Synergistic effects on soot formation in counterflow diffusion flames of acetylene-based binary mixture fuels

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

On the opposing effects of methanol and ethanol addition on PAH and soot formation in ethylene counterflow diffusion flames

Compositional effects on PAH and soot formation in counterflow diffusion flames of gasoline surrogate fuels

A reaction mechanism for gasoline surrogate fuels for large polycyclic aromatic hydrocarbons

The synergistic effect of soot formation refers to the interaction between different fuels during soot forming processes, which results in higher soot formation than any individual fuels. The present study experimentally investigates the synergistic effect of soot formation in co-flow diffusion flames of propane/ethylene fuel mixtures. The total carbon mass flow rate of the propane/ethylene mixture was kept constant at 0.5 mg/s, and the propane carbon ratio (RC) was defined as the ratio of carbon mass flow rate of propane to the total carbon mass flow rate. The laser-induced incandescence (LII) and light extinction (LE) techniques were applied to measure the soot volume fractions (SVF) at pressures of 0.1–0.5 MPa. The results showed strong synergistic effect in propane/ethylene mixtures at atmospheric conditions; however, increasing pressure weakens the synergistic effect. The LII intensity contours showed that the soot formation zone extends when synergistic effect occurs at RC = 0.1 and 0.2 for 0.1 and 0.3 Mpa. The normalized peak SVF showed that synergistic effect monotonically becomes weak with increasing pressure from 0.1 to 0.3 Mpa; meanwhile, the it still stayed strong at 0.2 Mpa when using normalized maximum soot yield, and then turned to be weaker as pressure increases. Further comparison analysis of the SVF profiles between RC = 0 and 0.1 revealed that the synergistic effect occurs at the two-wing area of the sooty flame at low axial flame height, and then gradually becomes stronger with increasing axial flame height in the soot zone for 0.1–0.3 Mpa. To illustrate the pressure effects on synergistic soot formation, numerical analysis in homogeneous closed reactor was conducted and it was found that The PAHs formation competition between C3H3 pathway and HACA mechanism results in the different soot formation phenomenon of ethylene/propane flames.

A comparative study of the sooting tendencies of various C5–C8 alkanes, alkenes and cycloalkanes in counterflow diffusion flames

Experiments and numerical simulation on soot formation in opposed-jet ethylene diffusion flames

Investigation of structural effects of aromatic compounds on sooting tendency with mechanistic insight into ethylphenol isomers

Experimental characterization of the different nitrogen dilution effects on soot formation in ethylene diffusion flames

The blending effect on the sooting tendencies of alternative/conventional jet fuel blends in non-premixed flames

Sooting characteristics of partially-premixed flames of ethanol and ethylene mixtures: Unravelling the opposing effects of ethanol addition on soot formation in non-premixed and premixed flames

This paper aims to provide a physical understanding of the pressure effect on soot formation in laminar diffusion flames. Soot formation in laminar coflow diffusion flames is strongly influenced by pressure. Although predicting soot formation at atmospheric pressure has been very accurate in literatures, there is still a lack of understanding of multiple soot formation processes at high pressures. However, few researches studied the effects of pressure on multiple steps in the soot formation. This work studies the pressure effect on detailed soot formation, which includes multiple physical processes of surface growth, surface OH oxidation, surface O2 oxidation, and collision kinetics. A pressure-dependent model is proposed by analyzing the pressure-dependent surface reactivity in surface reactions and the pressure-dependent collision kinetics in soot formation. Simulation is conducted in the pressure range from 1 atm to 20 atm, with experimental validation in the pressure range from 1 atm to 3.5 atm. In the pressure range from 1 atm to 3.5 atm, the predicted primary soot particle diameter and soot yield of cases with the pressure-dependent model are validated by experimental result. As pressure further increases from 5 atm to 20 atm, the pressure dependence of soot yield and surface reaction rate decreases due to the limit of oxidation. This study contributes to the understanding of the pressure effect on soot formation at high pressures in soot formation.

Acetylene black is a special type of carbon black, obtained from the thermal decomposition of acetylene. Acetylene flames enable the investigation of the soot optical properties. A reliable knowledge of the optical properties of acetylene soot is necessary for interpreting the optical measurements in flames and the development of acetylene black applications in industry. However, a wide variation in the optical properties of soot is observed in different formation conditions. The main factors affecting soot formation in flames are fuel composition, equivalence ratio, and reaction time connected with the height above a burner. In this study, we measured the absolute value of the refractive index function of acetylene soot E(m,1064) at a wavelength of 1064 nm, as well as the ratio of the refractive index functions E(m,1064)/E(m,532) at laser wavelengths of 532 nm and 1064 nm in a premixed acetylene/air flame using laser-induced incandescence. The soot structure was studied using high-resolution electron microscopy. The obtained results showed that E(m,1064) increased from 0.19 to 0.53 and that the ratio of E(m,1064)/E(m,532) increased from 1.12 to 1.55 according to the height above a burner. These changes in the optical properties are attributed to differences in soot structure, such as different distances between graphene planes inside soot crystallites, which decreased from 0.43 to 0.36 nm as the height above the burner increased from 5 to 20 mm. It was concluded that the optical properties and structure of acetylene soot differ from those formed in other hydrocarbon flames.

Ionization and soot formation in premixed flames

Influence of temperature and hydroxyl concentration on incipient soot formation in premixed flames