The spatial and temporal locations of autoignition for direct-injection compression-ignition engines depend on fuel chemistry, temperature, pressure, and mixing trajectories in the fuel jets. Dual-fuel systems can provide insight into both fuel-chemistry and physical effects by varying fuel reactivities and engine operating conditions. In this context, the spatial and temporal progression of two-stage autoignition of a diesel-fuel surrogate, n-heptane, in a lean-premixed charge of synthetic natural-gas (NG) and air is imaged in an optically accessible heavy-duty diesel engine. The lean-premixed charge of NG is prepared by fumigation upstream of the engine intake manifold. Optical diagnostics include high-speed (15kfps) cool-flame chemiluminescence-imaging as an indicator of low-temperature heat-release (LTHR) and OH* chemiluminescence-imaging as an indicator high-temperature heat-release (HTHR). NG prolongs the ignition delay of the pilot fuel and increases the combustion duration. Zero-dimensional chemical-kinetics simulations provide further understanding by replicating a Lagrangian perspective for mixtures evolving along streamlines originating either at the fuel nozzle or in the ambient gas, for which the pilot-fuel concentration is either decreasing or increasing, respectively. The zero-dimensional simulations predict that LTHR initiates most likely on the air streamlines before transitioning to HTHR, either on fuel-streamlines or on air-streamlines in regions of near-constant ϕ. Due to the relatively short pilot-fuel injection-durations, the transient increase in entrainment near the end of injection (entrainment wave) is important for quickly creating auto-ignitable mixtures. To achieve desired combustion characteristics, e.g., multiple ignition-kernels and favorable combustion phasing and location (e.g., for reducing wall heat-transfer or optimizing charge stratification), adjusting injection parameters could tailor mixing trajectories to offset changes in fuel ignition chemistry.

直喷式压缩点火发动机的自动点火的空间和时间位置取决于燃料化学成分，温度，压力和燃料射流中的混合轨迹。双燃料系统可以通过改变燃料的反应性和发动机工况来提供对燃料化学和物理作用的了解。在这种情况下，柴油燃料替代物两阶段自燃的空间和时间进程n-庚烷，以预混合的合成天然气（NG）和空气的稀薄预混合方式在光学可访问的重型柴油机中成像。NG的稀薄预混装料是通过在发动机进气歧管上游进行熏蒸来准备的。光学诊断包括高速（15kfps）的冷火焰化学发光成像（作为低温热释放（LTHR）的指示剂）和OH *化学发光成像（作为高温高温释放（HTHR）的指示剂）。NG会延长引燃燃料的点火延迟并延长燃烧持续时间。零维化学动力学模拟通过复制拉格朗日透视图来进一步理解，这些混合物沿分别源自燃料喷嘴或环境气体的流线演变，而对于这些混合物，引燃燃料浓度分别降低或升高。零维模拟预测，LTHR最有可能在过渡到HTHR之前先在空气流线上启动，无论是在燃料流线上还是在const恒定区域的空气流上。由于引燃燃料的喷射持续时间相对较短，因此在喷射接近结束时夹带的短暂增加（夹带波）对于快速创建可自动点燃的混合物很重要。为了获得期望的燃烧特性，例如多个点火核以及有利的燃烧定相和位置（例如，用于减少壁传热或优化装料分层），调节喷射参数可以调整混合轨迹以抵消燃料点火化学的变化。fuel恒定区域的燃料流线或空气流线上。由于引燃燃料的喷射持续时间相对较短，因此在喷射接近结束时夹带的短暂增加（夹带波）对于快速创建可自动点燃的混合物很重要。为了获得期望的燃烧特性，例如多个点火核以及有利的燃烧定相和位置（例如，用于减少壁传热或优化装料分层），调节喷射参数可以调整混合轨迹以抵消燃料点火化学的变化。fuel恒定区域的燃料流线或空气流线上。由于引燃燃料的喷射持续时间相对较短，因此在喷射接近结束时夹带的短暂增加（夹带波）对于快速创建可自动点燃的混合物很重要。为了获得期望的燃烧特性，例如多个点火核以及有利的燃烧定相和位置（例如，用于减少壁传热或优化装料分层），调节喷射参数可以调整混合轨迹以抵消燃料点火化学的变化。