the movement and collisions of lithospheric plates is the general cause for the ring of fire.
the movement and collisions of lithospheric plates is the general cause for the ring of fire.
what is the general cause for the ring of fire?
the movement and collisions of lithospheric plates
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in most low-speed and low-pressure cases, rotating stall comes prior to compressor surge; however, a general cause-effect relation between rotating stall and compressor surge has not been determined yet. on a constant speed line of a compressor, the mass flow rate decreases as the pressure delivered by the compressor gets higher. internal flows of the compressor are in a very large adverse pressure gradient which tends to destabilize the flow and cause flow separation. a fully developed compressor surge can be modeled as a one-dimensional global instability of a compression system which typically consists of inlet ducts, compressors, exit ducts, gas reservoir, and throttle valve. a cycle of compressor surge can be divided into several phases. if the throttle valve is turned to be a very small opening, the gas reservoir would have a positive net flux. the pressure in the reservoir keeps increasing and then exceeds the pressure at compressor exit, thus resulting in an adverse pressure gradient in exit ducts. this adverse pressure gradient naturally decelerates flows in the whole system and reduces the mass flow rate. the slop of a constant speed line near surge line is usually zero or even positive, which implies that the compressor cannot provide a much higher pressure as lowering the mass flow rate. thus, the adverse pressure gradient could not be suppressed by the compressor and the system would rapidly involves an overshoot of adverse pressure gradient which would dramatically reduce the mass flow rate or even cause flows to reverse. on the other hand, the pressure in the reservoir would gradually drops due to less flux delivered by the compressor, thus rebuilding a favorable pressure gradient in exit ducts. and then the mass flow rate would be recovered, and the compressor is back to work on a constant speed line again, which would eventually trigger the next surge cycle. therefore, compressor surge is a process which keeps breaking the flow path of a compression system down and rebuilding it. several rules of thumb can be inferred from the interpretation above. compressor surge in a system with a small gas reservoir is high-frequency and low-amplitude whereas a large gas reservoir leads to low-frequency and high-amplitude compressor surge; another rule of thumb is that compressor surge happens in a compressor with a large external volume and compressor stall tends to show up in a system with a short exit duct. it is also worth noting that the surge line of a compressor can have small variations in different systems, such as a test bench or an engine.
surge in compressors