Numerical Study of PAHs and Soot Emissions from Gasoline–Methanol, Gasoline–Ethanol, and Gasoline–n-Butanol Blend Surrogates

Abstract

Soot formation is an intricate phenomenon, and soot propensity of a fuel is interwoven with the fuel composition, physical and chemical properties, and combustion environment. The present study examines the hypothesis that in addition to the chemical composition of the fuel, the sooting nature of the fuel is closely coupled with its chemical property known as octane sensitivity (S). With this motivation, the present study numerically investigates the effects of gasoline surrogate composition and its property, octane sensitivity (S), on polycyclic aromatic hydrocarbons (PAHs) and soot emissions. Four-component toluene primary reference fuel (TPRF)–alcohol blends, comprising iso-octane, n-heptane, toluene, and one of the three different alcohols- methanol, ethanol, and n-butanol, are used as gasoline surrogates. A total of 320 TPRF–alcohol mixtures, with S in the range of 1–10, are examined under laminar counterflow diffusion flame conditions. A detailed chemical mechanism coupled with a comprehensive soot model, which includes reactions for soot inception, surface growth, PAH condensation, and oxidation, is adopted. The analysis indicates that the toluene content in the fuel mixture has a prominent effect, while the alcohol content and octane sensitivity of the fuel have a weak correlation with the PAHs and soot. Thus, it is not clear if any of these three variables, namely, toluene content in the fuel, alcohol content in the fuel, and S, are individually sufficient to characterize the PAHs and soot across various blends. For this reason, a new variable (X CHO) based on the elemental composition of the fuel mixture is identified and it is shown that X CHO along with S of the fuel characterize soot emissions satisfactorily. Further, a reaction path analysis indicates that the efficacy of alcohols in reducing soot emissions follows the order: methanol > ethanol > n-butanol.

Experimental Detection of Oxygenated Aromatics in an Anisole-Blended Flame

“…10% anisole addition to a reference fuel was chosen instead of using neat anisole due to the general range of biofuel–gasoline blends that are currently used in real commercial applications. Iso-octane was chosen as a base liquid hydrocarbon fuel because it is commonly used as a representative branched alkane and is one of the main components in gasoline surrogates. − The ratio of anisole/iso-octane/methane/O 2 /N 2 in the initial gas-phase mixture introduced into the flame is 1.06/1.56/8.00/23.42/65.96%. In this flame, 71.3% of the carbon is from iso-octane and anisole and 28.7% comes from methane.…”

Advanced Progress and Prospects for Producing High-Octane Gasoline Fuel toward Market Development: State-of-the-Art and Outlook

“…119 The largest consumer of MTBE is China. 120 Methanol is the third largest oxygenate on the market, used as an octane booster for motor gasolines. 121 The largest consumer is China, which occupies 95% of the market.…”

“…It is worth saying that this oxygenate is still widely used in Russia, EU countries, the Middle East, Africa, and Asia . The largest consumer of MTBE is China …”

Computational Study on the Impact of Gasoline-Ethanol Blending on Autoignition and Soot/Nox Emissions Under Gasoline Compression Ignition Conditions

“…In the context of improving the reactivity and lowering emissions from GCI engines, blends of gasoline and biofuels were examined by several studies [21][22][23][24][25][26][27][28][29][30][31][32][33]. Ethanol has been identified as one of the potential low-carbon biofuels due to its higher volatility that allows faster mixing, thus improving the homogeneity of the cylinder charge [34].…”

“…From fundamental understanding, E30 is less sooting due to the lower aromatic content (toluene) in the fuel and higher oxygen concentration in the fuel when compared to E10 fuel. In TPRFalcohol fuels, the formation of soot precursors has a strong correlation with toluene content of the fuel [31,35]. Higher toluene content in the fuel blend results in higher concentration of soot precursors and thus soot.…”