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Balagurunathan, JayakishanInvestigation of Ignition Delay Times of Conventional (JP-8) and Synthetic (S-8) Jet Fuels: A Shock Tube Study
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
The global depletion of petroleum-based fuels has led the world to more closely examine alternate fuels. Therefore, alternate fuels produced from feedstocks such as coal, soybeans, palm oil or switch grass through methods such as coal liquefaction, biomass gasification, and Fischer-Tropsch synthesis have been tested. Among these techniques, fuels generated using Fischer-Tropsch technologies are of interest because they produce clean burning hydrocarbons similar to those found in commercial fuels. Therefore, in this study the Fischer-Tropsch derived S-8 fuel was evaluated as a drop-in replacement for the jet fuel JP-8. The jet fuel JP-8 is comprised of n-, iso- and cyclo- alkanes as well as aromatics while the S-8 fuel is primarily comprised of n- and iso- alkanes. The composition of the fuel affects its ignition characteristics chemically and physically by either advancement or delay of time to ignition. Since this study focused on the chemical effects, the fuels were completely pre-vaporized and pre-mixed. A high pressure, high temperature heated single pulse shock tube was used for this study. The shock tube is an established experimental tool used to obtain ignition delay data behind reflected shock waves under operating conditions relevant to modern engines. The experiments were conducted over a temperature range of 1000-1600 K, a pressure of 19±2 atm, equivalence ratios of 0.5, 1 and 3, within a dwell time of 7.6±0.2 ms and an argon dilution of 93% (v/v). Ignition delay times were measured using the signal from the pressure transducer on the end plate with guidance from the optical diagnostic signal. Along with JP-8 and S-8, the ignition delay of n-heptane was also studied. N-heptane was chosen to represent the n-alkanes in the fuels for this study since it was present in both fuels and also to prove the fact that the n-alkanes were rate controlling. The results indicate that both S-8 and JP-8 fuels have similar ignition delays at corresponding equivalence ratios. The fuel-rich mixtures ignited faster at lower temperatures (<1150 K) and the fuel-lean mixtures ignited faster at higher temperatures (>1150 K). In the transition period between lower to higher temperatures (~1100-1200 K), the equivalence ratio had no significant effect on the ignition delay time. The results also show that the ignition delay time measurements of S-8 and JP-8 fuels are similar to the ignition delay of n-heptane at the equivalence ratio of Φ=0.5 and thereby indicate that the n-alkanes present in these fuels controlled the ignition under these conditions. The ignition delay results of S-8 and JP-8 at Φ=3.0 from this study were also compared to prior work (Kahandawala et al., 2008) on 2-methylheptane and n-heptane/toluene (80/20 liquid vol.%), respectively and found to be indistinguishable. This data serves to extend the gas phase ignition delay database for both JP-8 and S-8 and is the first known data taken for both these fuels at higher temperatures (>1000 K) for an equivalence ratio of 3.0 with argon as the diluent gas.

Committee:

Sukh Sidhu, Dr (Committee Chair); Philip Taylor, Dr (Committee Member); Moshan Kahandawala, Dr (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Alternative Energy; Automotive Engineering; Automotive Materials; Chemical Engineering; Chemistry; Energy; Engineering; Environmental Engineering; Mechanical Engineering; Petroleum Engineering; Technology

Keywords:

Ignition delay; shock tube; S-8; JP-8; Jet fuels; Fuel characteristics; heated shock tube; Fischer-Tropsch; Alternate fuels; alkanes; synthetic fuel; fuel; iso-alkanes; jayakishan balagurunathan

Abd El Hafeez, Nureldayim MousaThe critical properties of binary systems of certain fluorocompounds with alkanes /
Doctor of Philosophy, The Ohio State University, 1970, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Fluorine compounds;Alkanes

Nanjundiah, KumarStudy of Confinement and Sliding Friction of Fluids Using Sum Frequency Generation Spectroscopy
Doctor of Philosophy, University of Akron, 2007, Polymer Science

Friction and wear are important technologically. Tires on wet roads, windshield wipers and human joints are examples where nanometer-thick liquids are confined between flexible-rigid contact interfaces. Fundamental understanding of the structure of these liquids can assist in the design of products such as artificial joints and lubricants for Micro-electromechanical systems [MEMS]. Prior force measurements have suggested an increase in apparent viscosity of confined liquid and sometimes solid-like responses. But, these have not given the state of molecules under confinement. In the present study, we have used a surface sensitive, non-linear optical technique (infrared-visible sum frequency generation spectroscopy [SFG]) to investigate molecular structure at hidden interfaces. SFG can identify chemical groups, concentration and orientation of molecules at an interface.

