Abstract
This research investigated unsteady events such as stall inception, stall-cell development, and surge. Stall is characterized by a decrease in overall pressure rise and nonaxisymmetric throughflow. Compressor stall can lead to surge which is characterized by quasi-axisymmetric fluctuations in mass flow and pressure. Unsteady measurements of the flow field around the compressor rotor are examined. During the stall inception process, initial disturbances were found within the rotor passage near the tip region. As the stall cell develops, blade lift and pressure ratio decrease within the stall cell and increase ahead of the stall cell. The stall inception event, stall-cell development, and stall recovery event were found to be nearly identical for stable rotating stall and surge cases. As the stall cell grows, the leading edge of the cell will rotate at a higher rate than the trailing edge in the rotor frame. The opposite occurs during stall recovery. The trailing edge of the stall cell will rotate at the approximate speed as the fully developed stall cell, while the leading edge decreases in rotational speed in the rotor frame.
Highlights
The stable operation of an axial compressor at a given shaft speed is limited at low mass flows by compressor stall
This paper presents detailed unsteady experimental measurements from a transonic axial compressor in order to describe stall inception, stall cell development, and surging characteristics
These results show it is purely the poststall throttling point in conjunction with the system dynamics that determine whether surge will grow from rotating stall
Summary
The stable operation of an axial compressor at a given shaft speed is limited at low mass flows by compressor stall. Axial compressors may enter periods of stable rotating stall and surge during operation at off-design conditions This generally leads to decreased efficiency and increased blade vibration. They found that the most common type of stall inception for modern compressor designs is a spike-type This is when the initial stall cell develops on the order of a few rotor revolutions. During the brief stall recovery process, the pressure ratio returns to its prestall value Another stall inception event and surge cycle repeat as the stall point is reached again [11]. Instantaneous shroud and rotor exit unsteady pressure contours are presented during transient events in order to better understand the process of stall inception and stall development. A comparison between stall and surge events is given to describe how the onset of surge occurs [15]
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