The prediction accuracy of the non-linear vibratory response of bladed disc system with shrouded dampers depends on the modelling of bladed disc system, the friction contact model for depicting the non-linear constraint force, and the solution method of non-linear vibration equations of the bladed disc system. In order to improve the computation efficiency, the bladed disc system is assumed to be tuned in this article. Under this assumption, the vibratory response of the bladed disc system can be predicted based on a sector model having the cyclically symmetric constraint. This article particularly describes the formulation of the sector model and the infliction of cyclically symmetric constraint. The proposed three-dimensional (3D) friction contact model used to depict the non-linear constrained force is a numerical method, in which the relative motion of the contact surfaces is an arbitrary complex periodical one. The hybrid frequency–time domain (HFT) method is applied to solve the non-linear vibration equations of the bladed disc system for its high computation efficiency and computation accuracy. Finally, based on the sector model, numerical 3D friction contact model, and HFT domain method, a method is developed to predict the non-linear vibratory response of the bladed disc system with shrouded dampers.

With the rapid development of high-speed, oil-free turbomachinery, more and more attention is concentrated on compliant aerodynamic foil bearings. However, the common corrugated bump foil forming the compliant structure is so complicated that manufacturing it is time-consuming and troublesome. In this article, a simple type of aerodynamic foil thrust gas bearing with an elastic hemispherical convex dot support configuration is first proposed. Then experimental investigations on stability and its load capacity characteristic for this foil thrust bearing were conducted on a multi-functional thrust bearing test rig. The preliminary measurement and analysis are presented through the wave and spectrum of axial displacement response in the time and frequency domain. It is demonstrated that the proposed bearing can operate well and has good stability in tests, and experimental results show that the axial load can reach 25 N when the rotational speed is about 114 200 r/min.

The miniature high-speed gas-bearing turbomachinery is one of the research focuses in the fields of energy and cryogenic engineering in recent years. In this article, a new miniature static gas-bearing expansion turbine with a shaft diameter of 6 mm, turbine impeller diameter of 9 mm, and designed rotational speed of 300 000 r/min was developed. The developed prototype of this miniature expansion turbine is comprehensively introduced and the structure characteristics are presented. Then the preliminary mechanical and thermodynamic performances for the developed prototype are experimentally measured. Research results show that this developed expansion turbine has some noticeable features, such as stable operation with small vibration. It can reach 15 per cent over-speed and provide a quick temperature drop. Experimental verification demonstrates that both mechanical and thermodynamic performances agree with expected requirements. Hence, a strong base has been established in China to further develop miniature high-speed gas-bearing expansion turbines.

This article provides a dynamic model of a cylindrical roller bearing–rotor system by combining the finite element method of the rotor and the interaction between the components of the bearing to study the dynamic response of the rotor with asymmetric support mode. The shaft is discretized by beam elements with five degrees of freedom. The bearing inner ring is consolidated with the journal of the shaft. The simulation results show that variable compliance vibration can stimulate resonance of the rotor in the sub-critical speed region. The variable compliance vibration of the rolling bearings does not occur synchronously on both sides of the asymmetric supported rotor. The increase in radial load and clearance exacerbates variable compliance vibration, while rotor imbalance has a smaller impact on variable compliance vibration. Usually, the presented coupled model can be applied to the comprehensive analysis of the vibration characteristics of all components in any cylindrical roller bearing–rotor system.