Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 5 of 5
Full-Text Articles in Entire DC Network
Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty
Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty
Electronic Theses and Dissertations
Shock-tube experiments were performed with syngas mixtures near atmospheric pressure with varying equivalence ratios behind reflected shock waves. Pressure and hydroxyl radical (OH*) emission traces were recorded and used to calculate ignition delay time for a single mixture at equivalence ratios of [phi ]=0.4, 0.7, 1.0, and 2.0 over a range of temperatures from 913-1803 K. The syngas mixture was tested at full concentration as well as with 98% dilution in Argon. The full concentration mixtures were used to compare ignition delay time measurements with the theoretical calculations obtained through the use of chemical kinetics modeling using the Davis et …
Methane And Dimethyl Ether Oxidation At Elevated Temperatures And Pressure, Christopher Zinner
Methane And Dimethyl Ether Oxidation At Elevated Temperatures And Pressure, Christopher Zinner
Electronic Theses and Dissertations
Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy …
Wall Heat Transfer Effects In The Endwall Region Behind A Reflected Shock Wave At Long Test Times, Corey Frazier
Wall Heat Transfer Effects In The Endwall Region Behind A Reflected Shock Wave At Long Test Times, Corey Frazier
Electronic Theses and Dissertations
Shock-tube experiments are typically performed at high temperatures (≥1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to achieve ignition and require much longer test times (up to 15 ms) to fully study the chemical kinetics and combustion chemistry …
A Study Of Syngas Oxidation At High Pressures And Low Temperatures, Danielle Marie Kalitan
A Study Of Syngas Oxidation At High Pressures And Low Temperatures, Danielle Marie Kalitan
Electronic Theses and Dissertations
Ignition and oxidation characteristics of CO/H2, H2/O2 and CO/H2/CH4/CO2/Ar fuel blends in air were studied using both experimental and computer simulation methods. Shock-tube experiments were conducted behind reflected shock waves at intermediate temperatures (825 < T < 1400 K) for a wide range of pressures (1 < P < 45 atm). Results of this study provide the first undiluted fuel-air ignition delay time experiments to cover such a wide range of syngas mixture compositions over the stated temperature range. Emission in the form of chemiluminescence from the hydroxyl radical (OH*) transition near 307 nm and the pressure behind the reflected shock wave were used to monitor reaction progress from which ignition delay times were determined. In addition to the experimental analysis, chemical kinetics calculations were completed to compare several chemical kinetics mechanisms to the new experimental results. Overall, the models were in good agreement with the shock-tube data, especially at higher temperatures and lower pressures, yet there were some differences between the models at higher pressures and the lowest temperatures, in some cases by as much as a factor of five. In order to discern additional information from the chemical kinetics mechanisms regarding their response to a wide range of experimental conditions, ignition delay time and reaction rate sensitivity analyses were completed at higher and lower temperatures and higher and lower pressures. These two sensitivity analyses allow for the identification of the key reactions responsible for ignition. The results of the sensitivity analysis indicate that the ignition-enhancing reaction H + O2 = O + OH and hydrogen oxidation kinetics in general were most important regardless of mixture composition, temperature or pressure. However, lower-temperature, higher-pressure ignition delay time results indicate additional influence from HO2- and CO- containing reactions, particularly the well-known H + O + M = HO2 + M reaction and also the CO + O + M = CO2 + M and CO + HO2 = CO2 + OH reactions. Differences in the rates of the CO-related reactions are shown to be the cause of some of the discrepancies amongst the various models at elevated pressures. However, the deviation between the models and the experimental data at the lowest temperatures could not be entirely explained by discrepancies in the current rates of the reactions contained within the mechanisms. Additional calculations were therefore performed to gain further understanding regarding the opposing ignition behavior for calculated and measured ignition delay time results. Impurities, friction induced ionization, static charge accumulation, boundary layer effects, wall reaction effects, and revised chemical kinetics were all considered to be possible mechanisms for the model and measured data disparity. For the case of wall-reaction effects, additional shock-tube experiments were conducted. For the remaining effects listed above, only detailed calculations were conducted. Results from this preliminary anomaly study are at this time inconclusive, but likely avenues for future study were identified. Additional kinetics calculations showed that the large difference between the experimental data and the chemical kinetics models predictions at low temperatures can be explained by at least one missing reaction relevant to low-temperature and high-pressure experimental conditions involving the formation of H2O2, although further study beyond the scope of this thesis is required to prove this hypothesis both theoretically and experimentally.
Driver-Gas Tailoring For Test-Time Extension Using Unconventional Driver Mixtures, Anthony Amadio
Driver-Gas Tailoring For Test-Time Extension Using Unconventional Driver Mixtures, Anthony Amadio
Electronic Theses and Dissertations
To study combustion chemistry at low temperatures in a shock tube, it is of great importance to increase experimental test times, and this can be done by tailoring the interface between the driver and driven gases. Using unconventional driver-gas tailoring with the assistance of tailoring curves, shock-tube test times were increased from 1 to 15 ms for reflected-shock temperatures below 1000 K. Provided in this thesis is the introduction of tailoring curves, produced from a 1-D perfect gas model for a wide range of driver gases and the production and demonstration of successful driver mixtures containing helium combined with either …