The results of an experimental investigation of explosive-emission plasma dynamics in an ion diode with self-magnetic insulation are presented. The investigations were accomplished at the TEMP-4M accelerator set in a ...The results of an experimental investigation of explosive-emission plasma dynamics in an ion diode with self-magnetic insulation are presented. The investigations were accomplished at the TEMP-4M accelerator set in a mode of double pulse formation. Plasma behaviour in the anode-cathode gap was analyzed according to both the current-voltage characteristics of the diode （time resolution of 0.5 ns） and thermal imprints on a target （spatial resolution of 0.8 mm）. It was shown that when plasma formation at the potential electrode was complete, and up until the second （positive） pulse, the explosive-emission plasma expanded across the anode-cathode gap with a speed of 1.3±0.2 cm/μs. After the voltage polarity at the potential electrode was reversed （second pulse）, the plasma erosion in the anode-cathode gap （similar to the effect of a plasma opening switch） occurred. During the generation of an ion beam the size of the anode-cathode gap spacing was determined by the thickness of the plasma layer on the potential electrode and the layer thickness of the electrons drifting along the grounded electrode.展开更多
The surface of nodular cast iron （NCI） with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc （PTA） to induce a chilled structure with high hardness and favorable wear resistance. T...The surface of nodular cast iron （NCI） with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc （PTA） to induce a chilled structure with high hardness and favorable wear resistance. The effect of scanning speed on the microstructure, micro-hardness distribution, and wear properties of PTA-remelted specimens was systematically investigated. Microstructural characterization in-dicated that the PTA remelting treatment could dissolve most graphite nodules and that the crystallized primary austenite dendrites were transformed into cementite, martensite, an interdendritic network of ledeburite eutectic, and certain residual austenite during rapid solidifica-tion. The dimensions of the remelted zone and its dendrites increase with decreased scanning speed. The microhardness of the remelted zone varied in the range of 650 HV0.2 to 820 HV0.2, which is approximately 2.3-3.1 times higher than the hardness of the substrate. The wear re-sistance of NCI was also significantly improved after the PTA remelting treatment.展开更多
Relighting of jet engines at high altitudes is very difficult because of the high velocity, low pressure, and low tempera- ture of the inlet airflow. Successful ignition needs sufficient ignition energy to generate a ...Relighting of jet engines at high altitudes is very difficult because of the high velocity, low pressure, and low tempera- ture of the inlet airflow. Successful ignition needs sufficient ignition energy to generate a spark kernel to induce a so-called critical flame initiation radius. However, at high altitudes with high-speed inlet airflow, the critical flame initiation radius becomes larger; therefore, traditional ignition technologies such as a semiconductor igniter （SI） become infeasible for use in high-altitude relighting of jet engines. In this study, to generate a large spark kernel to achieve successful ignition with high-speed inlet airflow, a new type of multichannel plasma igniter （MCPI） is proposed. Experiments on the electrical char- acteristics of the MCPI and SI were conducted under normal and sub-atmospheric pressures （P = 10-100 kPa）. Ignition experiments for the MCPI and SI with a kerosene/air mixture in a triple-swirler combustor under different velocities of inlet airflow （60-110 m/s）, with a temperature of 473 K at standard atmospheric pressure, were investigated. Results show that the MCPI generates much more arc discharge energy than the SI under a constant pressure; for example, the MCPI generated 6.93% and 16.05 % more arc discharge energy than that of the SI at 30 kPa and 50 kPa, respectively. Compared to the SI, the MCPI generates a larger area and height of plasma heating zone, and induces a much larger initial spark kernel. Furthermore, the lean ignition limit of the MCPI and SI decreases with an increase in the velocity of the inlet airflow, and the maximum velocity of inlet airflow where the SI and MCPI can achieve successful and reliable ignition is 88.7 m/s and 102.2 m/s, respectively. Therefore, the MCPI has the advantage of achieving successful ignition with high-speed inlet airflow and extends the average ignition speed boundary of the kerosene/air mixture by 15.2%.展开更多
