大口径宽波段激光发射通道的正压密封

针对大口径宽波段高能激光发射系统内通道的防尘除湿问题,提出了内通道正压通风密封方法。该方法利用净化后的干燥洁净空气排出原有的空气,并在发射端口形成正压气流阻挡外界空气向内通道扩散,从而达到密封防护的目的。借助计算流体力学软件Fluent对发射系统内通道的正压通风流场进行了数值模拟和分析研究,研究显示洁净气流在发射端口处产生一定的风速和压差,从而形成了内部正压抵挡通道外空气的回流。对于10.6μm的长波激光,根据压力变化估计了通道内的折射率变化在10-7量级,引起的光程差约为1μm。最后,通过实验验证了仿真结果。结果表明:监测面的速度值比仿真结果稍大,但是速度变化基本相同,而且洁净气流在监测面保持有0.64m/s的正压速度,洁净空气的相对湿度从59%降至了29%,基本达到了正压通风系统防尘除湿的密封设计要求。

Positive seal in large-diameter and wide-band laser emission pipe

To prevent dust and moisture to enter the laser emission pipe of a high-energy laser emission system with large-diameter and wide-band, a positive pressure ventilation seal method for the laser emission pipe is proposed. This method uses purified, dry and clean air to exhaust original air, and allow a positive pressure flow on an emission port to resist the air diffusion into the laser emission pipe from outside and to achieve the sealing for the pipe. The numerical simulation and analysis for a flow field of the positive pressure ventilation in the laser emission pipe are performed by the CFD software-Fluent, and it shows that the clean air keeps a certain velocity and pressure on the emission port and could form a positive pressure airflow to resist the backflow from outside. For a long wavelength 10.6 μm laser, the variation of refractive index in the pipe is estimated to be a magnitude of 10^-7 based on the pressure change, which causes a 1 μm optical path difference. The simulation results are experimentally verified and the results show that the velocity varies of interior have nearly no difference, though its' velocity is a litter bigger than that of simulation, and there is a positive pressure airflow with 0.64 m/s.Moreover, the relative humidity of clean air has dropped to 29% from 59%, which basically reaches the design sealing requirements of the positive pressure ventilation system for dust-proof and dehumidification.