Vibration Analysis Of Centrifuge And Experiment Studies Of Damping Device

Centrifuge is a kind of mechanical equipment which is widely used in the industry to separate solids from fluid. Generally, the rotor of the centrifuge is designed as so-called the rigid shaft. But for some special industries such as the nuclear power industry flexible shall is needed. The working speed of flexible shaft is larger than the first order critical rotation speed. Some components may be destroyed owing to the violent vibration when the centrifuge rotates passing through the first order critical speed. Therefore, it is very important to reduce the vibration amplitude so as to ensure the safety operation of the centrifuge.In this thesis, experiments and numerical simulations were performed to study the vibration of the centrifuge with different rotating structures. Effects of different damping devices on the anti-vibration of the centrifuge were studied.Firstly, numerical simulations were carried out to analyze the flexible rotor structure and rigid rotor structure in order to obtain the vibration performance. Result shows that the vibration amplitude of the centrifuge can be controlled effectively by adding bearings. However, for the flexible rotor, the first order critical frequency is less than the working frequency, and the severe vibration may occur when the centrifuge rotates passing through the first order critical speed. It is necessary to install the damping devices to control the vibration amplitude of the centrifuge.Secondly, three kinds of dampers have been selected as the centrifuge's damping devices in line with the vibration performance of the centrifuge and vibration principle. Load-resistance ability, energy-dissipation capacity, property stability and the sensibility with temperatures of the dampers have been experimentally studied. Results show:(1) The damper KX-900 has bigger damping coefficient and thus, stronger to resist the load. However, its stability of the performance is lower with the increase of the frequency. The load-resistance capacity of BTA-900 and MTA-900 dampers is a little lower, but their performance is more stable. (2) The damper KX-900 is good at the energy-dissipation capacity in low frequency with small amplitude, but with the increase of the amplitude or frequency, the energy-dissipation capacity is declined sharply. However, area of hysteresis curve of the dampers BTA-900 and MTA-900 is slightly smaller than that of the damper KX-900 with the low frequency and small amplitude. The energy-dissipation capacity of the dampers BTA-900 and MTA-900 is able to maintain stability or in other words, less affected by the frequency and amplitude.. (3) The energy-dissipation capacity of the dampers BTA-900 and MTA-900 is quite well at 0?. But the area of load-displacement hysteretic curve of the damper BTA-900 is decreased with the increase of temperatures. The performance of the damper BTA-900 is not stable with the change of the temperatures. However, the area of the load-displacement curve of the MTA-900 can keep a better saturation meaning a better energy-dissipating capacity when changing temperatures.Thirdly, three kinds of damping spring are also chosen as the centrifuge's damping devices The dynamic stiffness, static stiffness and energy-dissipating capacity have also been experimentally studied. Results show:(1) The dynamic stiffness is less affected by the frequency. When the amplitude is constant, the dynamic stiffness of damping spring B100 is the biggest while the damping spring B101 is the lowest and the metal spring maintains a fixed value. With the increase of the amplitude and a constant frequency, the dynamic stiffness of rubber spring, especially the spring B100, is increased while the metal spring keeps constant. (2) Regarding the energy-dissipating capacity, the spring B101 is the best and the A101 spring is the worst. (3)The spring B100 is the best under the working condition of the centrifuge.Finally, the harmonic response analysis was performed to analyze the vibration performance of the centrifuge with or without damping devices. The maximum amplitude was obtained and the damping effects were analyzed. In addition, the speed-time eurvc at acceleration or deceleration working stage of the centrifuge was also given which is helpful for the safety operation of the equipment.