The results of an experimental investigation of the plasma dynamics in a magnetically insu- lated ion diode in bipolar-pulse mode are presented. The experiments were done at the pulsed TEMP-4M accelerator by formation...The results of an experimental investigation of the plasma dynamics in a magnetically insu- lated ion diode in bipolar-pulse mode are presented. The experiments were done at the pulsed TEMP-4M accelerator by formation of a first negative pulse (100 ns, 150-200 kV) and a second positive pulse (80 ns, 250-300 kV). The voltage-current diode characteristics were used to analyze the plasma behavior in the anode- cathode gap. It is shown that, during the first pulse, a discrete emissive surface is formed on the graphite potential electrode and a plasma forms by explosive-emission, which before the second pulse comes, fills the whole working surface of the electrode and spreads to the anode-cathode gap. An analytical expression is obtained for the total current in the cellular structure approximation. It is shown that the current build-up for a cathode surface with dis- crete emitting centers is described satisfac- torily by a modified Child-Langmuir formula wi- th a form factor decreasing from F = 6 to 1. It is found that, once plasma formation at the gra- phite potential electrode is complete and until the second positive pulse, the plasma speed is constant and equals 1.3 ±0.2 cm/μs.展开更多
7A52 aluminum alloy was cut with an integrated equipment for welding and cutting using water vapor plasma arc. Various cutting mediums were tested. The arc force, electron density and cutting speed in each medium were...7A52 aluminum alloy was cut with an integrated equipment for welding and cutting using water vapor plasma arc. Various cutting mediums were tested. The arc force, electron density and cutting speed in each medium were tested and calculated. The fractography and microstructure of the cuts were also analyzed. Results show that the arc force, electron density and cutting speed #wreased with increasing acetone concentration. However, above a certain value （40%）, higher acetone concentrations contribute little to the arc force and cutting speed. The microstrueture of material near the cut was greatly influenced by the water vapor plasma arc. While the microstructure of the material beyond 10 mm from the cut was hardly influenced by the cutting heat. It was demonstrated that the water vapor plasma arc can be used for cutting of aluminum alloys in open field or emergency situations.展开更多
The effect of various process parameters like welding current, torch height, welding speed and plasma gas flow rate on front melting width, back melting width and weld reinforcement of plasma arc welding on aluminum a...The effect of various process parameters like welding current, torch height, welding speed and plasma gas flow rate on front melting width, back melting width and weld reinforcement of plasma arc welding on aluminum alloy is investigated by using factorial design approach. Variable polarity plasma arc welding is used for welding aluminum alloy. Trail experiments are conducted and the limits of the input process parameters are decided. Two levels and four input process parameters are chosen and experiments are conducted as per typical design matrix considering full factorial design. Total sixteen experiments are conducted and output responses are measured. The coefficients are calculated by using regression analysis and the mathematical models are constructed. By using the mathematical models the main and interaction effect of various process parameters on weld quality is studied.展开更多
在Cu基底上,采用催化热解生长法制备了石墨化程度较高的碳纳米管阴极.当电子束能量达到1 Me V、梯度约为60 k V/ns时,发射束流强度达到15 k A,相应密度约为1 k A/cm2,束压、束流响应快,波形间几无延时.以50 Hz重复频率、约15 GW束功率...在Cu基底上,采用催化热解生长法制备了石墨化程度较高的碳纳米管阴极.当电子束能量达到1 Me V、梯度约为60 k V/ns时,发射束流强度达到15 k A,相应密度约为1 k A/cm2,束压、束流响应快,波形间几无延时.以50 Hz重复频率、约15 GW束功率强流发射时,波形稳定,随着频率增高,稳定性降低.发射炮次达1000后,表面形貌保持完整、界面无脱附;束压与束流基本满足空间电荷限制定律,发射机理属闪络型等离子体发射,等离子体速度约为3.9 cm/μs.展开更多
基金supported by the Federal Target Program "Scientific manpower of innovative Russia" during the years 2009-2013,under Project (No.P943)
文摘The results of an experimental investigation of explosive-emission plasma dynamics in an ion diode with self-magnetic insulation are presented. The investigations were accomplished at the TEMP-4M accelerator set in a mode of double pulse formation. Plasma behaviour in the anode-cathode gap was analyzed according to both the current-voltage characteristics of the diode （time resolution of 0.5 ns） and thermal imprints on a target （spatial resolution of 0.8 mm）. It was shown that when plasma formation at the potential electrode was complete, and up until the second （positive） pulse, the explosive-emission plasma expanded across the anode-cathode gap with a speed of 1.3±0.2 cm/μs. After the voltage polarity at the potential electrode was reversed （second pulse）, the plasma erosion in the anode-cathode gap （similar to the effect of a plasma opening switch） occurred. During the generation of an ion beam the size of the anode-cathode gap spacing was determined by the thickness of the plasma layer on the potential electrode and the layer thickness of the electrons drifting along the grounded electrode.
