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Rohaly, Matthew JosephDecomposition of Aromatic Amines in a Jet Fuel Surrogate
Master of Science (M.S.), University of Dayton, 2014, Chemistry
The thermal decomposition of aromatic nitrogen containing compounds in a jet fuel surrogate was studied. The surrogate fuel's decomposition was compared to the decomposition found in natural jet fuels. Then high performance liquid chromatography was used to examine the formation of any polar products from the thermal decomposition of the surrogate fuel. Gas chromatography coupled with mass spectrometry and nuclear magnetic resonance were employed to try and identify the polar products. The large amount of hydrocarbons masking the polar products made fractional collection necessary before any identification could be attempted. After fractional collections were employed several oxygen polar compounds were found and identified from the thermal decomposition of the surrogate fuel. However no nitrogen-containing compounds could be found. This is most likely due to the low concentration of the nitrogen-containing compounds within the surrogate. Due to the effectiveness of the surrogate fuel's thermal decomposition it remains a good candidate for further jet fuel studies that look at reactivity. HPLC was also very effective at observing the formation of polar products within the jet fuel, although it could not identify these products. The fractional collection method that was employed did improve the results of the identification process, but it did not manage enough separation between the polar compounds and the hydrocarbons present in the surrogate. It is likely that a further separation method is needed. GCMS was relatively ineffective at separating and identifying polar products from this reaction. This is due to the bulk hydrocarbons masking the polar product signals. GCMS was able to identify a oxygen-containing compound, but only because the elution point from this compound was far from the elution point of any hydrocarbon. NMR was effective at identifying polar compounds that were present in significant quantities, however the extremely low concentration of the polar products made this process much less effective as well. Overall for GCMS or NMR to be considered effective techniques for this analysis a better separation process must be utilized.

Committee:

David Johnson (Advisor)

Subjects:

Chemistry

Keywords:

jet fuels; jet fuel decomposition; nitrogen contaminants in jet fuels; polar products from jet fuel decomposition; jet fuel separation techniques;

Rhodes, Audry GayleTHE EFFECTS OF JP-8 JET FUEL ON THE IMMUNE SYSTEM OF TANK ENTRY WORKERS
MS, University of Cincinnati, 2001, Medicine : Environmental Health Sciences
Jet fuel is a common occupational exposure among commercial and military maintenance workers. JP-8 jet fuel, a military formulation, has been found to have immunotoxic effects in mice but little data exists for humans. The aim of this cross-sectional study was to determine if the number of immune cells in the peripheral blood was altered among tank entry workers, a group which has been determined in previous studies to have the highest exposure to JP-8 in the U.S Air Force. A total of 123 volunteers (45 tank entry workers) from three Air Force bases participated in the study. After adjusting for a number of covariates, tank entry workers were found to have higher numbers of white blood cells (p=0.01), neutrophils (p=0.05), and monocytes (p=0.02) and no differences in the numbers of total lymphocytes, T-cells, T-helper cells, T-suppressor cells, Natural Killer cells, and B-cells when compared with a low exposure group. Tank entry workers did not show any clinical effects of the increased immune cell counts. Although there were no differences in the number of lymphocytes among study groups, further investigations are needed to evaluate the functional ability of these cells to produce lymphokines and cytokines and modulate the immune system.

Committee:

Grace Lemasters (Advisor)

Keywords:

