SPH Direct Numerical Calculation For Theproblem Of Droplet Colliding Dry Surface: Dynamic Analysis Of The Droplet

Under the pressure of global warming and environmental pollution,people pay more and more attention to the emission of harmful gases from automobile engines.When the fuel is injected into the combustion chamber through the injector,the atomization phenomenon occurs.The atomization quality will affect the emission of harmful gas,and the outcome of a droplet impacting on a metal wall has a great influence on the atomization quality.In this paper,the dynamic change of a diesel droplet impinging on a dry surface is studied by using the smooth particle hydrodynamics(SPH)method,which provides theoretical guidance for reducing the emission of pollutants.Firstly,the SPH control equation with the surface tension term is established to solve the problem of droplet impacting on dry wall surface.A new substitution method is used to ensure the convergence of calculation in the problem of high density ratio of multiphase flow,which makes the calculation of the SPH method more stable.The parallel computing SPH program has been prepared to improve the computing efficiency.Secondly,the convergence of the SPH method and the weak compressibility of the fluid are verified by analyzing the variation of the density and the pressure of the droplet.The feasibility and the correctness of SPH method in the liquid drop collision are proved by studying the motion behavior and spreading factor of droplet.Thirdly,the quantity,average diameter,percentage of the second droplets and the kinetic energy of the diesel droplet are analyzed in depth.The results shows that the number of secondary droplets increases with time.The secondary droplets of small diameter is more likely to occur,and the secondary droplets of large diameter usually appears in the post-collision period.The energy dissipation of the secondary droplets is a reason for the decrease of the kinetic energy of the droplet.Finally,the effect of initial velocity on the secondary droplet phenomenon is analyzed.The higher initial velocity,the earlier generation time of the secondary droplets.At a certain moment,as the initial velocity increases,the number of secondary droplets becomes more.