Study on Physics and Chemistry of Distributed Combustion for Reducing Pollutants

这项研究将提供新的方法来燃烧低碳燃料（如天然气）和零碳燃料（如氢气）在一个新的燃烧模式称为分布式（或无焰）燃烧的理解。 以前的实验表明，无焰燃烧产生超低水平的污染物（一氧化氮和一氧化碳），是理想的低碳燃料。 然而，以前的工作是试错;改进的原因，实际限制和基本物理没有测量。 这项研究将采用PI独特的激光片千赫兹成像诊断技术，首次在这种新的无焰燃烧模式下拍摄化学反应层和局部气体温度的高速电影。 由此产生的实验数据库应提供优化操作条件和最大限度地减少污染物所需的理解。将传播该数据库，使其他人能够根据先进的计算机代码开发设计模型。一个专门设计的无焰燃烧室实验将在预热气体温度、内部气体再循环、湍流水平、气体压力和空气分级的大值下操作。 这将是第一次测量这种燃烧模式中发生的化学反应。除天然气外，还将选择促进自动点火的燃料（二甲醚、丙烷和氢-CO合成燃料）。HO 2自由基在化学中起着重要作用，甲醛和羟基也是如此。将首次使用PI的新荧光方法同时测量这些物质的浓度。 特别感兴趣的是看到湍流涡流如何进入化学反应层并扩大它们，这降低了温度梯度，并提供了更均匀的燃烧和更少的一氧化氮形成。 将进行千赫兹帧速率的气体速度场成像，提供关于基本物理过程的高速电影和信息。将记录这种新的无焰燃烧和传统火焰之间的界限。将测量无焰和自燃化学的时间尺度之间的关系。 这项研究是在一个高度湍流和现实的发动机环境中进行的，应该在这些现实的湍流条件和几个NSF资助的在台式化学实验室进行的自燃化学研究之间架起一座桥梁。

This research will provide understanding of new ways to burn low-carbon fuels (such as natural gas) and zero-carbon fuels (such as hydrogen) in a new combustion mode called distributed (or flameless) combustion. Previous experiments have shown that flameless combustion produces ultra-low levels of pollutants (nitric oxide and carbon monoxide) and is ideal for proposed low-carbon fuels. However, previous work was trial-and-error; the reasons for the improvement, the practical limitations and the underlying physics were not measured. This research will employ the unique laser sheet kilohertz imaging diagnostics of the PI to take high speed movies of the chemical reaction layers and local gas temperatures within this new mode of flameless combustion for the first time. The resulting experimental data base should provide the understanding needed to optimize the operating conditions and minimize pollutants. The data base will be disseminated to allow others to develop design models based on advanced computer codes. A specially-designed flameless combustor experiment will be operated at large values of preheat gas temperature, internal gas recirculation, turbulence levels, gas pressure and air staging. For the first time, the chemistry that occurs within this mode of combustion will be measured. Fuels will be selected that promote auto ignition (dimethyl ether, propane and hydrogen-CO synfuel) in addition to natural gas. The HO2 radical plays an important role in the chemistry, as well as formaldehyde and hydroxyl. Concentrations of these species will be measured simultaneously for the first time using the new fluorescence methods of the PI. Of particular interest is seeing how turbulent eddies enter into the chemical reaction layers and broaden them, which reduces the temperature gradients and provides a more uniform combustion with less nitric oxide formation. Gas velocity field imaging at kilohertz framing rates will be conducted provide high speed movies and information about the fundamental physical processes. The boundaries between this new regime of flameless combustion and conventional flames will be recorded. The relationship between the time scales of flameless and auto-ignition chemistry will be measured. This research is being conducted within a highly turbulent and realistic engine environment and should provide a bridge between these realistic, turbulent conditions and several NSF-funded chemistry studies of auto ignition that are being conducted in bench top chemistry labs.