The diffusion process of N2, O2 and CO2 into VG10 machine oil had previously been observed in such a way as measuring the pressure change of gas confined to a constant volume with the oil. Although the measured pressure changes of N2 and O2 had been properly predicted by the diffusion theory, it had not been the case with CO2. With suspicion that the dependency of a diffusion coefficient on the pressure could have influenced the results for CO2, which exhibits a much larger pressure change in the course of diffusion than N2 and O2, the diffusion process was otherwise observed in the present study under a constant pressure, using laser heterodyne interferometry. The diffusion of CO2 did not agree with its theoretical prediction again, which gave birth to an idea that a convective flow might occur in the oil by the density gradient produced by gas diffusion. Then Mach-Zehnder interferometry was introduced to observe gas-oil diffusion, proving natural convection did happen some time after the diffusion started. The diffusion process of CO2 before the occurrence of natural convection agreed well with the theoretical prediction, giving reliable values of its diffusion coefficient.
|Nippon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C
|Published - 2002 2月
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