油圧油中を浮上する単一気ほうの抵抗係数
1978 年 9 巻 4 号 p. 261-269
詳細
1978 年 9 巻 4 号 p. 261-269
The drag coefficients of single gas bubbles rising In hydraulic fluids of different kinds are presented. Tests are per formed over the bubble Reynolds number range of 5 ×10-5 to 10, and the following conclusions are obtained:
(1) The relation between the Reynolds number Re and the bubble drag coefficient Cd in three kinds of anti-wear type oils on the market are in good agreement with Stokes' equation except for bubbles in Re ranges greater than about 6×10-2.
(2) The values of Cd in high viscosity index hydraulic oils are somewhat larger than those obtained by Stokes' equation, and those in both a water-glycol and phosphate ester are equal to those obtained by the equation.
(3) The Re Cd relations for four kinds of base oils having different viscosity are very nearly the same as fiadamard Rybczynski's equation except for small bubbles less than about 0.4mm in diameter.
(4) If very small quantities of silicon type deforming agent are added in the base oil, the values of Cd increase Considerably. The addition of large quantities of polymetacrylate type viscosity index improver to the base oil also causes an increase in Cd. The additions of iso-butylen type viscosity index improver, alcohol type deforming agent and rust inhibitors have no effect on the drag coefficients.
(5) The drag coefficient is little influenced by the addition of A. C. Fine Test Dust.
