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The amount of non-paraffinic components is directly associated with fuel sensitivity (S), which is an important property for using low-octane and low-cetane fuels in direct injection engines. In this paper, we examine the effects of S and RON (research octane number) on the ignition and combustion behavior of naphtha fuel surrogates in homogeneous mixtures and diesel sprays. Two binary blends (PRF70 and PRF80) and four ternary blends (TPRF70-a, TPRF70-b, TPRF80-a, TPRF80-b), with varying amounts of iso-octane, n-heptane and toluene, are considered. Simulations are performed using a reaction mechanism with 109 species and 543 reactions. The mechanism is validated against the shock tube and rapid compression machine ignition data, and non-reacting spray data. Ignition simulations in homogeneous mixtures are performed using CHEMKIN-Pro for temperature range of 625–1250 K, equivalence range of ɸ = 0.5–2.0, and pressure of 55 bar. The study is then extended to examine the transient ignition and flame structure in liquid fuel sprays in a constant-volume combustion vessel using the CFD software CONVERGE. Results indicate that the temperature dependence of ignition characteristics in both homogeneous mixtures and sprays is strongly influenced by fuel sensitivity. In particular, it affects the NTC behavior and temperature dependence of the 1st and 2nd stage ignition processes. The ignition kernel structure in sprays is also strongly modified by fuel sensitivity, as the ignition kernel in ternary sprays involves richer mixtures, while that in binary sprays contains near stoichiometric mixtures. Consequently, the spray flame structure is also modified by fuel sensitivity. While the spray flame is characterized by partially premixed combustion involving a lean premixed zone (LPZ), a rich premixed zone (RPZ), and a nonpremixed zone (NPZ), the effect of sensitivity is to enhance the relative contribution of RPZ compared to those of NPZ and LPZ. In addition, due to enhanced ignitability, the flame in ternary sprays is located closer to the injector compared to that in binary sprays. The effect of higher RON is to increase the ignition delay time. Consequently, the ignition kernel involves relatively leaner mixtures, and the flame structure is characterized by increased contributions from LPZ compared to RPZ, and the flame liftoff length is increased. Increasing the initial reactor temperature has the opposite effect. A sensitivity analysis is performed to identify reactions that characterize the reduced and enhanced ignitability of ternary blends at low and high temperatures, respectively.

Autotrophic microalgae are a promising bioproducts platform. However, the fundamental requirements these organisms have for nitrogen fertilizer severely limit the impact and scale of their cultivation. As an alternative to inorganic fertilizers, we investigated the possibility of using amino acids from deconstructed biomass as a nitrogen source in the genus Dunaliella. We found that only four amino acids (glutamine, histidine, cysteine, and tryptophan) rescue Dunaliella spp. growth in nitrogen depleted media, and that supplementation of these amino acids altered the metabolic profile of Dunaliella cells. Our investigations revealed that histidine is transported across the cell membrane, and that glutamine and cysteine are not transported. Rather, glutamine, cysteine, and tryptophan are degraded in solution by a set of oxidative chemical reactions, releasing ammonium that in turn supports growth. Utilization of biomass-derived amino acids is therefore not a suitable option unless additional amino acid nitrogen uptake is enabled through genetic modifications of these algae. NSF Emerging Frontiers in Research and Innovation (EFRI) [1332341] This work was supported by a NSF Emerging Frontiers in Research and Innovation (EFRI) grant [Award Abstract #1332341].

Many nonwoven fabrics are made by melt spinning semicrystalline fibers followed by thermal bonding using heated calendar rolls. In this work, we have studied thermal bonding of polypropylene films to simulate bonding of nonwoven fibers. We have tried to relate the thermal bond strengths with the concepts of chain dynamics via interfacial adhesion development at symmetric polymer interfaces. This requires relating the microscopic dynamics of chains with macroscopic interfacial adhesion measurements. It was found that the interfacial bond strength was proportional to the fraction of the crystals melted. This required heating the interfacial region between the polymer layers into the melting region. Bond strengths were also related to process time as t1/2. This dependence is consistent with the literature for reptation, but is also due to the required thermal diffusion to bring the interfacial region to the bonding temperature. Finally, the bond strength is also dependent on the polymer molecular weight as 1/M1/2, which is consistent with forming the bonds via chain reptation, provided that the bonding time is less than the reptation time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010