Application: Combustion diagnostics
Product: IRis-F1
Nicolas Hunter Pinkowski, Pujan Biswas, Jiankun Shao, Christopher L Strand and Ronald K Hanson
Measurement Science and Technology; 2021
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Quantum-cascade-laserdual-comb spectroscopy (QCL-DCS) is a promising technology with ultra-fast time resolution capabilities for chemical kinetics, atmospheric gas sensing, and combustion applications. A pair of quantum-cascade frequency combs were used to measure absorbance from methane's 4 band between 1270 cm-1 and 1315 cm-1 at high-temperature and -pressure conditions that were generated using a high-pressure shock tube. Results here mark a major improvement over previous QCL-DCS measurements in shock tubes. Improvements came from a unique spectral-filtering strategy to correct for a bimodal power-spectral density of QCL frequency combs and careful optimization of the laser setup and experimental conditions. Our modified QCL-DCS was ultimately used to measure temperature within 2% and methane mole fraction within 5% by fitting HITEMP spectral simulations to spectra recorded at 4-μs temporal resolution. We measure temperature and species time-histories during methane pyrolysis at conditions between 1212-1980 K, and 12-17 atm, all at 4-μs resolution. Good agreement is observed with kinetic models, illustrating the potential of future applications of DCS in kinetics and combustion research.
Application: Combustion diagnostics, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Pinkowski, Nicolas Hunter; Ding, Yiming; Strand, Christopher L.; Hanson, Ronald K.; Horvarth, Raphael; Geiser, Markus
Measurement Science and Technology; 2020
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In the current study, a quantum-cascade-laser-based dual-comb spectrometer (DCS) was used to paint a detailed picture of a 1.0 ms high-temperature reaction between propyne and oxygen. The DCS interfaced with a shock tube to provide pre-ignition conditions of 1225 K, 2.8 atm, and 2% p-C3H4/18% O2/Ar. The spectrometer consisted of two free-running, non-stabilized frequency combs each emitting at 179 wavelengths between 1174 and 1233 cm−1. A free spectral range, {f_r}, of 9.86 GHz and a difference in comb spacing, {Delta }{f_r}, of 5 MHz, enabled a theoretical time resolution of 0.2 µs but the data was time-integrated to 4 µs to improve SNR. The accuracy of the spectrometer was monitored using a suite of independent laser diagnostics and good agreement observed. Key challenges remain in the fitting of available high-temperature spectroscopic models to the observed spectra of a post-ignition environment.
Application: Combustion diagnostics, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Guangle Zhang, Raphael Horvath, Dapeng Liu, Markus Geiser, Aamir Farooq
Sensors, MDPI; 2020
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Rapid multi-species sensing is an overarching goal in time-resolved studies of chemical kinetics. Most current laser sources cannot achieve this goal due to their narrow spectral coverage and/or slow wavelength scanning. In this work, a novel mid-IR dual-comb spectrometer is utilized for chemical kinetic investigations. The spectrometer is based on two quantum cascade laser frequency combs and provides rapid (4 µs) measurements over a wide spectral range (~1175–1235 cm−1). Here, the spectrometer was applied to make time-resolved absorption measurements of methane, acetone, propene, and propyne at high temperatures (>1000 K) and high pressures (>5 bar) in a shock tube. Such a spectrometer will be of high value in chemical kinetic studies of future fuels.
Application: Combustion diagnostics, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Pinkowski, N.; Strand, C. L.; Ding, Y.; Hanson, R. K.; Geiser, M.; Horvath, R.
Presentation at ISSW32; 2019
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Application: Combustion diagnostics, Gas analysis, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Peter Fjodorow, Pitt Allmendinger, Raphael Horvath, Jürgen Herzler, Florian Eigenmann, Markus Geiser, Mustapha Fikri and Christof Schulz
Applied Physics B volume 126, Article number: 193; 2020
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A dual-frequency-comb spectrometer based on two quantum-cascade lasers is applied to kinetics studies of formaldehyde (HCHO) in a shock tube. Multispectral absorption measurements are carried out in a broad spectral range of 1740–1790 cm–1 at temperatures of 800–1500 K and pressures of 2–3 bar. The formation of HCHO from thermal decomposition of 1,3,5-trioxane (C3H6O3, 0.9% diluted in argon) and the subsequent oxidation of formaldehyde is monitored with a time resolution of 4 µs. The rate coefficient of the decomposition of C3H6O3 (i.e., HCHO formation) is found to be k1 = 6.0 × 1015 exp(− 205.58 kJ mol−1/RT) s–1. For the oxidation studies, mixtures of 0.36% C3H6O3 and 1% O2 in argon are used. The information of all laser lines, along with the consideration of individual signal variance of each line, is utilized for kinetic and spectral analysis. The experimental kinetic profiles of HCHO are compared with simulations based on the mechanisms of Zhou et al. (Combust Flame, 197:423–438, 2018) and Cai and Pitsch (Combust Flame, 162:1623–1637, 2015).
Application: Combustion diagnostics, High resolution spectroscopy
Product: IRis-F1
Nicolas Hunter Pinkowski, Sean Joseph Cassady, Christopher L Strand and Ronald K Hanson
Measurement Science and Technology; 2020
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This work presents a methodology for using spectroscopic models to fit absorption-spectrum measurements made by a quantum-cascade-laser-based dual-comb (QCL-DCS) spectrometer for high-temperature kinetics research. A pair of quantum-cascade frequency combs was employed to detect methane's ν4 absorption features between 1270-1320 cm-1 in high-temperature shock-tube environments and extract methane mole fraction and gas temperature from the results. The methodology was first validated by comparing DCS measurements against modeled methane spectra at room temperature in a static cell, followed by assessing the fitting procedure in shock-heated mixtures of 2% methane in Ar at 1000 K. In both validation experiments, the tradeoffs between time resolution and measurement precision were explored. Measurements were achieved at a 4-μs measurement rate with 5% uncertainty for temperature and 4% uncertainty for mole fraction at 1000 K. Higher accuracy was achieved with longer measurement averaging, e.g. 1.8% uncertainty for temperature at 40-μs resolution. Finally, the DCS spectral-fitting methodology was demonstrated to capture temperature and methane time-history evolution during the pyrolysis of iso-octane, a primary gasoline reference fuel. Good agreement was observed with kinetic models, and future applications for DCS kinetics research are discussed.