The mechanical gas seal of aero engine has to face the problems of high wear rate and short lifetime.Surface texture has shown beneficial effects over the tribological characteristics.Here,a hydrodynamic model for dim...The mechanical gas seal of aero engine has to face the problems of high wear rate and short lifetime.Surface texture has shown beneficial effects over the tribological characteristics.Here,a hydrodynamic model for dimpled annular area of mechanical gas seal considering the″interaction effect″between adjacent dimples is developed based on the Reynolds equation.Different multi-row columns are chosen and the dimensionless pressure in radial and circumferential directions is calculated.The results indicate that the″interaction effect″is more obvious in the circumferential direction than in the radial direction,even when the area and depth of the dimples are same.Moreover,for the 5×5column,the dimensionless average pressure considering the″interaction effect″increases by45.41% compared with the 1×5column.Further analysis demonstrates that the model with the 5×5column can be more reasonable with the consideration of reducing the calculation error caused by boundary conditions to investigate the hydrodynamic effect for dimpled mechanical gas seal.展开更多
The geological condition of Chinese coal mines are complex and high gassy,which account for ffty percent to seventy percent.Because of the abundant pores and cracks around the drainage drilling hole,the gas concentrat...The geological condition of Chinese coal mines are complex and high gassy,which account for ffty percent to seventy percent.Because of the abundant pores and cracks around the drainage drilling hole,the gas concentration attenuates rapidly,and the effective gas drainage period is short.The traditional sealing materials of yellow mud and cement-sand grout will readily shrink after the drilling hole is sealed,the sealing length is short and the sealing quality is not satisfactory.Currently widely used polyurethane material will shrink when it comes into contact with water,and the price is also very high.In this study,taking cement as a base material,a novel composite sealing material mixed by expansion admixture,additive,and fbrin and coupling agent was developed and the sealing performance and expansion property of the material were also studied and analyzed.The FEI Quanta TM 250 environmental scanning electron microscope was used to investigate the microstructure of material.The results revealed that the new composite sealing material had a desirable expansion performance and a defnite fluidity convenient for grouting.The solidifed material,combining closely with the drilling wall,possessed an adequate strength and was not easy to shrink.Compared to the conventional polyurethane,the gas drainage concentration by drilling sealing exceeded 40 percent,and the sealing capacity improves5 times,the sealing effect increases signifcantly.展开更多
For dielectric barrier discharge lamps filled with various gas mixture ratios, the correlations between the excimer XeCl* emission and the sealed gas temperature have been founded, and a qualitative explication is pre...For dielectric barrier discharge lamps filled with various gas mixture ratios, the correlations between the excimer XeCl* emission and the sealed gas temperature have been founded, and a qualitative explication is presented. For gas mixture with chlorine larger than 3%, the emission intensity increases with the sealed gas temperature, while with chlorine about 2%, the emission intensity decreases with the increase in the gas temperature, and could be improved by cooling water. However, if chlorine is less than 1.5%, the discharge appears to be a mixture mode with filaments distributed in a diffused glow-like discharge, and the UV emission is independent on the gas temperature.展开更多
基金supported by the National Natural Science Foundation of China(No.51175246)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the NUAA Research Funding(No.NP2013306)
文摘The mechanical gas seal of aero engine has to face the problems of high wear rate and short lifetime.Surface texture has shown beneficial effects over the tribological characteristics.Here,a hydrodynamic model for dimpled annular area of mechanical gas seal considering the″interaction effect″between adjacent dimples is developed based on the Reynolds equation.Different multi-row columns are chosen and the dimensionless pressure in radial and circumferential directions is calculated.The results indicate that the″interaction effect″is more obvious in the circumferential direction than in the radial direction,even when the area and depth of the dimples are same.Moreover,for the 5×5column,the dimensionless average pressure considering the″interaction effect″increases by45.41% compared with the 1×5column.Further analysis demonstrates that the model with the 5×5column can be more reasonable with the consideration of reducing the calculation error caused by boundary conditions to investigate the hydrodynamic effect for dimpled mechanical gas seal.
基金fnancially supported by the National Natural Science Foundation of China(No.51274195)the Natural Science Foundation of Jiangsu Province(No.BK2012571)+3 种基金the Program for New Century Excellent Talents in University(No.NCET-12-0959)the China Postdoctoral Science Foundation(No.20090450930)the National Basic Research Program of China(No.2011CB201205)Qing Lan Project,and the Youth Foundation of China University of Mining and Technology(No.2007A003)
文摘The geological condition of Chinese coal mines are complex and high gassy,which account for ffty percent to seventy percent.Because of the abundant pores and cracks around the drainage drilling hole,the gas concentration attenuates rapidly,and the effective gas drainage period is short.The traditional sealing materials of yellow mud and cement-sand grout will readily shrink after the drilling hole is sealed,the sealing length is short and the sealing quality is not satisfactory.Currently widely used polyurethane material will shrink when it comes into contact with water,and the price is also very high.In this study,taking cement as a base material,a novel composite sealing material mixed by expansion admixture,additive,and fbrin and coupling agent was developed and the sealing performance and expansion property of the material were also studied and analyzed.The FEI Quanta TM 250 environmental scanning electron microscope was used to investigate the microstructure of material.The results revealed that the new composite sealing material had a desirable expansion performance and a defnite fluidity convenient for grouting.The solidifed material,combining closely with the drilling wall,possessed an adequate strength and was not easy to shrink.Compared to the conventional polyurethane,the gas drainage concentration by drilling sealing exceeded 40 percent,and the sealing capacity improves5 times,the sealing effect increases signifcantly.
基金This work is supported by Jiangsu Suzhou Purification Group Co.Ltd.
文摘For dielectric barrier discharge lamps filled with various gas mixture ratios, the correlations between the excimer XeCl* emission and the sealed gas temperature have been founded, and a qualitative explication is presented. For gas mixture with chlorine larger than 3%, the emission intensity increases with the sealed gas temperature, while with chlorine about 2%, the emission intensity decreases with the increase in the gas temperature, and could be improved by cooling water. However, if chlorine is less than 1.5%, the discharge appears to be a mixture mode with filaments distributed in a diffused glow-like discharge, and the UV emission is independent on the gas temperature.
