A low-speed axial compressor performs better when a slot cut in the casing, directly above the blade tip, allows air to escape by natural aspiration. The technique reduces tip leakage, one of the main sources of aerodynamic loss and instability in such machines.

Tip leakage arises because a pressure difference exists between the pressure and suction sides of the blade. That jump drives fluid through the small gap between the tip and the casing, forming a leakage vortex that degrades performance and can lead to stall. Controlling that flow without supplying external energy is a long-standing goal in turbomachinery design.

The team experimentally tested a passive solution: a slot in the casing wall that lets the leakage flow escape by natural aspiration, without auxiliary compressors or air injection. The study, carried out in a low-speed axial compressor, evaluates how the slot modifies the behaviour of the tip vortex and the machine's performance.

The results show that natural aspiration through the slot attenuates tip leakage and improves compressor operation. The strategy avoids the complexity and power consumption of active systems, making it attractive for applications where cost and reliability constrain the design.