| As an important energy storage element in the new energy industry, Lithium-ion battery is the high-tech product supported and developed by nation emphatically. The separator is one of the key components in the structure of lithium-ion battery. The comprehensive performance of the lithium-ion battery can be greatly improved by using the high-quality separator and the uniformity of the thickness of the separator is one of the important quality indexes for the separator. The thickness uniformity depends on the heating uniformity by the hot air in the stretching process, and heating uniformity depends on the uniformity of the hot wind speed. Meanwhile, the plenum chamber is the key equipment, which is to ensure that the hot air is uniform in the outlet. However, most of the plenum chambers are designed currently in accordance with the experience, so it is difficult to ensure the homogeneity of the hot air heating in practice.In this paper, the preheating section plenum chamber and the stretching section plenum chamber in the hot air heating system are respectively investigated and analyzed by using the method of the CFD (computational fluid dynamics) numerical simulation and experimental study, including the two plenum chambers internal flow field, experimental verification the numerical model, single factor analysis of the two plenum chambers’structure parameters, multi-factor analysis of the structure parameters of orifice plates, optimization design of the two plenum chambers’ structure parameters. The following work has been done in this dissertation:Firstly, the two plenum chambers’internal velocity field distribution and the outlet velocity uniformity are analyzed by using velocity deviation as the evaluation index. In addition, the working mechanism of the plenum chambers is proposed based on CFD numerical simulation results. The results of the numerical simulation and experiments show that the simulated results of the outlet velocity distribution agree well with experimental results, so the numerical model of the two plenum chambers is proved accurately. Furthermore, the experimental values of two plenum chambers’velocity deviation are respectively0.4m/s and0.5m/s, satisfying the engineering requirements.Secondly, through single factor analysis of the two plenum chambers’structure parameters, the rules about structural parameters and the outlet velocity deviation are described, and orifice plate affects greatest the outlet velocity deviation. Apart from orifice, optimal values of the other structural parameters are gotten.Thirdly, through multi-factor analysis(Orthogonal test) of structural parameters of orifice, the influence degree of the diameter, the length to diameter ratio and the thickness to diameter ratio on outlet velocity deviation is analyzed respectively. At the same time, the solutions are obtained, which are optimal factor level combination schemes for each of the two plenum chambers’ orifice plates. Besides, the empirical formula about orifice parameters and outlet velocity deviation is derived from dimensional analysis and multivariate linear regression theory. It can well forecast the outlet velocity deviation of different orifice parameters in the experimental range.Finally, the optimal structural parameters about these chambers are obtained according to the above research content. Orifice plate’parameters of the preheating section plenum chamber are:d=8mm,l=15mm, t=6mm, orifice plate’s parameters of the stretching section plenum chamber are:d=12mm,l=26mm, t=6mm, and the other structural parameters keep prototype sizes.The conclusions and rules of this paper can be used as the theoretical basis of the plenum chamber design, and provide theoretical guidance for retrofit of existing equipment. |
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