A single tube flow heat exchanger was designed and built to thermally stress Jet A-1 with air-saturated and deoxygenated levels of dissolved oxygen over a range of fuel temperatures, pressures, and flow rates. Liquid samples of thermally degraded Jet A-1 were analyzed using various physical and optical methods to determine which methods were sensitive enough to measure compositional changes in thermally degraded liquid fuel and to correlate these changes to the measured amount of deposits produced. Temperature programmed oxidation (TPO) was shown to be successful in measuring deposit quantity and structure, while UV-visible absorption and UV-visible fluorescence were sensitive enough to quickly measure the relative population growth of large aromatic compounds that lead to deposit formation in thermally stressed Jet A-1.

A single tube flow heat exchanger was designed and built to thermally stress Jet A-1 with air-saturated and deoxygenated levels of dissolved oxygen over a range of fuel temperatures, pressures, and flow rates. Liquid samples of thermally degraded Jet A-1 were analyzed using various physical and optical methods to determine which methods were sensitive enough to measure compositional changes in thermally degraded liquid fuel and to correlate these changes to the measured amount of deposits produced. Temperature programmed oxidation (TPO) was shown to be successful in measuring deposit quantity and structure, while UV-visible absorption and UV-visible fluorescence were sensitive enough to quickly measure the relative population growth of large aromatic compounds that lead to deposit formation in thermally stressed Jet A-1.

No description available.

The thermal oxidative stability of middle distillate fuels is a topic of considerable concern. There are several examples of ambient temperature oxidation of fuel, leading to particulate matter and filtration issues. It is shown that particulate matter values vary globally based on region and fuel type, suggesting the problem is more than mere inorganic matter. The variability of filtration times is not dependent on absolute particulate matter present; it is suggested to be dependent upon the nature or morphology of deposit. <br>For a more thorough understanding of the chemistry responsible for deposit formation, flask oxidation was employed to test the Soluble Macromolecular Oxidatively Reactive Species (SMORS) mechanism. Spectral data suggest the presence of alcoholic and carbonylic functionality, which is in agreement with how the SMORS mechanism defines deposit formation. It has also been determined that the introduction of compounds conceivably indigenous to jet fuels has a negative impact on deposit formation. In addition, it has been shown the elemental composition of thermally induced deposit entails significant heteroatom content. <Br>According to the SMORS mechanism, one of the primary reasons for deposit formation is the presence of radical initiators. The paraffinic blending of fuels shows promise in oxidatively stabilizing jet fuels. Research suggests blending reduces oxidation by diluting both the radical initiators and soluble deposit precursors. It is possible the use of this method could improve filter life and decrease operational costs. <br>A better understanding of the chemistry of deposit formation can lead to improved deposit inhibitors. Additives that have shown promise in bomb tubing studies were tested using flask oxidation. Additionally, extracted fuel polars reintroduced into the fuel at 0.3% v/v were tested for antioxidative activity. It was concluded the introduction of ppm levels of polar compounds extracted from fuel back into a fuel is very successful in limiting oxidative product formation. <br>One strategy for inhibiting deposit formation is the use of compounds that can act as oxygen/hydroperoxide scavengers. A linear free energy Hammett plot was developed for the reaction between molecular oxygen and triarylphosphines. Results indicate a very small positive charge buildup, suggesting a nonsynchronous concerted reaction. / Bayer School of Natural and Environmental Sciences / Chemistry and Biochemistry / PhD / Dissertation

Jet Propellant-8 (JP-8) is a military fuel associated with a large percentage of chemical exposures documented by the US Department of Defense. A fast and sensitive solid-phase microextraction–gas chromatographic–mass spectrometric method has been developed for the determination of 34 ‘marker compounds’ found in JP-8. Linear ranges were determined for each marker component and precision was measured for these components over four concentrations within each calibration range. The method was applied for the analysis of JP-8 components from soil. The use of SPME over other sample extraction techniques eliminates solvents, minimizes sample handling, and increases sensitivity.

In spite of recent attention to renewable sources of energy, liquid hydrocarbon fuels are still the main source of energy for industrial and transportation systems. Manufactures and consumers are consistently looking for ways to optimize the efficiency of fuel combustion in terms of cost, emissions and consumer safety. In this regard, increasing burning rate of liquid fuels has been of special interest in both industrial and transportation systems. Recent studies have shown that adding combustible nano-particles could have promising effects on improving combustion performance of liquid fuels. Combustible nano-particles could enhance radiative and conductive heat transfer and also mixing within the droplet. Polymeric additive have also shown promising effect on improving fire safety by suppressing spreading behavior and splatter formation in case of crash scenario. Polymers are also known to have higher burning rate than regular hydrocarbon fuels. Therefore adding polymeric additive could have the potential to increase the burning rate. In this work, combustion dynamics of liquid fuel droplets with both polymeric and nanoparticle additives is studied in normal gravity. High speed photography is employed and the effect of additive concentration on droplet burning rate, burning time, extinction and soot morphology is investigated. Polymer added fuel was found to have a volatility controlled combustion with four distinct regimes. The first three zones are associated with combustion of base fuel while the polymer burns last and after a heating zone because of its higher boiling point. Polymer addition reduces the burning rate of the base fuel in the first zone by means of increasing viscosity and results in nucleate boiling and increased burning rates in the second and third stages. Overall, polymer addition resulted in a higher burning rate and shorter burning time in most of the scenarios. Colloidal suspensions of carbon-based nanomaterials in liquid fuels were also tested at different particle loadings. It was found that dispersing nanoparticles results in higher burning rate by means of enhanced radiative heat absorption and thermal conductivity. An optimum particle loading was found for each particle type at which the maximum burning rate was achieved. It was observed that the burning rate again starts to reduce after this optimum point most likely due to the formation of large aggregates that reduce thermal conductivity and suppress the diffusion of species.

