Research On The Behaviors Of Particle-wall Impact With Adhesive Contact Model

The inertial impact mechanism between particles and wall surface is one of the main reasons for ash deposition.There are few researches on the impact process of micron particles at home and abroad,especially on the oblique impact process and the prediction of the dynamic characteristics of the impact process is not mature.In this paper,the impact behavior of micron particles and wall surface is studied deeply by combining experiment and numerical calculation method,which has guiding significance for how to control the ash accumulation on the wall of heat exchange pipe.Firstly,the process of silica particles impacting on the stainless steel surface was studied experimentally at different incident angles.In the experimental velocity range,the normal restitution coefficient of the particle increases with the increase of the incident velocity,and the plastic deformation has relatively little influence.Particles are more easily captured by the surface at a larger incidence angle.Secondly,based on the static contact model,two damping dissipation models are introduced to establish the dynamic equation.The damping coefficient was calculated and fitted by the single-coefficient model,and the critical capture velocity of the normal impact was determined to be 0.809m/s.For oblique impact,even if the normal velocity is less than the critical velocity,the particles will still rebound.When the incidence angle is less than 45°,gross sliding occurs,and the coefficient of kinetic friction is 0.435.The dynamic process of oblique impact is calculated by two models and the prediction results of rebound characteristics are compared.It is found that the single-coefficient model and the double-coefficient model can predict the tangential rebound velocity at a small incident angle well,and the double-coefficient model can obtain the overall trend line.Finally,the impact process of a single particle impacting the powdery layer is numerically calculated.For the impact process between the particle and wall（or particle）,the theoretical calculation results are consistent with the numerical calculation results in the case of undamped dissipation.The existence of damping dissipation increases the critical velocity when only the work of adhesive peeling is considered.The normal impact process of particle-particle（adhesive）-wall surface becomes more complicated due to the addition of adhesive particles.When the incident velocity is greater than 0.7m/s,it is found that the adhesive particles will detach from the wall surface.