3.3.2. The Quantities of Particles Striking the Wall and Mass Loss Per Unit Area

× × Figure 12 shows the variation of quantities of particles hitting the wall. Figure 13 reveals that the variation of mass loss per unit area caused by the erosion. During the simulation, the count method is used to study the particles collision wall. The results are shown in Table 3. Numbers of solid particle collisions is around 0.2 × 10 <sup>4</sup> of the maximum value at the straight section, and numbers of solid particle collisions is around 1.255 × 10 <sup>4</sup> of the maximum value at the elbow. It can be concluded that approximately 16.7% (1/6) of the total released particles hit the extrados of the elbow and caused a serious loss of quality. As time goes on, the quantity of particles striking the wall gradually increases, accompanied by an increase in the loss of metal quality. In addition, it can be found that the mass loss per unit area mainly occurs between 40 ◦ and 50 ◦ , with the most serious region between 43 ◦ and 48 ◦ , and gradually was spread to the surrounding area, forming oblique elliptical erosion area. The simulation results considering the presence of acidic substances can be verified from other papers [13].

**Figure 12.** The number of solid particles hitting the wall. (**a**) t = 2 s number of solid particle collisions; (**b**) t = 4 s number of solid particle collisions; (**c**) t = 6 s number of solid particle collisions; (**d**) t = 8 s number of solid particle collisions; (**e**) t = 10 s number of solid particle collisions; (**f**) t = 12 s number of solid particle collisions.

**Figure 13.** The evolution of mass loss per unit area (kg/m<sup>2</sup> ). (**a**) t = 2 s mass loss per unit area; (**b**) t = 4 s mass loss per unit area; (**c**) t = 6 s mass loss per unit area; (**d**) t = 8 s mass loss per unit area; (**e**) t = 10 s mass loss per unit area; (**f**) t = 12 s mass loss per unit area.


**Table 3.** Particle collision data over time.
