Abstract
Taking the diesel-methanol blended fuel as the research object，the influence of diesel-methanol blended fuel combustion on the formation of polycyclic aromatic hydrocarbons (PAHs) was studied. The kinetic mechanism of nheptane/toluenePAHs chemical reaction was constructed and verified by coupling AVLFire and Chemkin, the simulation was conducted by using the homogeneous zerodimensional reaction model of Chemkin, and the influences of mixing ratio, initial temperature, initial pressure and equivalent ratio on PAHs such as benzene, naphthalene, phenanthrene and pyrene (A1-A4) were analyzed.The results show that the peak drop of A1-A4 mole fraction are 5.4%, 14.6%, 21.5%, and 28.1% respectively and the valley increase of total yield are 0.86%, 18.91%, 20.84%, and 23.54% respectively when the methanol blending ratio increases from 0 to 20%. Accordingly, methanol has the more obvious inhibitory effect on PAHs with the more number of benzene rings. According to the reaction path, methanol decomposes into H2, OH, H and so on during the combustion, which enter the reaction path that consumes PAHs, especially PAHs with more benzene rings. As the initial temperature increases from 1 000 K to 1 200 K, the sharp rise time of incylinder temperature advances, the peak values of A1-A4 mole fraction increase by 0.67×10-5, 2.43×10-10, 5.23×10-14, and 0.93×10-14 respectively, hence the increase of initial temperature is beneficial to accelerate the generation of PAHs. The initial pressure increases from 0.1 MPa to 10 MPa, then all the peak arrival times of A1-A4 advance. The advancement is about 27 ms, which is equivalent to 93%. The free radicals of methanol molecular decomposition have a violent reaction with PAHs precursor, which is beneficial to promote the generation of PAHs. Besides, the peak values of A1-A4 mole fraction increase by 1 486%, 1 194 900%, 79 249 900%, and 29 269 900% respectively when the equivalence ratio increases from 0.5 to 1.5. The increase of equivalence ratio causes local hypoxia so as to promote the formation of PAHs.
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QIAN Yikai,WANG Zhong,LI Ruina,LIU Shuai,LI Lilin.
Factors Influencing Formation of Polycyclic Aromatic Hydrocarbons for Diesel-Methanol Blended Fuel[J]. Vehicle Engine. 2022, 0(1): 31-39
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