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

Abstract

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 ϭ 0.63 and C/O ϭ 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the identities and absolute concentrations of stable major, minor, and trace species by the direct analysis of samples withdrawn from the flames.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 C 18 H 10 (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 ϫ 10 Ϫ7.

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

“…The experimental setup used in this study has been described elsewhere [12,15] therefore, only a brief description will be given here. Atmospheric pressure, laminar, premixed, flat-flames of n-C 7 H 16 /O 2 /Ar and n-C 7 H 16 / oxygenate/O 2 /Ar were stabilized over a 50 mm diameter porous, bronze burner.…”

“…We estimated an accuracy of about G15% for the mole fractions of species determined by direct calibration. The flame temperatures were measured using rapid insertion technique with a silicon oxide-coated Pt-13% Rh/Pt, 0.075 mm thermocouple [12,15].…”

“…Their studies were limited to low-molecularweight species only. Recently, we [12] have investigated the micro-structure of laminar, premixed, atmospheric pressure, fuel-rich flames of n-heptane/oxygen/argon at equivalence ratios of 1.97 and 2.10. Stable major, minor and trace species mole fraction profiles were obtained by direct analysis of the flame samples.…”

Skeletal mechanism modelling of n -heptane/oxygen laminar coflow flame structure at pressures

“…n-Heptane (n-C 7 H 16 ) is an important component of gasoline, diesel and kerosene, and it is thought to be a good surrogate fuel to represent liquid transportation fuel [7,[13][14][15][16]. The combustion characteristics of n-heptane/oxygen are very important for the design of niche aerospace applications such as liquid propellant rocket engines.…”

Artificial neural network predictions of polycyclic aromatic hydrocarbon formation in premixed n-heptane flames

“…El Bakali et al [15] and Ingemarsson et al [16] have carried out quartz microprobe sampling and GC/MS analysis for the lowmolecular-weight species (e.g., up to benzene) concentration profiles in atmospheric pressure, premixed n-heptane flames at equivalence ratios of 1.9 and 1.0, respectively. Recently, we [17] have investigated the PAH formation in fuel rich (ϕ = 1.97 and 2.10) laminar, premixed n-heptane flames. The concentrations of aromatic and PAH compounds were increased with increasing equivalence ratio.…”