Question:
In an axial flow compressor, if the air stream is not able to follow the blade contour such phenomena is known as
In an axial flow compressor, if the air stream is not able to follow the blade contour such phenomena is known as
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Think of compressor blades as airplane wings. When an airplane wing tilts too far up (high angle of attack) and the air can't follow its curved shape, the plane loses lift and "stalls". The exact same aerodynamic definition applies to compressor blades!
Updated On: Jul 4, 2026
- Surging
- Haulling
- Stalling
- Chocking
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The Correct Option is C
Solution and Explanation
Concept:
Aerodynamic flow behavior across the rotating blades of an axial flow compressor depends heavily on the design angle of incidence. If flow conditions deviate from design specifications (e.g., due to reduced mass flow rate), the angle of incidence increases.
When this angle exceeds a critical threshold, the air stream can no longer adhere smoothly to the curved contour of the blade profile. This causes the boundary layer to separate from the suction surface of the blade, leading to a phenomenon known as Stalling. This flow separation creates highly turbulent wake regions, reduces pressure rise, and causes structural vibrations.
Step 1: Distinguish between compressor flow anomalies.
Let us review the operational phenomena listed in the options to differentiate them clearly:
• Surging: A complete breakdown of flow through the entire compressor, characterized by violent, cyclic pressure oscillations and flow reversal. It is a system-level instability.
• Stalling: A localized aerodynamic flow separation from the blade surface when the air stream cannot follow the blade contour. It can occur on a single blade or a group of blades (rotating stall).
• Choking: Occurs when the fluid velocity reaches the local speed of sound ($M=1$) at the minimum area cross-section (throat), fixing the mass flow rate at its maximum limit.
Step 2: Match the question description to the correct mechanism.
The specific phrase "air stream is not able to follow the blade contour" refers directly to boundary layer separation on an airfoil profile, which defines aerodynamic Stalling. This corresponds to Option (C).
Step 1: Distinguish between compressor flow anomalies.
Let us review the operational phenomena listed in the options to differentiate them clearly:
• Surging: A complete breakdown of flow through the entire compressor, characterized by violent, cyclic pressure oscillations and flow reversal. It is a system-level instability.
• Stalling: A localized aerodynamic flow separation from the blade surface when the air stream cannot follow the blade contour. It can occur on a single blade or a group of blades (rotating stall).
• Choking: Occurs when the fluid velocity reaches the local speed of sound ($M=1$) at the minimum area cross-section (throat), fixing the mass flow rate at its maximum limit.
Step 2: Match the question description to the correct mechanism.
The specific phrase "air stream is not able to follow the blade contour" refers directly to boundary layer separation on an airfoil profile, which defines aerodynamic Stalling. This corresponds to Option (C).
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