Effects of oxygenate concentration on species mole fractions in premixed n-heptane flames

Atmospheric pressure, laminar, premixed, fuel-rich flames of n-heptane/oxygen/argon and n-heptane/oxygenate/oxygen/argon were studied at an equivalence ratio of 1.97 to determine the effects of oxygenate concentration on species mole fractions. The oxygen weight percents in n-heptane/oxygenate mixtures were 2.7 and 3.4. Three different fuel oxygenates (i.e. MTBE, methanol, and ethanol) were tested. A heated quartz micro-probe coupled to an on-line gas chromatography/mass spectrometry has been used to establish the identities and absolute concentrations of stable major, minor, and trace species by the direct analysis of samples, withdrawn from the flames. The oxygenate addition has increased the maximum flame temperatures and reduced the mole fractions of CO, low-molecular-weight hydrocarbons, aromatics, and polycyclic aromatic hydrocarbons. The reduction in mole fractions of aromatic and polycyclic aromatic hydrocarbon species by an increase in oxygenate concentration was more significant

Effects of equivalence ratio on species and soot concentrations in premixed n-heptane flames

The micro-structure of laminar premixed, atmospheric-pressure, fuel-rich flames of n-heptane/oxygen/argon has been studied at two equivalence ratios (C/O = 0.63 and C/O = 0.67). A heated quartz microprobe coupled to an online gas chromatography/mass spectrometry (HP 5890 Series II/HP 5972) has been used to establish the identities and absolute concentrations of stable major, minor, and trace species by the direct analysis of samples withdrawn from the flames. Benzene was the most abundant aromatic compound identified. The largest PAH detected were the family of C18H10 (molecular weight of 226) that include cyclopenta[cd]pyrene and benzo[ghi]fluoranthene, with peak concentrations reaching 8 ppm and 6 ppm, respectively. Soot particle diameters, number densities, and volume fractions were determined using classical light scattering and extinction measurements. The largest soot particle diameter measured was about 18 nm and the soot volume fraction reached the amount of 4.9 × 10-7

Effects of oxygenate additives on polycyclic aromatic hydrocarbons (PAHs) and soot formation

Effects of three oxygenate additives (methanol, ethanol, and MTBE) on the formation of polycyclic aromatic hydrocarbons (PAHs) and soot in laminar, premixed, atmospheric pressure, fuel-rich flames of n-heptane were studied at an equivalence ratio of 2.10. A heated quartz microprobe coupled to online gas chromatography/mass spectrometry was used to establish the identities and absolute concentrations of major, minor, and trace species by the direct analysis of samples withdrawn from the flames. Benzene was the most abundant aromatic compound identified. The largest PAH detected was the family of C18H10 (molecular weight of 226) that includes cyclopenta[cd]pyrene and benzo[ghi]fluoranthene. Soot particle diameters, number densities, and volume fractions were determined using classical light scattering and extinction measurements. All the oxygenate additives studied reduced the mole fractions of aromatic and PAH species, as well as soot formation. However, the reduction in soot formation was comparable for different oxygenates under the experimental conditions investigated

Adsorption of water and ammonia on TiO2-anatase cluster models

Density functional theory (DFT) calculations performed at B3LYP/6-31G** level are employed to study water and ammonia adsorption and dissociation on (101) and (001) TiO2 anatase surfaces both represented by totally fixed and partially relaxed Ti2O9H10 cluster models. PM3 semiempirical calculations were also conducted both on Ti2O9H10 and Ti9O33H30 clusters in order to assess the effect of cluster size. Following dissociation, the adsorption of H2O and NH3 by H-bonding on previously H2O and NH3 dissociated systems, respectively are also considered. It is found that the adsorption energies and geometries of water and ammonia molecules on (101) and (001) anatase cluster models depend on surface relaxation. The vibration frequency values are also calculated for the optimized geometries. The adsorption energies and vibration frequency values computed are compared with the available theoretical and experimental literature