# Dynamics Investigation on Axial-Groove Gas Bearing-Rotor System with Rod-Fastened Structure
## 4 Results and Discussions
### Unbalance Responses Versus Rotating Speed \(\omega\)  
At different rotating speeds, the journal center of the rod-fastened rotor experiences different motion states. The parameters of the rod-fastened rotor and gas bearing are the same as those given in Table 2. In Figure 6, when \(\omega=1000\) rad/s, the dynamic motion of the rod-fastened rotor comes out of quasiperiodic motion. Figure 6 depicts the orbit and Poincare map of the journal center at the left bearing station, and Figure 6 depicts the orbit and Poincare map of journal center at the left disk station. The spectrograms of the rod-fastened at the left bearing and left disk stations are described in Figure 6. Figure 6 shows the comparison of the time series diagram at the left bearing and left disk stations. It can be seen that the amplitude at the left disk station is greater than the left  
Figure 4: Orbits comparison of the rod–fastened rotor and continuous integral rotor at \(\omega=1500\) rad/s: (**a**) comparison of the orbits at \(\omega=1500\) rad/s; (**b**) spectrogram of the continuous integral rotor at \(\omega=1500\) rad/s.  
Figure 5: Bifurcation diagram of the rod–fastened rotor at \(\omega=900\)–\(2500\) rad/s.  
bearing station, as shown in Figure 6c,d. When \(\omega=1500\) rad/s, the periodic motion of the rod-fastened rotor-gas bearing system is described in Figure 7. Figure 7a,b shows the orbit and Poincare map at the left bearing and left disk stations; the orbit is a single circle, and the synchronous behavior is inferred from the single projection point in the Poincare map. Figure 7c,d shows the comparison of the spectrogram and time series diagram at the left bearing and left disk stations; the amplitude at the left disk station is greater but similar to the quasiperiodic motion.  
When \(\omega=2000\) rad/s, the quasiperiodic motion of the rod-fastened rotor-gas bearing system is shown in Figure 8a-d. It can be seen in Figure 8a,b, the orbits of the journal center at the left bearing and left disk stations are periodic multirings, but not the standard circle; the Poincare map presents a closed loop on the projection plane, the quasiperiodic motion is more unstable than at \(\omega=1000\) rad/s. The spectrogram and time series diagram at the left bearing and left disk stations are described in Figure 8c,d; the amplitude of the left bearing is slightly greater than the one at the left disk station. In Figure 9, the rotating speed is 2500 rad/s, and the unbalance response of the rod-fastened rotor-gas bearing system is still quasiperiodic motion. Figure 9a,b shows the orbit diagrams and Poincare map at the left bearing and left disk stations, Figure 9c,d shows the spectrogram and time series diagram at the left bearing and left disk stations. The amplitudes of the journal center of the rod-fastened rotor gas bearing system are much greater, and the dynamic stability of the rod-fastened rotor-gas bearing system is obviously reduced.  
Figure 6: Quasiperiodic motion of the rod–fastened rotor at \(\omega=1000\) rad/s: (**a**) orbit and Poincaré map at the left bearing station; (**b**) orbit and Poincaré map at the left disk station; (**c**) comparison of spectrogram at the left disk and left bearing stations; (**d**) comparison of the time series diagram at the left disk and left bearing stations.