field in the large space,but the role of “air-rain” flow used in small space is unknown,neither the control of the situation of the fire.The idea of “air-rain” flow field bus is as follows:the supply system of “air-rain” is a top down out of air.The core of “air-rain” is to produce a top-down uniform flow velocity field,in this kind of flow field,the poisonous gases or harmful chemicals will be blown into the uniform opening platform floor,so the polluted air can be collected below the floor and centralized purification treatment with the existing technology,then back into the bus.Therefore,harmful chemicals in the bus will be inhibition of proliferation and the life safety of passenger can be guaranteed.In this paper of second and tired chapter,the bus with “air-rain” flow field and the ordinary bus were established with ANSYS ICEM CFD,and the structured grids were built combining with the characteristics of model;then based on the multi-component flows of computational fluid dynamics model with FLUENT software to carry on the numerical simulation,respectively compared the gas diffusion in the “air-rain” flow field and ordinary bus in empty and in manned bus when using gasoline as chemicals.simulation results show that the “air-rain” flow field bus is superior to the ordinary car on the proliferation of chemical substances.In the fourth chapter,the arson in the “air-rain” flow field bus was simulated with the FLUENT software,then compared with ordinary conditions.The eddy dissipation model(EDM)of combustion model and P-1 radiation model were chosen,then with the hypothesis of arson.Simulation results show that at low wind speed 0.1 m/s,the temperature is hierarchical in the “air-rain” bus which can not satisfy the escape conditions of passengers.Then the wind speed were increased to 0.3 m/sand 0.5 m/s,high temperature area mainly near the flame and in other regional the conditions oftemperature and the concentration of flue gas are meet the escape conditions of passengers,big air volume can reduce the diffuse speed of temperature meeting the condition for passenger comfort;In order to analyze the change trend of temperature in the bus more clearly,the velocity of “air-rain” flow field bus is 0.3 m/s with transient simulation,the consequence shows that temperature diffuse rapidly in the first 30 s,the high temperature area mainly near the flame after 30 s,and the other area is below 170℃,with smoke concentration less than 6%,which satisfy escape conditions of passengers.In the fifth chapter,according to Froude model combustion experiment model was designed 1:10,respectively compared the temperature distribution between“air-rain” conditions and normal bus.The experimental results and simulation results are consistent,which verified the correctness of the simulation.Finally it’s come to the conclusion that “air-rain” flow field can be used not only in the large space but also in a small space bus,which can effectively inhibit the spread of the chemicals with the speed at 0.1m/s;when there is a fire in the bus,the simulation results show that the increased wind speed at 0.3m/s,0.5m/s can control the spread of temperature smoke in bus.There is a low temperature area away from the flame,at this time passengers can escape from the low temperature area.According to the existing bus fan performance,energy conservation and economic conditions,the speed in “Air-Rain” flow field at 0.3 m/s is more feasible.Comprehensive above can be concluded that the “Air-Rain” flow field with 0.3m/s can control the spread of fire temperature and smoke,and the pollution of chemical attack,thus providing favorable conditions for passengers to escape.