Axial-flow compressor kinematics: In an axial compressor stage, the bulk flow of air proceeds essentially parallel to the machine axis (aside from small swirl components).

Introduction / Context:
Axial-flow compressors are widely used in gas turbines due to their high mass flow capability and compact geometry. Understanding the predominant flow direction helps with velocity triangle analysis.

Given Data / Assumptions:

• Multi-row rotor–stator blade rows.
• Design point, subsonic to transonic relative velocities.

Concept / Approach:
While rotors impart swirl and stators remove it, the through-flow (meridional component) is arranged to be nearly parallel to the axis to minimize diffusion losses and maintain steady blade incidence. Velocity triangles are constructed about this axial mean component.

Step-by-Step Solution:

Verification / Alternative check:
Stage analyses and CFD show small radial components for endwall effects, but the dominant component is axial by design.

Why Other Options Are Wrong:
“Incorrect” contradicts the definition; “only at stall” or “only in stators” are misunderstandings—stall disrupts axial uniformity, and both blade rows share the axial through-flow path.

Common Pitfalls:
Confusing swirl (tangential) with axial through-flow; both coexist but describe different components.

Final Answer:
Correct