Fund Project: Yunnan Province Applied Basic Research Fund (E(1)37M) 1 Induction Online Vertical Mixed-water Turbine Generator Set is an excellent machine widely used to convert water energy into electrical energy. Its rotor bearing system operates in the same way as all high-speed rotating machines, and inevitably there are varying degrees of vibration. However, its vibration is much more complicated than the general mechanical vibration. Firstly, there are many factors that cause the vibration of the hydro-generator set. Secondly, these factors are simultaneously dominated by the interaction and coupling of the operating unit system, and the response output of the unit's comprehensive vibration is controlled. Many scholars have carried out many fruitful theoretical studies on the individual factors that cause the vibration of the unit and achieved certain results, making it difficult to use the abnormal comprehensive vibration response output to correctly diagnose and analyze the unit failure.
In order to ensure the safe operation of the hydro-generator unit, the countries around the world generally adopt the following passive emergency measures according to their accumulated experience: First, according to the different devices and bearing forms of the unit, the allowable range of vibration is specified; The operating period of the operation is mandatory for the inspection and maintenance of the machine. The above emergency measures have played an important role in the safe operation of the unit. However, its shortcomings have not revealed the actual cause of the failure. The mandatory periodic maintenance system is likely to cause excessive maintenance of the unit. It not only affects production, but also costs a lot. In a sense, it is also difficult to ensure safe and reliable operation of the unit, and it is easy to form a vicious circle of ill-conditioned maintenance and morbid operation. Today, in the development and application of modern electronic technology and microcomputer technology, it is necessary to find a new method of fault diagnosis and analysis, from passive maintenance to active maintenance, from mandatory regular maintenance to on-line continuous monitoring and condition-based maintenance.
In this paper, the mechanism of vibration of hydro-generator unit is discussed in depth. On the basis of analyzing the influence of hydraulic, mechanical and electrical factors on the vibration of the unit system, the direct balance method of d*Alembert principle and the principle of Laicha gyro are considered. The above three factors are the dynamics governing equations of the unit system vibration. For the first time, the above three factors are discretely and decoupled, which clearly reveals the independent contribution of the above three factors to the vibration of the unit and the corresponding coupling relationship, which provides a theoretical basis for the establishment of a new unit fault diagnosis method.
2 Dynamic analysis of vibration mechanism and vibration response of the unit system The hydraulic turbine is the hydraulic prime mover of the hydro-generator unit. It uses the rotor blades to interact with the water flow to convert the water energy into the rotational mechanical energy of the shaft and further convert it into electrical energy. The common vertical mixed flow turbine generator set structure is as shown. The causes of the vibration of the hydroelectric generating unit are summarized as follows: hydraulic, mechanical and electrical factors. The overall vibration response of the unit system is evaluated by the amplitude of the vibration along the Z and X axes and the amplitude of the swing of the main shaft. To this end, we must start from the above three factors to discuss the mechanism of the unit system vibration, and establish the mathematical model between the force acting on the unit system and the vibration response of the unit caused by the above three factors.
2.1 The force of the water flow on the runner blade The right side of the above formula is the relative velocity force, the centripetal acceleration force and the Coriolis force. We can abbreviate the above expression as: () integral and according to the law of action and reaction, The equivalent rotation to the center of rotation of the runner can be obtained by the following hydraulic forces: the action torque of the water flow on the runner: K-turbine model coefficient; D, the standard diameter of the turbine; 1* one-column coordinate system radial Coordinate unit vector; Y - water bulk density; 0e * turbine effective over flow; Van * Vu2r2 - inlet and outlet water flow velocity moment.
In addition, when the unit load changes, the runner outlet water flow will generate pressure pulsation in the draft tube to form a spiral vortex vortex as shown. It is also the source of vibration of the unit. Its mathematical expression can be described as: mixed flow turbine tail The shape diagram of the inner belt of the water pipe is finally mentioned as the Karman vortex problem, which is only the exciting force acting locally on the rotor blade, because it consumes energy by damaging the blade and can be eliminated by the modification of the blade tail. Therefore, the vibration of the whole unit system is less affected. Even if the blade breaks, it will cause a sudden change of the torque of the runner, which is easy to identify from the fault diagnosis analysis. For the above reasons, it is omitted in the force analysis.
2.2 The mechanical and electrical factors caused by the mechanical reasons caused by the unit vibration is mainly caused by the imbalance of the unit's rotational mass, the inertial force generated by it is: electrical causes the unit vibration mainly comes from the gap between the stator and the rotor The magnetic pulling force caused by uniform rotation, the component of the magnetic pulling force along the X direction is given by the following formula; 9 the power angle of the generator; the generator power factor angle; the effective eccentricity of one machine pair; the axial length of the wi-rotor 2.3 Gyro effect of unit system rotation Because there is a certain gap when the upper and lower guide bearings of the unit are installed, the unit is equivalent to a gyro supported on the thrust bearing at high speed rotation to form a gyro effect. According to the theory of Laicha Gyro, the pitch of the main shaft The degree is described by the following equation: The lumped calculation model of the 3 hydro-generator rotor bearing system The lumped calculation model of the unit is shown by the right half. In the figure, the flange coupling is treated as a rigid coupling, and the upper and lower guide bearings and the thrust bearing are both hydrodynamic bearings, and the oil film force can be approximately linearly expressed as: not only the displacement component along the X and Z axes.
4 Dynamics governing equations for hydro-generators We apply the direct balance method of d*Alembert principle and the theory of Laicha gyro. From the above (1)-(10) formula, the following dynamic governing equations describing the vibration response of the system can be obtained: The angles of each matrix and displacement vector are abbreviated. For example, ~(13) describes the vibration of the unit system along the axial, horizontal and spindle swings after comprehensive consideration of hydraulic, mechanical and electrical factors. The law forms a one-to-one correspondence with the evaluation unit's comprehensive vibration response output. Of course, the above three equations can also introduce the generalized coordinate g, which is written as the following standard form: 5 Conclusion The dynamic equation of the vibration response of the unit system is established for the first time. The three factors of hydraulic, mechanical and electrical are discrete and solved, and the description is clearly described. The degree of influence and coupling relationship of hydraulic, mechanical and electrical factors on the comprehensive vibration response of the unit. It can be seen from equation (11) that only the hydraulic factors affect the axial vibration of the unit; from (13), it can be seen that the swing of the main shaft is the result of the coupling of hydraulic and mechanical factors, only the horizontal unit system. Vibration is the result of the coupling of hydraulic, mechanical and electrical factors. And the response of various factors of hydraulic force to the above vibrations is only partially or independently intervened. The above conclusions have proven to be correct through many examples of past downtime repair failures.
The discrete decoupling results of the hydraulic, mechanical and electrical factors that will occur simultaneously on the comprehensive vibration have laid a theoretical foundation for the new fault diagnosis methods for online continuous monitoring and condition-based maintenance.
For us to use the transfer matrix method or the finite element method
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