Based on two typical laminar plasma torches (LPT), i.e. a multi-electrode plasma torch (MEPT) with segmented anode structure and a two-electrode plasma torch (TEPT) with conventional structure, this paper studie...Based on two typical laminar plasma torches (LPT), i.e. a multi-electrode plasma torch (MEPT) with segmented anode structure and a two-electrode plasma torch (TEPT) with conventional structure, this paper studied the influence of the LPTs construction on the jet characteristics. Experiments were designed to measure their arc voltage, jet length, thermal efficiency and specific enthalpy using a home-made data acquisition system. With them, the jet characteristics of the two different LPTs were compared in detail. Results show that different plasma torch construction leads to distinctively different characteristics of the generated plasma jet. Based on the different jet characteristics, a plasma torch with appropriate construction could be used to meet the different application requirements.展开更多
Thermal steam plasma jet is promising for applications in environmental industries due to its distinctive characteristics of high enthalpy and high chemical reactivity. However, the performance of the steam plasma tor...Thermal steam plasma jet is promising for applications in environmental industries due to its distinctive characteristics of high enthalpy and high chemical reactivity. However, the performance of the steam plasma torch for its generation is limited by the problems of the large arc voltage fluctuation and serious erosion of the electrodes. In this study, a gas-stabilized steam plasma torch which can operate continuously and stably was designed. Experiments were conducted to reveal the effect of the different working parameters, including the anode diameter, the cooling water temperature, the arc current and the steam flow rate, on its Volt-Ampere characteristics, arc voltage fluctuation, thermal efficiency, jet characteristics and electrodes erosion. Results showed that the use of hot water to cool the electrodes can effectively prevent the condensation of steam on the inner wall of the electrodes, thus significantly reducing the arc voltage fluctuations and electrodes erosion. This is crucial for increasing the working life of the electrodes and ensuring long-term stability of the steam plasma torch. In addition, suitable anode diameter can greatly reduce the arc voltage fluctuation of the steam plasma torch and effectively improve the stability of the steam plasma jet. Furthermore, high arc current can effectively reduce the fluctuations of the arc voltage and increase the length and the volume of the steam plasma jet. Finally, using steam as the plasma forming gas can achieve higher thermal efficiency compared to air. An ideal thermal efficiency can be achieved by properly reducing the arc current and increasing the steam flow rate.展开更多
Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compa...Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode(NRE) and doublering electrode(DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power,making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient.In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.展开更多
The measured results show that the overexpanded supersonic jet velocity produced by low stagnation pressure (0.53 MPa) attenuates quickly, deviates greatly with smaller impact area and large energy loss. According to ...The measured results show that the overexpanded supersonic jet velocity produced by low stagnation pressure (0.53 MPa) attenuates quickly, deviates greatly with smaller impact area and large energy loss. According to the measured results and the analysis of lashing energy of jet on the bath, the technological parameters of nitrogen flow in slag splashing were proposed.展开更多
In order to study the interaction between two independent jets, a three-dimensional(3D) transient mathematical model is developed to investigate the flow field and acoustic properties of the two-stream jets. The res...In order to study the interaction between two independent jets, a three-dimensional(3D) transient mathematical model is developed to investigate the flow field and acoustic properties of the two-stream jets. The results are compared with those of the single-stream jet at Mach number 0.9 and Reynolds number 3600. The large eddy simulation(LES) with dynamic Smagorinsky sub-grid scale(SGS) approach is used to simulate the turbulent jet flow structure. The acoustic field is evaluated by the Ffowcs Williams–Hawkings(FW-H) integral equation. Considering the compressibility of high-speed gas jets, the density-based explicit formulation is adopted to solve the governing equations. Meanwhile, the viscosity is approximated by using the Sutherland kinetic theory. The predicted flow characteristics as well as the acoustic properties show that they are in good agreement with the existing experimental and numerical results under the same flow conditions available in the literature. The results indicate that the merging phenomenon of the dual-jet is triggered by the deflection mechanism of the Coanda effect, which sequentially introduces additional complexity and instability of flow structure. One of the main factors affecting the dual-jet merging is the aperture ratio, which has a direct influence on the potential core and surrounding flow fluctuation. The analysis on the noise pollution reveals that the potential core plays a fundamental role in noise emission while the additional mixing noise makes less contribution than the single jet noise. The overall sound pressure level(OASPL) profiles have a directive property, suggesting an approximate 25° deflection from the streamwise direction, however, shifting toward lateral direction of about 10° to 15° in the dual-jet. The conclusion obtained in this study can provide valuable data to guide the development of manufacturing-green technology in the multi-jet applications.展开更多
