Study On The Flow And Diffusion State Of Cigarette Smoke Based On CFD

The study of the physical structure of cigarettes has important theoretical significance in reducing the tar and harmful components.In this paper,the flow and diffusion state of the threedimensional cigarette smoke were numerically simulated from the physical structure of the cigarette by using the computational fluid dynamics simulation software Fluent,threedimensional reverse engineering reconstruction technology,X-ray three-dimensional CT microscopy and Geomagic Spark software.The main research content of this paper is as follows:(1)By determining cigarette paper thickness,porosity and average pore diameter,cut tobacco porosity,cigarette combustion temperature and so on,which provide parameters for the numerical simulation of cigarette smoke.Combined with PIV technology,using self-developed cigarette smoke experiment machine,the pressure,flow rate at the suction end of cigarette,and the inlet velocity of smoke at the combustion end of cigarette are all measured,which provide the boundary conditions for the numerical simulation of cigarette smoke.(2)The steady-state numerical simulation of three-dimensional cigarette smoke flow and diffusion is conducted by using the cigarette as a uniform porous medium.The distribution of CO mass fraction,smoke velocity,smoke pressure on the axial centerline of cigarette,air inlet velocity,CO mass fraction outside the cigarette paper.The effects of different cigarette paper thickness and porosity on the distribution are analyzed.The cigarette model is verified by internal temperature distribution and Darcy's law.(3)X-ray three-dimensional CT microscopy,Avizo Fire 8.1 software and Geomagic Spark software are used to reversely reconstruct the cigarette sheets,and the optimized cigarette sheets are obtained.The cigarette sheets are made meshed and spliced through ICEM software.And Fluent software is used for the numerical simulation of the cigarette sheets.From the above research,the following conclusions are obtained:(1)The porosity of cut tobacco is 0.66 ~ 0.75.Towards the suction end of cigarette,the mass fraction of CO decreases gradually,the smoke rate decreases first and then increases,and the negative pressure of smoke increases gradually on the axial centerline of cigarette.Towards the suction end of cigarette,the air inlet rate increases gradually,CO mass fraction decreases gradually outside the cigarette paper.(2)Both increasing the thickness and decreasing the porosity of cigarette paper will increase the CO mass fraction,decrease the smoke rate,increase the negative pressure of smoke at the same position on the axial centerline of cigarette,and decrease the air inlet rate outside the cigarette paper.The reduction of the porosity of cigarette paper will increase the CO mass fraction at the same position outside cigarette paper.As for the thickness of cigarette paper,the CO mass fraction at the same position outside cigarette paper of 50 ?m is larger than both of 40 ?m and 60 ?m.Under certain conditions,both decreasing the cigarette paper thickness and increasing the porosity of cigarette paper properly can reduce the mass fraction of harmful substances in mainstream smoke.(3)Combining reverse engineering and numerical simulation,the velocity distribution cloud map and velocity flow field of cigarette smoke in the actual three-dimensional cut tobacco flow passage are explored preliminarily,which has similar variation trend with the threedimensional numerical simulation of cigarette as a uniform porous medium.