Brazing Manufacture Of Atomizer And Numerical Simulation On The Characteristics Of Atomization Process

In the chemical industry,atomizers are often subjected to severe conditions in the production process,and wear problems caused by insufficient material performance and product quality problems caused by unreasonable structure design have seriously affected the atomization.Therefore,an atomizer with high-performance,long-life,wear-resistant and reasonable structure needs to be developed.In this paper,a silver-based active filler metal is self-designed for the brazing of polycrystalline diamond flake and super-fine grain cemented carbide to prepare a novel atomizer,and the brazing characteristics of the filler metal as well as the microstructure and mechanical properties of the joint were studied.Meanwhile,the CFD software FLUENT was applied to simulate the characterization of the internal&external flow field and the spray of this atomizer.In this paper,based on the traditional Ag-Cu-Ti brazing filler metal,the content of Ti were changed and Sn and Ni were added to obtain nine groups of active brazing filler metal with different compositions by the orthogonal design method.The results showed that the addition of Sn can effectively lower the melting point of the filler metal,and the increase of Ti content is beneficial to improve the spreading performance,while the range of solidus temperature and liquidus temperature would widen with the addition of other elements.The microstructure and mechanical behavior of the brazed joints prepared with nine groups of filler metal were also investigated.It is known that the microstructure is dominated by a worm-like gray Cu-solid-solution distributed in a white Ag-solid-solution matrix forming a net-shape or island-shape structure.The boundary layer is enriched with Ti,demonstrating that Ti C is formed by chemical reaction by the filler metal and diamond which leads to the bond of the materials.The joint prepared with Ag-Cu-4Ti-5Sn had the best performance in shear strength and hardness,reaching 330±22 MPa and 2009±274 MPa,respectively.The fracture morphology was also observed,and it was found that the fracture failure form developed from ductile-brittle mixed fracture to brittle fracture with the increase of other elements.For researching the characteristics of the internal flow field of the atomizer,numerical simulation based on the VOF method and the RSM turbulence model are carried out in this paper.The results showed that the spray cone angle obtained from the simulation was slightly higher compared with the actual experimental results,and the error range is within 20%.With the increase of inlet pressure,the water injection velocity increases,but the size of the spray cone angle had little change.At the same time,nozzle's structures,like the radius of swirl chamber,the height of swirl chamber,outlet thickness and diameter of the orifice,were changed by orthogonal design method to obtain nine groups of nozzles.Numerical simulations were conducted as well.The results show that the spray cone angle increases with the increase of swirl chamber radius and orifice diameter,and decreases with the increase of swirl chamber height and outlet thickness.The optimized nozzle takes radius of swirl chamber R=25 mm,height of swirl chamber L_s=8 mm,outlet thickness l_o=0.5 mm,diameter of orifice d_o=3 mm,and the numerical spray cone angle result reached 91.1°.Furthermore,the characteristics of the particles produced by the atomizer were also investigated.The size and shape of the particles produced respectively by the atomizer with(8.5 MPa pressure,3.2 mm aperture)and(10 MPa pressure,3.0 mm aperture)were studied by using imaging solution analysis.The Sauter Mean Diameter D32=90.21?m for the particles obtained from process 1 and for the particles obtained from process 2,D32=60.64?m.Both groups of powders had good sphericity,and the adhesion between powders was not serious.Based on the DPM model of FLUENT software,the particle characteristics under different inlet pressure and orifice diameter were further investigated by numerical simulation.The numerical results achieved a good match with the experimental results,and also showed that increasing the inlet pressure and reducing the outlet aperture were beneficial to refine the particles,but not to ensure the concentration of particle size distribution.