Christopher Brian Dreyer

Electronic structure and spectroscopic analysis of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ion pair.

Electronic and structural properties of the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulonyl)imide are studied using density functional theory (DFT) methods in addition to infrared and UV-vis spectroscopy. The DFT methods were conducted for both gas phase and solution phase using the integral equation formalism polarizable continuum model, while optical absorption experiments were conducted using neat and dilute methanol solutions. Three energetically similar conformers were obtained for each of the gas phase and solution phase DFT calculations. These multiple configurations were considered when analyzing the molecular interactions between the ion pair and for a molecular-level interpretation of the experimental IR and UV-vis spectroscopy data. Excitation energies of low-lying singlet excited states of the conformers were calculated with time-dependent DFT and experimentally with UV-vis absorption spectra. Difference density plots and excited-state calculations in the gas phase are found to be in good agreement with the experimental findings, while the implicit solvation model calculations adversely impacted the accuracy of the predicted spectra.

Laminar Burning Velocities for Hydrogen-, Methane-, Acetylene-, and Propane-Nitrous Oxide Flames

Mixtures of four fuels (hydrogen, methane, acetylene and propane) with nitrous oxide were studied to experimentally and numerically determine the laminar flame speeds at near atmospheric pressure (0.8 atm). Using the flat flame method, laminar flame speeds for these nitrous oxide flames were determined for different levels of dilution with nitrogen. A comprehensive hydrocarbon oxidation mechanism in the literature was integrated with a hydrogen-nitrous oxide sub-mechanism, and computational flame speed results using this mechanism were compared to experimental data. For all four fuel systems (hydrogen-, methane-, acetylene-, and propane-nitrous oxide), the compiled chemical mechanism under-predicted the measured laminar flame speeds over the whole range of equivalence ratio investigated. Flame speed sensitivity analyses for the hydrogen-, acetylene-, and propane-nitrous oxide systems have shown that the most sensitive reactions are within the hydrogen-nitrous oxide sub-mechanism. A revision to the reaction rate constant expression for the N2O + H ⇌ N2 + OH pathway, one of the most sensitive reaction steps, within the reported uncertainty has improved computational predictions of experimental flame speed data, although further optimization and validation of the kinetic mechanism are required.

CALIBRATION OF LASER INDUCED FLUORESCENCE OF THE OH RADICAL BY CAVITY RINGDOWN SPECTROSCOPY IN PREMIXED ATMOSPHERIC PRESSURE FLAMES

ABSTRACT Cavity ringdown spectroscopy (CRDS) of the hydroxyl radical (OH) has been explored in a laminar methane-air flame at atmospheric pressure over a range of equivalence ratio. Laser-induced fluorescence (LIF) of OH calibrated by CRDS in a lean flame compares well to PREMIX calculations using GRI-Mech 3.0. CRDS is a highly sensitive path-integrated diagnostic technique that can yield absolute absorber number densities via a relatively small number of measurable parameters. Among the chief advantages of CRDS is that the measurement is independent of laser power and that the same laser used for LIF can be used for CRDS with only a simple insertion of optics and detector for CRDS. Since LIF has a large dynamic range and high spatial resolution, it is the preferred OH diagnostic for flame studies; however, it is difficult to directly quantify LIF measurements. For this reason, quantitative OH LIF measurements are normally obtained by calibration of the LIF signal using an independent technique. The utility of quantitative OH CRDS measurements for calibration of LIF in these flames is shown.

Hydrogen- and C 1–C 3 Hydrocarbon-Nitrous Oxide Kinetics in Freely Propagating and Burner-Stabilized Flames, Shock Tubes, and Flow Reactors

A detailed, chemical mechanism has been compiled for modeling the combustion of C 1–C 3 hydrocarbon-nitrous oxide mixtures. The compiled, chemical mechanism has been compared and validated against available data in the literature, including flame structure measurements of hydrogen-nitrous oxide and ammonia-nitrous oxide flames, flow reactor data on hydrogen-nitrous oxide and moist, nitrous oxide decomposition mixtures, shock tube ignition delay data on hydrogen- and methane-nitrous oxide mixtures, experimental flame speed data on carbon monoxide-nitrous oxide mixtures, and experimental, laminar flame speed data for hydrogen-, methane-, acetylene-, and propane-nitrous oxide mixtures. Feature sensitivity studies and reaction path analyses have been employed to elucidate important pathways to the overall reaction rate for these systems, and include the nitrous oxide decomposition step (N 2 O(+M) ⇌ N 2 + O(+M)) and nitrous oxide reactions with H atoms (N 2 O + H ⇌ N 2 + OH and N 2 O + H ⇌ NH + NO). Modifications to the compiled mechanism were considered on the basis of the most sensitive reactions with the highest apparent rate constant uncertainty, to closely predict the various experimental data considered.

