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首页> 外文期刊>Mechanical systems and signal processing >A novel comprehensive evaluation method of the draft tube pressure pulsation of Francis turbine based on EEMD and information entropy
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A novel comprehensive evaluation method of the draft tube pressure pulsation of Francis turbine based on EEMD and information entropy

机译：基于EEMD和信息熵的混流式水轮机尾水管压力脉动综合评价新方法。

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Undesirable pressure pulsations will be induced by flow instabilities in the draft tube when the Francis turbine operates at off-design conditions, which have multiple effects on the steady operation, and the effects vary with the operating condition. Therefore, the establishment of a comprehensive state evaluation index of the draft tube pressure pulsation (DTPP) is of great practical significance. In this study, a comprehensive evaluation method of DTPP has been proposed based on Ensemble Empirical Mode Decomposition (EEMD) and information entropy. First, the frequency components of DTPP are separated by the EEMD method which is more suitable for the analysis of non-stationary pressure pulsation signal. Second, to eliminate the effects of noise, a targeted EEMD noise reduction method which is combined with autocorrelation analysis and wavelet soft-threshold de-noising method is designed for the DTPP signal. Then, index energy values of all frequency components are calculated and normalized, and the values of the signals' characteristic entropy are obtained by using the normalized index energy vector as the input vector. Finally, characteristic entropy values of all pressure pulsation signals measured from the draft tube are integrated into an index, which is named as the comprehensive characteristic entropy of DTPP (E_DTPP). The state of DTPP is comprehensively evaluated by E_DTPP. This method was evaluated by the actual measuring data of a 200 MW hydroelectric generating unit. The case study indicates that this single index can be utilized to evaluate the actual state of DTPP, and pressure pulsations will have distinct influence on the operation stability when E_DTPP increases obviously. The efforts of this study provide a novel and useful method for the comprehensive state evaluation of DTPP, and the E_DTPP could be used as an index for the stability of Francis turbine. (C) 2018 Elsevier Ltd. All rights reserved.
机译：当弗朗西斯水轮机在非设计状态下运行时，引流管中的流量不稳定会引起不希望的压力脉动，这会对稳定运行产生多种影响，并且影响会随运行条件而变化。因此，建立尾水管压力脉动状态综合评价指标具有重要的现实意义。本研究提出了一种基于综合经验模态分解（EEMD）和信息熵的DTPP综合评价方法。首先，通过EEMD方法分离DTPP的频率分量，该方法更适合于分析非平稳压力脉动信号。其次，为消除噪声影响，针对DTPP信号设计了有针对性的EEMD降噪方法，该方法结合了自相关分析和小波软阈值去噪方法。然后，计算并归一化所有频率分量的索引能量值，并且通过使用归一化的索引能量向量作为输入向量来获得信号的特征熵的值。最后，将从引流管测得的所有压力脉动信号的特征熵值集成到一个指标中，该指标称为DTPP的综合特征熵（E_DTPP）。 DTPP的状态由E_DTPP进行综合评估。该方法是通过200 MW水力发电机组的实际测量数据进行评估的。案例研究表明，该单一指标可用于评估DTPP的实际状态，当E_DTPP明显增加时，压力脉动将对运行稳定性产生明显的影响。这项研究的成果为DTPP的状态综合评估提供了一种新颖而有用的方法，E_DTPP可以作为混流式水轮机稳定性的指标。 （C）2018 Elsevier Ltd.保留所有权利。

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