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

在500 K和1200 K之间的低温区域中燃料混合物的自燃期间，燃料的不同反应链之间可能发生相互作用。我们的目标是调查这样的细节，在均相反应器中的特征二元混合物的长链脂肪烃异辛烷和正庚烷与乙醇或二甲醚（DME），分别在低温动力学。对于异辛烷和正庚烷，一个缓慢的链支化机制存在于低温制度，这是不是乙醇的情况下，然而。DME呈现出缓慢的支化机制，其中产生额外的甲醛，其可充当抑制剂。因此，在上述二元混合物中，预期脂肪族燃料的慢链支化将受到另一种燃料的存在的影响，因为两种燃料竞争自由基。由于不同化学成分的混合物用于几乎所有的技术应用中，本文所讨论的这种混合物的自燃低温动力学的研究是至关重要的。在主要研究人员Kohse-Höinghaus（比勒费尔德）和Peters（亚琛）的当前联合项目中，将在低温区域研究动力学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分析。在亚琛的重点将是数值计算和在比勒费尔德，重点将是实验。动力学机制将逐渐减少，以确定速率决定反应。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中以及在比勒费尔德的均相流反应器中。在充分搅拌的反应器中，将研究振荡，因为这些对化学动力学的细节非常敏感。将通过气相色谱法和快速碳氢化合物传感器分析稳定物质。此外，飞行时间质谱仪将用于测量半稳定物质的浓度，例如可能在振荡期间以相对较大的浓度形成的酮氢过氧化物。相反，流动反应器在静止条件下操作。在此，反应沿着规定的温度斜坡进行。在该装置中，包括自由基的所有物质原则上可通过分子束质谱（MBMS）和耦合气相色谱法沿反应路径沿着检测。测量将得到使用量子级联激光器的吸收光谱和具有光电离的MBMS实验的支持。在所有这些实验结果的基础上，将改进各自详细的动力学反应模型。

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.