Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered play...Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered playing an important role in the above applications bythe kinetic effect.In this work,an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals,as well as their excited states.The excited states,especiallythe atomic nitrogen and oxygen states were less investigated in previous works.The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes,as well as the microwave plasma.Based on the kinetics of molec-ular and atomic emitting states,the line-ratio method is presented to determine the electron density.The N_(2)(337 nm)/O(844 nm)and N_(2)(337 nm)/NO(γ)line ratios are used for the glide arc plasma andmicrowave plasma torch,respectively.Besides,the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges.Combined with the atmospheric pres-sure actinometry method,the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.展开更多
In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges a...In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges and the mean propagation velocity of the guided ionization waves are measured by the capacitive probe method in the discharge region.The space charges in the guided ionization waves are found to increase with the applied voltage,which enhances both the electric field near the streamer head and the propagation velocity.The applicability of the streamer mechanism to the propagation of the guided ionization waves is validated by this electrical diagnostic method.展开更多
The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma has been employed in recent years for the remediation of antibiotic pollution in...The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma has been employed in recent years for the remediation of antibiotic pollution in the environment. In this work, a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline(TC) in water. The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance. The discharge characteristics, chemical species’ concentration, and degradation rates at different parameters were systematically studied. Under the optimized conditions(working gas was pure oxygen, liquid flow rate was 100 mL/min, gas flow rate was 1 L/min,voltage was 20 kV, single treatment), TC was removed beyond 70% in a single flow treatment with an energy efficiency of 145 mg/(kW·h). The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after a single flow under pure oxygen conditions, affording fast TC degradation. Furthermore, long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC. Compared with other plasma treatment systems, this work offers a fast and efficient degradation method, showing significant potential in practical industrial applications.展开更多
This paper presents an experimental investigation into the runaway electron spectrum with a gas diode composed of a rough spherical cathode and plane anode under the excitation of a nanosecond-pulse generator in atmos...This paper presents an experimental investigation into the runaway electron spectrum with a gas diode composed of a rough spherical cathode and plane anode under the excitation of a nanosecond-pulse generator in atmospheric air.The runaway electron beams are measured by a collector covered with aluminum foil with a thickness from 0μm(mesh grid)to 50μm.The energy spectrum is calculated by an improved Tikhonov regularization called the maximum entropy method.The experimental results show that the transition state of the discharge consisted of multiple streamer channels stretched from the cathode with glow-like plasma uniformly distributed over the anode.The number of runaway electrons measured by the collector is in the order of 1010 in atmospheric pressure air with a gap spacing of 5 mm and applied voltages of70–130 kV.The cathode with a rough surface creates a more inhomogeneous electric field and larger emission site for the runaway electrons around the cathode,providing conditions for the coexistence of filamentary streamer and diffuse discharge.The reconstructed spectra show that the energy distribution of the runaway electrons presents a single-peak profile with energies from eU_(m/2)–2 eU_(m/3)(U_(m)is maximal voltage across the gap).展开更多
Partial discharge(PD)is the indicator of the insulation defect in cables.However,the pulse current method,which is widely adopted in land cables,cannot obtain PD signals of high-voltage direct current(HVDC)submarine c...Partial discharge(PD)is the indicator of the insulation defect in cables.However,the pulse current method,which is widely adopted in land cables,cannot obtain PD signals of high-voltage direct current(HVDC)submarine cables due to attenuation and installation position.To detect the PD of the HVDC submarine cable,a PD vibration diagnosis methodology using the embedded fibre based on the heterodyne interferometric phase-sensitive optical time-domain reflectometry(φ-OTDR)and Hilbert demodulation is proposed.The proposed method is verified by a PD experiment with preset defects in 220 kV submarine cables under DC voltage.The results show that the PD can be detected by fibre using the proposed method.Among the three types of PD generated in preset defects in 220 kV submarine cables under DC voltage,the inception voltage of corona discharge,internal airgap discharge and surface discharge is 18,14 and 14 kV,respectively.The peak value of the phase difference in corona discharge is the smallest,and the peak value of the phase difference in surface discharge is close to that in internal airgap discharge.A recommended parameter configuration is provided through statistical analysis,where a modulation frequency of 10 kHz and a pulse width of 100 ns achieve a 10%detection probability at 2.25 km fibre length and 10 m spatial resolution.展开更多
