The remaining of this paper is organized as follows: first, a time series autoregressive (AR) model is developed to predict surge point from the CFD simulation of a single impeller flow passage and validated by experimental results.
The sketch of dichotomy to reach the highest outlet static pressure at surge point is shown in Figure 4.
At surge point, flow separation occurs inside the impellers making it unsteady and changes its direction.
The surge point is dependent on multiple parameters such as the molecular weight and flow into the compressor.
Additionally, timing of the compressor ESD signal, the fuel gas shutoff signal, fuelgas manifold size (in the case of gas-turbine drivers), power-train inertias and compressor aerodynamic characteristics close to surge point
, all contribute to the complexity of the problem.
Once a surge occurs, the reversal of flow reduces the discharge pressure or increases the suction pressure, thus allowing forward flow to resume again until the pressure rise again reaches the surge point
. This surge cycle continues at a low frequency until some change is made in the process or compressor conditions.
Both systems operate close to the surge point
, and the HGBP opens to avoid surge, whenever required.
ASV should be sized for 1.8 to 2.2 times of maximum surge point flow rate.
A collection of surge points during varying compressor speed or varying inlet gas angle is fitted as surge line.
Opening of the recycle valve in the surge-control system effectively avoids surge by providing more flow and reducing compressor head, to move the compressor away from its surge point
. In Figure 1, the compressor rundown behavior is plotted over a head vs.
While the gas flow corresponding to this surge point
is fixed for a constant-speed compressor, it changes at each operating speed for a variable-speed compressor.
"I had three surge points
so I focused on getting to those and picking up my pace for six to eight seconds and then going back into cross country pace and finding where I'm supposed to be," Richtman said.