Abstract
Specific to a problem of large vibro-impact aris ing from the cutting unit of the hard rock tunnel boring machine (TBM), a hybrid magnetic coupler based on soft start was proposed in this paper. The mathematical model for total eddy current losses of such a coupler was established by field-circuit method. Then, magnetic-thermal coupling simulation was performed by virtue of three-dimensional finite element software. In addition, an experimental prototype was independently designed; by comparing the model with experimental data, validity of the above mathematical model was verified. The relevant research results indicated that calculated values were consistent with experimental values, and the magneto thermal coupling method could be applied to accurately analyze temperature distribution of the hybrid magnetic coupler. By contrast to the existing magnetic coupling of the same dimension, output efficiency of the hybrid magnetic coupler was improved by 1.2%. Therefore, this research technique can provide references for designing the cutting unit of hard rock TBM with a high start impact.
Highlights
The cutting unit serves as a core component of the hard rock tunnel boring machine (TBM), and its performance has a direct influence on structural strength and service life of the TBM [1,2,3]
TBM during running, a hybrid magnetic coupler based on soft start was proposed in this paper
A mathematical model was established for the total eddy current loss of the hybrid magnetic coupler based on a field-circuit method on the one hand; on the other hand, two types of 3D finite element software including ANSYS workbench and ANSOFT Maxwell were adopted to perform magneto thermal coupling simulations
Summary
The cutting unit serves as a core component of the hard rock tunnel boring machine (TBM), and its performance has a direct influence on structural strength and service life of the TBM [1,2,3]. Optimal design was carried out by Mohammadi et al for a single/double-disc magnetic eddy-current coupler in combination with the conventional Faraday’s law of electromagnetic induction and Ampere’s law, based on which an analytical model that can be adopted to deal with complex geometry and material performance is further proposed [17]. Combining the traditional barrel magnetic coupler and the double plate magnetic coupler, did the area of the induced magnetic field increase, but magnetizing could be performed both axially and radially to improve the corresponding propagation efficiency. A total eddy current loss model was set up for such a type of magnetic coupler to compare the output efficiency between it and the general double plate magnetic couplers. This study aims at lowering starting vibro-impact of the TBM cutting unit and to provide protection for such a cutting unit under the circumstance of regular overload
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