保持光传输通道内单一均匀的低吸收系数气体，对削弱内通道中的气体热效应有重要意义。采用气帘作为封装设备，对气帘的结构进行了设计。取气帘入口气体为氮气，出口气体为空气，借助现有计算流体力学软件FLUENT提供的组分输运模型，对气帘进行了数值模拟。结果表明，气帘入口段形成的平面射流可以阻挡外界空气的回流；在氮气与氧气相混合的区域内，尽管气体密度存在一定起伏，但气体密度变化的梯度方向与光传输方向基本是平行的，这种密度起伏只会对光场相位的活塞项产生影响，不会影响激光的远距离传输。最后，对气帘的性能进行了实验测试，实验结果表明，设计的气帘能够对管道内的气体进行密封，并避免了较大光程差的引入。

It is greatly significant to weaken the thermal blooming of beam path indoor by keeping the tube filled with single specific gas of uniform density and low absorption. The gas curtain is applied as sealing device, and the structure of gas curtain is elaborately designed. The fluid characteristic of gas curtain with nitrogen-filled inlet and air-filled outlet is modeled and simulated by the species transport model which is provided by the computational fluid dynamic software FLUENT. The simulated results indicate that the planar jet flow can indeed block off the refluence of the outside air. The gas density is undulant at the region with mixed nitrogen and air. However, the gradient direction of the gas density variation is parallel to the direction of beam transmission. This type of density variation only affects the piston item of optical phase, whereas it has no influence to the beam propagation. Finally, the experimental platform is established. The experimental results indicate that the designed gas curtain can seal the beam path indoor and reduce optical path difference.