Experimental and numerical investigations of the chemical kinetics of fuel mixtures in homogeneous low-temperature reactors

在500~1200K的低温范围内，燃料混合物自燃时，燃料的不同反应链之间可能会发生相互作用。我们的目标是研究长链脂肪族碳氢化合物异辛烷和正庚烷分别与乙醇或二甲醚(DME)的特征二元混合物在均相反应器中的低温动力学。对于异辛烷和正庚烷，在低温区域存在缓慢的链支化机制，而乙醇则不是这样。DME呈现出一种缓慢的分支机制，其中会产生额外的甲醛，这可能会起到抑制剂的作用。因此，在上述二元混合物中，由于两种燃料都在竞争自由基，因此可以预料到另一种燃料的存在会影响脂肪族燃料的慢链支化。由于在几乎所有的技术应用中都使用不同化学成分的混合物，因此从自燃的角度研究这种混合物的低温动力学是非常重要的。在主要研究人员Kohse-Höinghaus(Bielefeld)和Peter(Aachen)目前的联合项目中，将在低温条件下研究动力不同燃料的反应链的相互作用。在实验的基础上，对几种二元混合物进行了数值计算。在亚琛，重点将放在数值计算上，在比勒费尔德，重点将放在实验上。动力学机制将逐步简化，以确定决定速率的反应。实验将在两个不同的试验台上进行：在亚琛的均匀搅拌反应器和在比勒费尔德的均质流动反应器中。在充分搅拌的反应器中，将研究振荡，因为这些振荡对化学动力学的细节非常敏感。稳定的物种将通过气相色谱和快速碳氢化合物传感器进行分析。此外，飞行时间质谱仪将用来测量在相对较大浓度的振荡过程中可能形成的半稳定物种的浓度，如酮氢过氧化物。相反，流动反应器在静止状态下运行。在这里，反应沿着规定的温度梯度进行。在这个装置中，包括自由基在内的所有物种原则上都可以通过分子束质谱(MBMS)和耦合气相色谱的方法沿反应路径进行检测。这些测量将得到使用量子级联激光的吸收光谱和使用光致电离的MBMS实验的支持。在这些实验结果的基础上，将改进各自的详细反应动力学模型。

During self-ignition of fuel mixtures in the low-temperature regime between 500 K and 1200 K, interactions between the different reaction chains of the fuels may occur. We aim to investigate such details of the low-temperature kinetics in homogeneous reactors for characteristic binary mixtures of the long-chain aliphatic hydrocarbons iso-octane and n heptane with ethanol or dimethyl ether (DME), respectively. For iso-octane and n-heptane, a slow chain-branching mechanism exists in the low-temperature regime, which is not the case for ethanol, however. DME presents a slow branching mechanism where additional formaldehyde is produced which may act as an inhibitor. In the above binary mixtures it is therefore to be expected that the slow chain branching of the aliphatic fuel will be influenced by the presence of the other fuel, as both fuels compete for radicals. Since mixtures of different chemical components are used in nearly all technical applications, the investigation of low-temperature kinetics of such mixtures as discussed here with respect to self-ignition is of primary importance. In the present joint project of the principal investigators Kohse-Höinghaus (Bielefeld) and Peters (Aachen), the interaction of the reaction chains of kinetically different fuels will be investigated in the low-temperature regime. Several binary mixtures will be analyzed by numerical calculations on the basis of experiments. In Aachen the emphasis will be on the numerical calculations and in Bielefeld, the emphasis will be on experiments. The kinetic mechanisms will be progressively reduced in order to identify the rate-determining reactions. The experiments will be conducted at two different test benches: in the homogeneous well-stirred reactor in Aachen as well as in the homogeneous flow reactor in Bielefeld. In the well-stirred reactor, oscillations will be investigated, since these are very sensitive to the details of chemical kinetics. The stable species will be analyzed by means of gas chromatography and by a fast hydrocarbon sensor. In addition, a time-of-flight mass spectrometer will be used to measure the concentrations of semi-stable species such as ketohydroperoxides that may be formed during the oscillations in relatively large concentrations. The flow reactor, on the contrary, operates at stationary conditions. Here the reaction proceeds along a prescribed temperature ramp. In this set-up, all species including radicals can in principle be detected along the reaction path by means of molecular-beam mass spectroscopy (MBMS) and coupled gas chromatography. The measurements will be supported by absorption spectroscopy using quantum cascade lasers and MBMS experiments with photoionization. On the basis of all these experimental results, the respective detailed kinetic reaction models will be improved.