Typical ionization waves(IWs)are observed during the propagation of nanosecond pulsed atmospheric pressure plasma jets(APPJs)with argon flow,combining both the measurement of the axial electric field(Ez)and the tempor...Typical ionization waves(IWs)are observed during the propagation of nanosecond pulsed atmospheric pressure plasma jets(APPJs)with argon flow,combining both the measurement of the axial electric field(Ez)and the temporal resolved optical imaging.The movement of the luminous APPJ head is recognized as the development of the IW front,accompanied with the propagation of the peak electric field.Especially,the radial distribution of Ez transits from a central peak profile before the IW front arrives to a hollow profile after the pass of the IW front.As for the temporal Ez trend,there is a mode transition from the single-peak feature under a low peak voltage to the double-peak feature under a higher peak voltage,indicating the existence of both primary and secondary IWs.The effect of target conditions on the IWs in APPJs is also explored.With a metal target,no residual electric field is observed before imposing the high-voltage pulses.However,with a dielectric target,the residual surface charges generate a back-ground electric field in the opposite direction to that during IW propagation.In the free APPJ(with no target),on the voltage falling edge,a negative electric field drives the electron flow to compensate the positive ions left over during the forward IW propa-gation on the voltage rising edge.展开更多
Operating conditions of film capacitors are complex,and the problem of film insulation failure caused by repetitively pulsed voltage is becoming ever serious.Degradation of the film under repetitively pulsed voltage c...Operating conditions of film capacitors are complex,and the problem of film insulation failure caused by repetitively pulsed voltage is becoming ever serious.Degradation of the film under repetitively pulsed voltage cannot be accurately evaluated by the average breakdown electric field.In this paper,the effects of pulsed electric field and pulse repetition frequency on the breakdown in biaxially oriented polypropylene(BOPP)films are investigated.Three phases of BOPP degradation are proposed based on the voltage amplitude,i.e.,maintenance(M),decline(D),and near-zero(N).Evolution of the BOPP film from degradation to breakdown at different frequencies is presented.Meanwhile,transition of discharge mode and elemental composition of the film are analyzed.Experimental results show continuous heat generation under repetitive microsecond pulses is the dominant factor for degradation of BOPP film.The number of applied pulses and the repetitive stressing time decrease exponentially with increase of frequency.This research can be contributed to the safe and reliable operation of capacitors.展开更多
基金supported by the National Key Lab of Aerospace Power System and Plasma Technology Foundation,China(No.6142202210101)the National Science and Technology Major Project,China(No.J2019-Ⅲ-0013-0056)+2 种基金the National Natural Science Foundation of China(No.52025064)supported by the National Natural Science Foundation of China(Nos.52350072 and 52277167)the Beijing Natural Science Foundation,China(No.1242030)。
文摘Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered playing an important role in the above applications bythe kinetic effect.In this work,an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals,as well as their excited states.The excited states,especiallythe atomic nitrogen and oxygen states were less investigated in previous works.The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes,as well as the microwave plasma.Based on the kinetics of molec-ular and atomic emitting states,the line-ratio method is presented to determine the electron density.The N_(2)(337 nm)/O(844 nm)and N_(2)(337 nm)/NO(γ)line ratios are used for the glide arc plasma andmicrowave plasma torch,respectively.Besides,the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges.Combined with the atmospheric pres-sure actinometry method,the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.
基金supported by National Natural Science Foundation of China(Nos.10775087 and51907190)the State Key Laboratory of NBC Protection for Civilian(SKLNBC 2019–16)。
文摘In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges and the mean propagation velocity of the guided ionization waves are measured by the capacitive probe method in the discharge region.The space charges in the guided ionization waves are found to increase with the applied voltage,which enhances both the electric field near the streamer head and the propagation velocity.The applicability of the streamer mechanism to the propagation of the guided ionization waves is validated by this electrical diagnostic method.
基金supported by the National Science Fund for Distinguished Young Scholars(No.51925703)National Natural Science Foundation of China(Nos.52022096 and 52261145695)。
文摘The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma has been employed in recent years for the remediation of antibiotic pollution in the environment. In this work, a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline(TC) in water. The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance. The discharge characteristics, chemical species’ concentration, and degradation rates at different parameters were systematically studied. Under the optimized conditions(working gas was pure oxygen, liquid flow rate was 100 mL/min, gas flow rate was 1 L/min,voltage was 20 kV, single treatment), TC was removed beyond 70% in a single flow treatment with an energy efficiency of 145 mg/(kW·h). The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after a single flow under pure oxygen conditions, affording fast TC degradation. Furthermore, long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC. Compared with other plasma treatment systems, this work offers a fast and efficient degradation method, showing significant potential in practical industrial applications.
