希釈トンネル内の沈着が粒子状物質計測に及ぼす影響について

概要

論文の詳細を見る
In a previous report, the authors showed that half of sulfate in particulate matter (PM) was lost during total sampling of PM in a partial flow dilution system. In order to show the cause of this sulfate loss, deposition loss in the dilution tunnel of the measurement system was investigated. Since there is no description about the length of the dilution tunnel of this system in JIS B 8008 which describes the PM measuring method, a guideline for the length of a dilution tunnel was investigated. PM emissions of a laboratory diesel engine were obtained for various lengths of the dilution tunnel. The length of the dilution tunnel was varied between 10 to 40 times the inner diameter of the dilution tunnel. To investigate measurement results, particle diameter measurements of the PM in the dilution tunnel were performed and the deposition fractions of the particles were calculated. The results showed that changes in the length of the dilution tunnel had no meaningful influence on the PM emissions. This is supported by deposition calculation results which showed that the deposition fraction was small compared with the deviation of the PM emission measurements. Thus, a length of 10 to 40 times the inner diameter was obtained as a benchmark for the length of a dilution tunnel in a partial flow dilution system with total sampling.