Syngas is a mixture of hydrogen (H2), carbon monoxide (CO) and other species including nitrogen (N2), water (H2O), methane (CH4) and higher hydrocarbons. Syngas is a highly desired product because it is very versatile. It can be used for combustion in turbines or engines, converted to H2 for use in fuel cells, turned into diesel or other high-molecular weight fuels by the Fischer-Tropsch process and used as a chemical feedstock. Syngas can be derived from hydrocarbons in the presence of oxidizer or water as in steam reforming. There are many demonstrated methods to produce syngas with or without water addition including catalytic methods, plasma reforming and combustion. The goal of this study is to add to the understanding of non-catalytic conversion of hydrocarbon fuels to syngas, and this was accomplished through two investigations: the first on fuel conversion potential and the second on the effect of preheat temperature. A primarily experimental investigation of the conversion of jet fuel and butanol to syngas was undertaken to understand the potential of these fuels for conversion. With these new data and previously-published experimental data, a comparison amongst a larger set of fuels for conversion was also conducted. Significant soot formation was observed in experiments with both fuels, but soot formation was so significant in the jet fuel experiments that it limited the range of experimental operating conditions. The comparison amongst fuels indicated that higher conversion rates are observed with smaller molecular weight fuels, generally. However, equilibrium calculations, which are often used to determine trends in fuel conversion, showed the opposite trend. In order to investigate preheat temperature, which is one important aspect of non-catalytic conversion, experiments were undertaken with burner-stabilized flames that are effectively 1-D and steady-state. An extensive set of model calculations were compared to the obtained experimental data and was used to investigate the effect of preheat temperatures that were beyond what was achievable experimentally. Throughout the range of operating conditions that were tested experimentally, the computational model was excellent in its predictions. Experiments where the reactants were preheated showed a significant expansion of the stable operating range of the burner (increasing the equivalence ratio at which the flame blew off). However, increasing preheat temperature beyond what is required for stabilization did not improve syngas yields. / text

In the present doctoral thesis, fundamental experimental and numerical studies are conducted for the laminar, atmospheric pressure, sooting, coflow diffusion flames of Jet A-1 and synthetic jet fuels. The first part of this thesis presents a comparative experimental study for Jet A-1, which is a widely used petroleum-based fuel, and four synthetically produced alternative jet fuels. The main goals of this part of the thesis are to compare the soot emission levels of the alternative fuels to those of a standard fuel, Jet A-1, and to determine the effect of fuel chemical composition on soot formation characteristics. To achieve these goals, experimental measurements are constructed and performed for flame temperature, soot concentration, soot particle size, and soot aggregate structure in the flames of pre-vaporized jet fuels. The results show that a considerable reduction in soot production, compared to the standard fuel, can be obtained by using synthetic fuels which will help in addressing future regulations. A strong correlation between the aromatic content of the fuels and the soot concentration levels in the flames is observed. The second part of this thesis presents the development and experimental validation of a fully-coupled soot formation model for laminar coflow jet fuel diffusion flames. The model is coupled to a detailed kinetic mechanism to predict the chemical structure of the flames and soot precursor concentrations. This model also provides information on size and morphology of soot particles. The flames of a three-component surrogate for Jet A-1, a three-component surrogate for a synthetic jet fuel, and pure n-decane are simulated using this model. Concentrations of major gaseous species and flame temperatures are well predicted by the model. Soot volume fractions are predicted reasonably well everywhere in the flame, except near the flame centerline where soot concentrations are underpredicted by a factor of up to five. There is an excellent agreement between the computed and measured data for the numbers of primary particles per aggregate and the diameters of primary particles. This model is an important stepping-stone in the drive to simulate industry-relevant and multi-dimensional flames of practical liquid fuels, with detailed chemistry and soot formation.

In the present doctoral thesis, fundamental experimental and numerical studies are conducted for the laminar, atmospheric pressure, sooting, coflow diffusion flames of Jet A-1 and synthetic jet fuels. The first part of this thesis presents a comparative experimental study for Jet A-1, which is a widely used petroleum-based fuel, and four synthetically produced alternative jet fuels. The main goals of this part of the thesis are to compare the soot emission levels of the alternative fuels to those of a standard fuel, Jet A-1, and to determine the effect of fuel chemical composition on soot formation characteristics. To achieve these goals, experimental measurements are constructed and performed for flame temperature, soot concentration, soot particle size, and soot aggregate structure in the flames of pre-vaporized jet fuels. The results show that a considerable reduction in soot production, compared to the standard fuel, can be obtained by using synthetic fuels which will help in addressing future regulations. A strong correlation between the aromatic content of the fuels and the soot concentration levels in the flames is observed. The second part of this thesis presents the development and experimental validation of a fully-coupled soot formation model for laminar coflow jet fuel diffusion flames. The model is coupled to a detailed kinetic mechanism to predict the chemical structure of the flames and soot precursor concentrations. This model also provides information on size and morphology of soot particles. The flames of a three-component surrogate for Jet A-1, a three-component surrogate for a synthetic jet fuel, and pure n-decane are simulated using this model. Concentrations of major gaseous species and flame temperatures are well predicted by the model. Soot volume fractions are predicted reasonably well everywhere in the flame, except near the flame centerline where soot concentrations are underpredicted by a factor of up to five. There is an excellent agreement between the computed and measured data for the numbers of primary particles per aggregate and the diameters of primary particles. This model is an important stepping-stone in the drive to simulate industry-relevant and multi-dimensional flames of practical liquid fuels, with detailed chemistry and soot formation.

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