Research Papers: Gas Turbines: Structures and Dynamics

A Field Balancing Technique Based on Virtual Trial-Weights Method for a Magnetically Levitated Flexible Rotor

[+] Author and Article Information
Yingguang Wang

Science and Technology on Inertial Laboratory,
Beihang University,
Shining Building 403,
Xueyuan Road,
Beijing 100191, China
e-mail: wangyingguang_2005@126.com

Jiancheng Fang

Science and Technology on Inertial Laboratory,
Beihang University,
Shining Building 403,
Xueyuan Road,
Beijing 100191, China
e-mail: Fangjiancheng@buaa.edu.cn

Shiqiang Zheng

Science and Technology on Inertial Laboratory,
Beihang University,
Shining Building 403,
Xueyuan Road,
Beijing 100191, China
e-mail: zhengshiqiang@buaa.edu.cn

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 14, 2013; final manuscript received March 10, 2014; published online April 21, 2014. Assoc. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 136(9), 092502 (Apr 21, 2014) (7 pages) Paper No: GTP-13-1368; doi: 10.1115/1.4027214 History: Received October 14, 2013; Revised March 10, 2014

For a magnetically levitated flexible rotor (MLFR), the amount of residual imbalance not only generates undesired vibrations, but also results in excessive bending, which may cause it hit to the auxiliary bearings. Thus, balancing below the critical speed is essential for the MLFR to prevent the impact. This paper proposes a balancing method of high precision and high efficiency, basing on virtual trial-weights. First, to reduce the computed error of rotor's mode shapes, a synchronous notch filter is inserted into the active magnetic bearing (AMB) controller, achieving a free support status. Then, AMBs provide the rotor with the synchronous electromagnetic forces (SEFs) to simulate the trial-weights. The SEFs with the initial angles varying from 0 deg to 360 deg in the rotational frame system result in continuous changes in the MLFR's deflection. Last, correction masses are calculated according to the changes. Compared to the trail-weights method, the new method needs not test-runs, which improves the balancing efficiency. Compared to the no trail-weights method, the new method does not require a precise model of the rotor-bearing system, which is difficult to acquire in the real system. Experiment results show that the novel method can reduce the residual imbalance effectively and accurately.

Copyright © 2014 by ASME
Topics: Rotors
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Fig. 1

Structure diagram of the magnetically levitated motor

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Fig. 2

Imbalance distribution of the rotor

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Fig. 3

Schematic diagram of electromagnetic force applied in rotor-fixed coordinates frame

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Fig. 4

Supplying SEFs to the rotor through AMB control system

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Fig. 5

First three order mode shapes of the rotor

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Fig. 6

The experimental platform

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Fig. 7

Amplitude and phase of the control current in coil-Bx

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Fig. 8

Amplitude and phase of rotor's synchronous vibration at sensor-A

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Fig. 9

Amplitude and phase of rotor's synchronous vibration and bending at sensor-B

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Fig. 10

Rotor vibration at sensor-B

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Fig. 11

Speed-up curves of the rotor's synchronous vibration before and after balancing



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