The figure given below shows the curves between Head (H) and Flow (Q) for centrifugal pump impeller with different impeller vane exit angles For vane exit angle of 90°, following curve holds
To determine the correct curve for a vane exit angle of 90°, we need to understand the behavior of centrifugal pump impellers with different vane exit angles. The vane exit angle affects the head developed by the pump at different flow rates (Q).
For a vane exit angle of 90°:
- The vane is radial, which means that the fluid leaving the impeller is directed straight outwards, perpendicular to the axis of rotation.
- In such a case, the velocity component of the fluid in the tangential direction is minimal, resulting in a relatively flat head-flow curve.
- This implies that the head remains fairly constant irrespective of the flow rate, correlating to a horizontal line on the H-Q graph.
Based on the provided graph:
- Curve A - Represents an increasing-head curve, possibly for an impeller with backward-curved vanes.
- Curve B - Represents a horizontal line, indicating a constant head irrespective of flow rate. This aligns with the characteristics of a radial vane with a 90° exit angle.
- Curve C - Represents a decreasing-head curve, possibly for an impeller with forward-curved vanes.
Hence, the correct answer is curve B since it correctly represents the behavior of a centrifugal pump impeller with a 90° vane exit angle.
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