A friction cell was developed to study sliding of a smooth elastomeric lens against a sapphire surface. Experiments were done with dry sliding as well as lubricated sliding in the presence of linear alkane liquids. SFG spectra at the alkane / sapphire interface revealed ordering of the confined alkane molecules. These were more ordered than alkane liquid, but less ordered than alkane crystal. Cooling of the confined alkane below its melting temperature [TM] led to molecular orientation that was different from that of bulk crystal next to a sapphire surface. Molecules were oriented with their symmetry axis parallel to the surface normal. In addition, the melting temperature [Tconf] under confinement for a series of linear alkanes (n =15 - 27) showed a surprising trend. Intermediate molecular weights showed melting point depression. The Tconf values suggested that melting started at the alkane / sapphire interface.

In another investigation, confinement of water between an elastomeric PDMS lens and sapphire was studied. SFG spectra at the sapphire / water / PDMS interface revealed a heterogeneous morphology. The presence of peaks related to PDMS, as well as water, suggested water puddles in the contact area and the sapphire surface had a layer of bound water. This heterogeneity picture provides insight into high friction and stick-slip behavior found in boundary lubrication.

For the first time, a broadband SFG system has been coupled with a friction cell to study dynamics and molecular changes at an interface during sliding; sliding of confined alkane between sapphire and PDMS was investigated. A series of SFG spectra were taken while the confined alkane contact spot moved in and out of the laser beam. Even though the experiments were done 15°C above melting temperature, the spectra showed ordering of alkane molecules, similar to that of the confined crystal at the leading and trailing edge. The results suggest that a large portion of the resistance to sliding may come from ordering of molecules at the lens front.

Committee:

Ali Dhinojwala (Advisor)

Subjects:

Chemistry, Physical; Chemistry, Polymer; Engineering, Materials Science; Physics, Condensed Matter; Physics, Optics

Keywords:

sum frequency generation; SFG; PDMS; sliding friction; lubrication; spectroscopy; molecular structure; confinement; alkanes

ZHENG, TAOMOLECULAR SIMULATION OF DIFFUSION AND SORPTION OF ALKANES AND ALKANE MIXTURES IN POLY[1-(TRIMETHYLSILYL)-1-PROPYNE]
PhD, University of Cincinnati, 2000, Engineering : Chemical Engineering
In the present study, we investigated the sorption and transport of pure and mixed alkanes and gases (H2, CH4, C2H6, C3H8, i-C4H10, and n-C4H10) in Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) through the use of molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulations. The bonded constants in the DREIDING II and COMPASS force fields have been parameterized for PTMSP from AM1 and GAUSSIAN94 calculations of the dimer. The densities of amorphous cells generated from the two force fields agreed well with experimental data. Diffusion coefficients were calculated by means of the Einstein relationship using (NVT ensemble) MD simulation. There was good agreement between experimental and simulation diffusion coefficients for the gases and alkanes. MD trajectories indicated conformational changes of PTMSP that enable the formation of channels between adjacent holes of the free volume. The high mobility of the trimethylsilyl group studied by rotational time correlation analysis could facilitate channel formation. Sorption isotherms of alkanes in PTMSP were obtained by fixed-pressure GCMC simulation. The results for the pure-component isotherms were in qualitative agreement with experiment data. There was good agreement between simulation and experimental results for the solubility and dual-mode sorption parameters. Diffusion coefficients and solubilities obtained from transition-state theory (TST) simulation for light gases (H2 and CH4) agreed well with MD and GCMC simulations, whereas the agreement was not as good for larger condensable vapors. High overall free volume and free volume distribution contributed to the high gas permeability of PTMSP. There was excellent correlation between ln D and fa, the accessible free volume fraction, for PTMSP and each of the four alkanes. Fractional free volume obtained by Voorintholt grid search method was consistent with the experimental values. TST results indicated that the larger the gas molecule, the larger was the free volume element in which gas resided and the longer was the residence time. The simulated diffraction pattern was in good agreement with experimental data and indicated a large interchain distance for PTMSP. It was found from simulation that the solvent casting during PTMSP membrane preparation did not make much difference in terms of the final membrane density and fractional free volume. Four gas/vapor mixtures were investigated by MD and GCMC simulations - CH4/C3H8, CH4/n-C4H10, H2/C3H8, and H2/n-C4H10. It was found from GCMC simulation that the larger gas molecule was more competitive to the sorption site for binary gas mixtures. Compared with pure gas permeability, the permeability of the permanent gas in binary mixture decreased more than that of the condensable vapor. This behavior was consistent with a blocking mechanism suggested for permanent gas/condensable vapor transport in PTMSP.

