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摘要
SX blades of gas turbines, with inside cavity, curved surface and sharply varying section at the platform and the tip shroud, are usually complicated. Therefore, stray grains occur very easily. A new process of directional solidification, liquid metal cooling (LMC), is expected to solve this problem. Nevertheless, the aid of numerical simulation is necessary to optimize this process. In this paper, the mathematical model of LMC is established and the dynamically combined boundary condition during immerging is modeled via secondary development of ProCAST. Numerical simulation of temperature field and dendrite parameter by LMC process is done to investigate the influence of different processes on the solidification characteristics, such as temperature gradient, shape of mushy zone and defect indicators. Compared with conventional process, larger temperature gradient as well as narrower mushy zone is obtained by LMC. It also leads to shorter local solidification time in the thick part of blade, and thus the dendrite is finer. In addition, the single crystal growth into the platform is much easier with the mushy zone topology by LMC, which tends to stop the nucleation of stray grain. Therefore, higher withdrawal rate can be used to refine the dendrite, to prevent freckle or columnar-equiaxed transformation (CET), and to increase productivity.
- 出版日期2014
- 单位清华大学
