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为提高柴油机的燃烧热效率及有效降低有害排放物,在1台高压共轨单缸柴油机上,运用2段预喷和1段主喷组合的多段燃油喷射,并耦合高EGR率以实现低温预混合燃烧。在不同放热中心及EGR率的条件下,对比研究柴油及D10燃料(在柴油中掺入10%碳酸二甲酯)的排放性能。研究结果表明:随着放热中心(crank angle 50,CA50)后移,NOx排放显著降低,HC及CO排放的变化则相对平缓,PM排放呈先增加后降低的趋势;通过调整燃油喷射系统参数调控CA50(燃油路径)及采用EGR率(气体路径)均可实现对NOx的控制,但对其他排放物的作用效果却各不相同;高EGR氛围耦合较晚的CA50,即燃油路径与气体路径二者良好的匹配使用,可实现NOx和PM这2个目标变量的兼顾控制;与柴油相比,使用含氧燃料D10后,HC和CO均略有下降,NOx排放略有上升,但在PM排放方面可以获得大幅度的降低,可为NOx与PM排放之间的再平衡提供更大的空间。
In order to improve the combustion thermal efficiency of diesel engine and effectively reduce harmful emissions, a multi-stage fuel injection with a combination of two-stage pilot injection and one-stage main injection is used on a single high pressure common rail single-cylinder diesel engine and a high EGR rate is coupled to achieve low-temperature premixing combustion. Emissions performance of diesel and D10 fuels (incorporating 10% DMC in diesel) was compared under different heat removal centers and EGR rates. The results show that with the backward of the crank angle 50 (CA50), the NOx emission is significantly reduced, the HC and CO emissions are relatively flat, and the PM emission first increases and then decreases. By adjusting the parameters of the fuel injection system Regulating CA50 (fuel path) and adopting EGR rate (gas path) can both achieve control of NOx, but have different effects on other emissions. CA50 with a later coupling of high EGR atmosphere, ie, fuel path and gas path The good match between the two can achieve a balance between the two target variables of NOx and PM. Compared with diesel, both HC and CO decrease slightly and NOx emission slightly increase after using oxygen-containing fuel D10. However, Significant reductions in emissions can provide greater room for rebalancing NOx and PM emissions.