CAREER: Steady and Transient Dynamics of Catalyst-Assisted Combustion in Micro-Scale Power Generators

MEMS和其他微尺度器件的广泛使用的一个主要限制是合适的电源的可用性。燃烧具有较高的能量密度，是一种很有吸引力的动力源，但存在冷启动点火和持续燃烧控制等重大技术难题。考虑到微型燃烧室固有的高表面积体积比，使用多相催化反应来促进点火和扩大可燃极限是很有吸引力的。这是对与该策略相关的物理和化学过程的计算和实验研究。开发了先进的计算方法并通过实验测量进行了验证，并且专门针对小规模燃烧系统进行了参数研究。研究了两种正则构型。首先，通过用详细的表面和气相化学动力学来修正现有的一维暂态驻点流动程序，分析了催化剂表面上的驻点流动。参数研究涉及不同的燃烧模式、由于催化反应而改变的点火和消光极限，以及整体燃烧性能。此外，还研究了表面温度和进口流量的瞬时调制的影响，作为一种潜在的控制方法。其次，通过开发高保真的多维直接模拟程序来模拟微通道燃烧室，该程序提供了关于燃烧室过程的详细的时间和空间信息。评估了非预混燃烧模式(使用燃料和氧化剂的同轴供应)作为增强点火和产热的手段的可行性。对于两种结构，温度分布和产品种类组成的实验测量结果与计算结果进行了比较，以验证嵌入子模型。作为一种教育程序，交互式计算流体力学(CFD)工具是为热流体科学的本科生和研究生设计的。其中包括与广泛使用的动力学模拟程序包兼容的应用程序包，以及用于求解微分方程和模拟反应流数据的基于Web的工具。

A major limitation to the wide use of MEMS and other micro-scale devices is the availability of suitable power sources. Combustion is an attractive power source because of its high energy density, but there are major technical challenges including ignition from cold start and control of sustained combustion. Given the high surface-to-volume ratio inherent in a microcombustor, there is attraction in using heterogeneous catalytic reactions to promote ignition and to extend flammability limits. This is a computational and experimental study of the physical and chemical processes relevant to this strategy.Advanced computational methods are developed and validated with experimental measurements and parametric studies are done specifically targeted at small-scale combustion systems. Two canonical configurations are studied. First, stagnation-point flow over a catalytic surface is analyzed by modifying existing transient one-dimensional stagnation-point flow code with detailed surface and gas-phase chemical kinetics. Parametric studies address various combustion regimes, modified ignition and extinction limits due to catalytic reaction, and overall combustion performance. Also, the effects of transient modulation of the surface temperature and inlet flow are investigated as a potential control methodology. Second, a microchannel combustor is modeled by developing a high-fidelity multidimensional direct simulation code providing detailed temporal and spatial information on the combustor process. The feasibility of a nonpremixed combustion mode (using a coaxial supply of fuel and oxidizer) as a means of enhancement of ignition and heat generation is assessed. For both configurations, experimental measurements of temperature distribution and product species compositions are compared with computational results to validate embedded submodels.As an education program, interactive computational fluid dynamics (CFD) tools are designed for undergraduate and graduate students in thermo-fluid sciences. These include application packages that are compatible with widely used kinetic simulation packages and web-based tools for solving differential equations and simulating data on reacting flows.