Primary Research On Torsional Vibration Characteristic Of Variable Frequency Draught Fan System In Thermal Power Plant

Draught fan is the main auxiliary equipment in the thermal power plant.Meanwhile,it always consumes a lot of power energy in t he operation of thermal power unit.In order to solve the problem,many power generation company have carried out the variable speed driving,which has obtained good energy-saving effect.While,after implementation of inverter,the torsional vibration of the shafts become s serious,such as the blade fracture,large shaft fracture,and coupling damage,which endangers the unit and the power grid security.The research of the frequency conversion auxiliary torsional vibration,has important significance for ensuring the safety of the thermal power generation equipment,economic operation.Firstly,this paper analysis the original operation condit ion and load of the draft fan driven by constant speed and driven by variable speed,which further confir ms the operation condition and mechanical properties.Then this paper established torsional vibration model of the shaft ing and solved the shafting torsional vibration inherent characteristics by numerical analysis.And then combined with field cases,about torsional vibration fault of power plant,firstly,simulation experiment was carried out from the torsional vibration test bench,and we can obtain the torsional vibration data,and then we can verify the validity of the finite element analys is method.And then this paper analyzes the draught fan shafting torsional vibration mechanis m,including the geometric structure and frequency control of motor speed.The analys is of the effect that the geometric structure bring to the draft fan shafting torsional vibration,is advantageous to the reasonable design of induced draft fan rotor shaft system.In combination with auxiliary torsional vibration fault cases from Taishan power plant,this paper analyzed the shafting torsional vibration response of the actual draft fan system.we obtained the resonant frequency point and torsional displacement.To compare the constant speed operation and va riable speed operation by motor,we learned that,after changing the fan speed,resonance occured in draft fan shaft system.The torsional displacement becomes larger in comparation with the original operation condition,which leads to fan shaft fracture easily.In the end,this paper put forward the inhibit ion proposal of draft fan shafting torsional vibration.The paper has a certain reference value for promoting the safe and economic operation of large variable frequency auxiliary machinery in our country.