The letdown back-pressure regulating valve maintains pressure in the section of letdown upstream or the letdown heat exchanger to prevent the letdown liquid flashing to steam.
下泄背压控制阀维持下泄流上游段或下泄热交换器处的压力，防止压力过低引起流体汽化。
2
The non-symmetric refracted flow is possible to correspond to the non-symmetric entrance condition of upstream cross before sudden expansion section, and also to the symmetric entrance condition.
Along with the increase of the secondary flow pressure ratio, the shock move toward upstream divergent section and the thrust vector angle gradually increases;