The role of cold nitrogen gas and oil mist on tool wear and surface roughness is investigated in turning the K424 nickel-base super alloy with Sialon and SiC whisker-reinforced alumina ceramic tools. A new cooling sys...The role of cold nitrogen gas and oil mist on tool wear and surface roughness is investigated in turning the K424 nickel-base super alloy with Sialon and SiC whisker-reinforced alumina ceramic tools. A new cooling system is developed and used to lower the temperature of the compressed nitrogen gas. Experiments are performed in three different cooling/lubrication modes, i.e. the dry cutting, the cold nitrogen gas （CNG）, and the cold nitrogen gas and oil mist （CNGOM）. Experimental results show that the depth-of-cut notching severely limits the tool life in all the cooling/lubrication modes. Compared with the dry cutting, the use of CNG and CNGOMcan yield higher wear rate of depth-of-cut notching and worse surface finish.展开更多
The use of metalworking fluids during machining can generate oil mist and endanger the health of workers.In order to study the characteristics and emission laws of oil mist generated by machining,this study constructe...The use of metalworking fluids during machining can generate oil mist and endanger the health of workers.In order to study the characteristics and emission laws of oil mist generated by machining,this study constructed a test bench to simulate the turning process.Parameters affecting the oil mist generated in the minimum quantity lubrication(MQL)mode and flood cooling mode were studied by means of single-factor experiments,and the formation mechanisms of oil mist were analyzed.The results show that the oil mist generated by the MQL system has two main sources,the initial escape of oil mist into the air and the evaporation/condensation of oil mist.The centrifugation has almost no effect on oil mist formation in the MQL mode.The mass concentration of oil mist generated by the MQL system is proportional to the cutting oil flow rate.When the work-piece is at room temperature,increasing the air supply pressure and nozzle distance,increases the oil mist mass concentration.For the flood cooling mode,the concentration of centrifugal aerosol is linearly and positively correlated with the relative centrifugal force generated by the work-piece,and the coefficient of determination(R 2)is above 0.97.The oil mist mass concentrations in MQL mode is 8.33 mg/m^(3)~305.88 mg/m^(3).The MMD and SMD are 0.74μm to 4.42μm and 0.31μm to 2.14μm,respectively.The oil mist mass concentrations in flood cooling mode is 0.2 mg/m^(3)~22.42 mg/m^(3).The MMD and SMD are 1.81μm to 6.58μm and 0.45μm to 5.13μm,respectively.展开更多
The article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the ar...The article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the article suggests ways to reduce the amount of oil mist. For their implementation, a calculation methodology based on the substitution scheme of the hydraulic path of the bearing support unit is created which takes into account the design features of the bearing and the parameters of the environment around the oil bath. The methodology employed is presented. The numerical method of modelling the aerodynamic fields of the entire hydro generator is used to estimate the air flows and pressures in the oil bath zone of the thrust bearing. Additionally, the method made it possible to track suspected oil particles that could get from the thrust-bearing bath into the surrounding area of the generator. Measures are proposed to reduce the level of oil mist through the competent design of the oil vapour removal system from the bearing bath.展开更多
文摘The role of cold nitrogen gas and oil mist on tool wear and surface roughness is investigated in turning the K424 nickel-base super alloy with Sialon and SiC whisker-reinforced alumina ceramic tools. A new cooling system is developed and used to lower the temperature of the compressed nitrogen gas. Experiments are performed in three different cooling/lubrication modes, i.e. the dry cutting, the cold nitrogen gas （CNG）, and the cold nitrogen gas and oil mist （CNGOM）. Experimental results show that the depth-of-cut notching severely limits the tool life in all the cooling/lubrication modes. Compared with the dry cutting, the use of CNG and CNGOMcan yield higher wear rate of depth-of-cut notching and worse surface finish.
基金supported by National Key Research and Develop-ment Plan of the Ministry of Science and Technology of China(Grant No.2018YFC0705300)National Science Foundation of China(Grant No.51878442).
文摘The use of metalworking fluids during machining can generate oil mist and endanger the health of workers.In order to study the characteristics and emission laws of oil mist generated by machining,this study constructed a test bench to simulate the turning process.Parameters affecting the oil mist generated in the minimum quantity lubrication(MQL)mode and flood cooling mode were studied by means of single-factor experiments,and the formation mechanisms of oil mist were analyzed.The results show that the oil mist generated by the MQL system has two main sources,the initial escape of oil mist into the air and the evaporation/condensation of oil mist.The centrifugation has almost no effect on oil mist formation in the MQL mode.The mass concentration of oil mist generated by the MQL system is proportional to the cutting oil flow rate.When the work-piece is at room temperature,increasing the air supply pressure and nozzle distance,increases the oil mist mass concentration.For the flood cooling mode,the concentration of centrifugal aerosol is linearly and positively correlated with the relative centrifugal force generated by the work-piece,and the coefficient of determination(R 2)is above 0.97.The oil mist mass concentrations in MQL mode is 8.33 mg/m^(3)~305.88 mg/m^(3).The MMD and SMD are 0.74μm to 4.42μm and 0.31μm to 2.14μm,respectively.The oil mist mass concentrations in flood cooling mode is 0.2 mg/m^(3)~22.42 mg/m^(3).The MMD and SMD are 1.81μm to 6.58μm and 0.45μm to 5.13μm,respectively.
文摘The article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the article suggests ways to reduce the amount of oil mist. For their implementation, a calculation methodology based on the substitution scheme of the hydraulic path of the bearing support unit is created which takes into account the design features of the bearing and the parameters of the environment around the oil bath. The methodology employed is presented. The numerical method of modelling the aerodynamic fields of the entire hydro generator is used to estimate the air flows and pressures in the oil bath zone of the thrust bearing. Additionally, the method made it possible to track suspected oil particles that could get from the thrust-bearing bath into the surrounding area of the generator. Measures are proposed to reduce the level of oil mist through the competent design of the oil vapour removal system from the bearing bath.