The large eddy simulation(LES) of the flow characteristics in an annular jet pump(AJP) is conducted, and the flow characteristics are systematically analyzed from both time-averaged and instantaneous aspects. The ...The large eddy simulation(LES) of the flow characteristics in an annular jet pump(AJP) is conducted, and the flow characteristics are systematically analyzed from both time-averaged and instantaneous aspects. The jet expansion, the velocity distribution and the energy are considered to analyze the time-averaged evolution of the flow field in the AJP. The transient flow characteristics can also be acquired from the analysis of the turbulence intensity and the Reynolds stress. The simulation demonstrates that in the time-averaged characteristics, the potential cores increase linearly with the increase of the flow ratio. With the flow development, the jet half-width gradually increases and the residual energy coefficient decreases. Compared with the distribution of the time-averaged axial velocity, that of the instantaneous velocity is more complex and disorderly. The high intensity of the axial turbulence mainly occurs in the mixing layer and the near-wall regions of the diffuser. The annular distribution of the Reynolds stress is mainly in the mixing layer and the recirculation region. There is a low-stress zone between the mixing layer and the high-stress region in the wall-boundary layer. The intensity of the spanwise vortexes is larger than that of the streamwise vortexes, and therefore, the former make greater contribution to the total vorticity. This research provides a better understanding of the flow characteristics in the AJP.展开更多
The maximum rise-height,zero-buoyancy height,thickness of the spreading layer,minimum dilution and the height of the lower edge of the spreading layer are the important characteristic quantities of buoyant jets in str...The maximum rise-height,zero-buoyancy height,thickness of the spreading layer,minimum dilution and the height of the lower edge of the spreading layer are the important characteristic quantities of buoyant jets in stratified ambients.The scaling law is derived by the dimensional analysis of the influence factor on a buoyant jet.The characteristic quantities are found to converge to a single line under the unified scaling law.The correlation of the predicted results and experimental data is given.展开更多
Coherent jets are widely used in electric are furnace (EAF) steelmaking to increase the oxygen utilization and chemical reaction rates. However, the influence of fuel gas combustion on jet behavior is not fully unde...Coherent jets are widely used in electric are furnace (EAF) steelmaking to increase the oxygen utilization and chemical reaction rates. However, the influence of fuel gas combustion on jet behavior is not fully understood yet. The flow and combustion characteristics of a coherent jet were thus investigated at steelmaking temperature using Fluent software, and a detailed chemical kinetic reaction mecha- nism was used in the combustion reaction model. The axial velocity and total temperature of the supersonic jet were measured via hot state experiments. The simulation results were compared with the experimental data and the empirical jet model proposed by Ito and Muchi and good consistency was obtained. The research results indicated that the potential core length of the coherent jet can be prolonged by optimizing the combustion effect of the fuel gas. Besides, the behavior of the supersonic jet in the subsonic section was also investigated, as it is an important factor for controlling the position of the oxygen lance. The investigation indicated that the attenuation of the coherent jet is more notable than that of the conventional jet in the subsonic section.展开更多
基金supported by National Natural Science Foundation of China(No.51405315)the Laboratory of Precision Manufacturing Technology,CAEP(No.KF15002)
文摘Based on two typical laminar plasma torches (LPT), i.e. a multi-electrode plasma torch (MEPT) with segmented anode structure and a two-electrode plasma torch (TEPT) with conventional structure, this paper studied the influence of the LPTs construction on the jet characteristics. Experiments were designed to measure their arc voltage, jet length, thermal efficiency and specific enthalpy using a home-made data acquisition system. With them, the jet characteristics of the two different LPTs were compared in detail. Results show that different plasma torch construction leads to distinctively different characteristics of the generated plasma jet. Based on the different jet characteristics, a plasma torch with appropriate construction could be used to meet the different application requirements.
基金the support of the Key Research Program of the Sichuan Provincial Science and Technology Department,China(No.2017GZ0096)
文摘Thermal steam plasma jet is promising for applications in environmental industries due to its distinctive characteristics of high enthalpy and high chemical reactivity. However, the performance of the steam plasma torch for its generation is limited by the problems of the large arc voltage fluctuation and serious erosion of the electrodes. In this study, a gas-stabilized steam plasma torch which can operate continuously and stably was designed. Experiments were conducted to reveal the effect of the different working parameters, including the anode diameter, the cooling water temperature, the arc current and the steam flow rate, on its Volt-Ampere characteristics, arc voltage fluctuation, thermal efficiency, jet characteristics and electrodes erosion. Results showed that the use of hot water to cool the electrodes can effectively prevent the condensation of steam on the inner wall of the electrodes, thus significantly reducing the arc voltage fluctuations and electrodes erosion. This is crucial for increasing the working life of the electrodes and ensuring long-term stability of the steam plasma torch. In addition, suitable anode diameter can greatly reduce the arc voltage fluctuation of the steam plasma torch and effectively improve the stability of the steam plasma jet. Furthermore, high arc current can effectively reduce the fluctuations of the arc voltage and increase the length and the volume of the steam plasma jet. Finally, using steam as the plasma forming gas can achieve higher thermal efficiency compared to air. An ideal thermal efficiency can be achieved by properly reducing the arc current and increasing the steam flow rate.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11565003)the Jiangxi Province Academic Degree and Postgraduate Education and Teaching Reform Research Project (Grant No. JXYJG-2022-180)the Scientific Research Base Project of Gannan Normal University (Grant No. 22wdxt01)。
文摘Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode(NRE) and doublering electrode(DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power,making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient.In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.
