Instability in Axial Compressors — Lesson 2

This lesson covers the concept of instability in axial compressors, a significant aspect that limits the operation of the whole engine. It delves into the different forms of instability seen in modern-day axial compressors and their effects on compressor performance. The lesson also discusses the impact of inflow conditions on the initiation of instabilities and the implications of controlling instabilities on the performance of the engine. It further explains two different modes of instability - operational instability and aerodynamic instability, and their effects on the compressor's performance. The lesson also provides an understanding of rotating stall and surge, the major modes of instability.

Video Highlights

01:48 - Explanation of the two different modes of instability: rotating stall and surge.
14:26 - Explanation of the concept of compressor instability and the limits of operation of the engine.
31:00 - Discussion on the different types of instabilities that a compressor can encounter.
51:38 - Discussion on the impact of rotating stall and surge on the performance of the compressor.

Key Takeaways

- Instability in axial compressors is a significant aspect that limits the operation of the whole engine.
- There are two different modes of instability - operational instability and aerodynamic instability.
- Operational instability involves matching the performance characteristics of the compressor with the downstream components.
- Aerodynamic instability is the limitation of steady operation of the compressor due to surge and stall.
- Rotating stall and surge are the major modes of instability in axial compressors.
- Surge is an extreme instability which is encountered in an axial compressor, where there is a complete breakdown of stable operation of the compressor.
- Rotating stall can have a very high frequency of as high as 50 percent of the rotor frequency itself.