Design And Experimental Study Of An Turbomachinery Simulator Test Rig

Gas foil bearing is affiliated with sliding bearing, which adopts a single layer or multi-layer elastic structure foil as a supporting part, and a smooth top foil as bearing inner surface boundary to support the rotor. Gas foil bearing has excellent work performance under high temperature and high speed conditions, thus it is widely applied to high-speed turbomachinery. Since the use of ambient air(or other gaseous medium) as a lubricant, the oil-free mechanical system greatly reduce the costs of design, manufacture and maintenance, and it solve the oil-spilling problems caused by oil lubrication system, and become more environmentally friendly. Currently, the research of gas foil bearing technology focused on the theoretical study of the bearing elastic structure modeling, bearing’s important parameter simulation and rotor dynamics analysis. The research on bearing manufacture and experiments are relatively few, and application research for foil bearings is extremely scarce. Therefore, the high-speed oil free turbomachinery simulator test rig was designed and built, and experimental studies on gas foil bearing-rotor system were conducted. these would provide important engineering experience about bearing design, processing and practical application. In this paper, the main research work and results are as follows:(1) Reference to the current gas foil bearing application of turbomachinery, a high-speed oil free turbomachinery simulation test rig was designed and built. According to simulate operating conditions, the structural parameters of radial foil bearings and thrust foil bearings were designed, and the load capacity, the dynamic, static characteristics of them were predicted. At last, the rotor system was analyzed in rotor dynamics analysis. The results indicated that the load capacity of bearings satisfy the design requirements, and rotor system could avoid the critical speed in the operating speed range.(2) By using the rotating test rig, the effect of different bearing clearance on rotor system dynamic characteristics was studied. Combining with bearing analysis software and rotor dynamics analysis software, the system’s dynamic characteristic was predicted. Theoretical and experimental results show that, direct dynamic coefficients of Gas foil bearing increase while nominal clearance decreases. Subsynchronous motion onset speeds are analyzed and show that higher dynamic coefficients related to smaller nominal clearance delays the subsynchronous whirl generation. Synchronous response reflects that lower nominal clearance benefits the amplification factor(AF) when system passing through critical speeds.(3) By using the simulator test rig, the effects of unbalance on rotor system dynamic characteristics was studied. Experimental results demonstrate that, as the magnitude of unbalance increase, the critical speed of the rotor system decrease and the subsynchronous components become richer. These results indicated that gas foil journal bearings’ force coefficients are non-linear. In research of the effects of different loading direction on rotor system, the results showed that subsynchronous vibration is more acute when in-phase unbalance was loaded, and the synchronous vibration amplitude was higher when out-of-phase unbalance was loaded.