Rotaatiopysähdys

Rotaatiopysähdys, often translated as rotational stall or rotor stall, is a phenomenon that can occur in turbomachinery, such as compressors and fans. It happens when a portion of the rotor blades experiences stall, while other parts of the rotor continue to operate effectively. This uneven stalling leads to a complex flow pattern within the machine.

The primary cause of rotaatiopysähdys is an excessive angle of attack on some of the rotor blades. This can be due to variations in the incoming flow, such as uneven circumferential velocity or incidence angle changes, or inherent design characteristics of the blades themselves. When the angle of attack exceeds the critical value, the airflow separates from the blade surface, causing a loss of lift and an increase in drag.

The consequences of rotaatiopysähdys can be significant. It can lead to a reduction in the overall performance of the turbomachine, manifesting as a drop in pressure rise and mass flow. More critically, it can induce severe vibrations, noise, and potentially lead to irreversible damage to the rotating components if not addressed. The unsteady flow can also contribute to aerodynamic instability and resonance.

Detecting and mitigating rotaatiopysähdys is crucial in turbomachinery design and operation. Techniques like stall warning systems, active or passive flow control methods, and careful aerodynamic design are employed to prevent or manage this phenomenon. Understanding the conditions that lead to rotaatiopysähdys is essential for ensuring the reliability and efficiency of turbomachinery in various applications.