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When compressor surge happens, the operating point of a compressor, which is usually denoted by the pair of the mass flow rate and pressure ratio, orbits along a surge cycle on the compressor performance map. The unstable performance caused by compressor surge is not acceptable to machines on which a compressor is mounted to ventilate or dense air.
Axi-symmetric stall, more commonly known as compressor surge; or pressure surge, is a complete breakdown in compression resulting in a reversal of flow and the violent expulsion of previously compressed air out through the engine intake, due to the compressor's inability to continue working against the already-compressed air behind it. The ...
Surge points are the peak points on the characteristic curves (as in Figure 5.) left of which the pressure generated by the compressor is less than the pipe pressure and these points initiates the surge cycle.
Compressor surge is a particular problem during slam-accelerations and can be overcome by suitable adjustments to the fueling schedule and/or use of blow-off (bleeding air off the compressor, for handling purposes). In the particular example shown, a slam-acceleration from ground idle would cause a high-pressure compressor surge.
where is the heat capacity ratio / of the gas and where is the total (stagnation) upstream pressure. For air with a heat capacity ratio =, then =; other gases have in the range 1.09 (e.g. butane) to 1.67 (monatomic gases), so the critical pressure ratio varies in the range < / <, which means that, depending on the gas, choked flow usually ...
Effect of a pressure surge on a float gauge. Hydraulic shock (colloquial: water hammer; fluid hammer) is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly: a momentum change. It is usually observed in a liquid but gases can also be affected.
The pressure rise is indicated on the vertical axis as a ratio between inlet and exit stagnation pressures. A surge or stall line identifies the boundary to the left of which the compressor performance rapidly degrades and identifies the maximum pressure ratio that can be achieved for a given mass flow.
The pressure fluctuations are observed at low discharges and at flow rates(as indicated by the point "S" ) the pressure deceases. The pressure variations to the left of the point "S" causes for unsteady flow which are due to the two effects of Stalling and surging.