The Experts below are selected from a list of 2994 Experts worldwide ranked by ideXlab platform
V Vekselman - One of the best experts on this subject based on the ideXlab platform.
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analytical model of low and high ablation regimes in Carbon Arcs
Journal of Applied Physics, 2020Co-Authors: Alexander Khrabry, Igor D Kaganovich, A Khodak, V Vekselman, T HuangAbstract:Graphite ablation by an electric arc or a laser/solar flux is widely used for the synthesis of Carbon nanomaterials. Previously, it was observed in multiple arc experiments that the ablation rate is a strong nonlinear function of the arc current and it drastically increases at some threshold current. We developed an analytical model explaining this transition in the rate of ablation by an electric arc or a laser/solar flux. The model not only explains the observations but can also accurately predict the experimentally observed ablation rates. The model takes into account redeposition of Carbon back to the ablated surface, which is the key process responsible for the observed effects.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
Physics of Plasmas, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study the properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats the transport of heat and electric current in the plasma and electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, and emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and anode front surfaces, leading to the formation of electrode spots. The cathode spot is a well-known phenomenon, and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not previously reported. We conclude that the spot formation is not related to plasma instability, as commonly believed in the case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach the local chemical equilibrium state in the column region, while the local thermal equilibrium state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
arXiv: Plasma Physics, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats transport of heat and electric current in the plasma and the electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and the anode front surfaces leading to the formation of electrode spots. The cathode spot is a well-known phenomenon and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not reported before. We conclude that the spot formation is not related to plasma instability, as commonly believed in case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach local chemical equilibrium (LCE) state in the column region while the local thermal equilibrium (LTE) state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
J Chen - One of the best experts on this subject based on the ideXlab platform.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
Physics of Plasmas, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study the properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats the transport of heat and electric current in the plasma and electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, and emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and anode front surfaces, leading to the formation of electrode spots. The cathode spot is a well-known phenomenon, and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not previously reported. We conclude that the spot formation is not related to plasma instability, as commonly believed in the case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach the local chemical equilibrium state in the column region, while the local thermal equilibrium state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
arXiv: Plasma Physics, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats transport of heat and electric current in the plasma and the electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and the anode front surfaces leading to the formation of electrode spots. The cathode spot is a well-known phenomenon and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not reported before. We conclude that the spot formation is not related to plasma instability, as commonly believed in case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach local chemical equilibrium (LCE) state in the column region while the local thermal equilibrium (LTE) state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
Alexander Khrabry - One of the best experts on this subject based on the ideXlab platform.
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analytical model of low and high ablation regimes in Carbon Arcs
Journal of Applied Physics, 2020Co-Authors: Alexander Khrabry, Igor D Kaganovich, A Khodak, V Vekselman, T HuangAbstract:Graphite ablation by an electric arc or a laser/solar flux is widely used for the synthesis of Carbon nanomaterials. Previously, it was observed in multiple arc experiments that the ablation rate is a strong nonlinear function of the arc current and it drastically increases at some threshold current. We developed an analytical model explaining this transition in the rate of ablation by an electric arc or a laser/solar flux. The model not only explains the observations but can also accurately predict the experimentally observed ablation rates. The model takes into account redeposition of Carbon back to the ablated surface, which is the key process responsible for the observed effects.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
Physics of Plasmas, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study the properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats the transport of heat and electric current in the plasma and electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, and emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and anode front surfaces, leading to the formation of electrode spots. The cathode spot is a well-known phenomenon, and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not previously reported. We conclude that the spot formation is not related to plasma instability, as commonly believed in the case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach the local chemical equilibrium state in the column region, while the local thermal equilibrium state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
arXiv: Plasma Physics, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats transport of heat and electric current in the plasma and the electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and the anode front surfaces leading to the formation of electrode spots. The cathode spot is a well-known phenomenon and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not reported before. We conclude that the spot formation is not related to plasma instability, as commonly believed in case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach local chemical equilibrium (LCE) state in the column region while the local thermal equilibrium (LTE) state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
Igor D Kaganovich - One of the best experts on this subject based on the ideXlab platform.
