In order to study the mechanical properties and microscopic mechanism changes of microcrack propagation of FeNiCu alloy at different temperatures. In this paper, molecular dynamics methods were used to simulate uniaxial tensiles of FeNiCu alloy models containing microcracks and dislocations at 300, 500, 700, 900 K and 1 100 K, respectively. The microstructure evolution of FeNiCu alloys during tensile process was analyzed using Visualization software. Combined with the stress?strain curve and the energy change curve, the micro?mechanism effect of temperature on micro?crack propagation of FeNiCu alloy was emphatically analyzed. The results show that the higher the temperature in these five sets of temperatures, the greater the atomic spacing in the alloy and the more unstable the microstructure. However, the increase in temperature improves the plasticity of the alloy, so that the microscopic defects within it are healed to a certain extent under uniaxial loading, and the mechanical properties are maintained relatively stable. In addition, when the temperature rises, dissociative slip will be strengthened, which aggravates the emission and motion of the dislocation, and the dislocation product will be more likely to form microcracks, so that the dislocation <110> will form microcracks in multiple places in the slip direction.

Carbon capture, transport and storage (CCS) plays an important role in the process of carbon neutralization. The flow and heat transfer process of supercritical CO₂ and supercritical CO₂ mixture in a vertical circular tube was studied with supercritical CO₂, supercritical CO₂+CH₄ mixture (CH₄ mole fraction is 1%, 3%, 5%) and supercritical CO₂+N₂ mixture (N₂ mole fraction is 1%, 3%, 5%) as working fluids at a mass flow rate of 300～600 kg/(m²?s), heat flow density of 80～100 kW/m², and inlet pressure of 8～10 MPa. The results show that with the decrease of CH₄ and N₂ mole fraction in the working medium, the peak value of heat transfer coefficient of the working medium increases gradually, and its corresponding temperature increases gradually; the heat transfer coefficient of the working fluid increases with the increase of the mass flow rate, and the greater the mass flow rate, the greater the change range of the heat transfer coefficient; with the increase of inlet pressure, the peak value of heat transfer coefficient of working fluid decreases, and its corresponding temperature increases gradually. Turbulent kinetic energy, buoyancy and specific heat capacity at constant pressure are closely related to the heat transfer enhancement of supercritical CO₂ and its mixture.

The failure mechanism of pipeline cracking area of ground flare burner was studied. Through the combination of low?power macro analysis, material analysis, microscopic metallographic analysis, scanning electron microscope (SEM) micro morphology and energy spectrum analysis (EDS) and experiment, the causes of pipeline failure and cracking were found out. The sensitive environment (medium), the influence of sensitive materials and stress conditions on pipeline cracking failure were further analyzed. The results show that at a certain temperature, an acidic corrosion environment of H₂S+CO₂+H₂O is formed in the pipeline, and the stainless steel material of the flare burner pipeline is seriously sensitized and has serious intergranular corrosion; Intergranular corrosion causes grain spalling on the surface of pipe wall, resulting in pitting pits, which become the crack source of stress corrosion cracks; The flare burner pipeline will produce a certain degree of stress concentration in the process of manufacturing, processing and device operation. Under the condition of corrosive medium, sensitive material and stress concentration, the flare burner pipeline will fail due to intergranular stress corrosion cracking.

In order to reduce the heat resistance and improve stability of convective heat transfer in liquefied natural gas(LNG) vaporizer, the flow and heat transfer processes of supercritical pressure LNG were analyzed by numerical method in a vertical tube. The influence of heat fluxes and flow directions on heat transfer characteristics was discussed, and the effects of the flow field , the temperature field , and the turbulent kinetic energy changes on the heat transfer instability were investigated.The results show that the heat transfer of supercritical methane in vertical tube is unstable,at high heat flux density, the inner wall temperature and the average temperature of the pipe are unstable and and shock in the heat transfer deterioration range; At the low heat flow density , the local convection heat transfer coefficient is unstable , and it shocks in the heat transfer deterioration range; Under the same heat flux density, the heat transfer instability of upward flow is greater than that of downward flow, because the thermal influence of upward flow is greater than that of downward flow. The gas?like film is the main reason of heat transfer instability.