Catalytic Combustion of Hydrogen and Oxygen for an Electrolysis Micro Rocket Thruster

这项研究计划解决对化学推进系统日益增长的需求，该系统可以满足小型卫星对功率、尺寸和重量的严格要求。利用水电解在轨道上产生氢和氧，可以以无害的方式储存和利用高效推进剂。电解的使用避免了与类似的电力推进系统有关的功率限制，并将大大扩展小卫星可想象的任务范例。在不久的将来，特别令人感兴趣的是在空间碎片清除、卫星检查和立方体卫星星座方面的应用。为此，该项目的主要研究目标是确定和解决与开发利用电解推进剂捕获和催化点火的微推进器系统相关的主要技术瓶颈。为了实现这一目标，对H2/O2催化点火的初步研究必须扩展到化学计量混合物上。这将伴随着研究在调节热损失和粘性损失的同时保持温度极限的有效手段。这项工作的高潮将是微尺度化学计量H2/O2火箭设计最佳实践方法的初步轮廓。这种方法可以应用于概念设计和制造，随后是系统性能的量化。为此，主要研究目标已确定在三个关键领域的工作：微通道流动和催化燃烧-开发一个数值模型，能够捕捉多方面的微推力器流动状态，从喷射到喷嘴出口，结合合适的可压缩流动方案与燃烧模型。-根据实验数据，确定对流换热系数和摩擦系数的关键经验关系的合理度量。-确定H2/O2混合物中启动燃烧所需催化剂加热的下限，扩大目前仅关注富燃料混合物的微通道催化点火研究。-量化点燃混合物的瞬态和稳态特性，以及燃烧热能够维持持续点火的点。热控制-扩展数值模型，通过热建模捕捉燃烧过程的耦合动力学和燃烧室和喷嘴壁上的传热。-通过实验验证二维数值模型，包括单独的电阻加热测试以及通过外壁温度测量进行的催化燃烧实验。-探索和利用合适的热设计策略；使用经过验证的模型来确定最合适的冷却策略。系统级设计和优化-结合计算建模程序开发优化过程，旨在解决燃烧室内部作为催化表面和外部燃烧室作为发射表面的明确几何依赖性。-适当地设计和制造一种微推力器，能够在平衡热损失和粘性损失的同时实现理想的化学分解。该实验室原型将作为概念验证，因此将旨在提供推进系统的实现，展示其可行性，并提供性能特征的实验演示。-量化微推力器的系统级推进能力和性能指标，并确定进一步提高整体系统效率的方法。

This investigation plans to address the growing need for a chemical propulsion system which can cater for the strict power, size and weight requirements of small satellites. The use of water electrolysis to produce hydrogen and oxygen in orbit allows highly efficient propellants to be stored and utilized in a non-hazardous manner. The use of electrolysis avoids the power restrictions associated with comparable electric propulsion systems and would significantly extend the conceivable mission paradigms of small satellites. Of particular interest in the near future is the application to space debris removal, satellite inspection and CubeSat constellations.For this purpose, the primary research aim of this project is to identify and tackle the major technological bottlenecks associated with developing a microthruster system utilizing electrolysis propellant capture and catalytic ignition. In the pursuit of this, initial studies into H2/O2 catalytic ignition must be extended with a focus on stoichiometric mixtures. This will be accompanied by research into effective means of maintaining temperature limits while regulating thermal and viscous losses. The culmination of this work will be an initial outline of the best practice methodology of micro-scale stoichiometric H2/O2 rocket design. This methodology can then be applied to concept design and fabrication followed by the quantification of system performance. To this end, the primary research objectives have been identified under three key areas of the work:Microchannel Flow & Catalytic Combustion- Develop a numerical model which is capable of capturing the multifaceted microthruster flow regime from injection to nozzle exit, combining a suitable compressible flow scheme with a combustion model. - From experimental data, determine a justified measure of the key empirical relations of the convective heat transfer coefficient and the friction factor. - Determine the lower limit of necessary catalyst heating required to initiate combustion in stoichiometric H2/O2 mixtures, expanding current microchannel catalytic ignition investigations which have focused only on fuel rich mixtures. - Quantify the transient and steady state characteristics of the ignited mixture as well as the point at which the heat of combustion is able to maintain sustained ignition. Thermal Control- Expand the numerical model to capture the coupled dynamics of the combustion process and the heat transfer within the combustion chamber and nozzle walls through thermal modelling.- Validate the 2D numerical model through experimentation, consisting of stand alone resistive heating testing as well as investigations done in conjunction with catalytic combustion experiments by temperature measurements of the outer wall. - Explore and utilize a suitable thermal design strategy; using the validated model to determine the most appropriate cooling strategy.System Level Design and Optimization- Develop an optimization process in conjunction with a computational modelling procedure aimed at addressing the clear geometric dependence of both the inside of the combustor as a catalytic surface and the outer combustor as an emmissive surface. - Suitably design and fabricate a microthruster which is able to achieve a desirable chemical decomposition while balancing thermal and viscous losses. This laboratory prototype will serve as a proof of concept and will therefore aim to provide a realization of the propulsion system demonstrating its feasibility and providing an experimental demonstration of performance characteristics.- Quantify the system level propulsive capabilities and performance metrics of the microthruster and identify further means of improving the overall system efficiency.