Browsing by Subject "Ethylene"

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    Experimental Investigation into Combustion Torch Jet Ignition of Methane-Air, Ethylene-Air, and Propane-Air Mixtures
    (2010-12) Perera, Ukwatte Lokuliyanage Indika Upendra; Nalim, M. Razi; Xie, Jian; Zhu, Likun
    Ignitability and the ignition delay time of a combustible mixture in a long combustion chamber, ignited by a hot combustion torch jet generated in a pre-chamber was investigated experimentally in relation to application as a viable igniter method for wave rotor combustors. Methane-air, ethylene-air, and propane-air in varying equivalence ratios were investigated as the combustible mixture in the combustion chamber. The effects of variation in the torch jet fuel, initial equivalence ratio in the pre-chamber, and nozzle geometry on the ignitability and the ignition delay time of combustible mixtures were observed and analyzed. The single-channel wave-rotor combustion rig at Combustion and Propulsion Research Laboratory at the Purdue School of Engineering and Technology at Indiana University-Purdue University, Indianapolis was used for this study. High-speed video imaging techniques to observe the ignition and flame propagation in the combustion chamber and fast-response pressure transducers to measure the dynamic pressure fluctuations in the combustion chambers were used in the current study. The present work explains how the experimental procedure and preliminary testing was carried out in order to conduct the necessary testing to find the ignitability and ignition delay time of a combustible mixture. Ignitability of methane, ethylene, and propane were much broader in range compared to conventional spark ignitable lean and rich limit equivalence ratios. The methane and propane ignition lean limits were similar to radical activated ignition lean limits found in previous studies of the same fuels. Ethylene exhibited the widest range in equivalence ratios from 0.4 to 2.4, while methane had the narrowest ranging from equivalence ratio 0.4 to 1.4. The ignition delay studies indicated both chemical kinetics and mixing between the combustion torch jet and the combustible mixture were critical. The mixing phenomena dominated chemical kinetics; unlike in ignition delay studies conducted using shock heated ignition techniques. Ethylene-air mixtures had the shortest ignition delay times ~1 ms for lean but near-stoichiometric mixtures. Methane and propane indicated similar ignition delay time characteristics with lean near-stoichiometric mixtures. The fuel-air equivalence ratio which was used to generate the combustion torch jet and the torch jet nozzle geometry had a direct influence over the ignition delay time in the main chamber combustible mixture. The slightly rich fuel-air ratios used to generate the combustion torch jet had the lowest delay times in igniting the main chamber fuel-air mixtures.
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    Molecular and Physiological Responses of Soybean (Glycine max) to Cold and the Stress Hormone Ethylene
    (2019-05) Robison, Jennifer Dawn; Randall, Stephen K.; Balakrishnan, Lata; Watson, John C.; Blacklock, Brenda J.
    Abiotic stresses, such as cold, are serious agricultural problems resulting in substantial crop and revenue losses. Soybean (Glycine max) is an important worldwide crop for food, feed, fuel, and other products. Soybean has long been considered to be cold-intolerant and incapable of cold acclimation. In contrast to these reports, this study demonstrates that cold acclimation improved freezing tolerance in the domestic soybean cultivar ‘Williams 82’ with 50% enhancement of freezing tolerance after 5.2 +\- 0.6 days of cold exposure. Decreases in light dependent photosynthetic function and efficiency accompanied cold treatment. These decreases were due to an increase in photon dissipation likely driven by a decrease in plastoquinone (PQ) pool size limiting electron flow from photosystem II (PSII) to photosystem I (PSI). Cold-induced damage to operational photosynthesis began at 25 minutes of cold exposure and maximal photosynthesis was disrupted after 6 to 7 hours of cold exposure. Cold exposure caused severe photodamage leading to the loss of PSII reaction centers and photosynthetic efficiency. Comparisons of eight cultivars of G. max demonstrated a weak correlation between cold acclimation and northern cultivars versus southern cultivars. In the non-domesticated soybean species Glycine soja, the germination rate after cold imbibition was positively correlated with seedling cold acclimation potential. However, the overall cold acclimation potential in G. soja was equal to that of domestic soybean G. max reducing the enthusiasm for the “wild” soybean as an additional source of genetic diversity for cold tolerance. Despite being relatively cold intolerant, the soybean genome possesses homologs of the major cold responsive CBF/DREB1 transcription factors. These genes are cold-induced in soybean in a similar pattern to that of the cold tolerant model plant species Arabidopsis thaliana. In Arabidopsis, EIN3, a major component of the ethylene signaling pathway, is a negative transcriptional regulator of CBF/DREB1. In contrast to AtEIN3 transcript levels which do not change during cold treatment in Arabidopsis, we observed a cold-dependent 3.6 fold increase in GmEIN3 transcript levels in soybean. We hypothesized that this increase could prevent effective CBF/DREB1 cold regulation in soybean. Analysis of our newly developed cold responsive reporter (AtRD29Aprom::GFP/GUS) soybean transgenic lines demonstrated that inhibition of the ethylene pathway via foliar sprays (AVG, 1-MCP, and silver nitrate) resulted in significant cold-induced GUS activity. Transcripts of GmEIN3A;1 increased in response to ethylene pathway stimulation (ACC and ethephon) and decreased in response to ethylene pathway inhibition in the cold. Additionally, in the cold, inhibition of the ethylene pathway resulted in a significant increase in transcripts of GmDREB1A;1 and GmDREB1A;2 and stimulation of the ethylene pathway led to a decrease in GmDREB1A;1 and GmDREB1B;1 transcripts. To assess the physiological effects of these transcriptional changes; electrolyte leakage, lipid oxidation, free proline content, and photosynthesis were examined. Improvement in electrolyte leakage, a measure of freezing tolerance, was seen only under silver nitrate treatment. Only 1-MCP treatment resulted in significantly decreased lipid oxidation. Transcripts for CBF/DREB1 downstream targets (containing the consensus CRT/DRE motifs) significantly decreased in plants treated with ethylene pathway stimulators in the cold; however, ethylene pathway inhibition generally produced no increase over basal cold levels. To identify if GmEIN3A;1 was capable of binding to GmDREB1 promoters, the negative regulator GmEIN3A;1 and the positive regulator GmICE1A were cloned and expressed in Escherichia coli (E. coli). Preliminary binding results indicated that GmEIN3A;1 can bind to a double stranded section of the GmDREB1A;1 promoter containing putative EIN3 and ICE1 binding sites. GmICE1A is capable of binding to the same section of the GmDREB1A;1 promoter, though only when single stranded. Additional experiments will be required to demonstrate that GmEIN3A;1 and GmICE1A are capable of binding to the GmDREB1A;1 promoter and this work provides the tools to answer these questions. Overall, this work provides evidence that the ethylene pathway transcriptionally inhibits the CBF/DREB1 pathway in soybean through the action of GmEIN3A;1. Yet when GmCBF/DREB1 transcripts are upregulated by ethylene pathway inhibition, no consistent change in downstream targets was observed. These data indicate that the limitation in cold tolerance in soybean is due to a yet unidentified target downstream of CBF/DREB1 transcription.