Research Of Fault Diagnosis Of Hydro-power Set Based On Coupled Flexural And Torsional Vibrations And Shaft Orbits Recognition

With the research and application of the gaint and large capacity hydroupower set, the problem of vibration on hydro-unit shafts stands out. Researches on vibration mechanism have been carried out deeply and many efficient methods for status monitory and fault diagnosis have been explored. But Limitted by the level of the researches, many vibration faults could not be diagnosed exactly. It is a challenge for us to research the coupled lateral and torsional vibration and its mechanism. The achievements would help us understand the dynamic characteristics of the rotor comprehensively and rich the manners of analyzing the vibration to increase the accuracy of the fault diagnosis.Based on a single-disc rotor with rigid support, the differential equations of coupled vibrations influenced by gyro moments are established. The coupled vibration properties are discussed by numerical simulation. The response of the free lateral vibration has bigger amplitude than that without considering the gyro effect. The frequencies of lateral vibration contain 1X component,coupled |?±ωti| component and |ω1i±ωti| component. The frequencies of torsional vibration contain coupled |?±ω1i| and |?±ω2i| component. Because of no considering the effect of gravity, there are few 1X component in the response of the torsional vbration. These coupled components can represent the status of the hydro-power unit. The amplitude of the lower frequencies below 2Hz increases with the increment of the rotatinal speed of the rotor. Discreasing the mass eccentricity and the polar moment of inertia is the efficient method to keep the stability of the rotor.Based on the above discussion, the dissertation researches the coupled vibration characteristics of the parallel misalignment of fixed rigid coupling (FRC) and removable rigid coupling (RRC). Lateral vibration and torsional vibration are coupled by the eccentricities caused by unbalanced mass, mialignment and so on. For parallel misalignment of FRC, the frequencies of lateral vibration contain 1X component and the frequencies of torsional vibration contain DC component, 1X component and a bigger 2X component. The DC component does harm to the rotor. Its shaft orbit is ellipse. For parallel misalignment of RRC, the frequencies of lateral vibration contain 1X component and 2nX component which 2X component is bigger. The frequencies of torsional vibration contain DC component and 1X component. The shaft orbits are ellipse with two circles when 2X component is bigger and ellipse when 2X component is smaller.Next, the coupled vibration characteristics of vertical rubbing rotor are analyzed, which are different from the horizonal rubbing rotor. There three kind of running status: normal operation, partial rubbing and all-around rubbing: In normal operation, the frequencies of lateral vibration merely contain 1X component and the frequencies of tortional vibration contain few frequency components. When the status of partial rubbing happens, there are NX cmoponents or NX/2 components in the response of lateral vibration and NX cmoponents or NX/2 components in the response of torsional vibration. When rotor fall in the status of all-around rubbing, the frequencies of lateral vibration merely contain 1X component and 2X component and the frequencies of tortional vibration contain 1X component and 2X component. Some impact factors for the rubbing rotor, such as mass eccentricity and clearance, have been discussed. Unbalanced mass and and misalignment are main reasons of the increment of mass eccentricity. And the decrease of clearance also cause rotor rubbing. Hence, when the status of the unit goes worse, the increment of mass eccentricity and the decrease of clearance would cause rotor rubbing.By summarizing the studies published in recent years, the dissertation introduces three methods to identify the shaft orbits automatically and gives an evaluation for them. Modified Fourier descriptors method has the highest classification capability. However, it needs a fair complexity transformation. It is cumbersome that we must transfer shaft orbits to pixel image when we adopt the PJFMIs method. But the affine moment invariants method not only has a higher classification capability but also computes easily. It is much suit for practical application.At last, the dissertation applies the conclusions to practical application. In order to apply results to practice, monitoring and fault diagnosis system of coupled vibrations of hydro-power unit is developed. The total design, detailed function module and key technologies of the system are introduced in detail. Characteristics of flexural and torsional vibrations are applied to usual fault diagnosis.