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Research of Rotor Dynamics Characteristics under the Action of Air Force

Author: KongFanJin
Tutor: DingXueJun
School: Huazhong University of Science and Technology
Course: Power Engineering
Keywords: blade tip clearance force seal clearance force rotor nonlinear motion bifurcation chaos
CLC: TH113
Type: Master's thesis
Year: 2011
Downloads: 140
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Abstract

Along with the rapid economic development of all countries, the requirements of electricity demand also increased dramatically. But as the main unit generating power, their required coal carbon etc non-renewable resources are gradually reducing the storage. Therefore, the development and the production of large-scale steam turbine become the inevitable trend of thermal power generation. As follow problem force induced from flow become very serious come with continuous improvement of the steam turbine steam parameters. And there will be continued to serious development trend, the ultimate impact of the steam turbine safety operation. So, the study on rotor action of motion characteristics under the flow induced force is also becoming increasingly important.This paper firstly introduces the airflow excitation induced two main flow force, seal clearance excitation force and blade tip clearance excitation force caused by impeller eccentric. And respectively set up two kinds of flow induced force model, as also as rotor model. Then with Matlab as the main computing tool, analyze the dynamics equation of rotor under the two flow induced force use numerical calculation.There are two mainly parts of this paper, firstly, theoretical analysis of rotor stability, second, numerical technique was used to analyzed the rotor motion characteristics. In the theoretical analysis part, mainly analyses the action of balanced rotor system under the seal clearance excitation force and the relationship between blade tip clearance force and its influence factor. Results showed that, there exists the critical speed that the rotor can be happen Hopf bifurcation in under the action of the seal clearance excitation force alone. And the blade tip clearance excitation force will reduce with the increase of the average blade tip clearance and angle size of air out. On the contrary, it will increase with the increase of air intake rate, air density and angle size of air in.Second, in the numerical calculation part, the rotor system was calculated respectively without eccentric mass and eccentric mass by the rotor dynamic differential equation. Among them the calculation results of balanced rotor confirmed the conclusion that Hopf bifurcation will happens on the theoretical analysis. Besides, the computation result on the unbalanced rotor present that with the increase of rotor speed, the chaos occurs through the period-doubling bifurcations or the probable periodic motion under the two force joint action in both. And the results show,in low rotational speed the blade tip clearance excitation force play a leading role, on the contrary, in high rotational speed the seal clearance excitation force play a leading role.

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