文摘The measured results show that the overexpanded supersonic jet velocity produced by low stagnation pressure (0.53 MPa) attenuates quickly, deviates greatly with smaller impact area and large energy loss. According to the measured results and the analysis of lashing energy of jet on the bath, the technological parameters of nitrogen flow in slag splashing were proposed.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.N150204003)
文摘In order to study the interaction between two independent jets, a three-dimensional(3D) transient mathematical model is developed to investigate the flow field and acoustic properties of the two-stream jets. The results are compared with those of the single-stream jet at Mach number 0.9 and Reynolds number 3600. The large eddy simulation(LES) with dynamic Smagorinsky sub-grid scale(SGS) approach is used to simulate the turbulent jet flow structure. The acoustic field is evaluated by the Ffowcs Williams–Hawkings(FW-H) integral equation. Considering the compressibility of high-speed gas jets, the density-based explicit formulation is adopted to solve the governing equations. Meanwhile, the viscosity is approximated by using the Sutherland kinetic theory. The predicted flow characteristics as well as the acoustic properties show that they are in good agreement with the existing experimental and numerical results under the same flow conditions available in the literature. The results indicate that the merging phenomenon of the dual-jet is triggered by the deflection mechanism of the Coanda effect, which sequentially introduces additional complexity and instability of flow structure. One of the main factors affecting the dual-jet merging is the aperture ratio, which has a direct influence on the potential core and surrounding flow fluctuation. The analysis on the noise pollution reveals that the potential core plays a fundamental role in noise emission while the additional mixing noise makes less contribution than the single jet noise. The overall sound pressure level(OASPL) profiles have a directive property, suggesting an approximate 25° deflection from the streamwise direction, however, shifting toward lateral direction of about 10° to 15° in the dual-jet. The conclusion obtained in this study can provide valuable data to guide the development of manufacturing-green technology in the multi-jet applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51179134,11472197)
文摘The large eddy simulation(LES) of the flow characteristics in an annular jet pump(AJP) is conducted, and the flow characteristics are systematically analyzed from both time-averaged and instantaneous aspects. The jet expansion, the velocity distribution and the energy are considered to analyze the time-averaged evolution of the flow field in the AJP. The transient flow characteristics can also be acquired from the analysis of the turbulence intensity and the Reynolds stress. The simulation demonstrates that in the time-averaged characteristics, the potential cores increase linearly with the increase of the flow ratio. With the flow development, the jet half-width gradually increases and the residual energy coefficient decreases. Compared with the distribution of the time-averaged axial velocity, that of the instantaneous velocity is more complex and disorderly. The high intensity of the axial turbulence mainly occurs in the mixing layer and the near-wall regions of the diffuser. The annular distribution of the Reynolds stress is mainly in the mixing layer and the recirculation region. There is a low-stress zone between the mixing layer and the high-stress region in the wall-boundary layer. The intensity of the spanwise vortexes is larger than that of the streamwise vortexes, and therefore, the former make greater contribution to the total vorticity. This research provides a better understanding of the flow characteristics in the AJP.
文摘The maximum rise-height,zero-buoyancy height,thickness of the spreading layer,minimum dilution and the height of the lower edge of the spreading layer are the important characteristic quantities of buoyant jets in stratified ambients.The scaling law is derived by the dimensional analysis of the influence factor on a buoyant jet.The characteristic quantities are found to converge to a single line under the unified scaling law.The correlation of the predicted results and experimental data is given.
基金support by the National Natural Science Foundation of China(NSFC 51474024and 51334001)National Key Technology Research and Development Program of the 12th Five-year Plan of China(12FYP 2015BAF03B01)
文摘Coherent jets are widely used in electric are furnace (EAF) steelmaking to increase the oxygen utilization and chemical reaction rates. However, the influence of fuel gas combustion on jet behavior is not fully understood yet. The flow and combustion characteristics of a coherent jet were thus investigated at steelmaking temperature using Fluent software, and a detailed chemical kinetic reaction mecha- nism was used in the combustion reaction model. The axial velocity and total temperature of the supersonic jet were measured via hot state experiments. The simulation results were compared with the experimental data and the empirical jet model proposed by Ito and Muchi and good consistency was obtained. The research results indicated that the potential core length of the coherent jet can be prolonged by optimizing the combustion effect of the fuel gas. Besides, the behavior of the supersonic jet in the subsonic section was also investigated, as it is an important factor for controlling the position of the oxygen lance. The investigation indicated that the attenuation of the coherent jet is more notable than that of the conventional jet in the subsonic section.