Numerical Analysis on Steam Exciting Force Caused by Rotor Eccentricity

The steam exciting force has been proved to be great threat to the operation safety of steam turbines. The mechanism of steam exciting vibration cannot be profoundly revealed by simply analyzing the steam exciting force, especially in simplified models. Therefore, a full-circle stage of steam turbine with shroud and labyrinth seals was investigated by numerical simulator CFX. The instability of leakage flow and the pressure fluctuation were analyzed on the eccentric condition. The effects of leakage vortexes, the depth-width ratio of seal cavity, and the eccentricity on the steam exciting force were studied. Results show that the leakage flow is nonuniform in the circumferential direction with the change of front teeth vortexes, which causes the steam exciting force. The tangential and radial steam exciting force both increase with the eccentricity increasing. The effects of the depth-width ratio of seal cavity on the two forces are different. In addition, the pressure fluctuation caused by the leakage vortexes on the shroud surfaces is a main factor inducing the steam exciting force. This research provides a theoretical guidance for the operation safety and optimization of steam turbines.

Fault Diagnosis for Steam-flow Exciting Vibration of Ultra Supercritical 1000 MW Steam Turbine

With the increase in thermal power capacity, ultra supercritical units have become the mainstream of power industry. At the same time, with the improvement of the steam parameters and the lengthening of shafting, the production of steam flow excited vibration is frequent in the ultra supercritical units, which may seriously affect the reliability of the unit. This paper has taken steam flow excited vibration of a 1000MW turbine as an example in accordance with the experimental and theoretical causes of steam flow excited vibration to solve the problem of steam flow excited vibration by the proposed treatment plan. This can greatly improve the reliability of operation and the units with high load capacity.

Compaction Effect of Granular System with Parameters Changed

In this work, the numerical equation has been established to simulate the vibratory compaction system based on the hysteresis loop of Davidenkov and with the gap ignored between the piston and the materials, and the dynamical characteristics and influence of parameters on the vibration compaction effect were analyzed with different stiffness, damping, amplitude and mass. Two types of experiments were carried out to study the dynamical characteristics and validate the numerical analysis and simulation. The first type of experiments was done with the different exciting vibration amplitude. The second type of experiments was done with the different water saturation instead of the stiffness and damping. The numerical and experimental results show that the equivalent natural frequency and vibration amplitude of the system increased with the stiffness, exciting amplitude increased and damping decreased. The experimental results agree well with results from a theoretical model in general. The research results will be used in intelligent granular compaction in the future.

Experimental Modal Analysis of the Industrial Flat Sewing Machine Based on PolyMax Algorithm

In this paper, the free modal of the industrial flat sewing machine was researched, and the experimental measurement system is established. A modal analysis of industrial flat sewing machine is carried out through the method of single point exciting vibration and multipoint collecting signal. The PolyMax modal parameter identification method is applied to the modal analysis for frequency response function to get steady state diagram and then determine the modal parameters and modal shapes. According to Modal Assurance Criterion (MAC), the credibility of the calculation results is verified, and then modal parameters of industrial flat sewing machine get more reliable in order to provide the reference for further structure optimization and noise reduction of the flat sewing machine.

Dynamic Responses of the Powerhouse Structure of Hydropower Stations due to Hydraulic Excitation

As the capacity and water head of large hydropower projects become higher and higher, the flow-induced structural vibration of powerhouse becomes a very important problem for the design and operation process. Especially as the water head and the running speed are much higher for the pump-turbine than the general turbine, the hydraulic exciting vibration is very remarkable. In this paper the simulation results of free-vibration characteristics of powerhouse structure for different types were concluded and the frequency behavior of the pressure fluctuation in spiral case and draft tube were discussed. The structural dynamic responses under hydraulic exciting were presented including the dynamic responses of displacement, velocity, acceleration and stresses. Based on the vibration criterion of the powerhouse structure, the vibration evaluation was made.

Experimental Investigation of Characteristics of Vibratory Compaction System with Different Water Saturation

In this work, the numerical equation has been established to simulate the vibratory compaction system based on the hysteresis loop of Davidenkov and with the gap ignored between the piston and the materials, and the dynamical characteristics and influence of parameters on the vibration compaction effect were analyzed with different stiffness, damping, amplitude and mass with different water saturation. The two types of experiments were carried out to study the dynamical characteristics and validate the numerical analysis and simulation. The first type of experiments was done with the different exciting vibration amplitude. A second type of experiments was done with the different water saturation (3%, 8% and 17%) instead of the stiffness and damping. The numerical and experimental results show that the equivalent natural frequency and vibration amplitude of the system increased with the stiffness, exciting amplitude increased and damping decreased. The experimental results agree well with results from a theoretical model in general. The research results will be used in intelligent soil compaction in the future.