What type of impeller has a double curvature vane?

The type of impeller that features a double curvature vane is known as the Francis impeller. This design is characterized by its unique blade shape, which allows for more efficient fluid movement. The double curvature vanes help to smoothly guide the fluid, minimizing turbulence and optimizing energy transfer as the fluid passes through.

Francis impellers are commonly used in turbines, particularly in hydropower applications, where their design maximizes the conversion of kinetic energy into mechanical energy. The double curvature helps in achieving a better flow profile and contributes significantly to the overall efficiency of the turbine.

In contrast, the other types of impellers—open, enclosed, and semi-open—do not utilize the double curvature design and are tailored for different applications, often prioritizing ease of maintenance or specific flow requirements rather than the optimized fluid dynamics seen in Francis impellers.