In gas turbine engines,with the existence of the intense forced convection and significant buoyancy effects,temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics st...In gas turbine engines,with the existence of the intense forced convection and significant buoyancy effects,temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly.In this paper,numerical simulations were performed to analyze these influences for a free disk,with the laminar and turbulent flow respectively.The influences of temperature distribution on the heat transfer were observed by using incompressible cooling air,and temperature profiles of nth order monomial and polynomial were assumed on the disk.The analysis revealed that the heat transfer for two flow states on the free disk is determined by the exponent n of the monomial profile when specifying the rotating Reynolds number;for an arbitrary polynomial profile,the local Nusselt number can be deduced from results of monomial profiles.To study the effects of temperature level on heat transfer singly,monomial profiles were used and the local Nusselt number of compressible and incompressible cooling air were compared.And both for two flow states,the following conclusions could be drawn: the relative difference of local Nusselt number is mainly controlled by nondimensional local temperature difference,and almost independent of the monomial's coefficient C,exponent n and the rotating Reynolds number.Subsequently,a correction method for heat transfer of the free disk is presented and verified computationally,with which the local Nusselt number,obtained with a uniform and low temperature profile,can be revised by arbitrary distribution and high temperature magnitude.展开更多
To optimize the existing slurry for abrasive-free polishing(AFP)of hard disk substrate,a water-soluble free radical initiator,2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride(AIBI)is introduced to the H2O2-base...To optimize the existing slurry for abrasive-free polishing(AFP)of hard disk substrate,a water-soluble free radical initiator,2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride(AIBI)is introduced to the H2O2-based slurry.The polishing results show that,the material removal rate(MRR)of hard disk substrate polished with H2O2-based slurry containing AIBI is obviously higher than that without AIBI.The acting mechanism of the improved MRR is investigated.Electron paramagnetic resonances tests show that,by comparison with H2O2 slurry,H2O2-AIBI slurry provides higher concentration of hydroxyl radicals.Auger electron spectrometer analyses further demonstrate that the oxidation ability of H2O2-AIBI slurry is much greater than H2O2 slurry.In addition,potentiodynamic polarization tests show that the corrosion dissolution rate of hard disk substrate in H2O2-AIBI slurry is increased.Therefore that stronger oxidation ability and a higher corrosion dissolution rate of H2O2-AIBI slurry lead to higher MRR can be concluded.展开更多
文摘In gas turbine engines,with the existence of the intense forced convection and significant buoyancy effects,temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly.In this paper,numerical simulations were performed to analyze these influences for a free disk,with the laminar and turbulent flow respectively.The influences of temperature distribution on the heat transfer were observed by using incompressible cooling air,and temperature profiles of nth order monomial and polynomial were assumed on the disk.The analysis revealed that the heat transfer for two flow states on the free disk is determined by the exponent n of the monomial profile when specifying the rotating Reynolds number;for an arbitrary polynomial profile,the local Nusselt number can be deduced from results of monomial profiles.To study the effects of temperature level on heat transfer singly,monomial profiles were used and the local Nusselt number of compressible and incompressible cooling air were compared.And both for two flow states,the following conclusions could be drawn: the relative difference of local Nusselt number is mainly controlled by nondimensional local temperature difference,and almost independent of the monomial's coefficient C,exponent n and the rotating Reynolds number.Subsequently,a correction method for heat transfer of the free disk is presented and verified computationally,with which the local Nusselt number,obtained with a uniform and low temperature profile,can be revised by arbitrary distribution and high temperature magnitude.
基金Project supported by the National Natural Science Foundation of China(51175317)the Doctoral Program of Higher Education of China(20123108110016)
文摘To optimize the existing slurry for abrasive-free polishing(AFP)of hard disk substrate,a water-soluble free radical initiator,2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride(AIBI)is introduced to the H2O2-based slurry.The polishing results show that,the material removal rate(MRR)of hard disk substrate polished with H2O2-based slurry containing AIBI is obviously higher than that without AIBI.The acting mechanism of the improved MRR is investigated.Electron paramagnetic resonances tests show that,by comparison with H2O2 slurry,H2O2-AIBI slurry provides higher concentration of hydroxyl radicals.Auger electron spectrometer analyses further demonstrate that the oxidation ability of H2O2-AIBI slurry is much greater than H2O2 slurry.In addition,potentiodynamic polarization tests show that the corrosion dissolution rate of hard disk substrate in H2O2-AIBI slurry is increased.Therefore that stronger oxidation ability and a higher corrosion dissolution rate of H2O2-AIBI slurry lead to higher MRR can be concluded.
