EAGER: MINIMUM THERMAL CONDUCTIVITY AND THERMAL EXPANSION CERAMIC NANOCOMPOSITES FOR MICROCOMBUSTOR APPLICATION

EAGER：用于微燃烧器应用的最低导热率和热膨胀陶瓷纳米复合材料

• 批准号: 1232949
• 负责人: Ashwani Gupta
• 金额: $ 12万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1232949&HistoricalAwards=false
• 关键词: EAGER; MINIMUM; THERMAL; CONDUCTIVITY; EXPANSION

In micro-scale liquid fuelled combustion systems a finite volume of the combustor along with a finite residence time is required for fuel vaporization and mixing. At the small scale this time can be significant compared to the gaseous premixed residence time because mixing and vaporization at low Reynolds numbers is generally poor. In both conventional and small scale combustors swirl is often imparted to the oxidizer flow, the fuel flow, or both, in order to stabilize the flame and broaden the extinction limits. At the small scale the swirl flow can be provided by tangential injection, swirl vanes, or step increases in the cross sectional area of the combustor. In order to minimize the characteristic length of the combustion chamber a fundamental understanding of droplet transport, vaporization, and mixing at low Reynolds number is required. The project objective is to develop efficient and non-polluting very small volume micro-scale combustor that can be operated with gas and liquid fuels. Successful demonstration at microscale will allow portable micro-power generation for use in portable devices, such as, laptops, and also for applications in micro-propulsion and micro-satellites. The project aims to develop fuel flexible and efficient micro-combustor (combustion volume of the order of 0.0018 cubic inches). Such size combustor is smaller than flame quenching distance. The fundamental understanding developed via experiments and calculations will allow efficient heat recirculation back into the combustor to help alleviate thermal quenching of the flame. The fuel will be injected through a porous heat recuperator for pre-vaporization with measures taken to avoid fuel coking and deterioration of the porous media that can limit the operational life of the combustor and micro-thruster. To achieve the project objectives, set of novel tasks will be developed and tested using experiments and calculations to enrich knowledge and provide wider applications. This project will explore means to develop and deposit a novel and innovative ceramic nanostructured composite materials on inside walls of micro-scale combustor with ultralow thermal conductivity and near-zero thermal expansion so that no or minimal heat exchange occurs where it is not desired while maintaining high heat transfer on the other walls to preheat the reactants prior to fuel-air mixture entering the combustion volume. Efficient thermal management with efficient heat exchange between the exhaust gases and fresh reactant mixture is critical. A recuperator type heat exchanger will be used for heat exchange between the exhaust gases and incoming fresh fuel-air mixture. For the case of liquid fuel the vaporization of fuel will be via porous heat recuperator. The emphasis will be placed on zirconium-based ceramics for micro-combustor for micro-scale power applications. The approach used will be to manufacture specially-configured Zirconium-based nano-composites in which thermal conductivity and expansion can be altered by introducing multi-scale phonon scatters, i.e., rattling atoms (atomic scale) and interfaces (nanometer scale). Nanosize particles of ultralow thermal conductivity will be deposited on defined wall of the combustor for near zero thermal conductivity while maintaining high heat exchange on the other walls to enhance the efficiency and performance. This project will influence the development of next generation miniature scale combustion and propulsion devices for use in terrestrial and space applications.

在微尺度液体燃料燃烧系统中，需要有限的燃烧器以及有限的停留时间才能进行燃料蒸发和混合。与气态预混合的停留时间相比，这段时间在小规模上可能很重要，因为在低雷诺数下的混合和蒸发通常很差。在常规和小规模的中，燃烧器通常都会赋予氧化剂流动，燃料流量或两者兼而有之，以稳定火焰并扩大灭绝极限。在小尺度上，可以通过切向注入，漩涡叶片或燃烧室横截面区域的阶梯增加来提供漩涡流。 为了最大程度地减少燃烧室的特征长度，需要对液滴传输，汽化和在低雷诺数下进行混合的基本了解。该项目的目标是开发有效且非污染的非常小的体积微型燃烧器，可以用气体和液体燃料进行操作。在Mictoscale的成功演示将允许便携式微功率生成用于便携式设备，例如笔记本电脑，以及用于微渗透和微型卫星的应用。该项目旨在开发燃料柔性有效的微型燃烧器（燃烧量为0.0018立方英寸）。这种尺寸的燃烧器小于火焰淬火距离。通过实验和计算得出的基本理解将使有效的热再循环回到燃烧器中，以帮助减轻火焰的热淬火。燃料将通过多孔恢复器注入，以预先蒸发，并采取措施避免燃料焦化和多孔介质的恶化，从而限制燃烧器和微型捕捞的运行寿命。为了实现项目目标，将使用实验和计算来开发和测试一组新任务，以丰富知识并提供更广泛的应用。该项目将探索用于开发和沉积一种新颖而创新的陶瓷纳米结构的复合材料在微尺度燃烧器内壁上具有超动导热性和接近零的热膨胀的方式，因此，不需要在其他壁上保持高热量的燃料混合物的燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料 - 燃料的成分。 有效的热管理，在废气和新鲜反应物混合物之间有效的热量交换至关重要。恢复器型热交换器将用于排气和新鲜燃料空气混合物之间的热量交换。 对于液体燃料的情况，燃料的蒸发将是通过多孔恢复器。 重点将放在用于微尺度功率应用的微型燃烧器的基于锆的陶瓷上。所使用的方法是制造特殊配置的基于锆基的纳米复合材料，其中可以通过引入多尺度的声子散射（即嘎嘎作用原子（原子尺度））和接口（纳米计尺度）来改变热导率和扩展。超速导热系数的纳米颗粒将沉积在燃烧器的定义壁上，以取得接近零的导热率，同时保持其他壁上的高热量交换以提高效率和性能。该项目将影响下一代微型量表燃烧和推进设备，用于陆地和空间应用。