Abstract
An accurate modal analysis of the stepped rotor assembly is significant in the design process of rotors. The transfer matrix method (TMM) is widely used in the modal analysis of the rotor. However, the influences of the step and the assembling modes are not considered in the traditional TMM. In this paper, a modified transfer matrix method is presented for the modal calculation of the rotor in the turbomolecular pump. The stiffness reduction of stepped segments and the effect of assembled components are considered in this modified method. First of all, the traditional transfer matrix model is built. Then, the stepped segments of the rotor are changed into conical segments and the lumped mass model of conical segments is calculated. Next, the conicities of conical segments are analyzed and relations between conicities and dimensions of the rotor are discovered. Finally, the stiffness factors which can describe the effects of different assembling modes are introduced and optimized. The optimized stiffness factors are analyzed and explained from the perspective of contact stress. The modal of the stepped rotor assembly could be computed with high accuracy by using this method.
Highlights
The increase of the speed brings higher requirements for the static and dynamic analysis of the rotor. ough the application of the magnetic bearings can suppress the vibration of the rotor through different active control [2, 3], the dynamic design is still significant in the process of the rotor design
The uniform formulation of the dynamic vibration analysis of multispan beams was presented by using an efficient domain decomposition method and the vibration characteristics was obtained by using Rayleigh-Ritz method [5]. e main purpose of them is to establish a more accurate dynamic model
The results by the modified transfer matrix method (TMM) are close to the results of the modal test and the results by the modified finite element method (FEM). erefore, the modified TMM can enhance the accuracy of the modal analysis of the rotor assembly
Summary
High-speed motors show the advantages of high-power density, small volume, and small moment of inertia, which leads to extensive applications in the air blower, air compressor, and molecular pump, etc. [1]. Is change is not properly described in the mathematical model of beam theories Some scholars considered this influence and modified modal analysis model to reckon it in [18–23]. E multistepped rotor systems were analyzed using a new method called continuous segment method [21] All this literature solves the dynamic analysis of the stepped rotor by the numerical methods. E modal analysis of the rod-fastened rotor was studied and the flexural stiffness of the contact interface considering the pretightening force and bending moment was derived [26]. Is paper mainly proposes a modified TMM which includes the effects of the abrupt change and assembling modes of the stepped rotor assembly. E modal of the stepped rotor assembly could be computed with high accuracy by using this modified TMM Optimized stiffness factors are analyzed and explained from the perspective of contact stress. e modal of the stepped rotor assembly could be computed with high accuracy by using this modified TMM
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