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

激波管中的点火现象以及非理想效应对燃烧化学测量的影响：实验、建模和模拟

• 批准号: 279056804
• 负责人: Professor Dr.-Ing. Andreas Kempf
• 金额: --
• 依托单位: Institut für Energie- und Material-Prozesse (EMPI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/279056804?language=en
• 关键词: Ignition; phenomena; shock; tubes; influence

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.

激波管为化学动力学机制的发展提供了一个很好的平台，因为它们能够独立地研究高温反应，而不受混合或传输过程的干扰。在与实际重要的低温燃烧过程相关的中间温度下，若干固有现象可引起空间和时间的不均匀性。这种不均匀性导致早期的局部反应，因此无法直接解释所观察到的过程。这种“非理想”过程包括激波与边界层的相互作用、有限的隔板打开时间、激波分叉、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中的非均匀点火，以确定最适合的实验配置，使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样的反应条件，其中多重效应的串联使得数据解释成为不可能。在第一个项目期间，非理想的设施依赖的影响进行了调查。通过结合来自各种设施的数据和模拟的支持，实现了对这些影响的理解，并推导出了作为实验条件的函数的压力逐渐增加等测量量之间的相关性。第二阶段现在将进一步迈出重要一步，包括具有高提前点火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，CH 4、H2和C3 H6），关于（ii）使用新的激波管设计减轻非理想效应（约束反应体积，CRV）和插入，最后（iii）复杂燃料的研究（发生轻度着火;负温度系数，NTC）如正庚烷，这些现象对非均匀条件特别敏感。这些现象将在高-压力激波管与新设计的CRV测试部分，抑制远程点火。将应用扩展的诊断能力，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，重点关注非理想现象。将进行0 D、1D、2D和3D模拟，以支持对潜在效应的基本理解。具有明显NTC特性的燃料的点火将通过考虑由于边界层效应引起的温度和压力的变化来模拟。