JP-8; JET FUEL; HEALTH EFFECTS; IMMUNE SYSTEM; WHITE BLOOD CELLS

Sander, Zachary HugoHeat Transfer, Fluid Dynamics, and Autoxidation Studies in the Jet Fuel Thermal Oxidation Tester (JFTOT)
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
Modern military aircraft use jet fuel as a coolant before it is burned in the combustor. Prior to combustion, dissolved O2 and other heteroatomic species react with the heated fuel to form insoluble particles and surface deposits that can impair engine performance. For safe aircraft operation, it is important to minimize jet fuel oxidation and resultant surface deposition in critical aircraft components. The Jet Fuel Thermal Oxidation Tester (JFTOT) is a thermal stability test that measures the tendency for fuel to form such deposits and delivers a pass/fail grade for each fuel tested. However, the extent of oxidation and the corresponding deposition occurring in the JFTOT is not fully understood. A JFTOT Model Mark II was modified to include a bulk outlet thermocouple measurement and a downstream oxygen sensor to measure bulk oxygen consumption. Experimental results show a direct relationship between the bulk outlet temperature and JFTOT setpoint temperature with the bulk outlet less than the setpoint temperature. Several fuels were also tested at varying setpoint temperatures with complete oxygen consumption by 320°C and a wide range of oxygen consumption from 10-85% at 260°C. Due to the complex fluid flows in the JFTOT, computational fluid dynamics (CFD) was used to model the heat transfer and fluid flow. A three-dimensional simulation showed considerable recirculation within the JFTOT due to buoyancy effects from gravity and resulted in complex residence time behavior. In addition, CFD simulations performed with a pseudo-detailed chemical kinematic mechanism showed an under prediction in both oxidation and deposition for similar fuels tested experimentally but yielded bulk outlet temperature predictions of less than 2% error. Simulations of deposition were of the right order of magnitude and matched the deposit profile of comparable experimental ellipsometry data.

Committee:

Steven S. Zabarnick, PhD (Committee Co-Chair); Jamie S. Ervin, PhD (Committee Co-Chair); James T. Edwards, PhD (Committee Member)

Subjects:

Aerospace Engineering; Chemical Engineering; Chemistry; Energy; Engineering; Fluid Dynamics; Mechanical Engineering; Petroleum Engineering

Keywords:

JFTOT;CFD; heat transfer; oxidation; autoxidation; deposition; ellipsometry; jet fuel thermal oxidation tester; oxygen consumption; FT; fischer tropsh; hrj; jp-8; jet a-1; thermal stability; fluid mechanics; astm d3241; flir; interferometry; udri

Hui, XinFlame Studies on Conventional, Alternative, and Surrogate Jet Fuels, and Their Reference Hydrocarbons
Doctor of Philosophy, Case Western Reserve University, 2013, EMC - Mechanical Engineering

This dissertation presents work on the flame propagation and extinction of various liquid hydrocarbon fuels, including conventional and alternative jet fuels, surrogate fuels, and their reference hydrocarbon components. The laminar flame speeds and extinction stretch rates are experimentally determined by using a twin-flame counterflow setup integrated with a Digital Particle Image Velocimetry system for the flow field measurement. The experimental results are also compared with computed values obtained by using various published kinetic models for different fuels. In general, most of the simulation results agree with the experimental data with an average deviation less than 10%, which are reasonable considering the uncertainties in both experiments and kinetic models.

The results of this work show that the conventional Jet-A and alternative jet fuels share very similar flame speeds and extinction limits despite of their differences in the molecular composition. The results of two surrogate mixtures for Jet-A show that they are both able to reproduce very well the flame speeds and extinction limits of the target jet fuel. Additional studies on aromatic species relevant to the conventional jet fuels illustrate that the degree and position of alkyl substitution on the benzene ring have a strong effect on the reactivity of the aromatic components studied. By extending the flame propagation studies to elevated pressures up to 3 atm, it is found that the flame speed results at elevated pressures are consistent in the trend with atmospheric results. Further attempts are made to identify and quantify the effects of preheat temperature and pressure on burning rate.

This dissertation provides experimental flame speed and extinction data of high fidelity for jet fuels and relevant hydrocarbons. The fundamental data provided herein can serve as the benchmark database, and can be used in development and validation of combustion kinetic models.

