纳米TiO2添加剂对DMDF发动机大负荷燃烧及PM排放影响的试验研究

在一台电控增压中冷四缸柴油机的进气道上加装一套电控喷射装置,使其运行柴油/甲醇双燃料(DMDF)模式.研究了甲醇中Ti O_2添加剂的添加量及同一添加剂添加量在不同甲醇分散系喷射量时对发动机大负荷工况的燃烧和颗粒物(PM)排放的影响.结果表明,在甲醇中添加适量(30和100 mg·kg~(-1))的纳米Ti O_2能够使爆发压力升高,对燃烧有一定的促进作用,但添加过量(100 mg·kg~(-1))会对燃烧产生不利影响.加入纳米Ti O_2后,干炭烟烟度排放和积聚态颗粒数明显降低,在添加剂添加量为1000 mg·kg~(-1)时,最大降幅分别达到26.8%和29.4%,而核态颗粒物排放变化不大.在相同添加剂添加量下,增加甲醇分散系替代率R_m会使放热始点后移,放热更加集中,爆发压力增大,干炭烟烟度和颗粒物排放均大幅度降低.在添加剂添加量为100 mg·kg~(-1)时,与R_m=10%相比,R_m=40%时爆发压力增加0.94 MPa,放热率峰值增加53.5%,烟度、核态颗粒数、积聚态颗粒数和颗粒物总数的降幅分别达66.9%、42.3%、67.0%和58.0%.

Effects of nano-TiO2 on combustion and PM emissions of a diesel/methanol dual fuel engine at high loads

An electronic system was installed at the intake pipeline of a turbocharged, inter-cooling electronic unit pump diesel engine, which makes it possible to run in diesel/methanol dual-fuel(DMDF) mode. Experiments were conducted to investigate the effects of nano-TiO₂ concentration in methanol and the quantity of methanol injection for constant TiO₂ concentration on combustion and PM emission at high load operation. The results showed that explosion pressure was increased and the combustion process was promoted slightly when moderate amount of nano-TiO₂, like 30 mg·kg^-1 or 100 mg·kg^-1, was added into methanol. However, it may deteriorate the combustion when excessive additive was used. Emissions of the dry soot and accumulation mode particulate matter significantly decreased by using nano-TiO₂, and the decline reached to 26.8% and 29.4%, respectively when 1000 mg·kg^-1 additive was used, while it had little effect on nuclear mode particulate. For constant additive concentration in methanol, increasing methanol injection quantity can extend the ignition delay, leading to more concentrated heat release and higher explosion pressure,while the dry soot and PM emissions decreased significantly. Compared to 10% replacement rate of methanol dispersion, the explosion pressure at 40% replacement rate increased 0.94 MPa with a 53.5% incensement in peak of heat release rate. Meanwhile, dry soot, nuclear mode particle number, accumulation mode particle number and the total number of PM reduced by 66.9%, 42.3%, 67.0% and 58.0%, respectively.