Study On Internal Flow Characteristics Of Linear Air Permeability Standard

Linear air permeability standard is one of the special standard elements used in Tobacco metering. Linear air permeability standard have been used to calibrate air permeability tester in tobacco industry. To study the characteristics that flowrate of linear air permeability standard changes with ambient pressure or temperature, 3D numerical simulations of the internal flow field through 5 kinds of linear permeability standard are adopted. Based on FLUENT, the work listed as below has been completed in this paper.(1) On the theory, the application and advance of single ball filling model in porous fluid mechanics had been studied. The Ergun equation was adopted to describe the internal flow in porous media. Through measurement and calculation, two important parameters of the porous media(porosity and particle diameter) had been qualified. With introducing of Rasmussen equation of air state, the calculation accuracy of air‘s density and viscosity had been improved. Base on calculation of the Re number, the state of internal flow was analyzed. Thus, to successfully carry numerical simulation of linear air permeability standard, a series of relative conditions have been established.(2) The finite volume method for porous fluid mechanics calculation had been introduced in this paper. Consequently it led to the FLUENT software. Based on the UDF interface of Fluent, a C program about the Reassume equation was written. In this way, the density and viscosity of gas was customized.(3)In accordance with the practical size, 3D models of entity were established. The FLUENT was used to get the internal flow of linear permeability standard. Through several comparisons, it indicates that the numerical simulation results agree with that of experiments very well. Then, the simulations mainly include the effects of the pressure drop, ambient pressure and ambient temperature on the flowrate of linear permeability standard. After simulating the internal flow field under a series of different environmental factors, volume gas flowrate curves were obtained and corresponding formulas were given. The simulation data can be used to predict the error of environmental influences. These studies deepen the understanding of measurement accuracy of permeability of cigarette paper.