碳氢燃料的冷焰特性及机理研究

Cool flame is a special phenomenon determined by the low-temperature chemistry of hydrocarbon fuel. It has been regarded as a key process for engine knock and ignition timing control. In order to understand the characteristics and detailed low-temperature oxidation chemistry of hydrocarbon fuels, experiments and simulations will be conducted to study the generation and extinction of cool flame of typical hydrocarbon fuels. First, cool flame is achieved in diffusion flame experiments with radical addition. We will experimentally examine the effects of fuel concentration, stretch rate, temperature and pressure on the generation and stability of cool flame. Then, the detailed low temperature chemical reaction mechanism which can accurately reflect the cool flame features of hydrocarbon fuel will be established through measuring the cool flame structure and the distribution of typical intermediate species and conducting reaction path analysis. Using the detailed low-temperature oxidation mechanism of the typical fuels, cool flame characteristics will be analyzed using detailed numerical simulation. Finally, through the comparison between simulation results and experimental data, the low-temperature chemistry will verified and improved. A new effective method for low-temperature oxidation mechanism generation will be proposed. This work will provide new research method and experimental dada for studying low-temperature oxidation of hydrocarbon fuel. Furthermore, it also brings a new method for low-temperature oxidation mechanism generation. This study is helpful for deeply understanding the characteristics of low-temperature oxidation and combustion of hydrocarbon fuel, and it will promote the development of internal combustion engine combustion technology at low temperature.

冷焰是受碳氢燃料低温化学反应控制的特殊现象，是发动机爆震与着火控制的关键过程。为了深刻认识碳氢燃料的低温氧化特性及其详细化学反应机理，本课题采用实验测量和数值模拟相结合的方法系统地研究典型碳氢燃料冷焰产生与熄灭的基本规律。首先，在对冲扩散火焰的实验中通过自由基的控制获得稳定的冷焰，测量燃料浓度、拉伸率、温度和压力对碳氢燃料冷焰产生和稳定性等的影响。然后，测量冷焰的火焰结构和组分分布，在典型中间产物和化学反应路径分析的基础上，建立能精确反映碳氢燃料冷焰特性的详细低温氧化机理；基于所建的低温氧化机理，采用数值模拟详尽地分析冷焰特性。最后,通过模拟结果与实验结果的对比，验证和完善碳氢燃料低温化学反应机理，发展适用于建立详细低温氧化机理的新的有效方法。本课题将为碳氢燃料的低温氧化特性的研究提供新的有效方法和实验数据，有助于完善对碳氢燃料的低温氧化及燃烧特性的认识,并将促进内燃机低温燃烧技术的发展。

随着对能源转换过程清洁性和安全性的日渐重视，低温燃烧备受关注，受碳氢燃料低温化学反应控制的冷焰现象对低温燃烧特性的影响已不容忽视。冷焰直接关系到燃料着火、重整及发动机爆震等过程，也是深刻认识碳氢燃料低温氧化特性的基础。为了研究燃料的冷着火及火焰特性，本课题构建了自燃着火及对冲流火焰实验台，并对甲烷、二甲醚、庚烷等典型燃料进行了大量的实验，获得了丰富的低温氧化过程的实验数据；针对燃料复杂的低温氧化机理，开发了高效的机理构建、优化及简化工具，为大型燃烧机理，尤其是低温氧化机理在复杂反应流中的应用提供了有效的手段；为了探究冷焰的产生、熄灭的动力学机制，采用高精度的骨架机理进行了大量的反应流模拟试验，并结合实验结果进行了系统的动力学分析，获得了影响冷焰过程的核心组分、基元反应和反应路径，并首次提出了采用臭氧和甲醇协同控制冷焰的新方法，获得了稳定冷焰的有效措施；以燃料低温氧化过程的释热作为热源，构建了一套热电联供系统，通过理论和实验的手段，获得了较高的能源转换效率，为利用燃料低温氧化实现清洁、高效供能提供了新的思路。本课题的研究工作为深刻认识燃料的低温氧化特性以及寻求高效、清洁的能源转换途径创造了条件。