研究目的
To propose and describe the on-line measurement of oil-film pressure inside a journal bearing based on an optical fiber Bragg grating (FBG) for the first time, and to verify the feasibility of two methods (inserted and embedded) through experiments.
研究成果
The two novel methods for measuring oil-film pressure using FBG sensors were successfully demonstrated. The inserted method offers higher sensitivity but is prone to tangential forces, while the embedded method minimizes bearing damage with smaller size. Temperature compensation was effective. Experimental results aligned with simulations, showing pressure values around 10^4 Pa, and the FBG sensors are suitable for environments with strong electromagnetic interference, indicating potential for industrial applications.
研究不足
The inserted method may be subjected to tangential forces from oil flow if the sensor surface is uneven, potentially affecting accuracy. The embedded method has lower sensitivity and may not be suitable for all pressure ranges without higher resolution interrogators. Sensitivity can vary with different batches of rubber, and assembly factors like bolt fastening forces may influence results. The methods are limited to specific bearing geometries and may require optimization for broader applications.
1：Experimental Design and Method Selection:
Two methods for installing FBG sensors in journal bearings were designed: one involves inserting a packaged FBG into a hole in the bearing using rubber, and the other involves embedding the packaged FBG directly on the bearing surface. The rationale is to measure oil-film pressure with high sensitivity and minimal bearing damage, using FBGs for their multiplexing capability, absolute measurement, and immunity to electromagnetic interference.
2：Sample Selection and Data Sources:
A test rig was used, comprising a motor, gearing, lubrication system, and bearing system. The motor controlled shaft rotation speeds from 140 to 1400 r/min. Lubricant was provided by an oil pump, tank, and filters. The bearing had a Babbitt width of 34 mm with side leakage.
3：List of Experimental Equipment and Materials:
Equipment includes a motor (YS-7124, Wenling City Dacheng electrical machinery), oil pump, oil tank, filters, FBG sensors packaged with elastic rubber, structural adhesive (3M-DP490), copper pipe for temperature sensor, FBG interrogators (Smartscan by Smart Fibers Inc. and an interferometer-based system), and finite-element software for simulation. Materials include lubricant and rubber for packaging.
4：Experimental Procedures and Operational Workflow:
For the inserted method, an FBG was inserted into a hole in the bearing and calibrated for pressure and temperature sensitivity. For the embedded method, an FBG was embedded in the Babbitt and similarly calibrated. Experiments involved stepwise changes in rotation speed, data collection using interrogators (500 Hz for inserted, 5000 Hz for embedded), temperature compensation using a separate FBG sensor, and signal processing via fast Fourier transform to analyze frequency components.
5：Data Analysis Methods:
Data were analyzed using calibration curves for pressure and temperature sensitivity, fast Fourier transform for frequency-domain analysis, inverse Fourier transform to extract specific frequency components, and comparison with simulated values from finite-element software.
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