Airfoil Cascade Hub Injection

In a gas turbine engine, the pressure ratio throughout the compressor stage can increase to a critical state and cause the inlet flow of air to reverse its direction. This event is known as “surge” and can lead to catastrophic damage to aircraft engines. The team designed a simplified section of a gas turbine engine and tested a potential solution: stabilizing the pressure ratio by introducing a secondary inlet flow that decreases downstream pressure.

The test piece includes a 3D-printed bottom hub and top plate, stator airfoils, and a tube that introduces secondary flow using a standard air compressor. The team selected tubing components that would cause little pressure drop from the air compressor to the main inlet flow to ensure accurate data. The mass flow rate of air introduced into the main flow is controlled by varying inlet pressure from the compressor. The velocity of the secondary flow is manipulated to decrease downstream pressure.

The team conducted testing in a wind tunnel running at 100 mph. They recorded pressure using a pitot-static tube rake, which can change height based on the pressure change during computational fluid dynamics testing. This data will inform gas turbine engine design by determining exactly the velocity needed for the secondary inlet flow to help prevent a surge event.