In this paper,nitrogen dielectric barrier discharge（DBD） plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow（FN） in the range of 0-1...In this paper,nitrogen dielectric barrier discharge（DBD） plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow（FN） in the range of 0-1 m3/h,the plasma optical emission spectra（OES） were measured and studied.The vibration（T_（vib）） and rotation temperature（T_（rot）） of nitrogen were obtained,by fitting the rovibronic bands of N_2（C^3∏_u-B^3∏_g,0-1）,and by the Boltzmann plot method for purposes of comparison.T_（vib） increased up to 2481 K with increasing nitrogen flow till0.2 m3/h,and then decreased with further increasing FN,while Trot decreased monotonously and approached to-350 K for FN ≥ 0.6 m^3/h.The intensity of N_2（C^3∏_u-B^3∏_g,0-0,1-0,0-3） and N_2~＋（B^2∑_u~＋-X^2Σ_g~＋,0-0） exhibited similar evolution with increasing FN to those of the T_（vib） and Trot,respectively.The discharge photos revealed that the discharge filaments gradually decreased with increasing FN,and eventually disappeared,which implied that a discharge mode transition emerged with increasing FN.The possible mechanism for the discharge mode transition is studied in detail according to the vibration（T_（vib）） and rotation temperature（T_（rot）） of nitrogen.展开更多
A group of the stainless steel laser welding was performed using continuous wave （CW） laser and pulsed laser. During the welding process the laser induced plasma behavior was recorded by high-speed video camera, whi...A group of the stainless steel laser welding was performed using continuous wave （CW） laser and pulsed laser. During the welding process the laser induced plasma behavior was recorded by high-speed video camera, while the plasma spectrum was acquired by the spectrometer. The plasma temperature was calculated based on the spectroscopic analysis of the optical emission and the results show that different output mode of laser source led to big difference of plasma temperature. The high-speed video images showed that the plasma was very steady and kept certain strength in CW laser welding, while the plasma erupted a little later after the laser peak arising during the pulsed laser welding. During a period of time about 2 ms just after the laser peak arising during the pulsed laser welding, much more laser energy reached the workpiece. This made the workpicce fully penetrated with a lower average power.展开更多
基金supported by National Natural Science Foundation of China(Nos.11475040,11375041)the Fundamental Research Funds for the Central Universities(No.DUT14ZD[G]04)
文摘In this paper,nitrogen dielectric barrier discharge（DBD） plasma was generated in a quartz tube with coaxial wire-cylinder electrodes at atmospheric pressure.By varying the nitrogen gas flow（FN） in the range of 0-1 m3/h,the plasma optical emission spectra（OES） were measured and studied.The vibration（T_（vib）） and rotation temperature（T_（rot）） of nitrogen were obtained,by fitting the rovibronic bands of N_2（C^3∏_u-B^3∏_g,0-1）,and by the Boltzmann plot method for purposes of comparison.T_（vib） increased up to 2481 K with increasing nitrogen flow till0.2 m3/h,and then decreased with further increasing FN,while Trot decreased monotonously and approached to-350 K for FN ≥ 0.6 m^3/h.The intensity of N_2（C^3∏_u-B^3∏_g,0-0,1-0,0-3） and N_2~＋（B^2∑_u~＋-X^2Σ_g~＋,0-0） exhibited similar evolution with increasing FN to those of the T_（vib） and Trot,respectively.The discharge photos revealed that the discharge filaments gradually decreased with increasing FN,and eventually disappeared,which implied that a discharge mode transition emerged with increasing FN.The possible mechanism for the discharge mode transition is studied in detail according to the vibration（T_（vib）） and rotation temperature（T_（rot）） of nitrogen.
基金This project is supported by Natural Science Foundation of Tianjin （11JCYBJC06100） and State Key Lab of Advanced Welding and Joining （ AWPT-M12-08 ）.
文摘A group of the stainless steel laser welding was performed using continuous wave （CW） laser and pulsed laser. During the welding process the laser induced plasma behavior was recorded by high-speed video camera, while the plasma spectrum was acquired by the spectrometer. The plasma temperature was calculated based on the spectroscopic analysis of the optical emission and the results show that different output mode of laser source led to big difference of plasma temperature. The high-speed video images showed that the plasma was very steady and kept certain strength in CW laser welding, while the plasma erupted a little later after the laser peak arising during the pulsed laser welding. During a period of time about 2 ms just after the laser peak arising during the pulsed laser welding, much more laser energy reached the workpiece. This made the workpicce fully penetrated with a lower average power.
