In recent years, selective laser melting (SLM) has been widely used in aerospace, automobile, biomedicine and other fields. However, there still remain many challenges to obtain consistent parts at the different positions on the base plate, which could be harmful to the industrial mass-production. In SLM process, the process by-products that flow with the shielding gas may influence the microstructure and tensile properties of the parts placed on different positions of the base plate. In this study, the velocity field of the shielding gas with different shielding gas volume flows was simulated. The tensile properties of the samples fabricated with different shielding gas volume flow were experimentally studied. The results show that the shielding gas volume flow has a strong influence on the sample consistency, and proper increase in shielding gas volume flows can be beneficial to consistency and tensile strength.

Transverse jets in crossflow are widely used in energy systems, especially as dilution air jets, fuel/air mixers, and combustion equipment, and have received extensive attention and plenty of research. However, the studies of the circular transverse jet issued from a circular gap at the circumferential direction of a tube in crossflow are very limited. This paper studies a relatively new jet: the circular transverse jet. Firstly, numerical calculations are conducted under different turbulence models but with the same boundary conditions. By comparing the numerical results of different turbulence models with the existing experimental data, the turbulence model which is most suitable for the numerical calculation of the circular transverse jet is selected. Then, this turbulence model is used to calculate and analyze the flow field structure and its characteristics. It is found that due to the aerodynamic barrier effect of the high-velocity jet, a negative pressure zone is formed behind the jet trajectory; the existence of the negative pressure zone causes the formation of a vortex structure and a recirculation zone downstream the circular transverse jet; and the length/width ratio of the recirculation zone does not change with the changes of the crossflow and the jet parameters. It means that the recirculation zone is a fixed shape for a definite device. This would be fundamental references for the studying of fuel/air mixing characteristics and combustion efficiency when the circular transverse jet is used as a fuel/air mixer and stable combustion system.

Aiming at the problem of the narrow combustion stability boundary, a conical swirler was designed and constructed based on the concept of fuel distribution. The blowout performance was studied at specified low operating conditions by a combination of experimental testing and numerical simulations. Research results indicate that the technique of the fuel distribution can enhance the combustion stability and widen the boundary of flameout within the range of testing conditions. The increase of the fuel distribution ratio improves the combustion stability but leads to an increase in NOx emission simultaneously. The simulation results show the increase of the fuel distribution ratio causes contact ratio increase in the area of lower reference velocity and gas temperature increase. The increased contact ratio and temperature contribute to the blowout performance enhancement, which is identical to the analysis result of the Damkohler number. The reported work in this paper has potential application value for the development of an industrial burner and combustor with high stability and low NOx emission, especially when the combustion system is required to be stable and efficient at low working conditions.

In this work, three composite structures of nickel-aluminum bronze (NAB) bonded with SUS630 stainless steel with different intermediate layers were fabricated by laser deposition. The microstructure and corrosion behavior of NAB in 3.5 wt.% NaCl solution were studied. The NAB coating directly deposited on steel substrate contains a large number of Fe-rich dendrites due to the dilution by laser energy and the Cu-Fe liquid phase separation characteristics. The microstructures of NAB were independent and isolated well from the steel substrate when the nickel intermediate layer was applied. Immersion corrosion and electrochemical tests indicated that the composite structure with the nickel intermediate layer presented better corrosion resistance than direct deposited the NAB coating, especially with the NiCr alloy intermediate layer, which led to a shallower corrosion depth and formed a denser layer of protective corrosion products.