Optical sensor for oil film pressure measurement in journal bearings

In operation of journal bearings, the oil film pressure is one of the key parameters. Until now, measuring of the oil film pressure has been a demanding or even unfeasible task, especially in journal bearings carrying dynamic loads. A new approach that has been developed for experimental determination of the oil film pressure is based on optical technique. In the sensor design the optical fibre technique is utilized and the sensor is integrated in the sliding surface of the bearing providing the possibility to measure the actual oil film pressure under load. The finite element method (FEM) calculations have been used for optimizing the design of the sensor and for checking the structural characteristics of the design. The optical sensor was integrated in a hydrodynamic journal bearing made of bronze. A versatile bearing test rig was used for testing the journal bearing with integrated optical sensor. The tests were carried out with both static and dynamic loading. The oil film pressure was measured with different loads and speeds and the data was compared with simulated one. The results showed that the optical sensor was capable of measuring the oil film pressure in journal bearing at real operating conditions and the sensitivity of the sensor was good enough to verify the speed and load effects on pressure. According to this work, it is possible to increase the knowledge of true operating conditions of journal bearings by using the optical oil film pressure sensor. The knowledge can be utilized in the development work of safer and more efficient machines and engines with journal bearing carrying high and dynamic loads. The optical sensor can be used also in other applications for smart control of pressure.