Development of Particulate Matter Measurement by UV Absorbance on Marine Diesel Engine

光透射法是测量柴油机尾气中颗粒物浓度的有效方法之一。由于紫外光下的消光系数比可见光下的消光系数大，因此采用紫外光源可以提高测量精度。结果表明，在一定波长范围内，用该方法可以计算出直径为10 ~ 300 nm的聚苯乙烯标准粒子的消光系数和PM的折射率估算值。这种想法使得小的光路长度，高灵敏度和低浓度范围的颗粒高达0.03g/m3（0.1g/kWh）从柴油发动机排出。测量系统由波长为365 nm的高压汞灯、透镜、干涉滤光片和小型光传感器组成。输出信号由个人计算机系统进行真实的实时分析。检查了标准粒子和PM的吸收光谱。根据朗伯-比尔定律，通过吸光度确定浓度。该系统的应用使颗粒物浓度的直接测量与过滤采样法的测量结果基本一致。这一发展将导致船用发动机PM浓度的实用价值的建立。

Light transmittance is one of the effective measurement method of small particlulate matter (PM) concentration in diesel exhausted gas. The measurement is improved by UV light source, because the extinction coefficient in the UV is higher than in visible light. It was proved that the extinction coefficient of a standard particle of polystyrene and PM estimated refractive indices were calculated with the diameter from 10 to 300nm and some wavelength. That idea makes a small light path length, high sensitivity and low concentration range for particles up to 0.03g/m3 (0.1g/kWh) exhausted from a diesel engine. The measurement is composed of a high pressure Hg lamp with the wavelength of 365nm, lenses, an interference filter and a small light sensor. The output signal is analyzed at real time by a personal computer system. The absorption spectra of the standard particles and PM were examined. The concentration was determined by the absorbance with Lambert-Beer's law. Application of the system has enabled directly measurement of PM concentration which were in fair agreement with the data by filter sampling method. This development will lead to a building up of the practical value of PM concentration from marine engines.