Numerical study of the effect of oxygenated blending compounds on soot formation in shock tubes

Abstract

This numerical study deals with the influence of blends on the amount of soot formed in shock tubes, which were simulated by assuming a homogeneous plug flow reactor model. For this purpose, first, the reaction model used here was validated against experimental results previously obtained in the literature. Then, the soot volume fractions of various mixtures of methyl tert-butyl ether (MTBE)-benzene, isobutene-benzene, methanol-benzene, and ethanol-benzene diluted in argon were simulated and compared to the results of benzene-argon pyrolysis at 1721 K and 5.4 MPa. For MTBE, isobutene, methanol, and ethanol, small amounts of additives to benzene-argon mixtures promoted soot formation, for the shock tube model assumed, while higher concentrations of these additives led to smaller soot volume fractions in comparison to pure benzene-argon pyrolysis. The most significant soot promotion effect was found for the additives MTBE and isobutene. The channel for MTBE decomposition producing isobutene and methanol is very effective at temperatures beyond 1200 K. Thus, both MTBE-benzene and isobutene-benzene mixtures diluted in argon showed rather similar behavior in regard to soot formation. Special emphasis was directed toward the causes for the concentration-dependent influence of the blends on the amount of soot formed. Aromatic hydrocarbons and acetylene were identified as key gas-phase species that determine the trends in the formation of soot of various mixtures. From reaction flux analysis for phenanthrene, it was deduced that the combinative routes including phenyl species play a major role in forming PAHs, especially at early reaction times. It is found that the additives play an important role in providing material to grow side chains, such as by reaction channels including phenylacetylene or benzyl, which are confirmed to form aromatic hydrocarbons and thus to influence the amount of soot formed, particularly when the concentrations of the blends are increased.

A Study on the Emissions of Alternative Aviation Fuels

“…The present work is focusing on the following pollutants: CO, NOx, and unburned hydrocarbons (UHC) addressing acetylene and benzene considered as the major precursors of particles and soot [31][32][33][34][35][36][37]. Soot is formed 5 GTP-16-1529 -Braun-Unkhoff © 2016 by ASME.…”

“…Acetylene (C 2 H 2 ) and benzene (C 6 H 6 ) plays an important role in the formation of polyaromatic hydrocarbons (PAH) considered as major building blocks in soot formation [31][32][33][34][35][36][37]. Therefore, benzene and C 2 H 2 emission profiles serve as an indicator for a fuel's sooting tendency.…”

About the emissions of alternative jet fuels

“…A schematic diagram describing major pathways from fuel-break-up, aromatics to PAH and soot particles is given in Fig. 2; for details see [34][35][36][37][38]. Major emissions when burning kerosene in a jet engine [33] For a stoichiometric mixture and an ideal and complete combustion (no pollutants), CO 2 and water are the only products, besides energy released.…”

Experimental study of temperature influence on carbon particle formation in shock wave pyrolysis of benzene and benzene–ethanol mixtures

“…Another route of suppression effect of ethanol additives is the formation http of H 2 O after decomposition of ethanol and consequent consumption of hydrogen atoms, that promote HACA mechanism of surface growth of carbon particles, with production of OH and H 2 [8]. On the other hand, a small amount -10% replacement of benzene by oxygenated additives (MTBE, methanol, ethanol, isobutene) can promote the carbon particle formation due to peculiarity of the kinetics of blend pyrolysis [10]. The experimental study [4] showed an increase of soot amount in shock tube pyrolysis of 1% toluene + (1-3)% ethanol mixtures.…”