基金financially supported by the Key Project of China National Erzhong Group Co.(No.2012zx04010-081)
文摘The surface of nodular cast iron （NCI） with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc （PTA） to induce a chilled structure with high hardness and favorable wear resistance. The effect of scanning speed on the microstructure, micro-hardness distribution, and wear properties of PTA-remelted specimens was systematically investigated. Microstructural characterization in-dicated that the PTA remelting treatment could dissolve most graphite nodules and that the crystallized primary austenite dendrites were transformed into cementite, martensite, an interdendritic network of ledeburite eutectic, and certain residual austenite during rapid solidifica-tion. The dimensions of the remelted zone and its dendrites increase with decreased scanning speed. The microhardness of the remelted zone varied in the range of 650 HV0.2 to 820 HV0.2, which is approximately 2.3-3.1 times higher than the hardness of the substrate. The wear re-sistance of NCI was also significantly improved after the PTA remelting treatment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91541120,11472306,51336011,and 91641204)
文摘Relighting of jet engines at high altitudes is very difficult because of the high velocity, low pressure, and low tempera- ture of the inlet airflow. Successful ignition needs sufficient ignition energy to generate a spark kernel to induce a so-called critical flame initiation radius. However, at high altitudes with high-speed inlet airflow, the critical flame initiation radius becomes larger; therefore, traditional ignition technologies such as a semiconductor igniter （SI） become infeasible for use in high-altitude relighting of jet engines. In this study, to generate a large spark kernel to achieve successful ignition with high-speed inlet airflow, a new type of multichannel plasma igniter （MCPI） is proposed. Experiments on the electrical char- acteristics of the MCPI and SI were conducted under normal and sub-atmospheric pressures （P = 10-100 kPa）. Ignition experiments for the MCPI and SI with a kerosene/air mixture in a triple-swirler combustor under different velocities of inlet airflow （60-110 m/s）, with a temperature of 473 K at standard atmospheric pressure, were investigated. Results show that the MCPI generates much more arc discharge energy than the SI under a constant pressure; for example, the MCPI generated 6.93% and 16.05 % more arc discharge energy than that of the SI at 30 kPa and 50 kPa, respectively. Compared to the SI, the MCPI generates a larger area and height of plasma heating zone, and induces a much larger initial spark kernel. Furthermore, the lean ignition limit of the MCPI and SI decreases with an increase in the velocity of the inlet airflow, and the maximum velocity of inlet airflow where the SI and MCPI can achieve successful and reliable ignition is 88.7 m/s and 102.2 m/s, respectively. Therefore, the MCPI has the advantage of achieving successful ignition with high-speed inlet airflow and extends the average ignition speed boundary of the kerosene/air mixture by 15.2%.
文摘The results of an experimental investigation of the plasma dynamics in a magnetically insu- lated ion diode in bipolar-pulse mode are presented. The experiments were done at the pulsed TEMP-4M accelerator by formation of a first negative pulse (100 ns, 150-200 kV) and a second positive pulse (80 ns, 250-300 kV). The voltage-current diode characteristics were used to analyze the plasma behavior in the anode- cathode gap. It is shown that, during the first pulse, a discrete emissive surface is formed on the graphite potential electrode and a plasma forms by explosive-emission, which before the second pulse comes, fills the whole working surface of the electrode and spreads to the anode-cathode gap. An analytical expression is obtained for the total current in the cellular structure approximation. It is shown that the current build-up for a cathode surface with dis- crete emitting centers is described satisfac- torily by a modified Child-Langmuir formula wi- th a form factor decreasing from F = 6 to 1. It is found that, once plasma formation at the gra- phite potential electrode is complete and until the second positive pulse, the plasma speed is constant and equals 1.3 ±0.2 cm/μs.
文摘7A52 aluminum alloy was cut with an integrated equipment for welding and cutting using water vapor plasma arc. Various cutting mediums were tested. The arc force, electron density and cutting speed in each medium were tested and calculated. The fractography and microstructure of the cuts were also analyzed. Results show that the arc force, electron density and cutting speed #wreased with increasing acetone concentration. However, above a certain value （40%）, higher acetone concentrations contribute little to the arc force and cutting speed. The microstrueture of material near the cut was greatly influenced by the water vapor plasma arc. While the microstructure of the material beyond 10 mm from the cut was hardly influenced by the cutting heat. It was demonstrated that the water vapor plasma arc can be used for cutting of aluminum alloys in open field or emergency situations.
文摘The effect of various process parameters like welding current, torch height, welding speed and plasma gas flow rate on front melting width, back melting width and weld reinforcement of plasma arc welding on aluminum alloy is investigated by using factorial design approach. Variable polarity plasma arc welding is used for welding aluminum alloy. Trail experiments are conducted and the limits of the input process parameters are decided. Two levels and four input process parameters are chosen and experiments are conducted as per typical design matrix considering full factorial design. Total sixteen experiments are conducted and output responses are measured. The coefficients are calculated by using regression analysis and the mathematical models are constructed. By using the mathematical models the main and interaction effect of various process parameters on weld quality is studied.
文摘在Cu基底上,采用催化热解生长法制备了石墨化程度较高的碳纳米管阴极.当电子束能量达到1 Me V、梯度约为60 k V/ns时,发射束流强度达到15 k A,相应密度约为1 k A/cm2,束压、束流响应快,波形间几无延时.以50 Hz重复频率、约15 GW束功率强流发射时,波形稳定,随着频率增高,稳定性降低.发射炮次达1000后,表面形貌保持完整、界面无脱附;束压与束流基本满足空间电荷限制定律,发射机理属闪络型等离子体发射,等离子体速度约为3.9 cm/μs.