Committee:

Chih-Jen Sung (Committee Chair); James Tien (Committee Member); Joseph Prahl (Committee Member); Donald Feke (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

combustion; jet fuel; alternative fuels;surrogate fuels; liquid hydrocarbons

Sun, XiaoboForensic Applications of Gas Chromatography/Mass Spectrometry, High Performance Liquid Chromatography--Mass Spectrometry and Desorption Electrospray Ionization Mass Spectrometry with Chemometric Analysis
Doctor of Philosophy (PhD), Ohio University, 2012, Chemistry and Biochemistry (Arts and Sciences)

This dissertation includes three forensic applications of instrumental analysis techniques: gas chromatography/mass spectrometry (GC/MS), high performance liquid chromatography/electrospray ionization-mass spectrometry (HPLC/ESI-MS) and desorption electrospray mass spectrometry (DESI-MS). By using these instrumental analysis techniques and chemometric analysis, jet fuel samples, illicit drugs and Panax quinquefolius L (American ginseng) samples were analyzed rapidly and conveniently. Fast GC was combined with fast scanning quadrupole ion trap (QIT) MS and used to classify jet fuels for the first time by using a fuzzy rule-building expert system (FuRES) classifier. These data were pretreated with and without wavelet transformation (WT) and evaluated with respect to classification rates and 99.8±0.5% classification accuracy was obtained in both cases. Optimized-partial least squares discriminant analysis (o-PLSDA) was used as the positively biased control. The projected difference resolution (PDR) method was used to evaluate the fast GC and fast MS data. FuRES achieved perfect classifications for four models of uncompressed three-way data from two separate runs conducted four days apart.

DESI-MS was coupled with single droplet micro-extraction (SDME) to serve as a fast detection method demonstrated by the trace analysis of methamphetamine (MA) in aqueous solution and the detection of an organic reaction product from an ionic liquid (IL). Three-phase liquid SDME was conducted to enrich MA and the subsequent DESI-MS analysis displayed an average enrichment factor of 390-fold for MA. Two-phase liquid SDME was also conducted to directly extract the product of an organic reaction performed in a room temperature IL. The ionization of the resulting droplet extract by DESI allows one to directly examine the reaction product without interference from the ionic liquid.

Panax quinquefolius L samples grown in the United States and in China were quantitatively classified for the first time by using HPLC with an ESI mass spectrometer as the detector combined with chemometric analysis. Principle component analysis (PCA) and PDR were applied to evaluate the clustering and resolution of classes. With o-PLSDA as the control method, validated by using ten bootstraps and three Latin partitions (BLP), a FuRES classier gave a classification rate of 98 ± 3%, which was equivalent to the classification rate obtained by using o-PLSDA.

Committee:

Peter Harrington (Advisor); Glen Jackson (Committee Member); Hao Chen (Committee Member); Michael Jensen (Committee Member); Shigeru Okada (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Food Science

Keywords:

fast gas chromatography; high performance liquid chromatography; desorption electrospray ionization; mass spectrometry; FuRES; chemometrics; classification; single droplet micro-extraction; jet fuel; Panax quinquefolius L; ionic liquid; methamphetamine

Kerr, Kristen RitaDeposit Formation of Deoxygenated JP-8 Fuel with Added Hydroperoxides
Master of Science (M.S.), University of Dayton, 2013, Chemical Engineering
The performance of jet fuel is an important consideration as aircraft capabilities continue to improve. In addition to use as a propellant, jet fuel is used as a coolant for major subsystems. One of the consequences of using jet fuel as a coolant in high performance aircraft is the production of carbonaceous deposits that result from the autoxidation of fuel by dissolved oxygen. The deposits cause fouling of critical aircraft components and can lead to catastrophic failure. Autoxidation has been studied for decades, but the chemical mechanism by which deposits form is poorly understood. For this thesis, a single portion of the autoxidation mechanism, hydroperoxide decomposition, was isolated as a way to investigate the pathways that lead to fuel deposition. The carbonaceous deposits produced by JP-8 jet fuel were measured for a flowing, single-phase reaction system. Hydroperoxides were shown to cause significant deposit production in jet fuel, even in the absence of autoxidation. Hydroperoxide decomposition was isolated and deposition was also measured for fuel with selected chemical species added. Copper was studied for its effect on deposit production because of its known effect on catalyzing hydroperoxide decomposition. Acid was selected for study due to its known effect on synergistically catalyzing hydroperoxide decomposition when present with copper. Both species were shown to promote deposit production, individually and together, although not synergistically. Metal deactivator additive (MDA) was shown to have an extraordinary effect on decreasing deposition. Two tests were replicated using a fuel sample distinct from other tests performed for this thesis; the results indicate the effect of hydroperoxides and copper on deposition are not limited to a specific fuel sample. Several oxygenated fuels were also studied, in which hydroperoxide decomposition was not isolated. These fuels were shown to produce less surface deposits, but significantly more bulk deposits, than cases in which hydroperoxide decomposition was isolated. Several possible explanations are discussed. Copper was additionally shown to promote deposition in the case with oxygen and added hydroperoxides.

