The use of gas-assisted technology is very popular in injection molding for its significant effect of improving mechanical properties and quality of products. Accordingly, the demand of gas-assisted CAE technology is also in the rising. In current CAE technology the compressibility of gas is neglected and gas or air pressure is usually imagined as a constant, such as a given value of the pressure at the inlet. But in fact, gas is strongly compressible and its pressure changes from a low value of zero to a high one before it is stabilized. It leaves unknown if these facts have any influence on the quality or mechanical properties of products. The objective of this paper is to study the complex behavior of compressible gas flow in the gas-assisted injection molding process. For simplification the real 3D flow was reduced to a 2D one based on certain assumption. A numerical simulation model of 2D transient compressible gas flow based on the characteristic-based-split method (CBS) was presented and a corresponding software with VC+ + was established. Using this software a real simulation work was done. Its results could be taken as base data in further filling simulation. In addition, a pressure testing experiment was also done, and the comparison between simulation and experiment showed that the model presented in this paper was feasible.%气辅成型技术能够有效地改善产品力学性能、提高产品的质量,因此在注射成型生产中应用广泛,与之相应的气辅成型CAE技术也得到了快速发展.当前的气辅成型CAE技术中假定空气为不可压缩流体,忽略了空气的可压缩性,因此研究气辅成型过程中可压缩空气的流动行为具有一定的实际意义.针对气辅成型过程中可压缩空气流动的复杂行为,基于假设将复杂的三维(3D)流动问题转化为二维(2D).采用CBS方法建立2D瞬态可压缩空气流动的有限元分析模型,求解算法采用预共轭梯度法,并用VC++完成了算法编制,实现了可压缩空气流动过程的数值模拟,其压力结果可作为充填流动分析的基础数据.
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