Abstract Particle size distributions (PSDs) of engine blow-by aerosol are commonly obtained with an optical particle counter (OPC), but representative measurements are challenging due to high number concentrations, elevated temperatures, presence of saturated vapor, as well as unsteady flow conditions. A comprehensive study of blow-by aerosol sampling/conditioning and OPC performance in such an environment was therefore conducted, based on a commercial OPC (Palas Promo 2000). Single (1:9) and double-stage (1:80) sampling/dilution/conditioning systems were devised and their transfer functions characterized in the OPC sensor range of 0.3–17 μm. With (mostly inertial) particle losses >90% at 10 μm, correcting for them was crucial for reliable PSD measurements. The effect of saturated oil vapor on droplet growth during cool-down and dilution of the sample flow was investigated between 80 and 120 °C, based on actual vapor concentration data. Without dilution, droplet growth became significant above 100 °C while diluting 1:20 with 20 °C air suppressed growth. Tests of over-all sampling and dilution strategy with engine blow-by aerosol gave excellent reproducibility and good agreement (after loss corrections) with reference data regarding PSD in the 0.3–10 μm range as well as total mass. The actual engine blow-by PSD was significantly broader though, exceeding the OPC range on both ends. Number-to-mass conversion of OPC data under-reported total mass by 10%–20% (depending on sensor range) compared to weighed filter samples, provided OPC contamination with oil deposits was avoided. A re-calibration procedure is proposed to deal adequately also with pressure pulsations resulting from engine operation.

中文翻译：

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通过光学粒子计数器进行代表性测量的发动机窜气气溶胶的采样和调节

摘要 发动机漏气气溶胶的粒径分布 (PSD) 通常使用光学粒子计数器 (OPC) 获得，但由于高浓度、高温、饱和蒸汽的存在以及不稳定的流动条件，代表性测量具有挑战性. 因此，基于商业 OPC (Palas Promo 2000)，对这种环境中的窜气气溶胶采样/调节和 OPC 性能进行了全面研究。设计了单级 (1:9) 和双级 (1:80) 采样/稀释/调节系统，它们的传递函数在 0.3-17 μm 的 OPC 传感器范围内表征。在 10 μm 处（主要是惯性）粒子损失 >90%，对它们进行校正对于可靠的 PSD 测量至关重要。根据实际蒸汽浓度数据，在 80 到 120 °C 之间研究了饱和油蒸汽对样品流冷却和稀释期间液滴生长的影响。在没有稀释的情况下，液滴在 100 °C 以上的生长变得显着，而在 20 °C 的空气中以 1:20 稀释抑制了生长。使用发动机漏气气溶胶对整体采样和稀释策略进行的测试提供了极好的重现性和良好的一致性（在损失校正后），与关于 0.3-10 μm 范围内的 PSD 以及总质量的参考数据具有良好的一致性。然而，实际的发动机窜气 PSD 明显更广，在两端都超过了 OPC 范围。与称重的过滤器样品相比，OPC 数据的数量到质量转换低于报告的总质量 10%–20%（取决于传感器范围），前提是避免了油沉积物的 OPC 污染。