I believe that everyone will encounter the phenomenon o […]
I believe that everyone will encounter the phenomenon of fan surge, stall, and wind rush in the process of using the fanAC Blower Fans Manufacturers. Then what causes the fan's surging, stall, and wind rush? Next, I will briefly explain the reasons for everyone:
1. Stall and surge are two different concepts. Stall is a fluid dynamic phenomenon caused by the structural characteristics of the blade. Some of its basic characteristics, such as the rotation speed of the drainage zone, the starting point of the drainage, and the vanishing point, etc. , Has its own rules, and is not affected by the capacity and shape of the pump and fan piping system.
2. Surge is a manifestation of the oscillation characteristics of the pump and fan performance after coupling with the pipeline system. Its basic characteristics such as amplitude and frequency are governed by the capacity of the pump and fan pipeline system, and its flow, total pressure and shaft power The fluctuations are caused by unstable operating conditions. However, experimental studies have shown that the phenomenon of surge is always closely related to the rotation of the airflow in the blade duct, and the increase of the angle of attack is also related to the decrease of the flow rate. Therefore, in the unstable operating area where surging occurs, there is bound to be a rotating outflow.
3. The occurrence of stall does not necessarily cause surge, and the occurrence of surge must have already occurred; stall only belongs to the internal flow characteristics of the axial flow fan, and the surge is the coupling result of the internal and external characteristics of the axial flow fan, which is inevitable with the characteristics of the outlet pipeline contact. In actual operation, when the fan surges, the fan and pipes will produce great vibration and make noise. A stalled fan will not produce a lot of vibration, nor will it emit noise, as long as the rotor blades or speed are adjusted, it can continue to run.
4. Wind rush must occur in parallel pipelines. Stall and surge may not occur during wind rush, which is related to pipeline conditions. The wind rush phenomenon of general fans is mainly caused by changes in the resistance and local resistance of the pipeline system from the outlet of the two fans to the load point. If the air preheater on one side is seriously blocked by ash, the denitrification and desulfurization systems are blocked, the system with the booster fan, the booster fan fails. Will cause resistance along the way and local resistance.
A typical coal pulverizer system is arranged in line along the front and back walls of the boiler. Because the distance between the primary air inlet of each pulverizer and the primary air duct is very large, when one coal pulverizer trips, the output of the original two is balanced For the fan, because of the large resistance deviation along the way, the wind of a fan with a large resistance may be resisted, and the output of the two fans may be biased. Generally, the wind rush will not be very serious when the flow is large. However, if the flow is small, it may cause the fan to enter the stall and surge area, causing the fan to stall and surge, and form a serious wind-rush phenomenon. Therefore, if one of the two wind turbines stalls and surges, wind rush will definitely occur.