Committee:

Steven Zabarnick, Ph. D. (Committee Chair); Zachary West, Ph. D. (Committee Member); Kevin Myers, D. Sc., P. E. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Autoxidation; jet fuel; hydroperoxide decomposition; deposition; hydroperoxides; copper

McMasters, Brian PhilipEffect of Fuel Chemical Composition on Pyrolytic Reactivity and Deposition Propensity under Supercritical Conditions
Master of Science (M.S.), University of Dayton, 2014, Chemical Engineering
As modern hypersonic aircraft designs evolve, increasing heat sink capabilities are required. One potential approach is the use of endothermic fuels, which supplement fuel heat sink via sensible heating with endothermic chemical reactions. Endothermic reactions can proceed by thermal or catalytic decomposition of the fuel. Regardless of the specific methodology, thermal decomposition (pyrolysis) will occur at the expected reaction conditions. Improved understanding of the effect of chemical composition on supercritical pyrolytic reactivity and deposition propensity is needed to provide a basis of understanding for advanced fuel and system development. In this effort, a small-scale flow reactor system was developed to study the reactivity and deposition propensity of various hydrocarbon fuels and solvents of differing chemical composition. Experimental and computational studies were performed to investigate the relationship between fuel chemical composition and reactivity under supercritical conditions. Nine fuels and solvents of varying chemical composition were studied to evaluate pyrolytic reactivity and decomposition pathways. Chemical classes studied included normal paraffins, iso paraffins, and cycloparaffins in various combinations. Experimental studies were performed at reaction temperatures of 500-650°C and inlet flow rates of 0.50-3.00 mL/min, with a nominal system pressure of 500 psig. Corresponding equivalent residence times at these reaction conditions ranged from 0.2-11.4 sec. A fuel conversion metric was defined to allow comparison of the reactivity of multi-component fuels at equivalent inlet reaction conditions. Normal and iso-paraffinic solvents, as well as a blend of the two, had similar overall reactivities at equivalent inlet reactor conditions. Normal paraffins formed primarily lower-molecular weight normal paraffins and a-olefins, while iso-paraffins formed primarily lower-molecular weight iso-paraffins and branched olefins. It was observed that normal paraffins decomposed at a higher rate than iso paraffins in a blend of the two classes, indicating that iso-paraffins accelerate the relative decomposition rate of the linear compounds. Fuels and solvents with cycloparaffins had lower extents of conversion at equivalent reaction conditions. Aromatic species were formed at higher yields from fuels and solvents with higher cycloparaffin concentrations. It was observed that multi-component solvents decomposed under similar reaction pathways to single-component compounds; likewise, fully formulated fuels were found to decompose under similar pathways to multi component solvents of similar chemical compositions. The supercritical pyrolysis of the fuels and solvents was modeled as a first-order irreversible reaction to assist with reactivity comparisons among fuels and allow subsequent predictions. Supercritical pyrolysis was found to deviate from first-order reaction behavior at high conversion levels (> 30%), which limited the use of this simple kinetic analysis. The normal paraffinic solvent (Norpar-13) had estimated kinetic parameters of 60.7 kcal/mol activation energy and 1015.1 s-1 pre-exponential factor, while a specification JP-7 fuel sample was found to have kinetic parameters of 56.2 kcal/mol and 1013.5 s-1. Valid kinetic analysis is dependent upon accurate modeling of physical properties for estimation of residence times. A preliminary investigation of the deposition propensity of seven fuels and solvents was also performed in this effort. Significant differences in deposition rates were observed between fuels and solvents with similar chemical compositions, indicating that deposition propensity may not be solely determined by bulk chemical composition. Further investigation is needed to better understand the mechanisms of deposition formation in supercritical pyrolysis.

