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- 摘要
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- 实验方案
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Impact of multi-focus beam shaping on the process stability
摘要： Unwanted process defects occur during laser deep penetration welding. The formation mechanisms of the main process defects like spatters and pores are not completely identi?ed yet. Several methods like beam oscillation or laser power modulation are known to help reducing the occurrence of defects. These methods change the temporal energy input. It can be assumed that also beam shaping in?uences the energy input into the keyhole and has the potential to in?uence process defects as well. Due to the adapted energy input keyhole instabilities, that are assumed to in?uence the formation of the defects, can be avoided. A newly developed multi-focus beam shaping optic that creates multiple beam waists in axial direction is used in this work. The additional areas with increased intensities are used to modify the energy input in the keyhole in order to explain the mechanism of spatter formation and evaluate the potential of the axial beam shaping for defect suppression during laser deep penetration welding. It is found that the number of spatters can be reduced when the middle sections of the keyhole are illuminated with a high intensity. It can be concluded that spatters can be reduced when a keyhole collapse is avoided and a high enough energy input is guaranteed in the upper keyhole sections.
关键词： Pore and spatter formation,Laser deep penetration welding,Multi-focus optic,Axial beam shaping
更新于2025-09-04 15:30:14
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Molecular Modeling of CO2 and n-Octane in Solubility Process and α-Quartz Nanoslit
摘要： After primary and secondary oil recovery, CO2-enhanced oil recovery (EOR) has become one of the most mentioned technologies in tertiary oil recovery. Since the oil is confined in an unconventional reservoir, the interfacial properties of CO2 and oil are different from in conventional reservoirs, and play a key role in CO2 EOR. In this study, molecular dynamics simulations are performed to investigate the interfacial properties, such as interfacial tension, minimum miscibility pressure (MMP), and CO2 solubility. The vanishing interfacial tension method is used to get the MMP (~10.8 MPa at 343.15 K) which is in agreement with the reported experimental data, quantitatively. Meanwhile, the diffusion coefficients of CO2 and n-octane under different pressures are calculated to show that the diffusion is mainly improved at the interface. Furthermore, the displacement efficiency and molecular orientation in α-quartz nanoslit under different CO2 injection ratios have been evaluated. After CO2 injection, the adsorbed n-octane molecules are found to be displaced from surface by the injected CO2 and, then, the orientation of n-octane becomes more random, which indicates that and CO2 can enhance the oil recovery and weaken the interaction between n-octane and α-quartz surface. The injection ratio of CO2 to n-octane is around 3:1, which could achieve the optimal displacement efficiency.
关键词： molecular dynamics simulation,CO2-enhanced oil recovery,minimum miscibility pressure,α-quartz pore,n-octane
更新于2025-09-04 15:30:14