investigations on a permanent magnetic–hydrodynamic hybrid

Tribology International 35 (2002) 443–448 www.elsevier.com/locate/triboint Investigations on a permanent magnetic–hydrodynamic hybrid journal bearing Qingchang Tan ∗ , Wei Li, Bo Liu Department of Mechanical Engineering, Jilin University, Nanling Campus, Changchun 130025, People’s Republic of China Received 1 January 2002; received in revised form 5 March 2002; accepted 7 March 2002 Abstract In the present work, a permanent magnetic–hydrodynamic hybrid journal bearing is developed. The force of the journal bearing comes from the hydrodynamic film and the permanent magnetic field. When a hydrodynamic film does not form, such as during starting and stopping a machine, the journal bearing relies on the magnetic force to support the rotor system. This paper studies a model of the permanent magnetic force and develops an experimental rig of the journal bearing. Experiments show that the hydrodynamic film force uncouples with the magnetic force in the journal bearing. Predictions from the model are compared with experimental data. 2002 Elsevier Science Ltd. All rights reserved. Keywords: Journal bearing; Hydrodynamic lubrication; Permanent magnetic force 1. Introd uction From lubrication theory [1,2], we know that a hydrodynamic film does not form in journal bearings and a sta te of hy bri d friction may occur when starti ng and stopping a machine. The state of hybrid friction affects the work prop erties of journal bearings and causes bearing bushes to wea r. The state of hy bri d fri cti on als o affects the work of machines in a lot of situations. There- fore, it is needed to overcome the above drawbacks of journal bearings and to develop new bearing techno- logies. Hydro dyna mic–h ydros tatic hybr id journ al bearin gs and magnetic suspension bearings, as new bearing tech- nologies, ind eed eli min ate the dra wba cks of jou rna l bearings and improve the work properties of machinery. But the two kinds of bearings are complicated in structure, comprising components such as a hydraulic system, sensors, power amplifiers and controllers, so that they are expensive for ordinary applications. The present work tries to develop a permanent magnetic –hyd rody namic hybri d (PMHH) journ al beari ng. The force of the PMHH journal bearing comes from the ∗ Corresponding author. E-mail address: [email protected] (Q. Tan). 0301-679X/02/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved. PII: S0301 -679X (02)0 0026-9 permanent magnetic force and the hydrodynamic film. When a hydrodynamic film does not form, such as during starting and stopping a machine, the PMHH journal bearing relies on the magnetic force to support the rotor sys tem, pre ventin g the state of hyb rid fri cti on from occurring. This paper studies a model of force for the PMHH journal bearing and develops an experimental rig of the PMHH journal bea ring. Exp eri men ts show tha t the hydrodynamic film force uncouples with the magnetic force in the PMHH journal bearing, and the prin- ciple of the PMHH journal bearing can work. Predictions from the model are compared with data from the experi- men tal rig. Parameters of PMHH jou rnal bea rings are analyzed from the model and experiments. 2. Pri nci ple of the PMHH journal bear ing In the present work, the magnetic force of the PMHH journal bearing comes from a rare earth permanent mag- net. Permanent magnets are used instead of electromag- net s bec aus e of the fol lowing con sid era tio ns. Fir st, although electromagnets are active and controllable, sen- sor s, po wer amp lifiers and con trolle rs are nee ded for using electroma gnets in the sugg ested hybrid bearin g. And the use of sensors, power amplifiers and controllers causes the structure of the suggested hybrid bearing to

investigations on a permanent magnetic–hydrodynamic hybrid

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