Committee:

Matthew DeWitt, Ph.D. (Advisor); Kevin Myers, D.Sc. (Committee Member); Steven Zabarnick, Ph.D. (Committee Member); Donald Phelps, Ph.D. (Committee Member); Zachary West, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Endothermic fuels; Pyrolysis; Jet fuel; Deposition

Sinha, AmitStudy of Hydrocarbon and Carbonyl Compound Emissions from Combustion of Biodiesel Blends using Plasma and Swirl Stabilized Combustors
MS, University of Cincinnati, 2016, Engineering and Applied Science: Environmental Engineering

The thesis investigated carbonyl and hydrocarbon emissions from biodiesel blends with diesel or Α fuel. Different technologies were used to improve biodiesel combustion. Plasma was used to improve diesel–biodiesel combustion and improved swirl–stabilized fuel injectors were used to improve combustion from biodiesel–jet fuel. The diesel– biodiesel blended fuels′ combustion ⟨hydrocarbons and carbonyl compounds⟩ emissions were analyzed and interpreted for plasma on and plasma off conditions. Plasma assisted combustion ⟨PAC⟩ is known to improve fuel efficiency, enhance and stabilize combustion performance and enhance fuel reforming. Fuel–rich fuel⁄air mixture is introduced into a plasma field and further downstream, the secondary air is added resulting in overall fuel– lean condition mixture, and properly hold the flame inside the combustion chamber. It is found that the total hydrocarbons emission index ⟨EI⟩ & total carbonyls EI is lower for plasma on condition than for plasma off condition for a given fuel–air equivalence ratio ⟨Φ⟩. For plasma on, flame is sustained over a larger lean Φ than plasma off. The major carbonyls detected were acetone and acrolein.

Straight⁄ branched alkanes & methyl esters were the dominant hydrocarbons identified. The plasma′s thermal and kinetic effects helped in reducing the formation of incomplete oxidation products and extending the lean flammability limit; hence enhancing the overall combustion performance. Reduced hydrocarbons and carbonyls emissions from plasma can be used to further support the use of plasma as an environment friendly combustion technology even for viscous fuels like diesel and B20. A swirl stabilized pilot nozzle ⟨in atmospheric rig⟩ and a low–emission Multi–nozzle lean direct injection ⟨MLDI⟩ combustor ⟨in pressurized rig⟩ was used to burn pure Α fuel as well as its blends with biodiesel ⟨BJ20 & BJ50⟩ to compare the emissions. The various aspects of this combustor design have the goal of reducing residence time, resulting in lower overall nitrogen dioxide formation by the thermal pathway. In atmospheric rig, biodiesel blends ⟨BJ20 & BJ50⟩ yielded less carbonyls and hydrocarbons emissions compared to Α fuel for fuel–rich conditions. For pressurized rig, as pressure across a single stage nozzle ⟨pilot⟩ was increased, total carbonyls EI and hydrocarbons EI decreased for both BJ20 and Α, for same mixed combustor temperature. The minimum value was recorded for highest power operating condition i.e. multi– stage nozzles. Α, however, tended to produce lesser hydrocarbons and carbonyls compared to BJ20. The main carbonyls identified were acetone, formaldehyde, acetaldehyde, benzaldehyde & acrolein while alkanes, hexa⁄ octadecanoic acids, tridecanol & methyl esters ⟨only observed for BJ20 in pressurized rig⟩ were the dominant hydrocarbons emitted. Excess unburned hydrocarbons may well be due to unsuitability of the small nozzles in this experiment for biodiesel blends.

