Research On Dynamic Characteristic Analysis And Optimization Method Of Cooling Tower Fan Drive Shafts

Cooling tower fan,a part of the large rotating machinery and equipment,is the key of circulating water technology equipment in the petroleum,chemical,electric power industries.Due to working under the harsh conditions yearly,such as high temperature and strong corrosion,shaft fracture and coupling failure often happen.They lead to the breakdown of the working process and causes great economic losses.As a result,the study on the dynamic characteristics,vibration optimization and fault monitoring of the cooling tower fan drive line is necessary.Based on a comprehensive research on the common failures of cooling tower fan drive line,this article analyzes the modeling thought of the fan transmission shafting dynamics and studies the dynamics characteristics of transmission shafting by using transfer matrix method and finite method respectively.Taking the LF-80 type cooling tower fan of Sinopec branch as experiment platform for the vibration test,the article also studies the vibration characteristics of the fan transmission shafting and completes the comparison and analysis between the experimental test and theoretical calculation results.At last,it gets the conclusion that the application of transfer matrix method in the structural dynamic analysis has chain significant advantages.According to the analyzed results of the cooling tower fan transmission shafting dynamic characteristics,this article finds out the weak parts of the shaft failure.By using critical speed as the optimization goal of the drive line features,the shaft critical speed is studied when the wall thickness,diameter and material type of the shaft change.It analyzes the relationship between the bearing stiffness and dynamic characteristics of shafting.The shaft’s bearing sensitive is obtained by exploring different ways of loading elastic support influenced on shaft critical speed.By using the minimum vibration quantity as the optimization goal of the drive line features,it completes the damper optimization scheme and provides new ideas for shaft system optimization;Combined with the active vibration control technology,and on the basis of controllable bearings,a new method of the transmission shafting vibration controled actively to change dynamic characteristics of shafting is explored.This paper analyzes the main faults of cooling tower fan drive line.The commonly used method of fan drive line fault is also studied in this paper,such as frequency method,the axis trajectory monitoring method,1/4 axis monitoring method and current overload monitoring method.The monitoring methods is valid in the engineering application of the shaft failure monitoring,but in most cases the fault has occurred.Therefore,the analysis and research on the nature of the fan drive line fault is carried out,aiming to rotor micro cracks and crack extension.Combined with acoustic emission technology and using material internal states’ change of the drive line as acoustic emission source,a real-time online monitoring method which can realize reliable early detection is studied.The conclusion of this paper is not only suitable for cooling tower fan drive line,but also has a certain application reference value to other class of chain drive.