A Rapid Survey of the Compatibility of Selected Seal Materials with Conventional and Semi-Synthetic JP-8

Since the synthesis of a liquid hydrocarbon fuel from coal by Franz Fischer and Hans Tropsch in 1923, there has been cyclic interest in developing this fuel for military and commercial applications. In recent years the U.S. Department of Defense has taken interest in producing a unified battlespace fuel using the Fischer Tropsch (FT) process for a variety of reasons including cost, quality, and logistics. In the past year there has been a particular emphasis on moving quickly to demonstrate that an FT fuel can be used in the form of a blend with conventional petroleum-derived jet fuel. The initial objective is to employ this semi-synthetic fuel with blend ratios as high as 50 percent FT with longer range goals to use even high blend ratios and ultimately a fully synthetic jet fuel. A significant concern associated with the use of a semi-synthetic jet fuel with high FT blend ratios is the effect these low aromatic fuels will have on fuel-wetted polymeric materials, most notably seals and sealants. These materials typically swell and soften to some degree when exposed to jet fuel and the aromatic content of these fuels contribute to this effect. Semi-synthetic jet fuels with very low aromatic contents may cause seals and sealants to shrink and harden leading to acute or chronic failure. Unfortunately, most of the material qualification tests are more concerned with excessive swelling than shrinkage and there is little guidance offered as to an acceptable level of shrinkage or other changes in physical properties related to low aromatic content. Given the pressing need for guidance data, a program was developed to rapidly survey the volume swell of selected fuel-wetted materials in a range of conventional and semi-synthetic jet fuels and through a statistical analysis to make a determination as to whether there was a basis to be concerned about using fuels with FT blend ratios as high as 50 percent. Concurrent with this analysis data was obtained as to the composition of the fuel absorbed in fuel-wetted materials through the use of GC-MS analysis of swollen samples as well as other supporting data. In this presentation the authors will present a summary of the results of the volume swell and fuel absorbed by selected O-rings and sealants as well as a description of the measurement protocols developed for this program

Flow and chemical kinetics simulations of endothermic fuels

Advanced aircraft engines are reaching a practical heat transfer limit beyond which the convective heat transfer provided by hydrocarbon fuels is no longer adequate. One solution is to use an endothermic fuel that absorbs heat through chemical reactions. This paper describes the development of a two-dimensional computational model of the heat and mass transport associated with a flowing fuel using a unique global chemical kinetics model. Most past models do not account for changes in the chemical composition of a flowing fuel and also do not adequately predict flow properties in the supercritical regime. The two-dimensional computational model presented here calculates the changing flow properties of a supercritical reacting fuel by use of experimentally derived proportional product distributions. The present calculations are validated by measured experimental data obtained from a flow reactor of mildly cracked n-decane. It is believed that these simulations will assist the fundamental understanding of high temperature fuel flow experiments

Chemical Analysis of Jet Fuel Polar, Heteroatomic Species via High-Performance Liquid Chromatography with Electrospray Ionization-Mass Spectrometric Detection

High-performance liquid chromatography (HPLC) with electrospray ionization–mass spectrometry (ESI–MS) was used to identify several classes of heteroatomic, polar compounds containing oxygen, nitrogen, and sulfur in a variety of jet fuel samples. While nitrogen, oxygen, and sulfur compounds are present only at low concentrations in jet fuel, they contribute significantly to some important fuel properties. These trace, heteroatomic species can provide positive (e.g., improved lubricity) or negative (e.g., reduced thermal stability) impacts. Reversed-phase liquid chromatography with ESI–MS detection allows for the polar components to be selectively ionized and subsequently identified, despite the complex hydrocarbon fuel matrix. Phenols and carbazoles are detected in negative-ion [M – H]− mode, while anilines, pyridines, indoles, and quinolines are observed in positive-ion [M + H]+ mode. Accurate mass measurements allow for the molecular formula of the polar components to be determined, while different structural classes of isomeric compounds could be determined via HPLC separation and the formation of derivatives. Derivatization shifts the retention time, species masses, and potentially, the ion charge formed of specific compound classes, allowing them to be positively identified. The usefulness and limits of HPLC with ESI–MS for quantitation of these fuel polar, heteroatomic species are also explored

Development of methodologies for identification and quantification of hazardous air pollutants from turbine engine emissions

