| Reciprocating compressor is an important supercharging equipment in petrochemical industry,as the sturcture is complex and the compressed medium is flammable and explosive gas,it will not only cause huge economic losses,but also serious safety accidents while the failure occurs.The damage of crosshead bearing due to impact and friction in the running process is one of the main reasons of compressor failure,and crosshead bearing damage always causes increasing of temperature,thus,it is significant to establish a temperature monitoring system for crosshead bearing of reciprocating compressor.Compared with the electric sensors,the fiber Bragg grating(FBG)sensor has attracted much attention with its advantages such as small size,anti electromagnetic interference,intrinsic explosion-proof,easy to reuse and so on.Using FBG sensors to monitor the running status of mechanical equipment has become a research hotspot.However,it is very easy to cause the transmission wire winding when measuring the temperature of the crosshead bearing in motion.Aiming at this problem,this paper develops an aoptical signal wireless transmission device,which consists of two large fiber collimator and can be connected in the reciprocating movement,to obtain the temperature signal of the crosshead bearing.On the basis of this and the cloud platform,the remote temperature monitoring system of the crosshead bearing is designed.The main contents and conclusions are as follows:(1)Based on the movement characteristics of the crosshead bearing of reciprocating compressor and the advantages of the optical fiber sensing technology,a monitoring system of reciprocating compressor crosshead bearing temperature based on the optical fiber sensing technology is developed.(2)A FBG temperature sensor with small size and easy installation on the crosshead bearing was designed and the temperature sensitivities were studied experimentally.The results show that the sensitivity of the sensor is 10.21 pm/?,linear degree is over 99.9%,and the hysteresis error is only 0.97%.(3)In order to avoid transmission line winding,an optical fiber wireless transmitter is designed.,The relationship between the coupling efficiency and theaxial distance,lateral offset and axial angle in the reciprocating movement is analyzed by using the Gaussian beam coupling theory,the corresponding theoretical calculation formula is obtained and has been verified by experiment.(4)The dynamic characteristics of theoptical signal wireless transmission device were analyzed.Firstly,an experiment was carried out to measure the effective coupling efficiency of the optical signal wireless transmission device,and experimental results show that the critical coupling efficiency is not less than 20 dB.Then,by analysing the movement law of the reciprocating compressor crosshead,the theoretical calculation formula of the crosshead displacement,velocity,acceleration and crank angle is obtained.The analysis and experimental results show that the coupling signal of optical signal wireless transmission device can be demodulated when the response frequency of demodulation system is not less than 4380 Hz.Finally,the processing method of the coupling signal is studied.(5)A remote online monitoring system of crosshead bearing temperature based on Bmob cloud platform is developed.The following three tasks are completed: the method of obtaining the temperature data from the demodulation analysis module is studied;the concrete implementation method of adding and querying the temperature data in the Bmob cloud platform is investigated;a PC desktop program of the temperature monitoring terminal is designed.Finally,the function of the system is tested.The results show that the system can be used for remote on-line monitoring of crosshead bearing temperature.(6)The system was tested on the reciprocating compressor of Wuhan Petrochemical,which verified the feasibility of the application of the systemin temperature online monitoring of reciprocating compressor crosshead bearing. |
PDF Full Text Request