Abstract:

The inertial impact mechanism between particles and wall surface is one of the main reasons for ash deposition, and there are few researches on the impact process of micron particles at home and abroad. In this paper, the impact process of a single particle impacting the particle powdery layer was numerically calculated. The dynamic model of the normal collision between particles and walls was established to study the collision process between the particle and wall (or particle). For the impact process between the particle and wall (or particle), the theoretical calculation results were consistent with the numerical calculation results in the case of undamped dissipation. The existence of damping dissipation increased the critical velocity when only the work of adhesive peeling was considered. On this basis, the particle motion after particle collision with powdery layer was studied. The normal impact process of particle-particle (adhesive) -wall surface became more complicated due to the addition of adhesive particles. It was found that when the incident velocity was greater than 0.7m/s, the adhesive particles would detach from the wall surface during the collision process between silica particles-silica particles (adhesion)-stainless steel surface.

Key words: micro-particles, critical capture velocity, damping dissipation, powdery layer

摘要：

颗粒与壁面的惯性碰撞机制是换热管壁积灰的主要原因之一，且国内外对微米级颗粒撞击壁面过程的研究较少。本文对单颗粒撞击颗粒覆层的碰撞过程进行了数值计算。首先通过建立颗粒与壁面法向碰撞的动力学模型，对颗粒与壁面（或颗粒）之间的碰撞过程进行研究。对于颗粒与壁面（或颗粒）的碰撞过程，无阻尼耗散下，理论计算结果与数值计算结果一致。相对于仅考虑黏附剥离功的情况，阻尼耗散的存在使得临界捕集速度增加。在此基础上，研究了颗粒与颗粒覆层撞击后的颗粒运动情况。颗粒-颗粒（黏附）-壁面的法向碰撞过程由于黏附颗粒的加入变得更加复杂。计算发现，对于二氧化硅颗粒-二氧化硅颗粒（黏附）-不锈钢表面的碰撞过程，当入射速度大于0.7m/s时，黏附颗粒将从壁面脱离。

关键词: 微米颗粒, 临界捕集速度, 阻尼耗散, 颗粒覆层