Tham khảo tài liệu 'friction and lubrication in mechanical design episode 1 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Ì80 Chapter 6 disturbed from that position the whirl orbit will gradually decay to the equilibrium point. The minimum condition is reached for this case at a speed of 5000 rpm Fig. . Any increase in the speed beyond this value would produce limit cycle orbits Fig. with increasing amplitudes. Finally at a speed of 6200rpm the orbit becomes large enough to consume all the bearing clearance producing contact between the shaft and the sleeve neglecting the effect of large amplitudes and near-wall operation on the dynamic characteristics of the film . Three different whirl conditions were found to occur also for the unbalanced rotor as illustrated in Figs for an unbalance trư lb-sec2 and To 0. At low speeds the unbalance produces synchronous whirl with relatively high maximum eccentricity as shown in Fig. . The maximum eccentricity of the orbit decreases with increasing speed until a minimum condition is reached at a speed of 4900 rpm corresponding to this unbalance. Higher rotor speeds beyond the minimum condition begin to produce nonsynchronous whirl with increasing maximum eccentricities Fig. . Finally at a speed of 6100 rpm the orbit continues to increase until contact with the sleeve occurs Fig. . A summary plot for these different orbit conditions as affected by the magnitude of unbalance is given in Fig. . Isoeccentricity ratio lines are plotted from the steady-state orbits to illustrate the effect of speed and unbalance on the type and magnitude of the rotor vibration. A similar plot is given in Fig. for the peak eccentricity occurring during the rotor operation. These eccentricities generally occur during the transient phase before steady-state orbits are attained. Of particular interest is the minimum peak eccentricity locus shown in broken lines in Fig. . Also of interest is the sleeve contact curve. Although this curve is obtained with simplifying assumptions it serves to illustrate .
