Exhaust-stream particulate matter (PM) emission from combustion sources such as internal combustion engines are typically characterized with modest temporal resolutions; however, in-cylinder investigations have demonstrated significant variability and the importance of individual cycles in transient PM emissions. Here, using a Fast Exhaust Nephelometer (FEN), a methodology is developed for measuring the cycle-specific PM concentration at the exhaust port of a single-cylinder research engine. The measured FEN light-scattering is converted to cycle-resolved soot mass concentration ($C_m$), and used to characterize the variability of engine-out soot emission. To validate this method, exhaust-port FEN measurements are compared with diluted gravimetric PM mass and scanning mobility particle sizer (SMPS) measurements, resulting in close agreements with an overall root-mean-square deviation of better than 30%. It is noted that when PM is sampled downstream in the exhaust system, the particles are larger by 50–70 nm due to coagulation. The response time of the FEN was characterized using a “skip-firing” scheme, by enabling and disabling the fuel injection during otherwise steady-state operation. The average response time due to sample transfer and mixing times is 55 ms, well below the engine cycle period (100 ms) for the considered engine speeds, thus suitable for single-cycle measurements carried out in this work. Utilizing the fast-response capability of the FEN, it is observed that cycle-specific gross indicated mean effective pressure (GIMEP) and $C_m$ are negatively correlated ($R^2$: 0.2–0.7), implying that cycles with lower GIMEP emit more soot. The physical causes of this association deserve further investigation, but are expected to be caused by local fuel-air mixing effects. The averaged exhaust-port $C_m$ is similar to the diluted gravimetric measurements, but the cycle-to-cycle variations can only be detected with the FEN. The methodology developed here will be used in future investigations to characterize PM emissions during transient engine operation, and to enable exhaust-stream PM measurements for optical engine experiments.

来自燃烧源（例如内燃机）的废气颗粒物（PM）排放通常具有适度的时间分辨率。但是，缸内研究显示出显着的可变性以及瞬态PM排放中单个循环的重要性。在这里，使用快速排气浊度计（FEN），开发了一种用于测量单缸研究型发动机排气口处特定于循环的PM浓度的方法。将测得的FEN光散射转换为循环分辨的烟尘质量浓度（$C_{米}$），并用于表征发动机排出的烟尘排放的变化性。为了验证该方法，将排气口FEN测量值与稀释的重量PM质量和扫描迁移率粒度仪（SMPS）测量值进行比较，得出了一致的结论，总均方根偏差优于30％。需要注意的是，当在排气系统的下游采样PM时，由于凝结，颗粒会增大50-70 nm。FEN的响应时间使用“跳过点火”方案进行了表征，方法是在稳定状态下启用和禁用燃油喷射。由于样品传输和混合时间所致的平均响应时间为55 ms，远低于所考虑的发动机转速的发动机循环周期（100 ms），因此适合于此项工作中进行的单循环测量。$C_{米}$ 呈负相关（${\mathrm{[R}}^2$：0.2–0.7），这意味着GIMEP较低的循环会排放更多的烟灰。这种联系的物理原因值得进一步研究，但预计是由局部燃料-空气混合效应引起的。平均排气口$C_{米}$类似于稀释的重量测量，但只能使用FEN才能检测出周期之间的变化。本文开发的方法将用于未来的研究中，以表征瞬态发动机运行过程中的PM排放，并实现用于光学发动机实验的废气流PM测量。