【作者】 林震；

【导师】 刘宇；

【作者基本信息】 北京航空航天大学 ， 航空宇航推进理论与工程， 2011， 博士

【摘要】 水基火箭推进系统(water based rocket propulsion system)是一种基于氢氧质子交换膜燃料电池(PEMFC)、质子交换膜水电解池(SPE)以及空间气氢气氧推力器的空间推进系统。相比起传统的空间推进系统,水基火箭推进系统具有高比冲、高比功率和比能量、无污染以及与空间生保系统结合性好等优点。因此,水基火箭推进系统在未来的空间应用中具有巨大的发展潜力。本文综合应用了理论分析、数值模拟、针对性试验等研究方法,从分系统到总系统,逐步研究了水基火箭推进系统的空间性能。为研究PEMFC的空间性能,本文首先通过数值模拟,归纳总结了PEMFC的地面常规性能。然后通过研究不同重力环境对PEMFC内部物理化学过程的影响,分析了空间微重力环境可能引起的PEMFC性能变化。结果表明:在地面环境下,PEMFC可以通过合适的放置方式来对合适方向的重力加以利用,提高性能。而在空间微重力环境下则没有重力可以利用,PEMFC性能一般情况下会有所降低。但是,当控制PEMFC工况,使其内部产生的液态水较少,或者保证其入口气体流速足够大时,能够在很大程度上消除空间微重力环境带来的电池性能差异。为研究SPE的空间性能,首先通过比较现有的三种典型SPE的结构形式和工作特点,选出了最适合空间应用的SPE—静态供水质子交换膜电解池(SWF-SPE)。根据SWF-SPE的工作特点,建立了针对SWF-SPE的数学模型。基于该模型的计算结果表明:SWF-SPE相比起其它传统的SPE更容易膜失水,使得其极限电流密度较小,最大产气率相对较低。采用薄的质子交换膜作为电解质膜不仅能够提高SWF-SPE的最大产气率,而且能够提高其电解效率。为了评估适用于水基火箭推进系统的气氢气氧推力器的空间性能,本文从点火方式、喷注器方案、热防护方法、燃烧室压强以及设计混合比等方面进行了考察。结果表明:采用合适的技术方案的推力器能使水基火箭推进系统的综合实际比冲超过400 s。根据各分系统的空间性能研究结果,本文以当前普通PEMFC的性能参数和文献报道的SWF-SPE性能参数作为水基火箭推进系统的电池和电解池系统能够达到的性能指标,以400 s作为该系统的比冲指标,对其整系统的空间性能进行了综合分析。结果表明:水基火箭推进系统的高比冲和高比功率、比能量能够给其带来明显的质量优势。但是,该系统的储箱质量限制、电解池质量限制以及电解功率限制使得其空间应用有一定的局限性。为了定量分析水基火箭推进系统的空间性能,本文用该系统代替DFH-4上的传统推进系统,基于DFH-4的实际运行过程,进行了具体的空间任务分析。计算结果表明:执行变轨任务时,水基火箭推进系统适合采用较大推力,较短单次点火时间,多变轨周期的变轨策略;整个空间任务期间,采用水基火箭推进系统能够带来最大706 kg的质量节省,相当于实际DFH-4有效载荷(410 kg)的1.72倍。但是采用该系统变轨时间超过56天。另外,本文搭建了分体式水基火箭推进试验系统,并进行了关键性的分系统试验和整系统分析。其中,催化点火气氢气氧推力器分系统的催化点火试验验证了环境温度下气氢气氧推力器催化点火的可行性,并总结了相关的催化点火规律;PEMFC和SPE分系统初步的放电和电解试验获得了该分系统的放电和电解性能;基于试验数据的整系统分析表明该推进系统各分系统之间以及各分系统和空间任务之间存在相互适应和相互制约的关系,针对不同的空间任务,水基火箭推进系统中三个分系统的规模和性能需要进行合理的优化配置。该试验系统初步实现了水基火箭推进系统的概念,为理论研究提供了依据,也为今后进一步研究打下了基础。更多还原

