Dynamics research of a flywheel shafting with PMB and a single point flexible support

Flywheel energy storage system (FESS) is new advanced machinery which is intended for electric power storage and release. A FESS, which is suitable for the small flywheel, was developed with a permanent magnet bearing (PMB) and a single point flexible support, and its friction loss is very low. By means of the Lagrange theory, a dynamic model was established. The Campbell diagram, mode shapes, modal damping ratios and critical speeds were designed after the flywheel data at different operating speeds was obtained by numerical simulation. Based on the excitation test and single freedom vibration theory, the stiffness and damping coefficient of the upper and lower damper was measured. The influences of damper dynamic parameters on modes of flywheel rotor bearing system were discussed in detail. The comparison between the calculated unbalance response and the experimental response indicates that the dynamic model is appropriate. The results showed that the lower damper absorbed vibration energy of the flywheel rotor, which increased vibration of the damping body. And the bigger damping coefficient had better vibration absorption effect. The developed FESS is simple, stable and efficient in structure

Experimental research on dynamic characteristics of gas bearing-rotor with different radial clearances

The test rig of gas bearing-rotor system was established. The rotor was composed of turbine, compressor and four disks, it was supported by hydrostatic gas bearings. With this test rig, the dynamics of rotor bearing system with different bearing radial clearances were researched. Rotating speed of shaft could be higher with large bearing clearance, but speed soaring and low frequency oscillation occurred were dangerous to the shaft; with small bearing clearance, the speed soaring and low frequency oscillation could be eliminated and the dynamic characteristic was good, but rubbing deceleration was more likely to happen. Make a contrast of the dynamics with different radial clearances, it could be found that the dynamic characteristic of small radial clearance was good, but the threshold of safe amplitude was small, which limited the maximum speed

Experimental research on the dynamic characteristics of gas-hybrid bearing-flexible rotor system

High-speed gas bearings for turbomachinery can dramatically improve the isentropic efficiency of turbine plants. Vibrations, especially low-frequency vibrations caused by the gas-film self-excited vibrations, significantly affect the safety and economy of the turbomachinery, which is dangerous at high rotational speeds. This experimental study focuses on the dynamic characteristics of a flexible rotor supported by gas hybrid bearing and driven by a radial turbine with high-pressure air. Cylindrical whirling, conical whirling, and first-order bending natural frequencies that change with bearing supply pressures were obtained by experimental modal analysis. Nonlinear mechanic behaviors, including gas film half-speed whirling and gas-film whip, in the experiments were identified by nonlinear measurements and analyses. The occurrence mechanism of gas-film whirling and whip is also discussed in this paper. Experiments for eliminating and restraining whirling and whip were conducted to investigate the gas bearing-rotor system stability effect of bearing supply pressure and elastic foundation. Some simple and effective measures were given to improve the stable rotational speed

Research on speed’s influence on hydrostatic bearing’s stiffness

Reynolds equation considering speed is solved using finite element method. Orifice hydrostatic gas bearing’s pressure distribution, load capacity and stiffness are obtained. Speed’s influenced on stiffness is studied. Experiment is conducted on turbine expander. Rotor operates under unbalance mass’s excitation. By analysis whipping frequency’s relation with the natural frequency of rotor-bearing system, stiffness can be calculated. The experiment result shows that bearing’s stiffness changes with rotor’s speed. When rotor’s speed is between 10000-50000 r/min, stiffness increased by 9.6 %. Because gas whirl only happens when rotor’s speed is above the first critical speed, the method has limited speed range

Experimental research on instability fault of high-speed aerostatic bearing-rotor system

The experimental research on high-speed aerostatic bearing-rotor system with one compressor, one turbine and coaxial four discs was developed. The gas bearing-rotor system stability under different bearing supply pressure plans was studied by experiments. The paper also presents fault features of gas film whip instability, power frequency rubbing and low frequency rubbing, which provides experimental data for gas bearing-rotor system stability study

Experiment research on stability of herringbone grooved aerodynamic bearing-rotor system

Take experiment research on characteristics of turbine expansion engine’s shaft supported by herringbone grooved aerodynamic journal bearing, with the emphasis on its low frequency whirl. Get bearing’s taking-off speed and low frequency vibration characteristics by comprehensively analysis methods of spectrum diagram, haft orbit and time waveform and bifurcation diagram. The result shows that the graphite made herringbone groove hydrodynamic bearing can reach 37548 r/min and half-frequency vibration happens since 13021 r/min. With the speed up, rubbing exists and the amplitude of low frequency even bigger than power frequency. The result shows that the half-frequency is the main unstable factor

Experimental research on dynamic characteristics of a hybrid gas bearing-rotor system for high-speed permanent magnet machine

An experiment on the vibrational characteristics of a hybrid gas bearing-rotor system in a 45 kW high-speed permanent magnet machine test rig is conducted. Nonlinear methods of measurements and analyses, including bifurcation maps, frequency spectra, and axis orbits, are adopted to evaluate sub-synchronous vibration in rotor acceleration. The effects of bearing supply pressure and speed accelerating rates on the stability of the gas bearing-rotor system are determined. Experimental results show that half-speed whirling of the gas film is eliminated and the start of gas film whipping is delayed by using the appropriate bearing supply pressure plan, thereby improving stability. Meanwhile power frequency vibrational amplitude is the smallest during the acceleration process, including the critical speed, when the appropriate speed accelerating rates are employed

Rubbing dynamics behavior of a flywheel shafting with a single point flexible support

The flywheel energy storage system is a new kind conversion device which realizes electric energy and kinetic energy transform into each other. The dynamic characteristics of flywheel energy storage system have been studied extensively in recent years. A single point flexible support is suitable for the small flywheel system, because the friction loss is very low. The flywheel spin test system with a single point flexible support was built. The dynamic model of the flywheel shafting was established to calculate the critical speeds, modal shape and modal damping ratio at different speeds. The results show that the dynamic characteristics of the flywheel shaft are stable, and its structure is simple and efficient. The comparison between the calculated unbalance response and the experimental response indicates that the dynamic model is appropriate. When the flywheel started up and rotated at different speeds, the rubbing dynamics behavior was obtained by the experiment. Full rubbing occurred at high speed would damage the flywheel and stop, which should be tried to avoid

Influence of friction coefficient on rubbing behavior of oil bearing rotor system

The failure occurred frequently when rubbing, especially when the rotating machinery worked in abnormal conditions. The research of friction coefficient on rubbing behavior was not much. The model of rubbing rotor system was established. The rubbing characteristics of the different friction coefficient were compared and analyzed. The results showed the friction coefficient had no effect on motion of period 1, period 2 and period-doubling bifurcation, when rotating speed was low. With the increase of the friction coefficient, the chaotic motion transformed into quasi-periodic, and period N motion when rotating speed was in 760-820 rad/s. The chaotic motion disappeared when rotating speed was in 1260-1400 rad/s, and the zone of quasi-periodic motion was expanding