Axial-flow compressor terminology: the ratio of pressure rise occurring in the rotor (moving) blades to the total pressure rise in one stage is called what?

Introduction / Context:
Axial-flow compressor stages consist of alternating rows of rotor and stator blades. Several non-dimensional parameters describe how the pressure and energy addition are partitioned between these rows. One of the most important is the degree of reaction.

Given Data / Assumptions:

• A single axial compressor stage with one rotor and one stator.
• Steady, subsonic operation where classical definitions apply.
• Standard definition of stage pressure/enthalpy rise.

Concept / Approach:
The degree of reaction (R) is defined as the fraction of the static enthalpy (or static pressure) rise that occurs in the rotor relative to the total static rise across the stage. In enthalpy form: R = (Delta h_static in rotor) / (Delta h_static in stage)This definition translates directly to a “ratio of pressure rise in rotor to total pressure rise per stage” for low-Mach, near-incompressible assumptions.

Step-by-Step Solution:
Identify the rotor and stator contributions to static rise.Compute R = rotor static rise / (rotor + stator static rise).Recognize this ratio as the degree of reaction.

Verification / Alternative check:
Velocity triangles with R ≈ 0.5 show balanced static rise between rotor and stator, a common design target for many stages.

Why Other Options Are Wrong:

• Work factor: relates work input to blade speed; different concept.
• Slip factor: belongs to centrifugal compressors, quantifying reduction of tangential exit velocity.
• Pressure coefficient: relates pressure rise to dynamic head or blade speed squared.
• Flow coefficient: ratio of axial velocity to blade speed; not a pressure partition.

Common Pitfalls:
Equating degree of reaction with isentropic efficiency; one is a distribution metric, the other an effectiveness metric.

Final Answer:
Degree of reaction