Optical sensor for journal bearing oil film pressure measurements

The oil film pressure is one of the fundamental parameters influencing the operation of journal bearings. The oil film pressure is estimated by theoretical calculations, since the measurement of oil film pressure has been a demanding task in journal bearings, especially in bearings carrying dynamic loads. In this study a new approach to experimentally measure the oil film pressure has been developed and tested. The sensor design utilizes the optical fibre technique and the sensor is integrated in the sliding surface of the bearing thus providing the possibility to measure the actual oil film pressure under load without disturbing the contact conditions. The finite element method (FEM) calculations have been used for optimizing the design of the sensor and for ensuring the appropriate mechanical performance of the sensor design. The optical sensor was integrated into a hydrodynamic journal bearing made of bronze and a versatile bearing test rig was used for testing the operation of the optical sensor. The tests were carried out using both static and dynamic loading conditions with different loads and speeds. The experimental data was compared with the simulated one. The results showed that the optical sensor was capable to measure 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 the oil film pressure. According to this work, it is possible to increase the knowledge of true operating conditions of journal bearings by using the optical sensor for oil film pressure measurement. 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. This optical sensor configuration can be used also in other applications for measurement and control of pressure.