Design Considerations for Development of a Wire-Based Rock Cutting Mechanism for Space Exploration

Exploration and understanding of other celestial bodies will involve the same type of science used to understand our own planet earth. Specifically, much can be learned from studying the geology of the rocks present in a region of interest. One of the important tools used by geologists to understand and interpret rocks is a specimen called thin section. A thin section is produced by slicing a thin (typically 30 μm thick) plate or tablet from the rock. In this paper, the design of an autonomous rough cutter, used to produce the first stage of the specimen preparation, that is, a tablet (20 × 20 × 5 mm 3 ), is presented. Attention is given to the functional specification, the selection of cutting mechanism, in this case, diamond wire, and the design of the wire handling system. Also included are considerations of power usage, wire wear, and system configuration.

Pulsed cavity ringdown laser absorption spectroscopy in a hollow waveguide

Cavity ringdown laser absorption spectroscopy (CRDS) is a modified version of standard absorption spectroscopy (AS) for providing extremely sensitive measurements of gas species absorbing at a particular wavelength in a gas cell volume. Typically, the enhancement in sensitivity with CRDS is a 102-103 improvement over AS. Herein, we analyze incorporating pulsed CRDS into a hollow-waveguide (HWG) both for reducing the sample volume as well as enhancing the signal-to-noise ratio (SNR) by up to ~104 by injecting light into the HWG cavity through a small aperture in one of the cell mirrors. For low power instrument applications (i.e. planetary science), the enhancement in SNR results in a potential ~104 reduction in laser power for a comparable CRDS terrestrial laboratory measurement at one extreme, or a potential ~108 improvement in CRDS temporal resolution through reduced sample averaging with a fixed low-power laser source. A pulsed (vs. CW) laser source is employed to remove the requirement for a precision tuned laser cavity at ~wavelength spatial resolutions

System overview and characterization of a high-temperature, high-pressure, entrained-flow, laboratory-scale gasifier

The high-temperature, high-pressure, entrained-flow, laboratory-scale gasifier at the Colorado School of Mines, including the primary systems and the supporting subsystems, is presented. The gasifier is capable of operating at temperatures and pressures up to 1650 °C and 40 bar. The heated section of the reactor column has an inner diameter of 50 mm and is 1 m long. Solid organic feedstock (e.g., coal, biomass, and solid waste) is ground into batches with particle sizes ranging from 25 to 90 μm and is delivered to the reactor at feed rates of 2-20 g/min. The maximum useful power output of the syngas is 10 kW, with a nominal power output of 1.2 kW. The initial characterization and demonstration results of the gasifier system with a coal feedstock are also reported.

Cavity Ringdown Spectroscopy in a Hollow Bragg Waveguide: Electromagnetic Theory and Modeling

Cavity ringdown spectroscopy (CRDS) is a gas sensing technique in which an optical cavity is formed by two or more highly reflective mirrors. Herein we present an overview and historical perspective of CRDS implementations that seek to reduce or eliminate some of the disadvantages of conventional CRDS by modifications to the ringdown cavity (RDC). The hollow waveguide (HWG) CRDS concept that we introduce in this paper reduces some of the disadvantages of conventional CRDS by utilizing a hollow waveguide as the RDC. We develop the basic mathematical theory and model for the HWG-CRDS concept and provide an initial in-depth study of the Bragg waveguide for CRDS applications. We also discuss various aspects of design and performance characteristics of HWG-CRDS, including waveguide attenuation losses with and without gases in the waveguide core, transverse and longitudinal mode propagation behavior, and methods and analysis for the HWG-CRDS excitation.

A new experimental capability for the study of regolith surface physical properties to support science, space exploration, and in situ resource utilization (ISRU)

Many surfaces found on the Moon, asteroids, Mars, moons, and other planetary bodies are covered in a fine granular material known as regolith. Increased knowledge of the physical properties of extraterrestrial regolith surfaces will help advance the scientific knowledge of these bodies as well as the development of exploration (e.g., instrument and robotic) and in situ resource utilization (ISRU) systems. The Center for Space Resources at the Colorado School of Mines as part of the Institute for Modeling Plasma, Atmospheres, and Cosmic Dust of NASAs Solar System Exploration Research Virtual Institute has developed a novel system, called the ISRU Experimental Probe (IEP) that can support studies of dry and icy regolith from -196 to 150 °C and pressure from laboratory ambient pressure to 10-7 Torr. The IEP system and proof-of-concept results are presented in this paper.

Coal/Biomass Gasification at the Colorado School of Mines

This program was a 2.5 year effort focused on technologies that support coal and biomass gasification. Two primary tasks were included in the effort: 1) Coal/Biomass gasification and system optimization and 2) development of high temperature microchannel ceramic heat exchangers.