Gas emissions from an agricultural compression-ignition engine using Diesel, biodiesel and ethanol blends

ABSTRACT: Partial fuel replacement strategies arising from fossil sources used in compression ignition engines involve mixtures of mineral Diesel oil, biodiesel and ethanol to minimize the gas emissions. In this study, experimental assessments were performed on a multi-cylinder, turbocharged aftercooler, compression-ignition, agricultural tractor engine provided with electronic injection management and an exhaust gas recirculation (EGR) gas treatment system. Diesel oil containing low (BS10 -10 ppm) and high sulfur concentrations (BS500 - 500 ppm) was utilized, with 10% of biodiesel as a constituent established by Brazilian legislation, in blends with 5, 10, 15 and 20% of the total volume, made up of anhydrous ethanol with additives. Thus, there were eight fuels blends and two reference conditions (without ethanol). The emissions of CO, HC, NOx and the HC+NOx gases were estimated, corresponding to the eight operating modes (M) of the ABNT NBR ISO 8178-4 standard. From the findings, it was evident that with the rise in the ethanol concentrations in the fuel blends there was a corresponding increasing in the CO, NOx and HC+NOx emissions. The HC, on the contrary, exhibited a pattern of higher emissions for the high-sulfur fuels (BS500) at low loads. No difference was observed for the NOx emissions at high loads. In the other operation modes, different behaviors were expressed for the BS10, which sometimes showed an increase, while at other times a reduction in the NOx emissions. Regarding the BS500, the NOx emission increased when the ethanol concentrations rose. As the specific emissions of the NOx were higher than those of the HC (in g.kW-1.h-1), the behavior exhibited by the HC+NOx showed similarity to that of the NOx. When the directly analysis of the operating modes was taken into consideration, the use of ethanol triggered an upswing in the emissions, exceeding the threshold of MAR-1 and EURO V standards.

摘要：压燃式发动机采用化石燃料的部分替代策略，通常将矿物柴油、生物柴油与乙醇复配为混合燃料，以最大限度降低尾气排放。本研究针对一台配备电子喷射管控系统与废气再循环（exhaust gas recirculation，EGR）尾气处理系统的多缸涡轮增压中冷压燃式农用拖拉机发动机开展实验评估。实验使用了低硫（BS10，硫含量10ppm）与高硫（BS500，硫含量500ppm）两种柴油，按照巴西法规要求，基础柴油中预先添加10%体积占比的生物柴油，再将该基础柴油分别与占总容积5%、10%、15%、20%的含添加剂无水乙醇进行混合，由此共得到8种燃料混合试样，以及2种不含乙醇的基准工况。针对ABNT NBR ISO 8178-4标准规定的8种运行模式（M），分别测算CO、HC、NOₓ以及HC+NOₓ的尾气排放水平。实验结果表明，随着燃料混合试样中乙醇浓度提升，CO、NOₓ以及HC+NOₓ的排放水平均相应升高。而HC排放则呈现出相反的变化规律：在低负荷工况下，高硫燃料（BS500）的HC排放水平更高。在高负荷工况下，两种硫含量柴油的NOₓ排放并无显著差异。在其余运行模式中，BS10柴油的NOₓ排放表现出波动特性，有时排放升高，有时则出现降低；对于BS500柴油而言，乙醇浓度提升会导致NOₓ排放升高。由于NOₓ的比排放（单位为g·kW⁻¹·h⁻¹）高于HC，HC+NOₓ的排放变化规律与NOₓ较为相似。若直接对运行工况进行分析，乙醇的添加会引发排放上升，超出MAR-1与EURO V排放标准的限值要求。