激光焊接过程中，为了保护聚焦镜和保证焊接质量，通常在聚焦镜下布置一横向气帘喷嘴。根据气体动力学原理设计了一种超音速非对称拉法尔腔体结构的喷嘴，并建立了喷嘴内部拉法尔曲线方程。喷嘴的气流纹影试验表明，得到的气帘的发散角较小，同时对周围区域的扰动也很小。实际的焊接试验证明这种结构的喷嘴可以有效吹除飞溅，保护聚焦透镜。

In laser beam welding,an appropriate crossjet nozzle should be mounted under the welding head in order to protect the optics from the welding spatter and smoke. An ultrasonic crossjet with a non-symmetric Laval cavity is designed based on the aerodynamic theory. Schlieren trial show that a rigid flow with a small divergence is obtained,and no disturbing near the flow can be observed. Welding experiments prove that focusing mirror is well protected when such a crossjet is used.