A special bearing tester was constructed to investigate the damage behavior on the lubricated surfaces in bearings with the passage of weak electrical currents as low as^1 mA.The results showed that when polar glyceri...A special bearing tester was constructed to investigate the damage behavior on the lubricated surfaces in bearings with the passage of weak electrical currents as low as^1 mA.The results showed that when polar glycerine was used as the lubricant,many narrow and deep pits formed on the lubricated surfaces.In contrast,when the experimental conditions under the lubrication of the nonpolar paraffin oil were close to those under the lubrication of polar glycerine oil,damages on the lubricated surfaces were unobvious.Emergence of microbubbles in polar lubricants with the passage of electrical currents was proposed to be responsible for the observed damages on the lubricated surfaces.展开更多
The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances b...The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances between the inlet guide vanes and the impeller inlet of 280 mm, 380 mm and 460 mm. The efficiency-flow curves and the characteristic curves were obtained for the pump for various operation conditions. The experiment results demonstrated that the pre-whirl regulation widened the high efficiency zone and improved the hydraulic performance for off-design conditions with the proper pre-whirl angle. The axial distance between the inlet guide vanes and the impeller inlet influenced the pre-whirl regulation effect of the inlet guide vanes with the best pre-whirl regulation effect obtained for an axial distance of 380 mm. These results showed that an appropriate axial distance between the inlet guide vanes and the impeller inlet can improve the fluid flow at the impeller entrance with pre-whirl regulation for centrifugal pumps.展开更多
Based on the Cu-Zr-Ti ternary phase diagram,four sets of Cu-Zr-Ti multilayered films with various compositions of Cu20Zr36Ti44,Cu36Zr31Ti33,Cu49Zr24Ti27,and Cu67Zr16Ti17 were prepared and then the ion beam mixing was ...Based on the Cu-Zr-Ti ternary phase diagram,four sets of Cu-Zr-Ti multilayered films with various compositions of Cu20Zr36Ti44,Cu36Zr31Ti33,Cu49Zr24Ti27,and Cu67Zr16Ti17 were prepared and then the ion beam mixing was carried out.It turned out that the increase of Cu content doesn't always have a positive effect on the glass forming ability.The glass forming ability of Cu49Zr24Ti27 was degraded due to the appearance of a Cs Cl-type B2 structure Cu Zr phase in the eutectic region.The experimental observations justify the existence of the Cu Zr phase under the non-equilibrium condition.Possible formation mechanisms for the crystalline phase were also discussed in terms of the atomic collision theory.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51105221,91023016)the International Science&Technology Cooperation Project(Grant No.2011DFA70980)
文摘A special bearing tester was constructed to investigate the damage behavior on the lubricated surfaces in bearings with the passage of weak electrical currents as low as^1 mA.The results showed that when polar glycerine was used as the lubricant,many narrow and deep pits formed on the lubricated surfaces.In contrast,when the experimental conditions under the lubrication of the nonpolar paraffin oil were close to those under the lubrication of polar glycerine oil,damages on the lubricated surfaces were unobvious.Emergence of microbubbles in polar lubricants with the passage of electrical currents was proposed to be responsible for the observed damages on the lubricated surfaces.
基金supported by the National Natural Science Foundation of China (Grant No. 51176088)the National Basic Research Program of China ("973" Project) (Grant No. 2009CB724304) the General Financial Grant from the China Postdoctoral Science Foundation (Grant No. 2011M500315)
文摘The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances between the inlet guide vanes and the impeller inlet of 280 mm, 380 mm and 460 mm. The efficiency-flow curves and the characteristic curves were obtained for the pump for various operation conditions. The experiment results demonstrated that the pre-whirl regulation widened the high efficiency zone and improved the hydraulic performance for off-design conditions with the proper pre-whirl angle. The axial distance between the inlet guide vanes and the impeller inlet influenced the pre-whirl regulation effect of the inlet guide vanes with the best pre-whirl regulation effect obtained for an axial distance of 380 mm. These results showed that an appropriate axial distance between the inlet guide vanes and the impeller inlet can improve the fluid flow at the impeller entrance with pre-whirl regulation for centrifugal pumps.
基金The National Natural Science Foundation of China(Grant No.51131003)The National Basic Research Program of China("973"Project)(Grant Nos.2011CB606301,2012CB825700)The Administration of Tsinghua University
文摘Based on the Cu-Zr-Ti ternary phase diagram,four sets of Cu-Zr-Ti multilayered films with various compositions of Cu20Zr36Ti44,Cu36Zr31Ti33,Cu49Zr24Ti27,and Cu67Zr16Ti17 were prepared and then the ion beam mixing was carried out.It turned out that the increase of Cu content doesn't always have a positive effect on the glass forming ability.The glass forming ability of Cu49Zr24Ti27 was degraded due to the appearance of a Cs Cl-type B2 structure Cu Zr phase in the eutectic region.The experimental observations justify the existence of the Cu Zr phase under the non-equilibrium condition.Possible formation mechanisms for the crystalline phase were also discussed in terms of the atomic collision theory.
