page_title: Surge in compressors
section_title: Description
hierarchical_section_title: Surge in compressors / Description
caption_attribution_description: English: This is a sketch of a typical compressor performance map which includes constant speed lines and a surge line. Two cycles are drawn on the map to illustrate compressor deep surge and compressor mild surge.
context_page_description: Compressor surge is a form of aerodynamic instability in axial compressors or centrifugal compressors. The term describes violent air flow oscillating in the axial direction of a compressor, which indicates the axial component of fluid velocity varies periodically and may even become negative. In early literature, the phenomenon of compressor surge was identified by audible thumping and honking at frequencies as low as 1 Hertz, pressure pulsations throughout the machine, and severe mechanical vibration.
context_section_description: Compressor surge can be classified into deep surge and mild surge. Compressor surge with negative mass flow rates is considered as deep surge while the one without reverse flows is generally termed mild surge. On a performance map, the stable operating range of a compressor is limited by the surge line. Although the line is named after a surge, technically, it is an instability boundary which denotes onsets of discernible flow instabilities, such as compressor surge or rotating stall. When the mass flow rate drops to a critical value at which discernible flow instabilities take place, nominally, the critical value should be determined as a surge mass flow rate on a constant speed line; however, in practice, the surge line on a performance map is affected by specific criteria adopted for determining discernible flow instabilities.
caption: ..A typical compressor performance map