<div><p>Aircraft turbine engines are a significant source of particulate matter (PM) and gaseous emissions in the vicinity of airports and military installations. Hazardous air pollutants (HAPs) (e.g., formaldehyde, benzene, naphthalene and other compounds) associated with aircraft emissions are an environmental concern both in flight and at ground level. Therefore, effective sampling, identification, and accurate measurement of these trace species are important to assess their environmental impact. This effort evaluates two established ambient air sampling and analysis methods, U.S. Environmental Protection Agency (EPA) Method TO-11A and National Institute for Occupational Safety and Health (NIOSH) Method 1501, for potential use to quantify HAPs from aircraft turbine engines. The techniques were used to perform analysis of the exhaust from a T63 turboshaft engine, and were examined using certified gas standards transferred through the heated sampling systems used for engine exhaust gaseous emissions measurements. Test results show that the EPA Method TO-11A (for aldehydes) and NIOSH Method 1501 (for semivolatile hydrocarbons) were effective techniques for the sampling and analysis of most HAPs of interest. Both methods showed reasonable extraction efficiencies of HAP species from the sorbent tubes, with the exception of acrolein, styrene, and phenol, which were not well quantified. Formaldehyde measurements using dinitrophenylhydrazine (DNPH) tubes (EPA method TO-11A) were accurate for gas-phase standards, and compared favorably to measurements using gas-phase Fourier-transform infrared (FTIR) spectroscopy. In general, these two standard methodologies proved to be suitable techniques for field measurement of turbine engine HAPs within a reasonable (5–10 minutes) sampling period. Details of the tests, the analysis methods, calibration procedures, and results from the gas standards and T63 engine tested using a conventional JP-8 jet fuel are provided.</p><p>Implications: <i>HAPs from aviation-related sources are important because of their adverse health and environmental impacts in and around airports and flight lines. Simpler, more convenient techniques to measure the important HAPs, especially aldehydes and volatile organic HAPs, are needed to provide information about their occurrence and assist in the development of engines that emit fewer harmful emissions.</i></p></div

Transcriptional Profiling Suggests that Multiple Metabolic Adaptations are Required for Effective Proliferation of <i>Pseudomonas aeruginosa</i> in Jet Fuel

Fuel is a harsh environment for microbial growth. However, some bacteria can grow well due to their adaptive mechanisms. Our goal was to characterize the adaptations required for Pseudomonas aeruginosa proliferation in fuel. We have used DNA-microarrays and RT-PCR to characterize the transcriptional response of P. aeruginosa to fuel. Transcriptomics revealed that genes essential for medium- and long-chain <i>n</i>-alkane degradation including <i>alkB1</i> and <i>alkB2</i> were transcriptionally induced. Gas chromatography confirmed that P. aeruginosa possesses pathways to degrade different length <i>n</i>-alkanes, favoring the use of <i>n</i>-C_11–18. Furthermore, a gamut of synergistic metabolic pathways, including porins, efflux pumps, biofilm formation, and iron transport, were transcriptionally regulated. Bioassays confirmed that efflux pumps and biofilm formation were required for growth in jet fuel. Furthermore, cell homeostasis appeared to be carefully maintained by the regulation of porins and efflux pumps. The Mex RND efflux pumps were required for fuel tolerance; blockage of these pumps precluded growth in fuel. This study provides a global understanding of the multiple metabolic adaptations required by bacteria for survival and proliferation in fuel-containing environments. This information can be applied to improve the fuel bioremediation properties of bacteria

A comprehensive multi-omics approach uncovers adaptations for growth and survival of Pseudomonas aeruginosa on n-alkanes

Abstract Background Examination of complex biological systems has long been achieved through methodical investigation of the system’s individual components. While informative, this strategy often leads to inappropriate conclusions about the system as a whole. With the advent of high-throughput “omic” technologies, however, researchers can now simultaneously analyze an entire system at the level of molecule (DNA, RNA, protein, metabolite) and process (transcription, translation, enzyme catalysis). This strategy reduces the likelihood of improper conclusions, provides a framework for elucidation of genotype-phenotype relationships, and brings finer resolution to comparative genomic experiments. Here, we apply a multi-omic approach to analyze the gene expression profiles of two closely related Pseudomonas aeruginosa strains grown in n-alkanes or glycerol. Results The environmental P. aeruginosa isolate ATCC 33988 consumed medium-length (C10–C16) n-alkanes more rapidly than the laboratory strain PAO1, despite high genome sequence identity (average nucleotide identity >99%). Our data shows that ATCC 33988 induces a characteristic set of genes at the transcriptional, translational and post-translational levels during growth on alkanes, many of which differ from those expressed by PAO1. Of particular interest was the lack of expression from the rhl operon of the quorum sensing (QS) system, resulting in no measurable rhamnolipid production by ATCC 33988. Further examination showed that ATCC 33988 lacked the entire lasI/lasR arm of the QS response. Instead of promoting expression of QS genes, ATCC 33988 up-regulates a small subset of its genome, including operons responsible for specific alkaline proteases and sphingosine metabolism. Conclusion This work represents the first time results from RNA-seq, microarray, ribosome footprinting, proteomics, and small molecule LC-MS experiments have been integrated to compare gene expression in bacteria. Together, these data provide insights as to why strain ATCC 33988 is better adapted for growth and survival on n-alkanes