氧化催化转化器对柴油机颗粒物排放特性的影响

Effects of Diesel Oxidation Catalyst Technology on Characteristics of Particle from a Diesel Engine

摘要:

以某高压共轨重型柴油机为样机，研究氧化催化转化器（Diesel Oxidation Catalyst，DOC）对柴油机颗粒排放规律的影响.研究结果表明，各工况下，DOC后测点颗粒物质量浓度相对于前测点均有所下降，降幅随转速升高而减小，随着负荷的增大变化不大；外特性下，DOC对总颗粒、核态颗粒和聚集态颗粒的转化率均随着转速增加而波动下降，其平均转化率分别为21.5%,26.2%和15.4%；最大转矩转速1 400 r·min-1负荷特性下，DOC对总颗粒、核态颗粒、聚集态颗粒的转化率均随着负荷的增大先下降再上升，其平均转化率为34.6%,38.8%和27.3%；DOC对核态颗粒物的转化率高于聚集态颗粒物，在粒径为9~12 nm的范围内转化率达到最高，其他粒径范围内转化率大多介于20%~40%之间.

关键词:氧化催化转化器; 颗粒物; 质量浓度; 数量浓度; 粒径分布

Abstract:

The effects of diesel oxidation catalyst on the characteristics of particle was studied on a heavy duty diesel engine. The results show that particle mass concentrations of measuring point after DOC decrease compared to those before DOC, and the decreasing range reduces with the increase of engine speed, but differs insignificantly with the increase of engine load. When the engine is operating at full load, the conversion rates of total particles, nucleation mode particles and accumulation mode particles decline with the increase of engine speed, with an average conversion rate of 21.5%, 26.2% and 15.4%, respectively. At an engine speed of 1 400 r·min-1, the conversion rates of total particles, nucleation mode particles and accumulation mode particles decrease first and then increase with the increase of engine load, with an average conversion rate of 34.6%, 38.8% and 27.3%, respectively. The particle conversion rates of DOC to nucleation mode particles are higher than those of accumulation mode particles, and reach the peak when the particle size range from 9 to 12 nm. However, the particle conversion rate for the rest of the particle size vary from 20% to 40%.

Key words:diesel oxidation catalyst; particle; mass concentration; number concentration; size distribution