Committee:

Mingming| Lu (Committee Chair); Timothy Keener (Committee Member); Jongguen| Lee (Committee Member); David Munday (Committee Member)

Subjects:

Environmental Engineering

Keywords:

biodiesel;jet fuel;diesel;carbonyls and hydrocarbons;plasma;nozzles

Xu, ZhanfengPrediction and Classification of Physical Properties by Near-Infrared Spectroscopy and Baseline Correction of Gas Chromatography Mass Spectrometry Data of Jet Fuels by Using Chemometric Algorithms
Doctor of Philosophy (PhD), Ohio University, 2012, Chemistry and Biochemistry (Arts and Sciences)

Chemometric techniques were used to extract relevant information from near infrared (NIR) spectral data to accurately classify physical properties of complex fuel samples. Discrimination of fuel types and classification of flash point, freezing point, and boiling point of jet fuels were investigated. Optimal partial least squares discriminant analysis (oPLS-DA), fuzzy rule-building expert system (FuRES), and support vector machine (SVM) were used to build the calibration models between the NIR spectra and classes of physical property of jet fuels. oPLS-DA, FuRES, and SVM were compared with respect to prediction accuracy. The results indicated that combined with chemometric classifiers NIR spectroscopy would be a fast method to monitor the changes of jet fuel physical properties.

Six widely used approaches of preprocessing NIR spectra were compared with respect to property prediction of jet fuels by NIR spectroscopy. These approaches included calculating the derivatives of spectra, multiplicative signal correction (MSC), standard normal variate (SNV) transformation, orthogonal signal correction (OSC), and two feature selection methods interval partial least squares (iPLS) and genetic algorithm (GA). Partial least squares (PLS) and temperature-constrained cascade correlation network (TCCCN) were used to build the calibration model and the prediction performance are compared. The validation of the calibration model was conducted by applying the bootstrapped Latin partition method that can give a measure of the precision.

Chemometric tools were used to determine the concentrations of the main products namely triolein and trielaidin in the mixtures of thermally treated triolein, a naturally occurring glyceride of oleic acid. The products formed during the thermal treatment at each temperature had been analyzed both by infrared spectrometry and gas chromatography/mass spectrometry (GC/MS). The GC/MS analysis was performed after derivatization of the fatty acids into their methyl esters (FAMEs). The combined analysis revealed that the thermal treatment induces not only cis–trans isomerization but also fission and fusion in the molecules. A regularized baseline correction method that uses basis set projection to estimate spectral backgrounds had been developed and applied to GC/MS data. An orthogonal basis was constructed using singular value decomposition (SVD) for each GC/MS two-way data object from a set of baseline mass spectra. The novel component of this method was the regularization parameter that prevents overfitting that may produce negative peaks in the corrected mass spectra or ion chromatograms. The parameters for baseline correction were optimized so that the projected difference resolution (PDR) or signal-to-noise ratio (SNR) was maximized. This new baseline correction method was evaluated with two synthetic data sets and a real GC/MS data set. The prediction accuracies obtained by using the FuRES and PLS-DA as classifiers were compared. The results indicated that baseline correction of the two-way GC/MS data using the proposed methods resulted in a significant increase in average PDR values and prediction accuracies.

