## 4 Experiment: Wear Experiment Verification
### Comparison between Experimental and Numerical Results  
The wear characteristics of the experimental pump were numerically simulated using the numerical method and wear model described in Section 2, with boundary conditions identical to those of the pump wear experiment. The wear at the inlet and first- and second-stage impellers and guide vanes of the experimental pump were simulated, and the results obtained were compared to the experimental results, as shown in Figure 16.  
In Figure 16, it is shown that the numerically simulated wear is generally consistent with the experimentally observed wear, with some slight differences. At the inlet of the experimental pump, the solid particles caused severe wear at the radial inlet. This is because the radial inlet is the first part of the pump that comes into contact with the particles. Thus, owing to the particles being still fully intact at this stage and the particle collisions occurring at very high angles, severe wear occurred at this part of the pump.  
From the comparison results of the first-stage impeller in Figure 16, surface wear mainly occurred near their LE and TE. At the LE, solid particles moved in the axial direction into the impeller LE, and the rotations of the impeller resulted in their corresponding velocity changing from axial to radial. Consequently, this resulted in high-impact angles and collisions with the LE, thus causing severe wear at this location. The wear at the TE was primarily because the work done by the impeller increased the kinetic energy of the particles, whose tangential velocity was maximal at the TE, thus exacerbating wear at the TE. Moreover, the type of wear that occurred here was mainly abrasive wear.  
Figure 16: _Cont._From Figure (c)c, it can be seen that the wear on the second-stage impeller's surfaces was worse than that on the corresponding surfaces of the first-stage impeller because the particles experienced two rounds of acceleration by the second stage, and the resulting increase in particle kinetic energy also increased impact damage on the surfaces of the second-stage impeller's blades.  
However, on closely examining Figure (b)b,c, minute differences between the numerical and experimental results in the wear zones of the impeller blades can be observed. In the numerical simulation, the boundary of the pump inlet was configured such that the particles entered the pump with a uniform distribution. Thereafter, once the particles contacted the LE of the impeller blades, their velocities changed from axial to radial. However, the length of the impeller blades was insufficient for the axial velocities of the particles to completely change into radial velocities, and thus, the simulated wear at the LE of the impeller blades  
Figure 16: Comparison between numerically simulated wear and experimentally observed wear.  
was small and indistinct. Yet, after the particles were accelerated by the impeller, a large number of impacts occurred between the particles and the TE of the impeller blades, which greatly increased wear at the TE. In contrast, in the experiment, the particles did not enter the pump inlet with a uniform distribution; therefore, after the motor was turned on, the particles driven by the rotations of the impeller caused significant wear at the LE of the impeller blades.  
In Figure 16d,e, it may be observed that the most worn areas of the guide vane blades were located near their LE and that the first-stage guide vane exhibited worse wear than the second-stage guide vane at all corresponding locations. This is because the rated flow is the optimal operating point of the pump. After the solid-liquid two-phase flow has been guided and worked on by the first-stage impeller, first-stage guide vane, and second-stage impeller, the particle flow entering the second-stage guide vane becomes stable, which reduces the number of collisions between the particle and the second-stage guide vane's surfaces and thus reduces their wear.