Low nitrogen steam generator induced draft fan surge

The surge of the low-nitrogen steam generator's induced draft fan occurs due to an excessive pressure difference between the inlet and outlet of its stationary blades. This pressure difference is influenced by the pipeline resistance. For the same induced draft fan, surge is more likely to occur when the pipeline resistance is high at a given stationary blade opening. Please analyze this.

When the stationary blade opening of the low-nitrogen steam generator's induced draft fan is fixed, it generates corresponding wind pressure and flow rate. The fan operates stably without surge when the pressure and flow it produces are greater than or equal to the resistance of the flue gas duct. However, when the resistance of the flue gas duct increases, the pressure and flow at the fan outlet cannot overcome the duct system resistance, causing backflow. The backflow of flue gas reduces the duct resistance until it matches the fan outlet pressure, at which point the flue gas flows forward again. This back-and-forth flow of flue gas is called surge. Therefore, when the flue gas duct resistance is high, the induced draft fan is more prone to surge due to insufficient output.