Committee:

JOEL FRIED (Advisor)

Subjects:

Engineering, Chemical

Keywords:

Molecular simulation; Alkanes and Alkane Mixtures

Lin, HengCROSSOVER FROM UNENTANGLED TO ENTANGLED DYNAMICS: MONTE CARLO SIMULATION OF POLYETHYLENE, SUPPORTED BY NMR EXPERIMENTS
Doctor of Philosophy, University of Akron, 2006, Polymer Science
A two-bead move algorithm for dynamic Monte Carlo simulation has been designed to reflect the true randomness of local torsion dynamics on a high coordination lattice (2nnd lattice). All possible configurations of two consecutive beads of a chain on this high coordination lattice have been included in a library by this algorithm. The moves were implemented by randomly choosing one of the possible configurations from the library. Thus there is no artificial rule for the moves. The algorithm is capable of introducing new bond vectors to local configurations without going through chain ends. The chain-cross has been eliminated in this two-bead move algorithm. The algorithm is fast enough for simulating polyethylene (PE) melts ranging from C40 to C324 on a regular desktop computer. The results of our simulation confirmed there were finite chain length effects, e.g. chain length dependent friction coefficients and non-Gaussian statistics for short PE chains. A detailed comparison has been made among the experiments, prior simulations by other groups, and the results of our new algorithm. The diffusion coefficients scale with molecular weight (M) to the -1.7 power for short chains and -2.2 for longer chains at 180°C, which coincides very well with experimental results. Due to the finite chain length effect, no pure Rouse scaling in diffusion has been observed. The reptation-like slowdown can be clearly observed when M is above 2400 according to the mean square displacements of middle beads. The slope 0.25 predicted by the reptation theory was missing for the intermediate regime of diffusion; instead a slope close to 0.4 appeared, indicating that additional relaxation mechanisms exist in this transition region. The relaxation times extracted by fitting the autocorrelation function of the end-to-end vectors scale with M to 2.5 and 2.7 power using the reptation model and KWW equation, respectively, for entangled chains. The dynamic Monte Carlo algorithm has also been used for simulating a bimodal mixture of PE with one entangled component (M~4.5k) and one unentangled component (M~1k). Detailed normal mode analyses have been presented. Rouse dynamics have not been observed at the short time and distance scale. The KWW equation generally provides better fits than does the pure exponential decay for the data of normal mode relaxation. The KWW index â varies with the concentration and increases with the decrease of mode numbers until a plateau is reached. Tube dilation was observed before the gradual disappearance of a reptation-like slowdown with increasing short chain content in mixtures. Reasonable agreements have been reached when Hess theory and Pearson-von Meerwall model were used to fit the concentration-dependent diffusion coefficients of PE in the mixture. Additional bimodal mixtures of PE studied by our simulation involved a small amount of short N-alkane in an entangled PE matrix. Most of our data agree with the NMR experimental measurements. Extrapolating the concentration-dependent diffusion coefficients of N-alkanes to the trace limit did not lead to the complete restoration of Rouse scaling of the M dependence of the trace diffusion coefficients (Dtr). Although the M dependence of Dtr was found to be obviously weaker than that of the diffusion coefficients in monodisperse melts (Dmelt), a residue of the slope still exists. Thus, the commonly seen excessive M dependence of short polymer chains may result from two contributions. One is the non-iso-friction environment of the polymers at the different chain lengths, which can largely be eliminated by the trace diffusion measurements. Another one, which is related to the underlying physics of the residue of the slope in trace diffusion, is still mysterious. It may link to the non-Gaussian statistics of short polymer chains.

Committee:

Wayne Mattice (Advisor)

Keywords:

Polymer Dynamics; Monte Carlo Simulation; Spin Echo Pulse Gradient NMR; Diffusion; N-Alkanes; Rouse Theory; Reptation Theory

Groth, Richard HenryReactions of fluorinated functions and synthesis of fluorinated paraffins /
Doctor of Philosophy, The Ohio State University, 1956, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Alkanes

Otto, Bruce MichaelThe synthesis of some isomeric polyalkylcycloparaffins /
Doctor of Philosophy, The Ohio State University, 1963, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Alkanes

Williams, Frank Jarvis,1944-The chemistry of trans-bicyclo[n.1.0]alkanes /
Doctor of Philosophy, The Ohio State University, 1970, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Bicyclic compounds;Alkanes