气调包装机气体置换结构优化与内部三维流场模拟

目的 针对现有的气体置换装置存在工作过程中气体置换精度不高、置换率低、内部流场复杂紊乱等问题，对DF-520型气调包装机气体置换装置结构进行了改进以及内部流场数值模拟。方法 运用FLUENT软件在进口压力为20 kPa，混配O2体积分数为2%、CO2体积分数为28%、N2体积分数为70%的边界条件下对新旧2种换气装置进行数值模拟和对比分析，进一步通过样机试验对比分析2种模型的气体置换率和气体置换精度。结果 数值模拟结果表明，与旧构型相比，新构型置换腔内部气体流速较平均、强流区面积小、漩涡区少、气体流向一致性高、气体置换速度快;样机试验结果表明，新旧构型气体置换装置平均气体置换率分别为99.2%和95.6%，新构型目标气体体积分数标准差、平均相对偏差以及变异系数更小。结论 本研究表明，优化后的气体置换装置气流分布更稳定，置换精度达到设计要求，工作效率更高，适用于气调包装机的包装工作，能为后续研究提供思路。

Structural Optimization and Internal 3D Flow Field Simulation of Gas Displacement in MAP Machine

The work aims to improve the structure of the gas replacement device in DF-520 MAP machine and conduct internal flow field simulation to solve the problems of low accuracy and replacement rate and disordered internal flow field in operation of existing gas replacement device. The FLUENT software was used to make numerical simulation and comparative analysis for old and new gas replacement devices with boundary conditions of 20 kPa inlet pressure and gas mixture ratio of 2% O2, 28% CO2 and 70% N2. Subsequently, the accuracy and replacement rate of two models were compared via prototyping test. Numerical simulation results indicated that compared with old configuration, the replacement chamber of new configuration had relatively even gas flow rate, smaller strong current and vortex area, high-consistency gas flow direction and rapid gas replacement speed. Prototype test results showed that the average gas replacement rates of new and old configurations were 99.2% and 95.6%, respectively. Meanwhile, for new configuration, the standard deviation, average relative deviation and coefficient of target gas concentration ration were smaller than those of the old configuration. The optimized gas replacement device has more stable gas flow distribution and higher efficiency, with replacement accuracy meeting the design requirements and it is suitable for packaging processing and can provide a theoretical reference for further research.