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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

Tanim, Tanvir R.Modeling of a 5 kWe Solid Oxide Fuel Cell Based Auxiliary Power Unit Operating on JP-8 Fuel
Master of Science (MS), Ohio University, 2012, Mechanical Engineering (Engineering and Technology)

Solid Oxide Fuel Cells (SOFC) offer potential for high conversion efficiency, high energy utilization, low emissions and quiet operation. Because of the cost associated with hydrogen storage, coupling an onboard fuel reformer with a SOFC stack is an attractive option for small decentralized and Mobile Electric Power (MEP) generation and as an Auxiliary Power Unit (APU) for motor vehicles. In this study Aspen Plus simulation software is used to develop a 5 kWe APU model using JP-8 as a fuel. JP-8 is selected because of its near ubiquitous use by the U.S. Army and Air Force for ground and air operations. The SOFC platform is selected due to its inherent advantages including: high fuel conversion efficiency, compact design, low noise and emissions. In this study desulfurized JP-8 surrogate fuel is reformed in an onboard autothermal reformer (ATR). The resultant H2 and CO mixture is used as fuel for the SOFC stack. The steam rich anode exhaust is recycled to supply the ATR with thermal energy and steam required to reform the fuel. Such an implementation makes the proposed system lighter and more compact, avoiding the need for an external steam generator and additional heat source for the ATR” (Tanim & Bayless, 2011). Ni-YSZ based tubular and planar SOFC stacks operating at 910 °C and 850 °C, respectively are evaluated as part of the study. ATR performance from 700 °C to 850 °C in the H2O/C ratio range of 0.10-1.0 is investigated.

The tubular cell based system (T-SOFC) showed a maximum net AC efficiency of 39.55% at 700 °C reformer temperature and a minimum of 32.60% at 850 °C. The planar cell based system (P-SOFC) demonstrated a maximum and minimum efficiency of 37.10% and 29.20% at 700 °C and 800 °C reformer temperatures, respectively. Sensitivity analyses are conducted evaluating the effect of the fuel utilization factor (Uf) and the current density (j) to determine optimum system operating windows. Finally, the T-SOFC and P-SOFC systems are compared and the results are analyzed in terms of voltage, net AC efficiency and power density. The anode supported P-SOFC system demonstrated a higher operating current density range achieving higher efficiency and power density compared to T-SOFC system.

Committee:

Jason Trembly, PhD (Committee Chair); David Bayless, PhD (Committee Co-Chair); Gregory Kremer, PhD (Committee Member); JungHun Choi, PhD (Committee Member); Hugh Richardson, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

JP-8 Fuel; Autothermal Reformer; Solid Oxide Fuel Cell

Merling, Weston LeeAssessing the Compatibility of Alternative Jet Propulsion and Diesel Fuels with Selected Fuel System Elastomers
Master of Science (M.S.), University of Dayton, 2012, Chemical Engineering

Concerns about the future availability, security, price, and environmental impact of petroleum fuels have increased the interest of the United States Navy, and the United States Department of Defense in general, in developing drop-in alternative fuels produced from sources other than petroleum. These drop-in fuels must be used interchangeably with petroleum fuels and used without modification or replacement of existing materials or infrastructure. One area of concern is the compatibility of alternative fuels with the numerous polymeric materials used in modern fuel systems. Therefore, the purpose of this study was to characterize the behavior of selected fuel system elastomers in petroleum fuels and contrast this with the behavior in example alternative fuels. From this comparison the overall compatibility of these alternative fuels with the selected fuel system elastomers was assessed. The volume swell behavior of four nitrile rubber, two fluorosilicone and two fluorocarbon elastomeric O-ring materials as well as four sealant elastomeric materials was measured in nineteen conventional JP-5 and JP-8 jet fuels, fourteen conventional F-76 diesel fuels, three alternative jet fuels, and three alternative diesel fuels. The volume swell of the materials in the conventional fuels was used to characterize normal volume swell behavior; then the volume swell in the alternative fuels and the predicted volume swell in 50-50 blends of alternative and conventional fuel were compared to normal volume swell behavior.

Overall, the volume swell behavior of the nitrile rubber materials in the alternative fuels and the predicted 50-50 blends deviated the most from normal volume swell behavior, followed by the sealant materials, then the fluorosilicone materials, and finally the fluorocarbon materials. The nitrile rubber materials exhibited significantly lower volume swell in the alternative fuels and the predicted 50-50 blends than in the conventional fuels. The sealant materials also showed generally lower volume swell in the alternative fuels and predicted 50-50 blends, with some of the material and fuel combinations reaching normal volume swell behavior. Finally, the fluorosilicone and fluorocarbon materials largely exhibited normal volume swell behavior in the alternative fuels and predicted 50-50 blends. Therefore, the nitrile rubber and sealant materials showed the greatest potential for having compatibility issues with the tested alternative fuels, while the fluorosilicone and fluorocarbon materials appeared to be compatible with the tested alternative fuels.

Committee:

John L. Graham, PhD (Advisor); Kevin J. Myers, PhD (Committee Chair); Donald A. Klosterman, PhD (Committee Member)

Subjects:

Chemical Engineering

Keywords:

polymer-fuel interactions; O-rings; sealants; JP-5; JP-8; F-76

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