| With the progress of human civilization,indoor smoking has become a key social problem for researchers to study and pay attention to.Secondhand smoke has a great harm to human body.Therefore,how to reduce the harm of secondhand smoke is increasingly significant.At present,there are two main ways: 1.Reduction of the harmful substances in the cigarette;2.Decrease of cigarette smoke concentration in the smoking environment.In this paper,the reverse reconstruction technology and Computational Fluid Dynamics(CFD)were used to establish the mathematical model of cigarette smoke flow in the cigarette.The obtained mathematical model simulated the flow state of cigarette smoke in the tobacco and the filter tip part.Consequently,the smoke velocity,pressure,temperature,particle mass distribution and particle filtration efficiency of four kinds of cigarettes were analyzed.Subsequently,the mathematical model of cigarette smoke diffusion in smoking room was established by using PROE and CFD.The effect of amount of cigarette smoke and fresh air velocity on the velocity field distribution,pressure distribution,and particle mass fraction distribution were obtained by mathematical model.The purification efficiency of particle in the smoking room was further analyzed under different working conditions.This paper will provide practical guidance on the optimization and design of cigarette and smoking room.The main research contents are as follows:(1)Firstly,the parameters of mathematical model was obtained from the relevant test.The Nano Voxel X-ray three-dimensional microscope and Avizo Fire 8.1 software were carried out to measure the porosity of the cut tobacco from four kinds of special cigarettes.The porosity of cigarette filter was measured by using n-hexadecane.The peak temperature of cigarettes burning cones was measured by DATAPAQ-Q18 thermometer.The smoke velocity at the combustion end,the pressure at the suction end,and the smoke velocity at the suction end of cigarettes at different smoking frequencies were measured by synthetic system which combined the smoking machine,pressure gauge,and PIV system.The contents of particulate phase and gas phase components in the cigarette smoke were measured by using Cambridge filter and gas chromatograph.Consequently,the mass fraction of each component and the filtering efficiency of particulate phase were obtained.These parameters were used for the boundary conditions of mathematical model and the verification of the model.(2)Secondly,the purpose was to establish the mathematical model of smoke in the cigarette.Reverse reconstruction techniques were used to optimize the three-dimensional flow channels of the four kinds of cigarettes.It build the flow channels of the tobacco cut part and the filter nozzle part of cigarettes.Mesh splicing and mesh division were carried out for the mathematical models of the four kinds of cigarettes,which provided a suitable meshing model for the subsequent numerical simulation.The parameters of the cut tobacco and filter measured in the early experiment were inputted as boundary conditions to establish a mathematical model of cigarette smoke flowing inside of cigarette.The velocity-inlet and pressure-outlet are loaded by UDF function for internal gas flow transient simulation under the standard suction condition.The gas velocity,pressure,temperature,and particle phase mass fraction distribution of four kinds of cigarettes internal flue was analyzed by obtained mathematical model.The mathematical model had a high correctness by comparing the experimental and simulated results of the four kinds of cigarettes.Consequently,the overall velocity of smoke in cigarettes increased gradually with the passing of time and reached the maximum at 1.0 s,then decreased gradually.The internal pressure of cigarettes increased first and then decreased with the increasing time.Moreover,the pressure exhibited the biggest value at the suction end.The mass fraction of particulate matter in the four kinds of cigarettes increased gradually with the extension of time.At the initial moment of smoking,the filtering efficiency of particulate matter was close to 100%.After 2 s of standard smoking,the filtering efficiency of particulate matter in the four kinds of cigarettes decreased to the minimum.The mass fraction distribution cloud map of particulate matter showed that the filtration efficiency of particulate matter in smoke is as follows: No.4 cigarette >No.3 cigarette >No.1 cigarette >No.2 cigarette.(3)Based on the flow and diffusion of smoke in cigarettes,the efficiency of smoke purification in smoking room was optimized.Component transport model was used to simulate the diffusion and flow of cigarette smoke in the smoking room.Under different numbers of cigarettes and different fresh air speeds,the distribution of smoke velocity field,pressure distribution,and particle mass fraction distribution in the smoking room were simulated.Using PIV experiment to measure flue gas velocity.The accuracy of the CFD model was verified by comparing the simulated values of the smoke velocity and the experimental result from PIV experiment.As a result,in the smoking room,the smoke concentration and particle mass fraction mainly depends on the amount of smoke source,fresh air speed,air delivery,and exhaust mode,etc.When the amount of smoke source increased,the concentration of indoor smoke was increased and non-smokers are more harmful to second hand smoking.The seat near the exhaust outlet had the higher smoke velocity,higher smoke concentration,and larger particle mass fraction.The seat far away from the exhaust outlet and the mainstream area of smoke could effectively reduce passive smoking.When the fresh air speed increased,the smoke purification efficiency of the smoking room was greatly improved.Increasing fresh air volume is an effective method to reduce the concentration of smoke in smoking room.Combined with the comfortable wind speed requirements of smokers,the fresh air speed of 0.417 m/s is the best input condition for smoking room. |
PDF Full Text Request