Ishikawajima-Harima Heavy Industries Co
Ishikawajima-Harima Heavy Industries Co
Ishikawajima-Harima Heavy Industries Co
Ishikawajima-Harima Heavy Industries Co
Ishikawajima-Harima Heavy Industries Co
Ishikawajima-Harima Heavy Industries Co
出版者
宇宙開発事業団
出版者（英）
National Space Development Agency of Japan (NASDA)
Owing to generation of convection due to difference of surface tension based on temperature difference of surface of melts (Marangoni convection) in material processing utilizing microgravity in space, properties of crystal to be solidified and grown may be greatly affected. For the purpose of elucidating the liquid flow, experiment of flow visualization was carried out on system which simulated process of unidirectional crystal growth (Bridgeman method which seals crystal in an ample and makes crystal grow along axis). By combining the results of experiment and results of separately performed numerical simulation, it is possible to predict Marangoni convection and thereby heat transfer and mass transfer. In addition, if the relationship between heat transfer or mass transfer and crystal growth become clear, it is expected to obtain high quality crystal by controlling these parameters. The experiment was performed which simulated the case of forming the free surface at the grown crystal side with uniform width without contact of fused liquid to the ample wall under microgravity. Transparent paraffin liquid was used to visualize the flow in the liquid. After the paraffin was melted under microgravity, the free surface with temperature difference was formed and the movement of the tracer was took a picture by TV camera. In summary, the objects of the experiments are as follows: formation of liquid column with free surface, flow visualization, and observation of solidification phenomenon which simulate Marangoni convection and crystal growth. These experimental items were carried out in series. Under microgravity, the liquid column (25 mm in diameter, 24 mm in length) with the free surface (6.5 mm in length) was formed and maintained stably. The visualized images of the liquid column (shape of the liquid column, tracer in the liquid column) had been recorded in the video tape. But, the image quality was not sufficient. In spite of provision of requirements of formation of temperature difference on the free surface and suppression of buoyancy convection under microgravity, Marangoni convection did not occur. As result of constituents analysis and ground surface test after recovery of the samples from space, it was found that there was high possibility which Marangoni convection was suppressed by contamination of the free surface due to mixing of surfactant from outside into the liquid to be tested. Under no flow condition it was observed that solidification of interface developed flatly in solidification phenomena and the melting speed became slower than on ground surface because of floating of solid part of sample. In the present experiment, Marangoni convection did not occur and it was not observed. therefore, further experiments must be done after prevention of contamination and improvement of optical system and camera.
無重力下での材料製造過程におけるマランゴニ対流の研究
04116019.pdf
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