Fiber Bragg Grating-based Oil Film Pressure Measurement In Journal Bearing

Oil film pressure is one of the important parameters of journal bearings,which reflects the working state of the rotor system.Measuring oil film pressure is of great significance for the health monitoring of journal bearings.At present,the measurement of the oil film pressure in the bearing mainly utilizes various types of electrical sensors and light intensity optical fiber pressure sensors.In this dissertation,the on line measurement of oil film pressure inside a journal bearing based on an Optical Fiber Bragg Grating(FBG)is proposed and described.Due to its small size and high sensitivity,coupled with excellent immunity to external electromagnetic interference the FBG sensor is an ideal candidate for measurement in which a strong electromagnetic field exists e.g.in the case of electrical motors and generators.Experiments to verify the feasibility of both methods are described with parameters being measured over the full motor operating range.Experimental results of the oil film pressure measured by these two methods agree well with simulated values,demonstrating excellent prospects for using the sensing schemes described in this article as the basis for real industrial measurement systems.The main research contents are as follows:The research status of oil film pressure in bearings at home and abroad is introduced.Analyzing and comparing various oil film pressure sensors,two measurements based FBGs are described,one includes inserting the packaged FBG into the bearing using rubber named FBG-inserted and the other is involved the packaged FBG being directly embedded on the bearing surface named FBG-embedded.Temperature compensation by FBG temperature sensor in metal tube package.The inserted method has a higher sensitivity than the embedded version,while the embedded method incurs less damage to the bearing being small in size.Combining the finite element software to analyze the working principle of the sensor,simulate the dynamic and static pressure sensitivity of the sensor,and study the main factors affecting the sensitivity of the sensor.The sensitivity of the sensor was calibrated experimentally and the repeatability of the sensor was tested.The results showed that the sensitivity of FBG-inserted is 3.8×10~-44 pm/Pa in the range of 0 to 10~5 Pa,the sensitivity of FBG-embedded is 2.6×10~-55 pm/Pa in the range of 0to 1.7×10~5 Pa.Both sensors have good linear fit and repeatability.The temperature sensitivity of the two pressure sensors is 22.2pm/°C and 13pm/°C,respectively.The sensitivity of the temperature sensor is 12.8pm/°C.The oil film pressure problem in fluid dynamic pressure lubrication was studied by CFD method.The law of oil film pressure with eccentricity,load and speed of circular bearing and elliptical bearing were compared.The variation of pressure frequency domain information at different positions on elliptical bearings under irregular rotation of the journal was studied.Designed fiber grating sensor were used for bearing oil film pressure measurement experiment.The change of oil film pressure in bearing at different speeds was studied by adjusting the rotating shaft speed.Experimental results of the oil film pressure measured by these two methods demonstrated excellent prospects for using the sensing schemes described in this article as the basis for real industrial measurement systems.The influence of bearing vibration on the FBG sensors was tested on the vibration test bench.The results showed that the FBG sensors with elastic rubber package can effectively isolate the bearing vibration,which further proved the feasibility of using the FBG sensor for oil film pressure measurement.