Influence of Lubricant Film Cavitation On the Vibration Behaviour of a Semi-Floating Ring Supported Turbocharger Rotor with Thrust Bearing

This contribution investigates the influence of outgassing processes on the vibration behaviour of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly non-linear bearing properties, the rotor can be excited via the lubricating film, which results in sub-synchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend both on the kinematic state of the supporting elements and the thermal condition as well as the occurrence of outgassing processes. For modelling the bearing behaviour, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the 3D energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (Half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction and the thermal bearing condition are discussed.

PENGUJIAN EKSPERIMENTAL UNTUK MEMPELAJARI KARAKTERISTIK GETARAN PADA MODEL ROTOR GANDA KIT MENGGUNAKAN ANALISIS PETA SPEKTRUM DAN ORBIT

In modern technology, vibration signal is to be utilized in predictive maintenance application,more often when Dynamic Signal Analyzer (DSA) is invented. Unballance in rotor cause significantdeflection on rotated shaft and possible damage the machine. DSA is used in monitoring a condition ofbig rotation machines such as turbin, compressor, pump and generator. This research used double rotorsshaft system which was supported with journal bearing as a modification from the real rotation machines.Two of vibration characteristic as a sign of abnormal condition in rotation machine are unballance andoil whirl phenomenon. Meanwhile, oil whirl is seen in many rotation machines that use journal bearingas support its shaft. For rotation machine with high speed, oil whirl phenomenon can cause resonance inthe system, and then become the oil whip. Based on this condition that is very reasonable for makingearly detection, identification, and looking for the solution to prevent not wanted incident.

Emergence of tangential stiffness through the use of inclined orthotropic material

A flexible bearing support structure is effective for stabilizing the self-excited vibration of a bearing, such as oil whirl. The stabilization effect is increased if the structure has static tangential stiffness, where the reaction force is perpendicular to the displacement. In this study, it is shown that a support component made of inclined orthotropic material, which exhibits shear–extension coupling, can have tangential stiffness. The circumferential average of the tangential stiffness was found to vanish with a rotationally symmetric configuration of these components because the tangential forces of each component cancel out. However, the tangential force was recovered by allowing separation on the contact surface. A circular formation of an inclined orthotropic sheet that shows an axisymmetric stiffness matrix is proposed. Theoretical and numerical analyses clarified the effects of the friction coefficient, fitting interference, and degree of anisotropy of the material. Zero interference was found to be the best condition to maximize tangential stiffness.

The Challenge of Feedback in Fluid Power Tribotronic Control Systems

The hunt for increased efficiency and reliability of fluid power components have entailed a great deal of research on loss and wear mechanisms by means of computational tribology simulation in the last decades. The vast amount of theoretical work within tribology necessitates validation of the simulation models. The aim to validate such models has in recent years increased interest in sophisticated tribological measurement technology. A next level, for tribology in fluid power, is the integration of modelling, analysis and measurement technology with control to achieve active tribology, namely fluid power tribotronics. In this paper the challenge of feedback for tribotronic control loops in fluid power are addressed. Fundamental questions are in this regard to what extend do we need information? Is it necessary to measure fluid film thickness absolutely or dynamically, or do we even need in-situ information on the tribological joints? These questions are analysed in this paper by use of a dynamic lubricated journal-bearing model. From this analysis a conclusion on the oil whirl limit is found, which reveal an interesting perspective and potential risk in the application of feedforward in tribotronic control of lubricated journal-bearings. Finally, a discussion is concluded with the submission of relevant open research directions for fluid power tribotronic control systems.

Stepwise Intelligent Diagnosis Method for Rotor System with Sliding Bearing Based on Statistical Filter and Stacked Auto-Encoder

Since the raw signal collected from the sliding bearing is contaminated with background noise, and it is difficult to obtain high-precision results for the traditional methods due to the low signal-to-noise ratio (SNR). Therefore, a stepwise intelligent diagnosis method based on statistical filter and stacked auto-encoder (SAE) that is established with several auto-encoders is proposed to identify several faults of sliding bearing in a rotor system. Firstly, the statistical filter is utilized to reduce the interference information for the different abnormal states and to increase the SNR. Secondly, the stepwise intelligent diagnosis based on SAE is performed to learn the useful fault features, and it can automatically complete the fault diagnosis which is contributed with the superiority binary classification to fully mine the relationship between the fault characteristics and the health condition of bearing. Finally, the diagnosis of the oil whirl and structural faults in a rotor system is cited as an example to demonstrate the effectiveness of proposed method. It can effectively illustrate the advantages of the stepwise diagnosis method to obtain the maximum diagnostic accuracy.

The effect of three-lobed bearing shapes in floating-ring bearings on the nonlinear oscillations of high-speed rotors

Floating-ring bearings are widely used in automotive turbocharger machinery because of their robustness, low cost and their suitability under extreme rotation speeds. This type of bearings, however, can become a source of noise due to oil whirl/whip instability. The stabilizing effect of lobed bearing shape is known in the literature, which encourages the researchers to substitute plain cylindrical full floating bearings with lobed geometries in their outer and inner clearances to prevent the rotor-bearing system from developing oil whirl/whip instability or to reduce its amplitude of response when oil whirl/whip instability takes place. In this study, a novel concept of a floating-ring bearing with three-lobed clearances in its inner and outer films is modelled. In order to perform transient simulations, a very time-efficient approximate solution for the Reynolds equation to the geometry of three-lobed bearings is presented. Using the run-up simulation method, the nonlinear dynamic behaviours of a real turbocharger rotor supported by the novel concept of three-lobed floating-ring bearings are systematically investigated. The newly obtained results show that the sub-synchronous vibrations can be thoroughly suppressed with high preload factor at the cost of a moderate increase in the synchronous vibrations. Hence, the three-lobed floating-ring bearings design is an attractive alternative to plain cylindrical floating-ring bearings for automotive turbocharger applications.