In a mixed flow centrifugal pump, the through-flow within the impeller passages combines two components. State whether the statement “the flow through the impeller is a combination of radial and axial flows” is correct.

Introduction:
Centrifugal pumps are categorized by the direction of flow leaving the impeller: radial, axial, or mixed. Mixed-flow pumps are preferred when higher specific speeds are needed than purely radial impellers can provide, while still maintaining good head characteristics.

Given Data / Assumptions:

• Mixed-flow impeller with blade geometry imparting both radial and axial velocity components.
• Steady, incompressible flow at design conditions.

Concept / Approach:
In mixed-flow impellers, the velocity triangle at outlet shows significant meridional (axial) component alongside radial ejection, unlike purely radial pumps where the exit velocity is largely radial. This blend increases discharge for a given head and diameter, aligning with higher specific speed requirements.

Step-by-Step Solution:
1) Impeller blades are swept to direct part of the flow axially.2) Outlet velocity components: V_r (radial) and V_a (axial) both non-zero.3) Diffuser/volute converts kinetic energy to pressure for both components.4) Performance curves reflect mixed nature: greater Q at moderate head compared to radial-only designs.

Verification / Alternative check:
Specific speed trends place mixed-flow pumps between radial and axial types, substantiating the combined-flow description.

Why Other Options Are Wrong:
Incorrect/only at design/diffuser-only/low specific speed: the mixed character is inherent to impeller geometry and persists across typical operating ranges.

Common Pitfalls:
Assuming all centrifugal pumps are strictly radial; ignoring axial component in mixed-flow designs.

Final Answer:
Correct