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本文根据气体动力学的二元理论论述了扩散泵喷嘴角度与喷嘴扩张车的关系，认为喷嘴角度在一定范围内变化时，喷嘴的扩张率也要作相应地改变，方能取得良好的抽气性能。与此同时，各级喷嘴之间的级间距离不该用喷帽内壁面的角度来计算，而应根据射流上界面的角度来计算。文章同时分析了一级喷嘴扩张率对返油率的影响以及直筒泵对喷嘴扩张率在结构方面的限制，提出了用凸腔泵取代直筒泵的建议，以降低返油提高抽速。
In this paper, based on the binary theory of gas dynamics, the relationship between the nozzle angle of the diffusion pump and the nozzle expansion car is discussed. It is considered that when the nozzle angle changes within a certain range, the nozzle expansion rate should be changed accordingly to obtain a good suction performance. At the same time, the interstage distance between the nozzles at different levels should not be calculated by the angle of the inner wall of the spray cap, but should be calculated according to the angle of the jet upper interface. In the meantime, the influence of the first-stage nozzle expansion rate on the oil return rate and the restriction on the nozzle expansion rate by the straight-tube pump are also analyzed. The suggestion of replacing the straight-tube pump by the convex-cavity pump is put forward, so as to reduce the return oil and increase the pumping speed.