Biodiesel has great potential as an alternative fuel for diesel engines. However, poor low-temperature flow property and high viscosity of biodiesel limit its use in engines. Therefore, alcohol comes into researchers’ eyes as a promising additive for diesel–biodiesel (DB) blends. In this study, the effects of lower and higher alcohol contents with different speeds on combustion and emissions characteristics were investigated in a modified single cylinder diesel engine. The results indicated that the maximum pressure rise rate (MPRR) maintained a consistent drop ratio as speed increased from 1500 rpm to 1800 rpm for the tested fuels. However, B10E10 (10% biodiesel and %10 ethanol by volume) had a big drop, which meant that engine’s power ability had a big loss at high speed. The declining rate with speed decreased for indicated thermal efficiency (ITE) when adding alcohol to diesel–biodiesel blends, especially n-pentanol. Moreover, compared with other tested fuels, B10P10 (10% biodiesel and 10% n-pentanol) had smaller cycle variation and more stable combustion state as speed changed, despite it had the highest coefficient of variation (COV) at 1000 rpm. It can be found that has advantages in combustion stability, and can well reduce the total hydrocarbon (THC) and carbon monoxide (CO) emissions under the condition of medium speed commonly used by vehicle. Overall consideration, using diesel/biodiesel/alcohol ternary fuels may be a better choice for diesel engines.

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柴油发动机中柴油/生物柴油/酒精混合物的性能和排放特性

生物柴油作为柴油发动机的替代燃料具有巨大的潜力。但生物柴油低温流动性差、粘度高限制了其在发动机中的应用。因此，研究人员将酒精视为一种有前景的柴油-生物柴油（DB）混合物添加剂。在本研究中，在改进的单缸柴油发动机中研究了不同速度下较低和较高的酒精含量对燃烧和排放特性的影响。结果表明，对于测试燃料，随着速度从 1500 rpm 增加到 1800 rpm，最大压力上升率 (MPRR) 保持一致的下降率。而B10E10（按体积计10%生物柴油和10%乙醇）则下降幅度较大，这意味着发动机在高速行驶时动力能力损失较大。当向柴油-生物柴油混合物中添加酒精（尤其是正戊醇）时，指示热效率（ITE）的下降率随速度下降。此外，与其他测试燃料相比，B10P10（10％生物柴油和10％正戊醇）尽管在1000rpm时具有最高的变异系数（COV），但随着速度变化，其循环变化更小，燃烧状态更稳定。可以发现，其在燃烧稳定性方面具有优势，在车辆常用的中速工况下，能够很好地降低总碳氢化合物（THC）和一氧化碳（CO）的排放。综合考虑，使用柴油/生物柴油/酒精三元燃料可能是柴油机更好的选择。