磁流体动力循环有效功率优化

The effective power optimization for magnetohydrodynamic power cycle

以有效功率作为目标函数,基于已有研究建立的磁流体动力(MHD)循环模型,应用有限时间热力学理论,研究其最优性能。导出恒温热源条件下MHD循环的有效功率表达式,分析循环参数对有效功率性能的影响,比较最大有效功率和最大输出功率两种目标函数下循环的性能差异。结果表明,当MHD发电机和压缩机效率ηc=ηe=1时,有效功率与效率之间的关系曲线为类抛物线型。当ηc、ηe均小于1时,有效功率与效率之间的关系曲线呈扭叶型。最大有效功率对应的效率始终大于最大输出功率对应的效率。以最大有效功率为目标优化时,虽然牺牲部分输出功率,但循环效率有较大提高,有效功率目标函数体现了功率与效率的折中。

In this paper, based on the magnetohydrodynamic(MHD) power cycle model established in the previous literature, the optimal performance of the MHD cycle is studied with the effective power as the objective function by applying finite time thermodynamics theory. The expression of effective power of the MHD cycle coupled to constanttemperature heat reservoirs is derived. The influences of the cycle parameters on the effective power performance are analyzed, and the performance differences of the cycle under the maximum effective power and the maximum power output conditions are compared. The obtained results show that, when the efficiencies of compressor and MHD generator are ηc= ηe= 1, the relationship curve between effective power and efficiency is parabolic-like one;when ηc and ηe are less than 1, the curve between effective power and efficiency is loop-shaped one returning to the origin. The efficiency corresponding to the maximum effective power is always larger than that corresponding to the maximum power output.Compared with the maximum power output condition, although part of the power output is sacrificed when the maximum effective power is taken as optimization objective, the thermal efficiency of the cycle can be greatly improved. The effective power objective function reflects the trade-off between power output and efficiency.