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

广泛使用MEMS和其他微尺度器件的一个主要限制是合适的电源的可用性。由于其高能量密度，燃烧是一种有吸引力的动力源，但存在主要的技术挑战，包括冷启动点火和持续燃烧的控制。考虑到微燃烧室固有的高表面体积比，使用非均相催化反应来促进点火和扩大可燃性限制是有吸引力的。这是一个与该策略相关的物理和化学过程的计算和实验研究。先进的计算方法被开发出来，并通过实验测量和参数研究进行验证，专门针对小规模燃烧系统。研究了两种典型构型。首先，通过修改现有的具有详细的表面和气相化学动力学的瞬态一维停滞点流动代码，分析了催化表面上的停滞点流动。参数研究解决了各种燃烧机制，由于催化反应而改变的点火和熄灭限制，以及整体燃烧性能。此外，作为一种潜在的控制方法，研究了表面温度和进口流量的瞬态调制的影响。其次，通过开发高保真度多维直接仿真代码对微通道燃烧室进行建模，提供燃烧室过程的详细时空信息。评估了非预混燃烧模式（使用燃料和氧化剂的同轴供应）作为增强点火和产生热量的手段的可行性。在这两种配置下，将温度分布和产品成分的实验测量结果与计算结果进行了比较，以验证嵌入的子模型。作为一项教育计划，交互式计算流体动力学（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包和基于网络的工具兼容的应用程序包，用于求解微分方程和模拟反应流的数据。

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.