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analytical model of low and high ablation regimes in Carbon Arcs
Journal of Applied Physics, 2020Co-Authors: Alexander Khrabry, Igor D Kaganovich, A Khodak, V Vekselman, T HuangAbstract:Graphite ablation by an electric arc or a laser/solar flux is widely used for the synthesis of Carbon nanomaterials. Previously, it was observed in multiple arc experiments that the ablation rate is a strong nonlinear function of the arc current and it drastically increases at some threshold current. We developed an analytical model explaining this transition in the rate of ablation by an electric arc or a laser/solar flux. The model not only explains the observations but can also accurately predict the experimentally observed ablation rates. The model takes into account redeposition of Carbon back to the ablated surface, which is the key process responsible for the observed effects.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
Physics of Plasmas, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study the properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats the transport of heat and electric current in the plasma and electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, and emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and anode front surfaces, leading to the formation of electrode spots. The cathode spot is a well-known phenomenon, and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not previously reported. We conclude that the spot formation is not related to plasma instability, as commonly believed in the case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach the local chemical equilibrium state in the column region, while the local thermal equilibrium state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
arXiv: Plasma Physics, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats transport of heat and electric current in the plasma and the electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and the anode front surfaces leading to the formation of electrode spots. The cathode spot is a well-known phenomenon and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not reported before. We conclude that the spot formation is not related to plasma instability, as commonly believed in case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach local chemical equilibrium (LCE) state in the column region while the local thermal equilibrium (LTE) state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
A Khodak - One of the best experts on this subject based on the ideXlab platform.
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analytical model of low and high ablation regimes in Carbon Arcs
Journal of Applied Physics, 2020Co-Authors: Alexander Khrabry, Igor D Kaganovich, A Khodak, V Vekselman, T HuangAbstract:Graphite ablation by an electric arc or a laser/solar flux is widely used for the synthesis of Carbon nanomaterials. Previously, it was observed in multiple arc experiments that the ablation rate is a strong nonlinear function of the arc current and it drastically increases at some threshold current. We developed an analytical model explaining this transition in the rate of ablation by an electric arc or a laser/solar flux. The model not only explains the observations but can also accurately predict the experimentally observed ablation rates. The model takes into account redeposition of Carbon back to the ablated surface, which is the key process responsible for the observed effects.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
Physics of Plasmas, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study the properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats the transport of heat and electric current in the plasma and electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, and emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and anode front surfaces, leading to the formation of electrode spots. The cathode spot is a well-known phenomenon, and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not previously reported. We conclude that the spot formation is not related to plasma instability, as commonly believed in the case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach the local chemical equilibrium state in the column region, while the local thermal equilibrium state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.
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validated two dimensional modeling of short Carbon Arcs anode and cathode spots
arXiv: Plasma Physics, 2020Co-Authors: J Chen, Alexander Khrabry, Igor D Kaganovich, A Khodak, V VekselmanAbstract:In order to study properties of short Carbon Arcs, a self-consistent model was implemented into a CFD code ANSYS-CFX. The model treats transport of heat and electric current in the plasma and the electrodes in a coupled manner and accounts for gas convection in the chamber. Multiple surface processes at the electrodes are modeled, including the formation of space-charge limited sheaths, ablation and deposition of Carbon, emission and absorption of radiation and electrons. The simulations show that the arc is constricted near the cathode and the anode front surfaces leading to the formation of electrode spots. The cathode spot is a well-known phenomenon and mechanisms of its formation were reported elsewhere. However, the anode spot formation mechanism discovered in this work was not reported before. We conclude that the spot formation is not related to plasma instability, as commonly believed in case of constricted discharge columns, but rather occurs due to the highly nonlinear nature of heat balance in the anode. We additionally demonstrate this property with a reduced anode heat transfer model. We also show that the spot size increases with the arc current. This anode spot behavior was also confirmed in our experiments. Due to the anode spot formation, a large gradient of Carbon gas density occurs near the anode, which drives a portion of the ablated Carbon back to the anode at its periphery. This can consequently reduce the total ablation rate. Simulation results also show that the arc can reach local chemical equilibrium (LCE) state in the column region while the local thermal equilibrium (LTE) state is not typically achieved for experimental conditions. It shows that it is important to account for different electron and gas temperatures in the modeling of short Carbon Arcs.