Numerical Simulation And Experimental Study On Film Formation Mechanism And Film Thickness Distribution Of Electrostatic Air Spray

Electrostatic air spraying is a spraying method,which combines the characteristics of air spraying and electrostatic spraying.It has good film forming quality and high coating transfer rate,and has become an increasingly widely used coating method.Accurate spray deposition model can optimize spray process parameters,spray trajectory and uniformity of control coating thickness.Th erefore,It has important theoretical guiding significance and practical application value,which study the electrostatic air spray film formation mechanism and film thickness distribution to establish accurate spray deposition model and offline programming of spray robot and spray automation.Aiming at the problem that the coating particles are coupled by multiple fields such as electrostatic field,gas-liquid two-phase flow field and target field,and the coating film formation mechanism and coating thickness distribution law are not clear during the electrostatic air spraying process,this paper takes electrostatic air spraying as the research object,based on the multi-field multi-phase flow coupling theory and CFD simulation,the film formation mechanism and coating thickness distribution of electrostatic air spray under the coupling of electrostatic field,air flow field and discrete fog field are studied.The main research contents are as follows:(1)Combined with the multi-field coupling theory,through the analysis of the electrostatic air spraying mechanism,the multi-fields studied in this paper were the electrostatic field,air flow field and discrete fo g field,and the three coupling relationships and the main characterizations of each field were obtained.A multi-field coupling calculation model under cone-jet mode was established based on the Euler-Lagrange approach.Based on the finite volume method,the static electrostatic air spraying under multi-field coupling was simulated and the interaction of electrostatic field,air flow field and discrete fog field in electrostatic air atomization process was qualitatively analyzed.(2)Based on the Euler-Euler method,a planar and circular arc dynamic spray paint deposition model is established.Dividing the plane and arc surface control fields into static and motion domains,the local remeshing coupled with spring smoothing was adopted to calculate the dynamic mesh in the motion domain.Based on the finite volume method,the PC-SIMPLE algorithm was used to solve the discrete control domain model,and the distribution of the spray flow field and film thickness of the arc surface with the same plane and curvature b ut different concave and convex was obtained.During dynamic spraying,the movement of the spray gun and the turbulence effect of the spray flow field result in uneven coating thickness distribution.Under the condition of the same spray conditions and spray parameters,,due to the width of the spray cone and the collision angle of the droplets with the spray wall,and the maximum thickness of the spray coating and the width of the coating are different,the maximum thickness of the spray coating and the width of the coating are different for the plat plane and the arc surface with the same curvature but different concave and convex.(3)A gantry frame spray experiment platform was built and a plane dynamic spray test was carried out.By comparing the simulated values and experimental values of the film thickness values at different positions of the same section,the simulation and experimental errors are within 10%,and the film thickness distribution law of the same section is similar to the experiment,which can achieve better fitting.The result verifies that the proposed spray paint deposition model can be used to explore the dynamic spray film formation mechanism.