基金supported by the National Science Fund for Distinguished Young Scholars(Grant No.51925703)National Natural Science Foundation of China(Grant Nos.52022096 and 51907190)the Royal Society–Newton Advanced Fellowship,UK(Grant No.NAF\R2\192117)。
文摘This paper presents an experimental investigation into the runaway electron spectrum with a gas diode composed of a rough spherical cathode and plane anode under the excitation of a nanosecond-pulse generator in atmospheric air.The runaway electron beams are measured by a collector covered with aluminum foil with a thickness from 0μm(mesh grid)to 50μm.The energy spectrum is calculated by an improved Tikhonov regularization called the maximum entropy method.The experimental results show that the transition state of the discharge consisted of multiple streamer channels stretched from the cathode with glow-like plasma uniformly distributed over the anode.The number of runaway electrons measured by the collector is in the order of 1010 in atmospheric pressure air with a gap spacing of 5 mm and applied voltages of70–130 kV.The cathode with a rough surface creates a more inhomogeneous electric field and larger emission site for the runaway electrons around the cathode,providing conditions for the coexistence of filamentary streamer and diffuse discharge.The reconstructed spectra show that the energy distribution of the runaway electrons presents a single-peak profile with energies from eU_(m/2)–2 eU_(m/3)(U_(m)is maximal voltage across the gap).
基金the National Natural Science Foundation of China(Grants.52437007,52550007 and 52277167).
文摘Partial discharge(PD)is the indicator of the insulation defect in cables.However,the pulse current method,which is widely adopted in land cables,cannot obtain PD signals of high-voltage direct current(HVDC)submarine cables due to attenuation and installation position.To detect the PD of the HVDC submarine cable,a PD vibration diagnosis methodology using the embedded fibre based on the heterodyne interferometric phase-sensitive optical time-domain reflectometry(φ-OTDR)and Hilbert demodulation is proposed.The proposed method is verified by a PD experiment with preset defects in 220 kV submarine cables under DC voltage.The results show that the PD can be detected by fibre using the proposed method.Among the three types of PD generated in preset defects in 220 kV submarine cables under DC voltage,the inception voltage of corona discharge,internal airgap discharge and surface discharge is 18,14 and 14 kV,respectively.The peak value of the phase difference in corona discharge is the smallest,and the peak value of the phase difference in surface discharge is close to that in internal airgap discharge.A recommended parameter configuration is provided through statistical analysis,where a modulation frequency of 10 kHz and a pulse width of 100 ns achieve a 10%detection probability at 2.25 km fibre length and 10 m spatial resolution.
基金the National Science Fund for Distinguished Young Scholars(Grant No.51925703)the National Natural Science Foundation of China(Grant Nos.51637010,51777204,51907190,and 52011530026)+1 种基金the Royal Society-Newton Advanced Fellowship,UK(Grant No.NAF\R2\192117)the build-up of the E-FISH system in June 2018,supported by the Chinese Academy of Sciences President’s International Fellowship Initiative under contract 2018VEA0004.
文摘Typical ionization waves(IWs)are observed during the propagation of nanosecond pulsed atmospheric pressure plasma jets(APPJs)with argon flow,combining both the measurement of the axial electric field(Ez)and the temporal resolved optical imaging.The movement of the luminous APPJ head is recognized as the development of the IW front,accompanied with the propagation of the peak electric field.Especially,the radial distribution of Ez transits from a central peak profile before the IW front arrives to a hollow profile after the pass of the IW front.As for the temporal Ez trend,there is a mode transition from the single-peak feature under a low peak voltage to the double-peak feature under a higher peak voltage,indicating the existence of both primary and secondary IWs.The effect of target conditions on the IWs in APPJs is also explored.With a metal target,no residual electric field is observed before imposing the high-voltage pulses.However,with a dielectric target,the residual surface charges generate a back-ground electric field in the opposite direction to that during IW propagation.In the free APPJ(with no target),on the voltage falling edge,a negative electric field drives the electron flow to compensate the positive ions left over during the forward IW propa-gation on the voltage rising edge.
基金supported in part by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid under Grant U2166215.
文摘Operating conditions of film capacitors are complex,and the problem of film insulation failure caused by repetitively pulsed voltage is becoming ever serious.Degradation of the film under repetitively pulsed voltage cannot be accurately evaluated by the average breakdown electric field.In this paper,the effects of pulsed electric field and pulse repetition frequency on the breakdown in biaxially oriented polypropylene(BOPP)films are investigated.Three phases of BOPP degradation are proposed based on the voltage amplitude,i.e.,maintenance(M),decline(D),and near-zero(N).Evolution of the BOPP film from degradation to breakdown at different frequencies is presented.Meanwhile,transition of discharge mode and elemental composition of the film are analyzed.Experimental results show continuous heat generation under repetitive microsecond pulses is the dominant factor for degradation of BOPP film.The number of applied pulses and the repetitive stressing time decrease exponentially with increase of frequency.This research can be contributed to the safe and reliable operation of capacitors.
