直接/间接煤制油对重型柴油机燃烧和排放的影响

Effects of Direct or Indirect Coal Liquefaction Fuels on Combustion and Emissions of Heavy-Duty Diesel Engine

在一台高压共轨重型柴油机上,通过试验研究煤直接液化(DCL)燃油及煤间接液化(ICL)燃油对柴油机燃烧和排放的影响.结果表明,在小负荷时,相比柴油燃料,DCL滞燃期较长,预混燃烧比例较高,最大压力高升率较大,而ICL滞燃期较短;预混燃烧比例较低,最大压力升高率较小,在扩散燃烧阶段两种煤制油的放热率均高于柴油,燃烧持续期均短于柴油.随着负荷增大,不同燃料的燃烧特性差异逐渐减小.两种煤制油的有效热效率低于柴油,其中DCL的有效热效率略高于ICL.煤制油均可获得较低的NOx和碳烟排放,但煤制油的HC和CO排放稍高于柴油.对于ESC循环加权结果,DCL和ICL的有效热效率相对柴油分别降低2.6%和3.4%;ICL在降低NOx方面强于DCL,相对柴油降低2.5%,在降低碳烟方面稍差于DCL,DCL的碳烟降幅63.1%大于ICL的53.7%;对于ICL,其HC增大幅度为17.1%,CO增大幅度为9.1%,均分别小于DCL的32.4%和29.5%.

The effects of two types of coal-to-liquid fuels (i.e.,direct and indirect coal liquefaction,DCL and ICL) on the combustion and emissions of a diesel engine were investigated on a high-pressure common-rail heavyduty diesel engine. Results showed that under low load,the ignition delay of DCL was longer than that of diesel fuel,which caused a higher premixed combustion ratio and a higher maximum pressure rise rate. However,the ignition delay of ICL was shorter than that of diesel fuel,which caused a lower premixed combustion ratio and a lower maximum pressure rise rate. During diffusion combustion,the heat release rates of both types of coal-toliquid fuels were higher than that of diesel fuel,while their combustion durations were shorter. With the increase in load,the differences in combustion characteristics among different fuels gradually decreased. The brake thermal efficiencies (BTE) of both DCL and ICL were lower than those of diesel fuel,and the BTE of DCL was a little higher than that of ICL. The NOx and soot emissions of both DCL and ICL were lower than those of diesel fuel, but their HC and CO emissions were higher. Based on ESC weighed results,the BTEs of DCL and ICL were reduced by 2.6% and 3.4%,respectively. ICL was better than DCL in reducing NOx emissions,and its emissions were 2.5% lower compared with diesel fuel. The soot reduction of DCL was 63.1%,which was higher than that of ICL (53.7%). For ICL,the increases in HC and CO were 17.1% and 9.1%,respectively,which were lower than those of DCL (32.4% and 29.5%,respectively).