The steam injector relies on which fluid dynamic principle?

• A. Venturi principle
• B. Bernoulli principle
• C. Pascal's law
• D. Archimedes principle

Answer: (A)

At the heart of a steam injector is how a fast-moving jet creates suction. When steam passes through a narrow throat, its speed increases and the pressure in that constricted region drops. This pressure drop pulls in feedwater from the surrounding line, and the two fluids mix inside the injector. The energy of the steam then drives the mixture into the boiler, effectively pumping water without any moving parts. This behavior—the creation of a low-pressure region by rapid flow through a constriction—is the Venturi principle. The other principles describe different situations (static pressure transmission, buoyancy, or general energy concepts) and don’t specifically explain how the injector entrains and raises the water.