Ignition phenomena in shock tubes and the influence of non-ideal effects on measurements of combustion chemistry: Experiments, modeling, and simulations

激波管为化学动力学机制的发展提供了一个很好的平台，因为它们可以在不受混合或传输过程干扰的情况下对高温反应进行孤立的研究。在与实际重要的低温燃烧过程相关的中间温度下，一些固有现象可能导致空间和时间的不均匀性。这种不均匀性导致了早期的局部反应，因此阻碍了对观察到的过程的直接解释。这种“非理想”过程包括激波与边界层的相互作用、有限隔膜打开时间、激波分岔、预点火热释放和热粒子点火。该提案的总体目标是研究高压激波管内的不均匀点火，以确定最适合的实验配置，从而实现直接或模型支持的数据解释。实验和模拟的结合也将有助于拒绝这种反应条件，在这种情况下，多种效应的串联使数据无法解释。在第一个项目期间，研究了非理想设施依赖效应。通过结合不同设施的数据和模拟的支持，实现了对这些影响的理解，并推导了测量量之间的相关性，例如压力的逐渐增加作为实验条件的函数。第二阶段现在将向前迈出重要的一步，包括具有高预燃倾向的选定燃料的化学依赖效应，这通过气体动力学和反应热释放之间的反馈放大了不均匀性。重点将放在(i)使用具有可调低反应性的燃料和燃料混合物（即CH4、H2和C3H6）进行长时间试验，（ii）使用新的激波管设计（限制反应体积，CRV）和插入物减轻非理想影响，以及（iii）研究复杂燃料（轻度点火的发生；负温度系数，NTC），如正庚烷，它们对非均匀条件特别敏感。这些现象将在高压激波管中进行研究，该激波管具有新设计的抑制远程点火的CRV试验段。将应用扩展诊断功能，通过测量压力、温度和具有高空间和时间分辨率的局部点火来关注非理想现象。将进行0D， 1D， 2D和3D模拟，以支持对潜在效果的基本理解。考虑边界层效应引起的温度和压力变化，模拟了具有明显NTC行为的燃料的着火过程。

Shock tubes provide an excellent platform for the development of chemical kinetics mechanisms because they enable the isolated investigation of high-temperature reactions without interference by mixing or transport processes. At intermediate temperatures that are relevant for practically-important low-temperature combustion processes, several inherent phenomena can induce spatial and temporal non-uniformities. Such non-uniformities lead to early localized reactions and therefore prevent a straight-forward interpretation of the observed process. Such “non-ideal” processes include interaction of the shock wave with boundary layers, finite diaphragm opening times, shock-wave bifurcation, pre-ignition heat release, and ignition by hot particles. The overall target of the proposal is to investigate non-uniform ignition in a high-pressure shock tube to determine the best-suited experimental configurations that enable straight-forward or model-supported data interpretation. The combination of experiment and simulation will also help to reject such reaction conditions, where a concatenation of multiple effects makes data interpretation impossible. In the first project period, non-ideal facility-dependent effects were investigated. Through combination of data from various facilities and the support of simulation, understanding of these effects was achieved and correlations between measured quantities such as the gradual increase in pressure as a function of experimental conditions were deduced. The second period will now go one important step further and include chemistry-dependent effects of selected fuels with high propensity to pre-ignition, which amplify non-uniformity through feedback between gas dynamics and reaction heat release. The focus will be on (i) experiments with long test times using fuels and fuel mixtures with tunable low reactivities (i.e., CH4, H2 and C3H6), on the (ii) mitigation of non-ideal effects using a new shock-tube design (constrained reaction volume, CRV) and inserts, and finallyon (iii) investigations of complex fuels (occurrence of mild ignition; negative temperature coefficients, NTC) such as n-heptane, which are especially sensitive to non-uniform conditions.These phenomena will be investigated in a high-pressure shock tube with a newly designed CRV test section that suppresses remote ignition. Extended diagnostics capabilities will be applied, focusing on non-ideal phenomena by measuring pressure, temperature, and localized ignition with high spatial and temporal resolution. Simulations in 0D, 1D, 2D, and 3D simulations will be performed to support the fundamental understanding of the underlying effects. The ignition of fuels with pronounced NTC behavior will be simulated by considering the change of temperature and pressure due to boundary layer effects.