Dynamic Characteristics Analysis of Circumferential Rod Fastening Rotor-Bearing System Considering Contact Stiffness

doi:10.12096/j.2096-4528.pgt.21052

Abstract

Abstract:

In order to explore the dynamic characteristics of the circumferential rod fastening rotor-bearing system, a numerical model of three-dimensional Gaussian random rough surface was established by using the method of autocorrelation function. Moreover, the geometric model of rough surface was generated by Ansys APDL. Abaqus software was used to simulate the contact of rough surface, and the contact stiffness of rough surface under different preloads was obtained. The finite element model of the circumferential rod fastening rotor-bearing system of a certain type of gas turbine considering the contact stiffness was also established. The dynamic characteristics of the system with different preloads and clearances of bearing assembly were calculated. It is shown that critical speed of rotor-bearing system increases nonlinearly with the increase of preload, and the amplitude of unbalance response increases with the increase of preload and clearance of bearing assembly as the rotor has passed the critical speed.

Key words: rod fastening rotor, contact stiffness, assembly clearance of bearing, dynamic characteristics

CLC Number:

TK05

Ying CUI, Han ZHANG, Yuxi HUANG. Dynamic Characteristics Analysis of Circumferential Rod Fastening Rotor-Bearing System Considering Contact Stiffness[J]. Power Generation Technology, 2021, 42(4): 447-453.

Figures/Tables 14

Fig.1 Numerical modeling method of rough surface

Fig.2 Numerical representation of rough surface

Fig.3 Geometry model of rough surface

Fig.4 Finite element contact analysis model

Tab. 1 Parameters of material plastic constitutive relation

应力/MPa	塑性应变	应力/MPa	塑性应变
418	0	908	0.350 00
500	0.015 81	921	0.450 00
695	0.056 00	932	0.550 00
780	0.095 00	955	0.650 00
829	0.150 00	988	0.750 00
882	0.250 00	1 040	0.850 00

Tab. 2 Normal contact stiffness under different preloads

预紧力/kN	法向接触刚度/(10⁹ N/m)	预紧力/kN	法向接触刚度/(10⁹ N/m)
10	16.35	60	98.12
20	32.71	70	114.48
30	49.06	80	130.83
40	65.42	90	147.19
50	81.77	100	163.54

Fig.5 Three dimensional solid model of circumferential rod fastening rotor

Fig.6 Four-tilting pad bearing

Fig.7 Finite element model of circumferential rod fastening rotor-bearing system

Fig.8 Variation of critical speed with preload

Fig.9 Vibration mode of circumferential rod fastening rotor-bearing system with 50 kN preload

Fig.10 Unbalanced response of rod fastening rotor-bearing system with different preloads

Tab. 3 Dynamic parameters of bearing with different assembly clearances

装配间隙C_b/μm	刚度/(10⁸ N/m)	阻尼/(10⁴ N·s/m)
50	3.67	4.90
60	2.12	2.83
70	1.34	1.78

Fig.11 Unbalanced response of rod fastening rotor system with different assembly clearances of bearing

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