火星大气条件下基态CO_(2)放电简化集合

Numerical study on simplified reaction set of ground state species in CO_(2) discharges under Martian atmospheric conditions

近年来,人类对火星的探索活动不断掀起新的热潮.研究表明,火星尘暴内的强电场可能引发CO_(2)大气放电现象.对其中的放电机理进行分析不但有助于深化对火星地表演化的认识,也为基于放电等离子体技术实现火星原位制氧提供了可能.本文在深入分析火星CO_(2)放电过程的基础上,基于图论与粒子依赖性分析的方法,结合整体模型,提出了一种定量确定火星大气条件下CO_(2)放电简化集合的方法.首先从反应粒子构成的网络拓扑图及粒子间相互作用关系入手,筛除C_(2)O,C_(2)O_(2)^(+),O_(4)^(-)等低活跃粒子,得到CO,CO_(2)^(+),CO_(3)^(-)等主要粒子,实现对粒子种类的选取;随后基于反应速率分析,定量获得各反应对CO_(2)放电过程的贡献比重,最终确定包含16种粒子、67种反应的基态CO_(2)放电反应简化集合.数值模拟表明,使用简化集合与初始集合的计算结果一致,这也给出了火星大气条件下CO_(2)放电的关键过程.从方法学上来讲,本文的研究为进一步实现复杂化学等离子体体系中,反应粒子与反应种类的自动化、精确化与智能化选择提供依据,同时本文提供的方法能够定量分析反应粒子之间的相互关系,从而为精确研究火星CO_(2)放电中的各种产物,实现基于放电等离子体技术的火星原位制氧奠定理论基础.

The exploration of Mars has attracted increasing interest in these years.The experiments and simulations show that strong electric field triggered by the dust storms in the Martian atmosphere may cause CO_(2) discharge.Studies on this phenomenon will not only help deepen our comprehension on the evolution of Martian surface,but also provide a possibility to realize the in-situ oxygen generation on Mars based on plasma chemistry.In this paper,a zero-dimensional global model is used to simplify the complicated description of CO_(2) chemical kinetics,therefore a reduced chemistry can be obtained for detailed numerical simulation in the near future.At the beginning of simplification,the graph theoretical analysis is used to pre-treat the original model by exploring the relationship between reacting species.Through the study of connectivity and the topological network,species such as O2,e,and CO prove to be important in the information transmission of the network.While gaining a clearer understanding of the chemistry model,dependence analysis will be used to investigate numerical simulation results.In this way a directed relation diagram can be obtained,where the influence between different species is quantitively explained in terms of numerical solutions.Users could keep different types of species correspondingly according to their own needs,and in this paper,some species with low activeness such as C_(2),O_(5)^(+),O_(4)^(-),and species with uncertainties such as C_(2)O_(2)^,CO_(4)^(+) are removed from the original model.As for the reduction of specific reactions among species,the reaction proportion analysis based on the calculation of reaction rates is used to obtain the contribution of each reaction to the entire process of CO_(2) discharge,through which the important reactions can be selected.Finally,a simplified chemistry model of CO_(2) discharge based on Martian atmospheric conditions,including 16 species and 67 reactions,is established.The numerical simulations show that the trends of species densities based on the simplified chemistry model are highly consistent with those based on the original one,and considerations about the CO_(2) conversion and the energy efficiency are also in line with expectations,which can help deepen the understanding of the essential process of CO_(2) discharge under Martian atmospheric conditions.In addition,the quantitative results of the relationship between reactive species will lay a theoretical foundation for the accurate analysis of various products in Martian dust storm discharges and the realization of Mars in-situ oxygen generation technology based on plasma chemistry.