The ignition behavior of n-dodecane micro-pilot spray in a lean-premixed methane/air charge was investigated in an optically accessible Rapid Compression-Expansion Machine at dual-fuel engine-like pressure/temperature conditions. The pilot fuel was admitted using a coaxial single-hole 100 µm injector mounted on the cylinder periphery. Optical diagnostics include combined high-speed CH₂O-PLIF (10 kHz) and Schlieren (80 kHz) imaging for detection of the first-stage ignition, and simultaneous high-speed OH* chemiluminescence (40 kHz) imaging for high-temperature ignition. The aim of this study is to enhance the fundamental understanding of the interaction of methane with the auto-ignition process of short pilot-fuel injections. Addition of methane into the air charge considerably prolongs ignition delay of the pilot spray with an increasing effect at lower temperatures and with higher methane/air equivalence ratios. The temporal separation of the first CH₂O detection and high-temperature ignition was found almost constant regardless of methane content. This was interpreted as methane mostly deferring the cool-flame reactivity. In order to understand the underlying mechanisms of this interaction, experimental investigations were complemented with 1D-flamelet simulations using detailed chemistry, confirming the chemical influence of methane deferring the reactivity in the pilot-fuel lean mixtures. This shifts the onset of first-stage reactivity towards the fuel-richer conditions. Consequently, the onset of the turbulent cool-flame is delayed, leading to an overall increased high-temperature ignition delay. Overall, the study reveals a complex interplay between entrainment, low T and high T chemistry and micro-mixing for dual-fuel auto-ignition processes for which the governing processes were identified.

在光学可访问的快速压缩膨胀机中，在类似双燃料发动机的压力/温度条件下，研究了稀-预混合甲烷/空气进料中正十二烷微飞行员喷雾的着火行为。使用安装在气缸外围的同轴单孔100 µm喷油器导入引燃燃料。光学诊断包括组合式高速CH ₂O-PLIF（10 kHz）和Schlieren（80 kHz）成像用于检测第一阶段点火，同时高速OH *化学发光（40 kHz）成像用于高温点火。这项研究的目的是增强对甲烷与短时引燃燃料自动点火过程相互作用的基本认识。将甲烷添加到空气中可显着延长引燃喷雾的点火延迟，同时在较低温度和较高甲烷/空气当量比的情况下效果会增强。第一CH ₂的时间间隔发现O检测和高温点火几乎恒定，而与甲烷含量无关。可以将其解释为甲烷主要降低了冷焰反应性。为了了解这种相互作用的潜在机理，实验研究辅以一维小火焰模拟（使用详细的化学方法），以确认甲烷的化学影响会降低稀燃燃料混合物的反应性。这将第一阶段反应的发生转移到燃料丰富的条件。因此，湍流的冷火焰的发生被延迟，导致整体的高温点火延迟增加。总体而言，该研究表明，夹带，