Simulation And Experimental Study Of N- Butylbenzene-N-Heptane Diesel Surrogate Fuel

With more stringent emission regulations of internal combustion engine have been proposed, and further engine technologies are desired to develop, the three-dimensional numerical simulation technology has become an indispensable tool for the development of advanced combustion mode. For simulation of diesel engine, the composition of surrogate fuels and precision of mechanism directly affects the accuracy of the numerical simulation results.This study choose n-butylbenzene which has strong representative of alkylbenzene as surrogate composition of monocylic aromatics. Firstly, analysis the main oxidation reaction path of n-butylbenzene detail chemical kinetics mechism (contains 960 species,4330 reactions). Methods of decreasing the number of species and reactions were applied using reaction path analysis, sensitivity analysis, and DRG method to obtain a reduced n-butylbenzene mechism (contains 138 species,694 reactions). Then, the calculation result of the reduced mechanism of n-butylbenzene were compared with ignition delay time of n-butylbenzene in shock tube and rapid compress machine, and concentration of intermediate production in jet stirring reactor. It turned out that reduced mechanism can objectively reflected the n-butylbenzene oxidation combustion process. In order to build n-butylbenzene-n-heptanes diesel surrogate fuel, previous obtained reduced mechanism was combined with reduced mechanism of n-heptane, and then relevant reaction parameters was adjusted according to the comparison between calculation results and ignition delay time in experiment. NOx formation and PAH prediction mechanism were added to it, and finally built a n-butylbenzene-n-heptane diesel surrogate fuel mechanism containing 161 species,862 reactions.Experimental investigation was carried out to study the combustion and emission characteristics of four typs of fuels i.e. commercial diesel,20% toluene +80% n-heptane (TRF20),20% n-butylbenzene+80% n-heptane (BRF20) and 30% n-butylbenzene+70% n-heptane (BRF30). Compared with commercial diesel, the results indicated that BRF30 had similar characteristics with TRF20 in cylinder pressure, heat release rate as well as NOx,CO and THC emissions. However, for the particles size of soot, the figure of BRF30 was better than TRF20 in light-duty, while the figure of TRF20 was much better than BRF30 in terms of heavy-duty.At last, the n-butylbenzene-n-heptane diesel surrogate fuel mechanism contains forecast soot and NOx formation mechanism was calculated using the three-dimensional simulation software AVL-Fire coupled with chemical kinetics program Chemkin.Compared to simulated and experimental values in cylinder pressure, heat release rate and emissions, the results showed that this mechanism can accurately reflect the commercial diesel combustion characteristics of diesel engines, and soot emissions trends can be predicted to some extent.