Abstract:

When computational fluid dynamics (CFD) is used to simulate the flow field characteristics of a gas bearing-rotor system, the thickness of the gas film is one of the crucial structural parameters. However, due to the shape and size errors generated during the machining of parts and the deviation caused by the system assembly, there are certain deviations in the spatial morphology and scale between the actual gas film and the ideal design gas film. Then the reliability and accuracy of the numerical solution are affected. In this paper, the concept of effective gas film thickness of flow field is proposed, and the reasonable equivalent gas film thickness is determined by the comparison and analysis of the bidirectional fluid-structure coupling numerical simulation and experimental results. The results show that the bidirectional fluid-structure coupling numerical simulation method can reveal the transient characteristics of the gas film flow field and the changing law of the rotor attitude, and predict and evaluate whether the gas bearing-rotor system can operate safely, saving the test cost. The rotor inclination Angle is used as the comparative analysis feature, which provides a direct reference for the analysis of the system performance deviation between the numerical simulation results and the experimental test results. The establishment of equivalent gas film thickness can simplify the numerical simulation model to the greatest extent, improve the efficiency of numerical simulation, and the results have a certain reliability. Taking the gas supply pressure of 0.6MPa and the unilateral steady-state loading force of 80N as examples, the equivalent gas film thickness predicted in the fluid-to-solid coupling simulation model was established and corrected through error analysis and approximation, and the relative error of the system inclination Angle was controlled within 5% in the end, which greatly improved the consistency between the numerical simulation results and the actual engineering system performance. It provides a reliable method and basis for the application of gas bearing rotor simulation system in structural design, performance prediction and evaluation.

Key words: gas bearing-rotor system, two-way fluid-structure coupling, equivalent gas film thickness, model modification