Xanthan gum solutions with different mass concentrations were used to study the chaotic characteristics induced by the impeller of perturbed six-bent-blade turbine(6 PBT) in a stirred vessel. Based on the velocity tim...Xanthan gum solutions with different mass concentrations were used to study the chaotic characteristics induced by the impeller of perturbed six-bent-blade turbine(6 PBT) in a stirred vessel. Based on the velocity time series obtained by the experiment of particle image velocimetry(PIV), with the software MATLAB(R2016a), the distributions of the largest Lyapunov exponent(LLE) and Kolmogorov entropy(K entropy) of the system, as two important parameters for characterizing the chaotic degree, were investigated respectively. Results showed that both of the LLE and K entropy increased with the increasing speed at the beginning. As the speed was up to 200 r·min-1, the two parameters reached the maximal values meanwhile, corresponding to 0.535 and 0.834, respectively, which indicated that the chaotic degree of the flow field was up to the highest level. When the speed was increased further, both of the LLE and K entropy decreased on the contrary, which meant that the chaotic degree was decreasing. It was also observed that the chaotic characteristics of flow field were hardly affected by the fluid rheology and the detecting positions. The research results will enhance the understanding of the chaotic mixing mechanism and provide a theoretical reference for optimizing impeller structure.展开更多
针对中性点接地系统铁磁谐振过电压故障带来的危害,应用非线性动力学分岔理论和混沌理论,研究中性点接地系统在非全相运行时系统容性参数和感性参数不利配合造成的串联谐振问题:首先,分析铁磁谐振等值电路,建立类Duffing-van der Pol的...针对中性点接地系统铁磁谐振过电压故障带来的危害,应用非线性动力学分岔理论和混沌理论,研究中性点接地系统在非全相运行时系统容性参数和感性参数不利配合造成的串联谐振问题:首先,分析铁磁谐振等值电路,建立类Duffing-van der Pol的动力学模型系统;其次,将最大Lyapunov指数(largest Lyapunov exponent,LLE)作为辨识系统非线性运动状态的指标,并确定系统混沌状态的指标阈值,建立了QR分解的Duffing-van der Pol系统Lyapunov指标计算模型,在此基础上,提出了基于LLE的系统状态辨识方法;最后,以实际工程为例,遍历系统参数所有可能的取值,分析不同工况下的Lyapunov指数范围,并确定了谐振状态转变的参数临界值,研究结果可为电力部门规划阶段和系统运行维护阶段避免铁磁谐振故障提供理论依据。展开更多
基金Supported by the the Natural Science Foundation of Shandong Province,China(ZR2018LE015)
文摘Xanthan gum solutions with different mass concentrations were used to study the chaotic characteristics induced by the impeller of perturbed six-bent-blade turbine(6 PBT) in a stirred vessel. Based on the velocity time series obtained by the experiment of particle image velocimetry(PIV), with the software MATLAB(R2016a), the distributions of the largest Lyapunov exponent(LLE) and Kolmogorov entropy(K entropy) of the system, as two important parameters for characterizing the chaotic degree, were investigated respectively. Results showed that both of the LLE and K entropy increased with the increasing speed at the beginning. As the speed was up to 200 r·min-1, the two parameters reached the maximal values meanwhile, corresponding to 0.535 and 0.834, respectively, which indicated that the chaotic degree of the flow field was up to the highest level. When the speed was increased further, both of the LLE and K entropy decreased on the contrary, which meant that the chaotic degree was decreasing. It was also observed that the chaotic characteristics of flow field were hardly affected by the fluid rheology and the detecting positions. The research results will enhance the understanding of the chaotic mixing mechanism and provide a theoretical reference for optimizing impeller structure.
文摘针对中性点接地系统铁磁谐振过电压故障带来的危害,应用非线性动力学分岔理论和混沌理论,研究中性点接地系统在非全相运行时系统容性参数和感性参数不利配合造成的串联谐振问题:首先,分析铁磁谐振等值电路,建立类Duffing-van der Pol的动力学模型系统;其次,将最大Lyapunov指数(largest Lyapunov exponent,LLE)作为辨识系统非线性运动状态的指标,并确定系统混沌状态的指标阈值,建立了QR分解的Duffing-van der Pol系统Lyapunov指标计算模型,在此基础上,提出了基于LLE的系统状态辨识方法;最后,以实际工程为例,遍历系统参数所有可能的取值,分析不同工况下的Lyapunov指数范围,并确定了谐振状态转变的参数临界值,研究结果可为电力部门规划阶段和系统运行维护阶段避免铁磁谐振故障提供理论依据。
