What is the purpose of the diffuser vanes in directing flow from the impeller?

• A. Direct the flow from the impeller to the manifold at an angle designed to retain the energy imparted by the impeller
• B. Increase the flow velocity
• C. Create turbulence to mix air
• D. Cool the air

Answer: (A)

Diffuser vanes work to turn the fast, high-energy flow leaving the impeller into a slower, more directed stream while converting the kinetic energy into static pressure. By shaping the flow and guiding it to the manifold at the proper angle, they preserve as much of that energy as possible so the downstream system receives a higher pressure without simply accelerating the air further. This energy-retaining redirection is what boosts pressure and ensures smooth, efficient delivery to the next stage.

The other ideas don’t fit the diffuser’s role: increasing velocity would waste the energy that the diffuser is meant to convert into pressure; creating turbulence is generally undesirable for steady, efficient flow; and cooling the air is not the diffuser’s purpose.