| Based on the traditional and 3M Company melt-blown process, the production line of sound-absorbing materials for car-using was effectively improved and new parts were added, including staple fiber opening and delivering framework, as well as double-drum receiving composite forming equipment. Three curled polyester staple fiber and flame-retardant PP meltblown fibers were selected as raw materials and the final product has a three-dimensional network structure, with light quality, pollution-free, excellent sound absorption, good plasticity, easy to paste, flame retardant, etc. It is of great significance in promoting the progress of inhome meltblown composite nonwoven technology to break the monopoly of foreign technology.However, during debugging process specimens, it showed that there was a greater difference in sound-absorbing properties between the samples and the corresponding products of 3M under the case of similar physical performance. Through the electron microscopy images, it was found that the mixed uniformity of the sample staple and meltblown fibers was much poorer in contrast to the 3M samples. As the staple open loose and meltblown process is relatively stable, this paper presents the improvement program:using Fluent fluid simulation software to research the flow field inside the staple conveying nozzle as means to select optimal nozzle model and determine the optimum amount of air supply.Fluent fluid simulation software, currently a world leader in computational fluid dynamics (CFD) software, is the ideal tool for study of fluid flow. On the one hand, vividly and visually directly access to various flow parameters can be obtained through the numerical simulation of the nozzle flow with Fluent; the high costs of start-up test would be saved on the other hand.Firstly, the model of the staple delivery area was simplified. The opening roller airflow around the field and complement wind airflow field were united into one entrance, composed by 7 wind speed inlets of the model; establish three nozzle models as research objects, including the servicing bend-tube, and two re-design straight nozzles.Secondly, the airflow inside the nozzle was assumed as a viscous, incompressible steady turbulence and the transportation process heat exchange was omitted, that is to say, the airflow is isenthalpic. The standard k-? model was chosen to calculate, while using a separate solver implicit scheme to solve, combined with the boundary conditions of the boundary function method for the numerical simulation, simulation of the residuals of the main parameters and mass flow rate of the import and export of monitoring.Then, based on the above the numerical simulation results, the velocity and pressure distribution of staple conveying air field in different nozzle structure models was analyzed and finally concluded that:the amount of air supply is Q2=156.6m/min, with the 37.5° chamfer export straight tube configuration is the best process. Under the conditions of this process configuration, relatively stable staple conveying flow field can provided, making fiber delivery smoothly, which improved the mixed uniformity of staple and meltblown fibers in the final product.Finally, the production line was improved and debugged according to the optimum configuration derived from the simulation. Then the samples with thickness and areal density close to 3M products were chosen for sound absorption performance comparison analysis, the results indicated that the subject trialsamples achieved close sound-absorbing properties of 3M, verifying the accuracy of the numerical simulation results. |
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