# Aerodynamic Window Sealing of a Large-Aperture Channel for High-Power Laser Transmission
## 4 Experimental Verification  
The seal test experiments for the large-aperture channel were performed in a laboratory environment, and the experimental platform was fabricated, as shown in Figure 9. Fan blowing was used to simulate the ambient wind speed, and the maximum fan gear speed was approximately 6 m/s. The number of particles of different particle diameters in the channel was measured using an airborne particle counter, and the gas speed in the channel was measured using a heated thermometer anemometer. In the axial blowing scheme, we opened the axial blowing valve and closed the radial blowing valve, and then turned on the air purification equipment and fan. After the flow field in the channel reached stability, the heated thermometer anemometer was used to measure the wind speed at 12 points in the channel \(L=20\) mm, and the distribution of the point locations is shown in Figure 10. The wind speed at each point was measured through three experiments, and the average value was compared with the simulated data, as shown in Table 1. It is evident that the experimentally measured values are slightly larger than the simulation results, which are considered to be caused by the instability of the purge gas volume flow, external environmental factors, manual measurement errors, and instrumentation errors. Fundamentally, in the Y direction, the wind speed increases with the decrease in the Y coordinate, and in the X direction, it is basically symmetrical around the center of the monitoring surface. The velocity distribution law is the same as the simulation results, which proves that the numerical simulation model of the channel is accurate, and the numerical model can be used to analyze and study the sealing effect of the large-aperture channel to the ambient gas. Figure 8: Variation curves of \(c\) with \(c_{\text{out}}\) at the position of \(L=100\) mm for different \(v_{\text{out}}\). Figure 9: Large-aperture channel sealing experimental model. Based on the previous wind speed test experiment, we carried out the first group of the number of particles measurement experiments. We opened the radial blowing valve and controlled \(v_{\rm a}=1\) m/s. After the flow field reached stability in the channel, the number of particles at different \(L\) was measured three times with the airborne particle counter under the condition of multiple \(l\) values. After completing the statistics, we conducted the second group of the number of particles measurement experiments. The radial blowing was fixed at \(l=0\) mm. We changed the value of \(v_{\rm a}\) by adjusting the axial and radial blowing valves. After the flow field reached stability in the channel, the number of particles at different \(L\) was measured three times using the airborne particle counter. The number of particles of different particle diameters in the channel was used to calculate the value of \(c_{\rm m}\), where \(c_{\rm m}\) indicates the mean particle mass concentration of the monitoring surface. The \(c_{\rm m}\) variation curves of the large-aperture channel for the experimental measurement of the different blowing scheme are presented in Figure 11. Figure 11a depicts the \(c_{\rm m}\) variation curves with \(L\) for different \(l\). It can be observed that each curve \(c_{\rm m}\) tends to a stable value at \(L>80\) mm. However, the pure gas also contains a few dust particles, the stable value is not zero. It can be proved that the channel prevents the dust particles from blowing in. Moreover, the \(c_{\rm m}\) of the \(l=0\) mm curve is relatively small and stabilizes at \(L=60\) mm with the fastest stabilization rate, indicating the best sealing performance at this location. Figure 11b displays the \(c_{\rm m}\) variation curves with \(L\) for different \(v_{\rm a}\). It can be observed that when \(v_{\rm a}\geq 0.8\) m/s and \(L>80\) mm, \(c_{\rm m}\) eventually converges to a stable value. As \(v_{\rm a}\) becomes larger, the \(c_{\rm m}\) value stabilizes faster, and the \(c_{\rm m}\) value at the same \(L\) position grows smaller.