Committee:

Peter de B. Harrington, PhD (Advisor); Hao Chen, PhD (Committee Member); Glen P. Jackson, PhD (Committee Member); Wei Lin, PhD (Committee Member); Shiyong Wu, PhD (Committee Member)

Subjects:

Analytical Chemistry; Chemistry

Keywords:

chemometrics; NIR; GC/MS; PLS-DA; TCCCN; FuRES; SVM; PDR; projected difference resolution; classification; prediction; baseline correction; jet fuel; triolein

West, Zachary JohnStudies of Jet Fuel Autoxidation Chemistry: Catalytic Hydroperoxide Decomposition & High Heat Flux Effects
Doctor of Philosophy (Ph.D.), University of Dayton, 2011, Mechanical Engineering

Jet fuel has been used as an aircraft and engine coolant for decades. However, one problem associated with heating the fuel is the occurrence of deposition reactions that foul critical fuel system components. If left unchecked, these fuel system deposits can cause catastrophic failure. The chemical pathways leading to fuel oxidation and deposition are not fully understood. In order to better understand these pathways, the kinetic parameters of hydroperoxide decomposition, relevant to jet fuel oxidation, have been measured in the presence of potential homogeneous catalytic sources, i.e., dissolved metals and naphthenic acids. The addition of dissolved metal alone was found to increase the decomposition rate of hydroperoxides, while the addition of naphthenic acids alone was found to have little effect on the rate. However, the combination of dissolved metal and naphthenic acids is shown to synergistically increase the decomposition rate of hydroperoxides. The catalytic effect of metal and naphthenic acids on real fuel deposition rates was explored, and in general followed similar trends to the hydroperoxide rate data.

Separate thermal oxidation experiments were conducted with jet fuel to explore advanced cooling schemes, e.g., regenerative cooling. Regenerative cooling schemes are often characterized by large heat fluxes and high wetted wall temperatures. Due to the complex experimental fluid flows and severe heat transfer conditions, computational fluid dynamics (CFD) with chemistry was used to predict chemical reaction rates and species concentrations. Some of the resulting kinetic data for hydroperoxide decomposition was incorporated into a revised pseudo-detailed chemical kinetic model, which was used in the CFD with chemistry computations. The relatively severe heat transfer conditions: heat fluxes of 0.26 and 0.49 Btu/s-in2 (43 and 81 W/cm2), wall temperatures of up to about 660°C, and bulk fluid temperatures as low as 27°C, caused the formation of large radial thermal gradients. In one case, heating of the fuel was sufficient to transition the flow from laminar to turbulent, which enhanced the reaction rate for some reactions. The large thermal gradients and high wall temperatures, coupled with flow conditions, created unique zones of chemical activity within the flow field. These zones of chemical activity included the localized depletion of dissolved oxygen within the boundary layer. CFD with chemistry was able to provide spatial resolution to the complex flow field to assist with experimental analysis.

Committee:

Jamie S. Ervin (Committee Co-Chair); Steven Zabarnick (Committee Co-Chair); Dilip Ballal (Committee Member); James T. Edwards (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Mechanical Engineering

Keywords:

jet fuel; thermal stability; CFD

Jiang, HuaEffect of Changes in Flow Geometry, Rotation and High Heat Flux on Fluid Dynamics, Heat Transfer and Oxidation/Deposition of Jet Fuels
Doctor of Philosophy (Ph.D.), University of Dayton, 2011, Mechanical Engineering

Jet fuel is used in high-performance military flight vehicles for cooling purposes before combustion. It is desirable to investigate the influence of the flow and heating conditions on fuel heat transfer and thermal stability to develop viable mitigation strategies. Computational fluid dynamics (CFD) simulations and experiments can provide the understanding of the fuel physical phenomena which involves the fluid dynamics, heat transfer and chemical reactions. Three distinct topics are studied: The first topic considers the effect of flow geometry on fuel oxidation and deposition. Experiments and CFD modeling were performed for fuels flowing through heated tubes which have either a sudden expansion or contraction. It was found that the peak deposition occurs near the maximum oxidation rate and excess deposition is formed near the step. This study provides information for the fuel system designer which can help minimize surface deposition due to fuel thermal oxidation.

