Yu Jiong Gu

Fault Statistical Classification and Fault Mode Analysis of Steam-Induced Vibration of Steam Turbine

Steam-induced vibration fault seriously affects the reliable operation of supercritical steam turbine. A lot of actual cases of steam-induced vibration of steam turbine were collected in this work. Based on the cases, steam-induced vibration fault was statistical and classified by fault severity, fault reason, occurrence load and happened time. The results show that steam-induced vibration usually occurs after turbine runs one year later and turbine is with a high load. Oil temperature change is the main running parameters which affect steam-induced vibration. Distribute steam mechanism, especially improper opening and order of adjustment valve, is the most important factor causing steam-induced vibration fault. Meanwhile, based on the FMEA method, fault mode of steam-induced vibration was analyzed in detail.

The Principle, Review and Prospect of Wave Energy Converter

Abstract: Being confronted with the severity of the energy and environment problems, the world attaches more and more importance to the potential of wave energy. Based on the necessity and feasibility of wave power development, the basic principles of wave energy converter are in this paper firstly. Then some kinds of WEC’s principle, merits and drawbacks, technology application are reviewed, such as OWC, raft, Tapchan, point absorber, Salter, pendulum. After that, wave energy developing conditions in some typical countries are recommended. After reviewing the features of various wave energy converters and WEC application examples in some countries, prospect and a few problems in wave energy utilizing are stated briefly.

High-Cycle Fatigue P-S-N Curve Estimating Method Based on Maximum Likelihood Method for Turbine Coupling Bolt Materials

The tensile fatigue tests and S-N curve fitting results of the coupling bolt material 25CrMo were given in this paper. It has been proved that the high-cycle fatigue properties of the bolt material can be accurately described by the three-parameter exponential S-N curve model by comparing the fitting results based on different S-N curve models. The fatigue limit of the high-cycle P-S-N curve calculated by the traditional maximum likelihood method was proved to have a high probability of being higher than the accurate fatigue limit. Therefore, a modified method based on maximum likelihood method was proposed so as to calculate the high-cycle P-S-N curve more accurately. The P-S-N of 25CrMo calculated using the modified method was given in this paper.

Study on the Method of Online Adaptive Adjustment Method for Torsional Vibration Model of Turbine Shafting

The accuracy of safety analysis can be guaranteed when the torsional vibration model is adjusted online according to the inherent characteristics of the torsional vibration of the shafting. Torsional stiffness of model is set as the object for adjustment. The sensitivity of the natural frequency of torsional vibration model to structure parameters is analyzed and the sensitivity of the natural frequency of torsional vibration model to torsional stiffness is calculated. According to the difference between the natural frequency of torsional vibration which is get from actual shafting and the natural frequency of torsional vibration which is calculated by torsional vibration model, the adaptive adjustment of the torsional stiffness of mode is solved by using the method of Taylor expansion which ignore two times or more correction. The logic structure of the adaptive process of torsional vibration model is designed and the online adaptive function of torsional vibration model is implemented in the torsional vibration safety and analysis system. The torsional vibration modelof 1000WM turbogenerator is used as an example and the accuracy of the method is verified.

Research and Application on Fault Diagnosis for Steam Turbine Using Multi-Parameter Fusion

For the running situation of supercritical and ultra-supercritical steam turbine unit, a fault diagnosis method of steam turbine based on multiple parameters fusion is proposed. The association of the fault mode with the vibration parameters, the thermodynamic parameters and the operational parameters is built, according to fault development mechanism, equipment operation data and professional experience. The overall state evaluation of mechanical equipment is given, the reliability of fault diagnosis is improved, and the need of the steam turbine fault diagnosis is met, by means of comprehensive evaluation of multiple parameters. Example applications verify this method.

Study of Intelligent Fault Diagnosis Method for Turbo-Generator Unit Based on Support Vector Machine and Knowledge

For the low efficiency and poor accuracy of turbo-generator Unit s fault diagnosis, this paper divided the common 18 kinds of vibration fault into four categories, and took advantage of support vector machine to distinguish the fault cluster for early fault diagnosis according to the characteristics of vibration signal spectrum. For different fault cluster, different fault pattern recognition model was established. With the use of certain symptom group and weighted fuzzy logic, this article engaged in knowledge reasoning to obtain the specific fault recognition mode. Besides, the searching methods of fault cause, fault influence and troubleshooting measures in the knowledge base were proposed, which made the diagnosis process more meticulous and comprehensive. Case analysis shows that it is feasible to use this method to develop a system for intelligent fault diagnosis of turbo-generator unit, which is valuable for further study in more depth.

Fault Diagnosis Approach for Incipient Bearing Fault in Wind Turbine under Variable Conditions

For the extreme operating environment and variable working conditions of wind turbine and difficulty in finding fault feature accurately and promptly, a new incipient bearing fault method based on selecting optimal IMF (Intrinsic Mode Function) and Hilbert spectrum was proposed. Firstly, non-stationary time-domain signals are converted to stationary or quasi-stationary angle-domain signals; secondly, the EMD (Empirical Mode decomposition) method is used to decompose modal for angular waveform signal and obtain the IMF, and optimal IMF components are selected by cross-correlation criteria and kurtosis criteria to reconstructing signal. Finally, the reconstruction signal is processed by using Hilbert transformation to obtain the marginal spectrum. The paper finally verifies the effectiveness of the proposed method through experiment.

Research on Fault Diagnosis Method of Steam Turbine Unit Based on the Theory of Super Ball

A fault diagnosis method of steam turbine based on the theory of super ball is proposed, which combines density clustering with hierarchical clustering. The correlation of vibration and thermal parameters is introduced as the clustering factors. The efficiency of diagnosis,the sensitivity of noise and the accuracy of diagnosis are improved. Experiments show that the method and the selection of clustering factor are feasible.

Analysis on Torsional Vibration Characteristics of Turbo-Generator Units Based on Finite Element Method

The torsional vibration problems of turbo-generator shafts are increasing widespread and sever under the coupled action between the turbo-generator unit and the power grid because of the complicated power grid structure. Thus, the accurate solution of torsional vibration inherent characteristics of the shafts is of great significance to do the safety evaluation. The finite element method (FEM) with higher accuracy is adopted to calculate the torsional vibration inherent characteristics in this paper. A 1000 MW turbo-generator shaft is taken as a studying object and its torsional vibration finite element (FE) model and solving process are introduced, using ANSYS software as implementation platform of the FEM. The simulation results show that the torsional vibration characteristics calculated by FEM are accurate and reliable.

Analysis on Torsional Stresses in Turbo-Generator Shafts due to Two-Phase Short-Circuit Fault

Taking a 660MW turbine generator shaft system as a target system, the torsional stresses responses are calculated under two-phase short-circuit fault by the finite element (FE) method which can obtain torsional stresses in local areas accurately. The results show that torsional stresses threaten the safety of shafts appear at the first several cycles of the vibration. And the amplitude of stress in weak cross sections located between the low pressure cylinder and the generator is much greater. In addition, the proportion of torsional stresses frequency components in different sections is distinct. The results are helpful to improve the safety management level of the unit.