How does an axial-flow compressor raise air pressure?

An axial-flow compressor increases air pressure by utilizing rows of aerodynamically shaped blades that interact with the airflow as it moves parallel to the axis of rotation.12

The process functions through the following mechanism:

• Velocity Manipulation: As air passes through the alternating rows of rotating and stationary blades, its velocity is repeatedly increased and decreased.2
• Energy Conversion: During each increase in velocity, the kinetic energy of the gas is raised. When the velocity is subsequently decreased, that kinetic energy is converted into an increase in pressure.2
• Diffusion: For subsonic flow, the blade passages—which act as highly curved airfoils—are designed to increase the flow area. This expansion reduces the flow velocity between the passages, effectively diffusing the flow and resulting in a rise in pressure.1

Because each stage provides only a small pressure increase, axial-flow compressors require multiple stages to achieve the necessary compression ratios for gas-turbine engines. Designers must carefully balance blade shape and rotational speed to maintain efficiency and prevent "stalling," a condition where flow separates from the blades.1