Experimental Research On The Evolution Of Polycyclic Aromatic Hydrocarbons During Diesel Combustion Process For Different Fuels

In order to investigate the evaluation of the polycyclic aromatic hydrocarbons (PAHs) in diesel engine combustion process, n-heptane was used as the reference of the straight-chain alkanes in diesel fuel, toluene was used as the reference of the aromatic hydrocarbons in diesel fuel and F-T diesel was used as the reference of straight-chain, branched-chain, cyclic alkanes. With the total cylinder dumpling system of diesel engine, three kinds of fuel were used, the gas/particulate phase PAHs was collected with the PUF/XAD-2/PUF cartridges and the glass filter.The PAHs were analyzed by the large-volume programmed temperature vaporization (PTV) injection technique in GC-MS, and the major work and achievements are listed as follows:1. The total mass of PAHs in the combustion process of three kinds of fuel were within the range of the 1.6 ~ 14.3μg/cycle, and with an increases of the fuel injection advance angle, the total mass of PAHs increased.2. The sampling angle of the max. value of each PAHs in the combustion process for n-heptane/toluene were smaller than that for n-heptane, which might imply that the benzene ring could promote the formation of PAHs, which made the peak value of PAHs earlier. The trend of the PAHs in combustion process for F-T diesel were similar with that for burning n-heptane, which might imply that that the branched-chain, cyclic alkanes and straight-chain alkanes about the impact of PAHs were similar.The PAHs in combustion process for the n-heptane and n-heptane/toluene, the mass of two-ring PAHs in n-heptane were more, the mass of four-ring PAHs were less, the other-ring PAHs were almost equality, which description benzene ring could make the two-ring PAHs convert to four-ring PAHs.3. Because the quality of SOF accounted for 64% ~ 95% of PM, the trends of the PM were as same as SOF. They were all earlier reduced, then increase, then decrease. The mass of SOF in combustion process for n-heptane was the most in the three kinds of fuel, it was within the range of 0.09 ~ 0.26mg, that for F-T diesel was the least, within the range of the 0.04 ~ 0.21mg. This might imply that the benzene ring and branched-chain, cyclic alkanes can promote combustion, reducing the generation of SOF. The soot in combustion process for three kinds of fule presented a unimodal trend. The mass of soot in combustion process for n-heptane was the least in the three fuels, within the range of the 0.005 ~ 0.584mg. This might imply that the benzene ring and branched-chain, cyclic alkanes can promote the generation of Soot. Meanwhile, with the fuel injection advance angle increases, the mass of the PM, SOF, Soot were reduced.The trends of PAHs/Soot (mol/g) of PAHs in combustion process for three kinds of fuel were basically the same, were first reduced and then increased. This implied that PAHs were converted to the trend of Soot in the premixed combustion phase. In the premixed combustion phase of the combustion process PAHs / Soot of two-ring PAHs and three-ring PAHs were reduced within the range of 50%~95%. This might imply that conversion of PAHs to the soot would consume a large amount of two-ring, three-ring PAHs.