掺混聚甲氧基二甲醚对柴油机排放的影响

Effects of polyoxymethylene dimethyl ethers/diesel blends on emissions of diesel engine

为研究聚甲氧基二甲醚(PODE)/柴油混合燃料对柴油机颗粒物(PM)粒径分布和各模态颗粒捕集效率的影响,将PODE按照体积百分比0%、10%、20%和30%与柴油混合,在不对柴油机做任何改动的情况下,进行排放测试,测量NO_x排放和DPF前后的颗粒粒径分布.结果表明:随着PODE掺混比提高,NO_x排放在10%~50%负荷工况下呈上升趋势,75%~100%负荷工况下呈先上升后下降的趋势;NO_2/NO_x随着PODE掺混比的提高呈上升趋势.PODE的添加可有效降低PM排放.与柴油相比,燃用PODE掺混比20%的混合燃料时,降低PM效果最好;100%负荷工况下,PM总数量浓度降低了18.93%,总体积浓度降低了31.27%.掺混PODE,使DPF对PM的捕集效果减弱,10%~50%负荷工况下较为明显,但捕集率依然可以达到95%以上.

The aim of this study was to evaluate the effect of polyoxymethylene dimethyl ethers （PODE）/diesel blends on particle size distribution and filtering efficiency of different modes of particulate matter （PM）. The emission experiments were carried out on a diesel engine without any modification fueled with PODE/diesel blends by volume ratio of 0%, 10%, 20% and 30% respectively, and nitrogen oxide （NOx） emission and particle size distribution were measured in the upstream and downstream of diesel particulate filter （DPF）. The results showed that NOx emission increased as the load conditions increased from 10% to 50%, while it showed a decline before it increased close to 100% load conditions. Meanwhile, the NO2/NOx ratio increased with the increasing blending ratio of PODE in the blended fuel under various loads, which indicated that PODE played a positive role in PM reduction. PODE/diesel blends ratio of 20% presented the best performance on PM reduction. Under 100% load condition, the total particle number and the particle volume concentrations with PODE/diesel blends ratio of 20% was decreased by 18.93% and 31.27% respectively compared with the pure diesel. Blending PODE in diesel showed negative effect on the PM reduction by DPF, especially under the load conditions of 10%~50%, but the overall filtering efficiency was still more than 95 %.