## 2 Method and Materials
### Experimental Verification of the Model  
To verify the accuracy of the numerical simulation model and the feasibility of the optimization measures, a 1:10 scaled-down single-chamber model was constructed, and a flow field distribution experimental platform was designed and built. Since this study focuses on optimizing the bag filter structure, particularly the airflow organization before entering the filter chamber, the experimental model does not include the filter bags. Instead, the tubesheet holes are used to represent the positions of the filter bags. The impact of the upper box is neglected to facilitate the measurement of airflow velocity at the outlet of each filter bag. Moreover, by replacing the deflectors in the hopper, different optimization models can be experimentally validated.  
The flow field distribution experiment is based on the principle of similarity. Therefore, it is crucial that the model maintains geometric consistency with the actual device, and that the fluid within the model operates in the second self-similarity region. Before conducting the formal experiment, the airflow was gradually adjusted using a flow control valve to determine the critical velocity at which the Euler number (\(Eu\)) remains approximately constant relative to the Reynolds number, ensuring that the experimental process meets the necessary requirements.  
The experimental procedure is as follows: First, the CF-11-2A frequency conversion fan provides the required system airflow. Once the flow field distribution within the model stabilizes, the wireless thermal anemometer Testo 405i is used to measure the airflow velocity at the outlets of each filter bag at the top of the experimental model's tubesheet. The experimental setup and the corresponding simulation model are shown in Figure 4.  
Given that the experimental model is scaled down and simplified, and no particulate matter is introduced in the experiment, numerical simulations were also conducted under the same conditions for comparison and analysis. This ensures logical consistency and accuracy between the two methods. A flow field distribution experiment and corresponding simulation were conducted on the original scaled-down single-chamber model. Airflow uniformity evaluation indices were calculated based on both experimental and simulation data, and the results are shown in Table 1.  
As shown in Table 1, the relative error between the simulation and experimental results for the maximum flow rate uneven amplitude (\(\Delta K_{qi}\)) in the original model is relatively large, at 11.7%. The primary reason for this discrepancy is that \(\Delta K_{qi}\) is sensitive to extreme values. In contrast, the relative errors for \(\Delta\overline{K}_{\zeta}\), \(\sigma\), C\({}_{v}\), and the average outlet air velocity (\(\overline{v}_{out}\)) are all less than 10%. These four indices, which consider the flow distribution across all filter bags, mitigate the influence of extreme values, making them more suitable for quantitative comparison and analysis between the numerical simulation and the experiment. In conclusion, the relative errors are within a reasonable range, confirming that the CFD model design and numerical simulation settings for the bag filter are valid. The numerical simulation results can accurately reflect the actual flow field distribution, and the results can serve as a reference for the optimization design of the bag filter.