Two-stage aerosol formation in low-temperature combustion

FUEL

卷:304

Article

El Hajj, O.¹  Atwi, K.¹  Cheng, Z.¹  Christianson, M. G.²  Dewey, N. S.²  Rotavera, B.^1,2  Saleh, R.¹ 

[1] Univ Georgia, Sch Environm Civil Agr & Mech Engn, Athens, GA 30602 USA

[2] Univ Georgia, Dept Chem, Athens, GA 30602 USA

关键词: Low temperature combustion;    Aerosols;    Toluene;    n-Heptane;    Soot;    Two-stage Ignition;   

DOI  :  10.1016/j.fuel.2021.121322

来源: Elsevier

【 摘 要 】

Low-temperature combustion is a promising strategy for reducing pollutant formation in internal combustion engines. However, there is a lack of understanding of how the chemistry governing the differences in ignition between low-temperature and conventional combustion affects the emission rates and physicochemical properties of particulate matter (aerosols). Here, we conducted combustion experiments in an atmospheric-pressure reactor controlled at constant equivalence ratio (phi = 2.3) and O2/N2 = 0.06, and at temperatures varied between 250 degrees C and 1035 degrees C. We used two fuels: toluene, which has high sooting propensity, and n-heptane, which has a comparatively lower sooting propensity but exhibits two-stage ignition that is not present in toluene combustion. We performed real-time measurements of aerosol size distributions, volatility, and light-absorption properties. We also performed offline molecular-size characterization. Aerosols emitted from both fuels were comprised of light-absorbing organics that are categorized as brown carbon. At the highest combustion temperature (1035 degrees C), the aerosol emissions from toluene combustion were a factor of 20 larger than n-heptane. The aerosol emissions from toluene combustion had more abundance of large molecular-size species, were less volatile, and were more light-absorbing than n-heptane. For both fuels, aerosol emission factors exhibited a steep drop with decreasing temperatures. However, there was a resurgence in aerosol emissions at lower temperatures with a peak at 290 degrees C for n-heptane combustion that was not observed for toluene. This is consistent with chemical kinetics simulations that show prominent two-stage ignition behavior for n-heptane, but not for toluene.

【 授权许可】

Free