In the second area of study, the fuel passed heated rotational test articles to investigate the effect of rotation on fuel heat transfer. The coupled effects of centrifugal forces and turbulent flow result in fuel temperatures that increase with rotational speed. This indicates that the convective heat transfer is enhanced as rotational speed increases. This work can assist the understanding of using jet fuel to cool the turbine engine.

In the third segment of research, the fuel was exposed to “rocket-like” conditions. This investigation is to explore the effect of high heat flux and high flow velocity on fuel heat transfer and oxidation/deposition. Simulations show a temperature difference over several hundred degrees in the radial direction within the very thin thermal boundary layer under rapid heating. The fuel contacting the interior wall is locally heated to a supercritical state. As a result, the heat transfer is deteriorated in the supercritical boundary layer. Both simulated and measured deposit profiles show a peak deposit near the end of the heated section. These observations may eventually have an application to the design of high speed supersonic vehicles with improved cooling capabilities.

Committee:

Jamie S. Ervin, PhD (Advisor); Steven Zabarnick, PhD (Committee Co-Chair); Timothy J. Edwards, PhD (Committee Member); Kevin P. Hallinan, PhD (Committee Member)

Subjects:

Aerospace Engineering; Mechanical Engineering

Keywords:

jet fuel; heat transfer deterioration; high heat flux; temperature peak; supercritical; fuel properties; nozzle; sudden expansion/contraction in flow path; fuel deposition; turbulence models; rotation passage; recirculation flow; excess deposition

Flora, GiacomoFuel Structure Effects on Surrogate Alternative Jet Fuel Emission
Doctor of Philosophy (Ph.D.), University of Dayton, 2015, Mechanical Engineering
The emergence of alternative jet fuels has opened new challenges for the selection of practical alternatives that minimize the emissions and are suitable for existing gas turbine engines. Alternative jet fuels are in the early stages of development, and little fundamental emissions data are currently available. An accurate knowledge of their combustion behavior is highly important for a proper fuel selection based on emissions. This dissertation work investigated the oxidation of different alternative fuel surrogates composed of binary mixtures in order to correlate fuel composition with emissions. The proposed surrogate mixtures included n-dodecane/n-heptane (47.5/52.5 by liq. vol.), n-dodecane/iso-octane (47.9/52.1 by liq, vol.), n-dodecane/methylcyclohexane (49/51 by liq. vol.) and n-dodecane/m-xylene (75/25 by liq. vol.) mixtures. Experiments were carried out at the UDRI heated shock tube facility, and covered a pre-ignition temperature range of 950–1550 K at a pre-ignition pressure of ~16 atm, an equivalence ratio of 3, an argon concentration of 93% (by mol), and under homogeneous gas-phase conditions. Experimental data were modeled using the 2014 SERDP mechanism for jet fuel surrogates (525 species and 3199 reactions). Similar ignition delay times were measured for the tested surrogate blends, confirming previous observations regarding the controlling role of normal alkanes during the induction period. The experimental observation was also compared with modeling results reporting reasonably good agreements. A kinetic analysis of the SERDP 2014 mechanism was also performed, highlighting the major chemical pathways relevant to the pre-ignition chemistry, especially the role of the hydroperoxyl radical at the low temperatures. A wide speciation of combustion products was also carried out under the test conditions. All the aliphatic blends reported similar emissions, whereas the presence of m-xylene produced lower emissions than the aliphatic surrogate blends at lower temperatures. For certain species (light gases) this experimental observation was also supported by the kinetic mechanism predictions. However, aromatic species formed from combustion of n-dodecane/m-xylene surrogate blend were always overestimated by the model and in poor agreement with experimental observations. The results also confirmed the role of acetylene as assisting growth of large PAHs and formation of soot.

Committee:

Sukhjinder S. Sidhu, Ph.D. (Committee Chair); Kahandawala Moshan S. P, Ph.D. (Committee Member); Dewitt Matthew J., Ph.D. (Committee Member); Stouffer Scott, Ph.D. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

combustion; jet fuel surrogates; ignition delay time; emissions; shock tube