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    基于碳烟的超细颗粒物PN检测仪校准系统设计与研制

    Design and Development of a Calibration System for Soot-Based Ultrafine Particle PN Detectors

    • 摘要: 为有效控制移动源颗粒物排放,缓解日益严峻的大气污染问题,我国自国五阶段起在法规中明确提出柴油车颗粒物数量浓度(Particle Number, PN)的控制要求,并在国六阶段进一步将PN限值监测范围扩展至轻型车。然而,当前市场上用于法规认证与执法的PN检测设备品牌众多,虽已出台针对PN计数效率及计数线性等关键技术参数的法规标准,但行业内尚未建立完善、统一且可溯源的PN监测校准体系。计量溯源链条的缺失,直接导致数据一致性差、可靠性不足,使得现行国六标准在实际执行中面临挑战。针对该迫切需求,本文设计了一套基于横向淬火碳烟颗粒发生的校准系统,可稳定可控地生成形态和性质高度接近真实机动车尾气排放的碳烟颗粒物。在计量原理上,系统通过精密测量带电颗粒感应微电流,将颗粒物数量浓度直接溯源至国际单位“安培(A)”,实现了PN检测仪的快速、可靠校准。性能验证结果显示:研制的碳烟颗粒发生装置具有极高稳定性,可稳定产生10~100 nm标准碳烟颗粒;核心分级部件差分电迁移率分析仪(Differential Mobility Analyzer, DMA)在10 nm至100 nm等各个关键粒径上的筛分偏差均小于2.0%;法拉第杯气溶胶静电计(Faraday Cup Aerosol Electrometer, FCAE)测量各个粒径的线性系数优于99.6%,计数效率保持在100.0%~110.0%范围内。应用测试结果表明,该系统在台架式PN设备、便携式排放测量系统PN模块(Portable Emissions Measurement Systems Particle Number Module, PEMS-PN)校准中表现出优异的适用性,校准所得计数效率与设备出厂标称值的绝对误差均小于 ± 6.7%。

       

      Abstract: In order to effectively control mobile source particulate matter emissions and mitigate the increasingly severe issue of atmospheric pollution, environmental regulations in China have imposed strict control requirements on the particle number (PN) concentration of diesel vehicles since the China V stage. These requirements were further expanded in the China VI stage to include light-duty vehicles. However, the current market features a multitude of PN detection devices from various manufacturers. Although specific regulations for key technical parameters—such as PN counting efficiency and counting linearity—have been promulgated, a unified and traceable calibration system remains absent. This lack of a robust metrological traceability chain compromises data consistency and undermines measurement reliability, posing significant challenges to the implementation of China VI Standards. To address this critical gap, this study designs and develops a calibration system based on a transverse-quenched soot particle generation system. This system is capable of generating soot particles that are stable, controllable, and highly similar in morphology and properties to real vehicle exhaust emissions. From a metrological perspective, the system measures the micro-current induced by charged particles, directly tracing the particle number concentration to the ampere, a base unit of the International System of Units (SI). This approach eliminates reliance on secondary transfer standards, enabling rapid, high-precision, and reliable calibration of PN detectors. Rigorous laboratory tests were conducted to validate the metrological performance of the system. The results indicate that the developed soot particle generation device exhibits exceptional stability, capable of producing standard soot particles in the 10 nm to 100 nm size range. The differential mobility analyzer (DMA), a core component for particle sizing, demonstrates superior performance, with sizing deviations strictly controlled to less than 2.0% across all key particle size nodes from 10 nm to 100 nm. Furthermore, the Faraday cup aerosol electrometer (FCAE), serving as the reference standard, shows excellent linearity in measuring various particle sizes, with a linearity coefficient greater than 99.6%, and its counting efficiency is maintained stably within the range of 100.0% to 110.0%. Application test results demonstrate that the system possesses outstanding versatility in practical engineering applications. In calibration experiments involving both bench-top PN equipment and the Portable Emissions Measurement System Particle Number (PEMS-PN) module, the system exhibited excellent applicability. The counting efficiency obtained from the calibration aligns closely with the manufacturers' nominal values, with errors consistently within ±6.7%. These results verify the precision of the proposed calibration system and provide strong technical support for solving the traceability issues of PN equipment under the China VI Standards.

       

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