盘式磁流体发电机中最佳种子份数变化规律研究

Study on changing rule of optimal seed fraction in disk MHD generator

在磁流体发电机中,为了提高工质电导率,通常需要加入少量低电离电位的碱金属,即种子。前期研究表明,在一定工况下存在最佳种子份数使发电机性能最优。本文通过非稳态准一维数值模拟,研究了盘式磁流体发电工质电离、等离子体流动和发电机性能特性,获得了热源参数和磁感应强度对最佳种子份数影响的变化规律,提出较宽最佳种子份数变化范围的调控方法。模拟结果表明,对于所给定的发电通道,在热源条件一定时,随着磁感应强度增加,最佳种子份数及其变化范围减小,种子流量的控制越精确。当磁感应强度一定时,随着热源滞止压力降低,最佳种子份数几乎保持不变,而且,最佳种子份数的变化范围增大,降低了种子流量控制的要求。另外,磁感应强度越低,在较低的热源滞止压力条件下,最佳种子份数变化范围越宽。

In order to improve the conductivity of working fluid,a small amount of alkali metal with low ionization potential,i.e.seed,is usually added to the MHD generator.The previous research shows that there is an optimal seed fraction to optimize the performance of the generator.At the same time,the performance of generator is very sensitive to the seed fraction.In this paper,the characteristics of working medium ionization,plasma flow and generator performance of disk MHD power generation are studied by unsteady quasi-one-dimensional numerical simulation.The simulation results show that,for the given generation channel,when the heat source condition is fixed,with the increase of magnetic flux density,the optimal seed fraction and its range of variation decrease,and the control of seed flow is more accurate.When the magnetic flux density is constant,the optimal seed fraction will remain almost unchanged with the decrease of the stagnation pressure of the heat source,and the range of the optimal seed fraction will increase,which will reduce the requirement of seed flow control.In addition,the lower the magnetic flux density is,the wider the variation range of the optimal seed fraction is under the condition of lower stagnation pressure of heat source.