Suppression of the Forward Rub in Rotating Machinery by an Asymmetrically Supported Guide

In rotating machinery, rubbing occurs between the rotor and the stator, at the seal, between the rotor and the guide and between the rotor and the backup bearing. The backward rub or the partial impact vibration can be avoided by lubricating the contact surface sufficiently in order to decrease the friction. However, forward rub may still occur in such a case with a lubricated contact surface. Once such a forward rub occurs, it remains even if the rotational speed increases to much larger than the first bending critical speed and it is difficult to escape from this forward rubbing condition automatically. This paper proposes the suppression method of this forward rub by introducing the directional difference in the support stiffness of the guide or the backup bearing. The nonlinear theoretical analysis clarifies and explains the usefulness of the proposed method and it is also validated experimentally.

The Influence of Damping Coefficient on Vibration Characteristic of a Rub-Impact Rotor under Axial Thrust

A model of a rub-impact rotor system under axial thrust is established based on the classic impact theory and analyzed by the Lagrangian dynamics and bifurcation theories. The rubbing condition is modeled using the impact-contact idealization, which consists of normal and tangential forces at the rotor-to-stator contact point. The effects of lateral damping and rotor rotating speed on the rotor system response are investigated in detail. It is demonstrated that the system goes through an extraordinary route to bifurcation. Periodic, quasi-periodic and chaotic motions are found as the system parameters change.

Study on Mechanism and Experiment of Engine Cylinder by Laser Honing

The diesel engine cylinder was processed by laser honing (LH) device, the structure morphology was observed with scanning electric mirror (SEM), and lubricant consumes and wear performances were measured, at the same time the mechanism of LH and effects of laser parameters on LH results were analyzed. The experimental results are shown that LH is a kind of phase transformation treatment by laser, which processes a hardening belt in the certain distributing form on the work-piece surface, and forms the hardness distribution of soft and hard material alternatively; LH may lower the engine oil consumes 30%-60%, and reduce the pollution of the catalyst machine, and lower the grain let of the engine oil 25%-30%. LH intentionally machines the grain cave, which has the certain angle, depth, and width etc.. The surface microcosmic sculpting has the lubricating function for usage process, and storage and transport lubricant, which improves the rubbing condition, then lower the part wear and increase the other performances. The short-wave laser is more applicable to the LH process, which improves the lubrication condition, and increases the service life of the engine and the efficiency, and lowers the engine oil consumes.

Case History: Generator Rotor Shorted Turn Induced Vibration Excursion

The diagnosis of a generator rotor vibration in a 1,000 MW nuclear plant unit is presented. Several vibration excursions were recorded between July and August 2002. The excursions were somewhat repetitive in shape, but erratic and presented a clearly worsening trend, which threatened the continuous operation of the unit. In addition to high bearing vibration levels, the vibration force was transmitted to the Generator’s Current Transformers showing vibration levels in excess of 18 mils. The diagnosis of the rotor vibration excursions was simultaneously conducted by the Original Equipment Manufacturer (OEM) and a third party. An existing rubbing condition in the exciter and the generator hydrogen seals is presumed to have contributed to the elevated vibration levels reached during the excursion. A flat orbit in the generator side of one of the low pressure rotors was also recorded during the investigation. The existing rubbing condition caused discrepancy in the diagnostic between both parties. The OEM attributed the excursions to that rubbing condition while the third party attributed it to Generator Rotor Shorted Turns. Later inspection of the generator rotor revealed that the second diagnostic was correct. The characteristics of the vibration condition, the trouble shooting approach and the solution are described in this article.

Case History: Generator Rotor Shorted Turn Induced Vibration Excursion

The diagnosis of a generator rotor vibration in a 1,000 MW nuclear plant unit is presented. Several vibration excursions were recorded between July and August 2002. The excursions were somewhat repetitive in shape, but erratic and presented a clearly worsening trend, which threatened the continuous operation of the unit. In addition to high bearing vibration levels, the vibration force was transmitted to the Generator’s Current Transformers showing vibration levels in excess of 18 mils. The diagnosis of the rotor vibration excursions was simultaneously conducted by the Original Equipment Manufacturer (OEM) and a third party. An existing rubbing condition in the exciter and the generator hydrogen seals is presumed to have contributed to the elevated vibration levels reached during the excursion. A flat orbit in the generator side of the low pressure rotor LP-C was also recorded during the investigation. The existing rubbing condition caused discrepancy in the diagnostic between both parties. The OEM attributed the excursions to that rubbing condition while the third party attributed it to Generator Rotor Shorted Turns. Later inspection of the generator rotor revealed that the second diagnostic was correct. The characteristics of the vibration condition, the trouble shooting approach and the solution are described in this article.