【Abstract】 Water based rocket propulsion system is a space propulsion system, which contains a proton exchange membrane fuel cell (PEMFC) subsystem, a solid polymer electrolyzer (SPE) subsystem and a space GH2/GO2 thruster subsystem. Comparing to custom propulsion system, water based propulsion system has the advantages of high specific impulse, high power ratio, no pollution and good compatibility with space life sustain system. So, water based propulsion system is promising in the future space applications. In this paper, theoretic analysis, numerical simulation and experimental studies are introduced, and the space performance of water based propulsion, from its subsystems to the whole system, are gradually studied.In order to study the space performance of PEMFC, firstly, the conventional performance of PEMFC on the earth is studied. Then, the effect of different gravity situation on the physical and chemistry process of PEMFC is studied. Furtherly, the effect of the micro gravity environment on the PEMFC performance is studied. It is indicated that, on the earth, the gravity can be suitably utilized to improve the PEMFC performance. In space, as no gravity can be utilized, the PEMFC performance will slightly decline. But, the slight decline of the PEMFC performance can be greatly eliminated through controlling the liquid water generation rate inside the PEMFC or providing enough inlet flow velocity for the PEMFC flow channels.In order to study the space performance of SPE, the configuration and characteristic of three typical SPE are compared with each other. Static water feed SPE (SWF-SPE) is considered the most suitable SPE to space application. According to the operating characteristics of SWF-SPE, a simulation model is constructed. Based on this model, several results are concluded: the membrane of SWF-SPE is more possibly to dehydrate, which will lead to smaller current density limitation and lower gas producing rate. Thicker proton exchange membrane is in favor of improving the utmost gas producing rate and the electrolyte efficiency of SWF-SPE. In order to evaluate the space performance of the GH2/GO2 thruster adapting to water based propulsion system. The aspects of ignition method, fuel spray method, heat resistant method, designed combustion pressure and designed mixture ratio are discussed. It is indicated that well designed thruster can make the real specific impulse of water based propulsion beyond 400 s.According to the conclusion mentioned above, the performance of conventional PEMFC and the reported SWF-SPE are used to evaluate the space performance of the whole water based propulsion system. The specific impulse of the whole system is considered as 400 s. In this case, comprehensive analysis of the whole water based propulsion is introduced. It is indicated water based propulsion system can obtain great mass advantages because of its high specific impulse and high power ratio. But, the limitation of its tank mass, SWF-SPE mass and electrolyte power will lead to some limitation of its space application.In order to quantitatively analyze the performance of water based propulsion system, the custom propulsion system of DFH-4 is replaced by water based propulsion system. Based on the actual process of DFH-4, a specific space mission is constructed and analyzed. It is indicated that, during the orbit transfer mission, water based propulsion system prefer to the strategy of higher thruster, shorter single step fire and more transfer steps; During the whole space mission, water based propulsion system can save 706 kg mass for the DFH-4 satellite, which is 1.72 times the payload of DFH-4. But the system will increase the orbit change time to more than 56 days.On the addition, a separated water based propulsion experimental system is constructed in this paper. Some important subsystem experiments and whole system analysis are introduced. According to The catalytic ignition of the GH2/GO2 thruster based on the thruster subsystem, the feasibility of the GH2/GO2 thruster catalytic ignition is validated. And the law of GH2/GO2 catalytic ignition is obtained. According to the primary power generation experiment of PEMFC subsystem and the primary electrolytic experiment of SPE subsystem, the power generation and electrolytic performance of these two subsystems are obtained. Based on the experiment results, the whole system analysis is conducted. It is indicated the subsystems of the water based rocket propulsion system and the space missions are restraint with each other and need to be adapt to each other. For different space missions, the configuration of the three subsystems needs to be carefully optimized. The experimental system primarily realized the conception of water based rocket propulsion system. It is the accordance and foundation of further studies.更多还原