摇摆参数对自然循环系统混沌脉动影响分析

Effect of rolling parameters on chaotic oscillation of a natural circulation system under rolling motion

针对摇摆参数对自然循环系统中流量混沌脉动的影响,用非线性时序分析的方法对实验结果进行了分析研究.基于相空间重构理论,计算不同摇摆参数下时间序列的关联维(CD)、K2熵和最大Lyapunov指数(MLE)等几何不变量值,根据计算结果分析摇摆参数对自然循环系统混沌脉动的影响.分析结果表明:摇摆周期越短、摇摆振幅越大,混沌出现时的无量纲功率越大;摇摆周期对混沌脉动边界的影响大于摇摆振幅的影响;当摇摆周期为5 s时,由于摇摆引起的波谷型脉动与密度波型脉动频率相近而发生共振作用,流量脉动的混沌特征减弱.

In light of the effect of rolling parameters on chaotic oscillation of a natural circulation system under rolling motion, a non-linear time series analysis method was used to analyze the experimental resuhs. The geometric invariants, including the correlation dimension （CD）, Kolmogorov entropy （K2 entropy）, and maximum Lyapunov exponent （ MLE）, were determined based on the phase space reconstruction theory. The effect of rolling parameters on chaotic oscillation of a natural circulation system under rolling motion conditions was studied based on the results of the geometric invariant calculations. Results indicate that the non-dimensional power becomes larger as the rolling period becomes shorter or rolling amplitude larger when chaotic oscillation appears. The effect of the rolling period on the chaotic oscillation boundary is more evident than that of the rolling amplitude. Chaos characteristics are weakened when the rolling period is equal to 5 s because resonance arises when the frequency of trough-type flow oscillation caused by rolling motion and the frequency of density wave oscillation are closer.