Study on Characteristics of Particulate Matter from 4-Stroke Marine Diesel Engine by Hot Dilution Method

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<p>  The harmful exhaust emissions from marine diesel engines are NOx, SOx, and PM (Particulate Matter). In recent years, there are problems of global warming and rising sea levels. When the BC (Black Carbon) in the PM falls on sea ice in the high-latitude region, an albedo of the sea ice surface decreases and its absorption of solar radiation increases. This promotes sea ice melting. Then marine diesel engines are strongly required to reduce the PM emission in the exhaust gas. However, the actual state of the PM emission from marine diesel engines has been not entirely cleared. In this paper, particle size distribution and mass concentration of PM from a high speed four-stroke engine (3L13AHS, 73.55 kW) were measured by hot dilution method. In the hot-dilution method, exhaust gas from the engine is diluted by the rotary disk type diluter with high temperature air. This method allows exhaust gas dilution while preventing condensation of volatile component in the PM. PM particle size distribution in the diluted exhaust gas was measured by the SMPS (Scanning Mobility Particle Sizer). The effect of the dilution ratio on the particle size distribution and mass concentration of the PM was examined. In the experiment, the test engine was operated according to a propeller load curve and a constant speed with four load conditions (25%, 50%, 75% and 100%). Furthermore, the change of the number concentration of the PM in the sampling tube was examined. The results of this experiment are as follows: The particle diameter distributions obtained by the hot dilution show the mono-modal distribution and the bi-modal distribution depending on the operating condition of the engine. The mode diameters are 100 to 120 nm, except for the low load condition. It is found that the dilution ratio has a great effect on production of nucleation mode particles of small size region at the low engine load under constant speed operation. Therefore, it can be understand that volatile components are contained at a high concentration on exhaust gas. For the total number concentration measured by the SMPS, the maximum value is obtained at 75% load of the propeller load operation. The number concentration of the PM in the diluted exhaust gas decreases in the sampling tube for transfer from the diluter to the SMPS. The decrease rate of number concentration of the PM becomes higher for smaller particle sizes. While the dilution ratio of exhaust gas does not affect the decrease rate, the decreases rate increases as the tube length increases.</p>

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