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Ignition delay times (IDTs) and laminar flame speeds (SL) of C9H20 (nonane) isomers are systematically investigated. IDTs of normal nonane (n-C9), 2-methyloctane (2mC8), 2,4-dimethylheptane (24mC7), and 2,2,4,4-tetramethylpentane (2244mC5) are experimetally obtained by a shock tube facility and numerically simulated by a chemkin 0-D reactor model. Further, laminar flame speeds (SL) of n-C9 and 2244mC5 are measured by spherical expanding flames in a constant-temperature, constant-pressure dual-chamber cruciform burner over a wide range of the equivalence ratio (Φ = 0.7–1.4), which are used to compare with numerically simulated results obtained by chemkin 1-D flame speed model. Detailed reaction mechanisms of KUCRS, LLNL and JetSurF ver.02 are used for numerical simulations. It is found that experimental IDTs increase with the number of methyl branches, especially in low-temperature and negative temperature coefficient (NTC) regions, where the increase of IDT with the number of methyl branches are well predicted by KUCRS. We also find that the measured values of SL of highly branched 2244mC5 are smaller than those of n-C9 at all values of Φ studied, of which measured SL data are successfully reproduced by the 1-D flame speed model with KUCRS. These results are important to our understanding of reaction characteristics for highly branched nonane isomers and for the designing of optimal alternative fuels in internal combustion engines.

Laminar and turbulent minimum ignition energies (MIEL and MIET) of a lean primary reference automobile fuel (PRF95; 95% isooctane/5% n-heptane) and air mixture at the equivalence ratio of 0.8 at 373 K with large Lewis number Le ≈ 2.95 >> 1 using small and large pin-to-pin electrode spark gaps (dgap) are measured in a dual-chamber, constant temperature/pressure, fan-stirred 3D cruciform burner capable of generating near-isotropic turbulence. Each MIE datum is statistically determined at 50% ignitability by 18–30 repeated runs over a range of ignition energy (Eig). We find two ignition transition (IT) modes. (1) A non-monotonic IT at small dgap = 0.8 mm with the lowest MIET = 13.9 mJ ( u′c, MIET increases drastically (>> MIEL), because turbulence re-asserts its dominant role. (2) A regular IT at large dgap = 2 mm is found where MIEL is only 2.05 mJ, in which the increasing slopes of MIET with u′ change from gradually to exponentially when u′ > u′c ≈ 2.3 m/s. In the post-transition when u′ ≥ u′c, the averaged ratio of MIE at dgap = 0.8-mm and 2-mm (MIE0.8/MIE2.0) is 1.64 > 1, suggesting that using large dgap = 2-mm has a higher ignition probability than using small dgap = 0.8-mm for the lean-burn gasoline surrogate in intense turbulence. Finally, we estimate the uncertainties of burning velocities at u′ = 0 and 2.76 m/s, which are respectively less than 2% and 6% when using small/large Eig ≈ MIE/70 mJ and/or dgap = 0.8-mm/2-mm. These results are relevant to spark ignition gasoline engines operated in lean-burn turbulent condition.

Based on the growth kinetics of the SiO2particles, we studied the kinetic hetero-precipitation process on the interface of polystyrene (PS) microscale particles. The nanoscale SiO2shell thickness increased with increasing time and was proportional to the square root of the initial concentration of TEOS precursor while governed by hetero-precipitation process. Moreover, the hetero-precipitation process followed the first-order growth mechanism of silica onto the surface of templating PS pariticles. Properly controlling the reagent concentrations could alleviate and even avoid, to a certain extent, aggregation among PS@SiO2particles that could otherwise have an adverse effect on the properties and applications of those composite particles and the corresponding SiO2hollow products.

Self-supporting hierarchically-structured hollow ordered porous carbon spheres (HOPCSs) have been synthesized successfully using hollow ordered mesoporous silica spheres (HOMSSs) with MCM-41 pore structure within shells as templates. The SEM and TEM observations show that the final HOPCS product presents spherical morphology with hollow interiors. The results of HRTEM, small angle X-ray Diffraction (SAXRD) and N-2 adsorption desorption isotherms confirm that the HOPCS inversely replicate the MCM41 hexagonally-stacked ordered microstructures within shells and possess the ordered porosity. Furthermore, the formation of ordered porous structures within HOPCSs is due to the two aspects below: (i) the inverse carbonaceous replicas filling in hexagonally-stacked mesopores in HOMSSs are compacted tangentially due to curvature difference along the radial direction, self-supporting ordered porous structures after removing silica template; (ii) the additional carbon deposition layers exist on the outside surface of the replicas, cooperatively cementing the carbon fillers.