"喷口面积" can be translated into English as "nozzle exit area" or "jet orifice area", depending on the specific context and application.
Nozzle exit area is commonly used in engineering, especially in fluid dynamics and propulsion systems, referring to the cross-sectional area at the outlet of a nozzle.
Jet orifice area is another possible translation, often used when describing the opening through which a fluid (such as water, gas, or steam) is ejected, like in a jet engine or a water spray nozzle.
In most technical contexts, "nozzle exit area" would be the more precise and widely accepted term.