Biography:

In the past R. Mitchell Spearrin has collaborated on articles with Daniel I. Pineda and Kevin K. Schwarm. One of their most recent publications is Multi-isotopologue laser absorption spectroscopy of carbon monoxide for high-temperature chemical kinetic studies of fuel mixtures. Which was published in journal Combustion and Flame.

More information about R. Mitchell Spearrin research including statistics on their citations can be found on their Copernicus Academic profile page.

R. Mitchell Spearrin's Articles: (5)

Multi-isotopologue laser absorption spectroscopy of carbon monoxide for high-temperature chemical kinetic studies of fuel mixtures

AbstractA laser absorption diagnostic technique, probing the mid-infrared vibrational bands of 12C16O and 13C16O near 4.9 µm, was developed for sensitive multi-isotopologue temperature and concentration measurements in high-temperature gaseous systems. Transitions in each of the P-branches of the fundamental bands of 12C16O and 13C16O were chosen based on absorption linestrength, relative spectral isolation, and temperature sensitivity. Five total rovibrational transitions are spectrally-resolved over a  ∼ 1.2 cm−1 domain using a 50 kHz triangle scan function with a distributed-feedback quantum cascade laser, yielding a 100 kHz effective measurement rate of both isotopologues and respective temperatures, independent of mixture composition. In addition, relevant broadening parameters for the P(0,22) transition of 13C16O near 2007.8767 cm−1 were measured to enable higher time resolution ( > 1 MHz) measurements using fixed-wavelength methods. Time-resolved multi-isotopologue thermometry performance was validated in a shock tube over a range of temperatures (1100–2400 K) relevant to combustion kinetics investigations. The technique is utilized in shock-heated oxidation experiments with isotopically labeled fuel mixtures, simultaneously measuring both carbon monoxide isotopologues throughout the reactions. To the authors’ knowledge, these results demonstrate the first use of carbon isotope labeling with laser absorption spectroscopy to observe distinct competitive oxidation among different fuel components.

High-pressure and high-temperature gas cell for absorption spectroscopy studies at wavelengths up to 8 µm

Highlights•Optical gas cell design for absorption spectroscopy studies at extreme conditions.•CaF2 optics enable mid-wave IR measurements up to 8 µm at both  > 100 atm and  > 1000 K.•Evidence of line mixing and undocumented transitions observed in ν4 band of CH4.

Design-build-launch: a hybrid project-based laboratory course for aerospace engineering education

Highlights•10-week rocket design-build-launch course developed for aerospace education.•Project-based learning hybridized with structured laboratory sessions.•Integration of industry-relevant analytical tools, manufacturing & testing methods.

Constrained reaction volume shock tube study of n-heptane oxidation: Ignition delay times and time-histories of multiple species and temperature

AbstractIgnition delay times of normal heptane have been measured at temperatures ranging from 651 to 823 K and at pressures between 6.1 and 7.4 atm at an equivalence ratio of 0.75 in 15%O2/5%CO2/Ar and in 15%O2/Ar mixtures behind reflected shock waves in a shock tube. Time-history measurements of fuel, OH, aldehydes (mostly CH2O), CO2, H2O, and temperature were also measured under these conditions. These time-histories provide critically needed kinetic targets to test and refine large reaction mechanisms. Measurements were acquired using a novel constrained reaction volume approach, wherein a sliding gate valve confined the reactant mixture to a region near the endwall of the shock tube. A staged-driver gas filling strategy, combined with driver section extensions, driver inserts, and driver gas tailoring, was used to obtain constant-pressure test times of up to 55 ms, allowing observations of the chemistry in the Negative Temperature Coefficient (NTC) region. Experiments with conventional shock tube filling were also performed, showing similar overall ignition behavior. Comparisons between current data and simulations using the Mehl et al. n-Heptane mechanism (2011) are provided, revealing that the mechanism generally under-predicts first-stage ignition delay times in the NTC region, and that at low temperatures it over-predicts the extent of fuel decomposition during first stage ignition.

Single-ended mid-infrared laser-absorption sensor for time-resolved measurements of water concentration and temperature within the annulus of a rotating detonation engine

AbstractA novel single-ended mid-infrared laser-absorption sensor for time-resolved measurements of water mole fraction and temperature was developed and deployed within the annulus of a hydrogen/air-fed rotating detonation engine (RDE). The sensor transmitted two laser beams targeting mid-infrared water transitions through a single optical port on the outer wall of the cylindrical RDE annulus and measured the backscattered radiation from the RDE inner surface using a photodetector for a round-trip path of 1.52 cm. Optimizing the sensor's optical arrangement using numerical ray tracing to minimize interference from optical emission, beam steering, and scattered laser light from window surfaces was essential to sensor performance. Scanned-wavelength-modulation spectroscopy with second-harmonic detection and first-harmonic normalization was implemented to allow for frequency-domain multiplexing of the two lasers and to suppress non-absorbing interference sources such as beam-steering and emission. Tunable diode lasers near 2551 and 2482 nm were modulated at 100 and 122 kHz, respectively, and sinusoidally scanned across the peaks of their respective water transitions at 10 kHz to provide a measurement rate of 20 kHz and detection limit of 0.5% water by mole. Experimentally derived spectroscopic parameters enabled water and temperature sensing with respective uncertainties of 7.3% and 5.3% relative to the measured values. Time-resolved and time-averaged sensor measurements of gas temperature and water vapor mole fraction allow quantitative evaluation of the combustion progress at the measurement location and thus provide a design tool for RDE optimization. Broadly, this single-ended laser sensor should find applications in other combustion systems where optical access is limited.

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