An Experimental Study Of Duel Fuel Combustion Mode Based On Dual Injection

An experimental study of DFSC(Dual Fuel Sequential Combustion,DFSC)combustion and RCCI(Reactivity Controlled Compression Ignition,RCCI) combustionwas conducted by applying two-stage fuel supplying method.In DFSC combustion, in order to investigate the effects of premixed ratio(rp) and PIequivalence ratio, DI equivalence ratio and overall equivalence ratio on the process ofcombustion, high cetane number fuel, n-heptane is injected in the port to be ignitedspontaneously in the compression stroke before TDC(Top Dead Center) to release activegroup and heat. Since n-heptane has low boiling point with perfect atomizationcharacteristics, it can form a homogeneous mixture before the direct injection of gasoline/n-butyl alcohol, thus it will form fuel concentration stratification, compositionstratification and temperature stratification. The main results are summarized as: with theincrease of rp and overall equivalence ratio per cycle, the heat release timing of DIadvanced; the maximum pressure and maximum mass-averaged temperature increase; COincrease initially and then decrease; HC remain at a constant level; NOx increase slightly.The oxygen content inhibits the soot exhaust significantly.In RCCI combustion, in order to investigate the effects of premixed ratio(rp) and PIequivalence ratio, DI equivalence ratio and overall equivalence ratio on the process ofcombustion, high cetane number fuel, n-heptane is injected directed into the cylinder andhigh octane number fules gasoline/n-butyl alcohol is injected in the port to investigate thecombustion and exhaust character. The main results are summarized as: with the increaseof rp and PI equivalence ratio per cycle, the heat release concentrates and advanced; themaximum pressure and maximum mass-averaged temperature increase; CO and NOxincrease initially and then decrease; soot decrease monotonously. The delay of DI timingcan lower NOx significantly.It is found by the comparison of DFSC and RCCI that: the indicated thermalefficiency of RCCI combustion mode is generally higher than that of DFSC when the equivalence ratio of h-heptane is small; the CO and HC emission of RCCI is relatively lowwhen the equivalence ratio of gasoline is small; the NOx and soot emission of RCCI isgenerally higher than that of DFSC with the same equivalence ratio;with the smaller totalequivalent ratio or larger premixed ratio, the indicated thermal efficiency of RCCI mode isgenerally higher than that of DFSC; the CO emission of RCCI is lower than DFSC whenthe premixed ratio is small; with the same pre-mixed ratio, HC and NOx emissions ofRCCI are generally higher than those of DFSC and RCCI has small soot emission only inthe condition with larger equivalence ratio and premixed ratio.