Research On3D Measurement For Hydrodynamic Pressure Of Sliding Bearing Based On MEMS

Hydrodynamic film is the main factor that affects the bearing performance. The oilfilm pressure distribution is generally derived by Reynolds equation. During the solution,both simplification to the physical model of the bearing and assumption and idealization tothe experimental condition can lead to the error between simulation result and real situation.The effective experiment is necessary for a comprehensive research on the oil film pressuredistribution as well as other parameters of journal bearings.The purpose of this thesis is to study the3D hydrodynamic film pressure distributionof journal bearings. Through literature review and investigation, the current journal bearingtest rigs are comprehensively summarized. Both advantages and disadvantages of test rigsare analyzed. Based on the research on the lubrication theory of infinitely long journalbearings, the characteristic of hydrodynamic film pressure is obtained, i.e. nonlinearparabolic profiles at both axial and circumferential direction. The factors affectinghydrodynamic film characteristics of journal bearings are summarized, i.e. shaft speed,eccentricity, oil film clearance and ratio of length to diameter.Based on the above theory, Fluent, a popular CFD software around the world, isapplied to simulate the hydrodynamic film pressure distribution of journal bearings. Therelationship between3D pressure distribution and the above factors are studied. It isconcluded that under given condition, the faster rotational speed of the axis, the largereccentricity, the smaller gap，the larger aspect ratio can make a larger oil film pressure and astronger bearing capacity. The position of the maximum pressure do not depend on thespeed of the spindle.According to the simulation results of hydrodynamic pressure distribution from Fluent,an innovation design to the journal bearing test rig is conducted and a completeexperimental and measurement scheme is formalized. The innovation is to use a slidingguide rail to link journal bearing and test rig, which can a relative movement between them.In addition to the rotation of the sensor with the shaft, a complete3D measurementapproach is formalized to the hydrodynamic film pressure of journal bearings. Thecomponents of the test rig are chosen based on MEMS theory, which make it possible ofthis scheme to apply in the measurement of the inner hydrodynamic film pressure of turbochargers.