Theoretical Analysis Of Lubrication Mechanism And Performance Optimization Of A Hemispherical Spiral Grooved Gas Bearing

Gyroscope is a kind of device for the sensor and maintains direction, which is designed based on the theory of angular constant momentum. Because of its independence on any external information and can measure the carrier attitude parameters relative to the inertial space ability, it is widely used in aviation, aerospace and other fields. Spherical spiral grooved aerodynamic bearings(SSGBs) can support radial loads and provide axial load capacity. They are thus suitable for use in aerospace and navigation as supporting and lubrication components of inertial components such as gyroscopes.Currently, the investigation for SSGBs was still at the stage of trial test and preliminary theory study. There had not yet formed a complete theoretical analysis and design system. The early analyses of air lubricated bearing were concentrated on journal bearings or thrust bearings. There are few investigations to study the performance of aerodynamic SSGBs, although several researchers presented many analyses on the incompressible liquid lubricated or aerostatic spherical bearings.This paper put forward an aerodynamic spherical spiral grooves bearing, which partly grooved on the rotor and the outer bearing is smooth. The bearing can realize "suction alone", do not need external pressurized air supply. Spherical bearings offer the advantages of relative insensitivity to misalignment and the possibility of combining the functions of both thrust and journal bearings. The theoretical lubrication model of SSGBs had been built in the paper based on the principle of gas lubrication. Parameter transformation and oblique coordinate transformation were thus applied in this study to modify the governing equations into the planar oblique coordinate system. The Green’s theorem and an eight-point method were also utilized to deal with film thickness discontinuity. Therefore, the modified governing equations could be solved using the finite difference method by employing technical mathematical tool MATLABA○REA to obtain the pressure distribution. Then, a detailed parametric analysis on the static and dynamic performance of the SSGB was presented in this paper using finite difference method associated with the perturbation method. Again, this paper also proposed a nonlinear numerical analysis method to study the stability and unbalance response of SSGBs through orbit simulation. The influences of nominal clearance and groove depth on the dynamics of SSGBs, which were predicted by critical mass and threshold speed of the rotor and the vibration amplitude of the unbalance response, were performed in this paper to provide theoretical references for bearing design and lifetime evaluation. Besides, the predictions of this proposed theory model show good agreement with the available experimental data, which indicates the validation of this theoretical analysis.Finally, this paper systematically summarized the theoretical methods and built an automatic analysis software for the structure design and performance evaluation of the spherical spiral grooved aerodynamic bearing.