Dissertation > Industrial Technology > Machinery and Instrument Industry > Mechanical parts and gear > Moving parts

Hopf Bifurcation of a Jeffcott Rigid Rotor with Oil-Film Forces and Steam Forces

Author LiuJiHao
Tutor CaoShuQian
School Tianjin University
Course General and Fundamental Mechanics
Keywords Rotor Nonlinear airflow force Nonlinear Oil Film Force Hopf bifurcation
Type Master's thesis
Year 2008
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The large rotating machinery is one of the key equipment of modern industrial society , affect the stability of the rotor-bearing system in the variety of nonlinear motivating factor , especially nonlinear oil film force on the rotor shaft system stability . Gas excitation of the important issues of the steam turbine rotor stability , especially for supercritical and ultra-supercritical steam turbine rotor , the problem is more prominent . At present , the research on this issue , mostly restricted airflow force model the nonlinear gas excitation mechanism is relatively small , especially taking into account the failure of the rotor under the combined effect of the gas excitation and nonlinear oil film force steady state conditions, the research is not very good . In this paper, nonlinear dynamics theory and methods , to short bearing support rigid Jeffcott rotor system as the research object , and to study the stability of the rotor in both nonlinear force . The papers work includes the following sections: 1 . Reviewed the oil film instability and gas excitation Research ; 2 . Rigid Jeffcott balanced rotor the dimensionless nonlinear oil film force and non-linear airflow force movement differential equation; variable substitution of dimensionless equations corresponding perturbation equation disturbance equation . The study found that : when the air flow velocity V increases relative intake balanced rotor system critical instability speed ahead and then its behavior at the critical point at the Hopf bifurcation study and draw the corresponding Hopf bifurcation diagram . Using numerical integration methods to get the system in the domain bifurcation diagram of the different parameters , as well as certain parameters , the motion of the rotor phase diagram , Poincaré map . The results showed that the relative gas velocity V is fixed value , as the speed increases , the motion characteristics of the periodic motion . When the interaction the airflow force and oil film force , the critical instability speed than airflow force is not considered in advance . V to relative air intake speed as the bifurcation parameter , research in rotor speed case law of motion , the study found : As V increases , the system suddenly Almost Periodic instability amplitude with increasing V, increases. Through this study , the steam turbine rotor instability mechanism under the combined action of the the nonlinear air force and oil film force has a certain understanding results provide some basis for the diagnosis and control of the turbine rotor instability .

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