Research On Fiber Sensing Technology For Online Temperature Monitoring Of Reciprocating Compressor Crosshead Bush

Reciprocating compressors are important power equipment for flammable and explosive gases in the petrochemical industry.Once a failure occurs,it will cause production stoppage and serious security consequences.As a core component of transmission mechanism,the crosshead bush is one of the main reasons of the failure of transmission mechanism because of its strong impact and friction in the working process.Therefore,the abnormal high temperature is the most direct representation of its failure,it is necessary to monitor the crosshead bush temperature in real time.Due to the package size,electromagnetic interference and wire winding of the existing electrical sensors,it is impossible to online in-situ monitor the crosshead bush temperature and other parameters.Combining the advantages of FBG,the key fiber sensing technology for online temperature monitoring was studied in this paper.The main work of this paper is summarized as follows:(1)The principle of optical signal extraction technology for online monitoring of moving parts was studied,and optical signal space transmission scheme based on collimators was proposed.The relation between coupling efficiency and the axial distance,lateral offset and axial angle in the optical space transmission was analyzed by gauss coupling theory.(2)After the motion model of the transmission mechanism has been established,the movement laws of crosshead bush were obtained by simulation.A sensing technology and signal processing method for online monitoring of the crosshead bush were developed,and a data acquisition API was designed for optical performance monitoring module.(3)Based on the sensing characteristics of FBG,a miniature sensor was packaged,which could be embedded in the crosshead bush for temperature measurement.The experimental results of calibration showed that the sensor had good temperature sensing performance.The sensitivity was 10.59 pm/°C,the linearity was over 99.98 %,and the return error was only 0.67 %.(4)A multi-peak detection algorithm based on the Hilbert Transform was proposed to overcome the shortage of traditional single peak detection algorithms,which could extract the Bragg wavelengths from the reflection spectrum in WDM systems.This algorithm introduces the thought of Divide and Conquer,including splitting the reflection spectrum and single peak detection.(5)For the U-shape wavelength data collected in the field test,two methods based on wavelength or intensity characteristics were proposed to obtain accurate Bragg wavelength,which could avoid 0.2-0.3 nm wavelength drift error to improve the accuracy.Finally,the online temperature monitoring of the crosshead bush has been achieved.