New insights into the shock tube ignition of H2/O2 at low to moderate temperatures using high-speed end-wall imaging

Ninnemann, Erik; Köroğlu, Batikan; Pryor, Owen; Barak, Samuel; Nash, Leigh; Loparo, Zachary; Sosa, Jonathan; Ahmed, Kareem A.; Vasu, Subith

doi:10.1016/j.combustflame.2017.08.021

Cited by 71 publications

(16 citation statements)

References 58 publications

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“…These ignition cases may be termed 'mild ignition', following the terminology of Oppenheim [36]. Similar observations have recently been made in the shock tube imaging study of Ninnemann et al [15], where they ascribed 'mild ignition' to high-concentration hydrogen ignition cases at T < 1000 K. [14]), combustion product deposits, diaphragm pieces from previous experiments, or interaction of the reflected shock wave with the boundary layer. However, it should be noted that the locations of the initial emission spots were not the same from one experiment to another.…”

Section: High-speed Imaging Experimentsmentioning

confidence: 60%

“…Such ignition cases represent localized ignition processes, as described later with OH* imaging experiments, and should not be used as such for validating chemical kinetic models. To this end, we would like to differ with the conclusions of the recent study of Ninnemann et al [15] who argued that the low-temperature hydrogen ignition cases affected by preignition were adequately modeled by simulations with dP/dt correction. In fact, one can observe clearly in Fig.…”

Section: Ignition Delay Time Measurementsmentioning

confidence: 76%

“…Troutman et al [14] analyzed the inhomogeneous combustion of n-heptane mixtures and related their findings to optical window recessions and cleanliness in the shock tube facility. Recently, Ninnemann et al [15] observed preignition for high-concentration hydrogen/oxygen mixtures, identifying mild combustion events starting with weak flame kernels.…”

Section: Introductionmentioning

confidence: 99%

“…High-speed OH* chemiluminescence may be related to the rate of heat release of the observed phenomenon [22]. Some imaging experiments have recently been performed in shock tubes for the investigation of combustion homogeneity with various fuels, such as n-heptane, hydrogen and syngas [14][15][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

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Shock tube studies of ethanol preignition

Figueroa-Labastida

Badra

Elbaz

et al. 2018

Combustion and Flame

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CitationFigueroa-Labastida M, Badra J, Elbaz AM, Farooq A (2018) Shock tube studies of ethanol preignition. . Available: http://dx. AbstractUnderstanding premature ignition or preignition is of great importance as this phenomenon influences the design and operation of internal combustion engines. Preignition leading to super-knock restricts the efficiency of downsized boosted engines. To gain a fundamental understanding of preignition and how it affects an otherwise homogeneous ignition process, a shock tube may be used to decipher the influence of fuel chemical structure, temperature, pressure, equivalence ratio and bath gas on preignition. In a previous work by Javed et al.[1], ignition delay time measurements of nheptane showed significantly expedited reactivity compared to well-validated chemical kinetic models in the intermediate-temperature regime. In the current work, ethanol is chosen as a representative fuel that, unlike n-heptane, does not exhibit negative temperature coefficient (NTC) behaviour. Reactive mixtures containing 2.9% and 5% of ethanol at equivalence ratios of 0.5 and 1 were used for the measurement of ignition delay times behind reflected shock waves at 2 and 4 bar. Effect of bath gas was studied with mixtures containing either Ar or N2. In addition to conventional side-wall pressure and OH* measurements, a high-speed imaging setup was utilized to visualize the shock tube crosssection through a transparent quartz end-wall. The results suggest that preignition events are more likely to happen in mixtures containing higher ethanol concentration and that preignition energy release is more pronounced at lower temperatures. High-speed imaging shows that low-temperature ignition process is usually initiated from an individual hot spot that grows gradually, while hightemperatures ignition starts from many spots simultaneously which consume the reactive mixture almost homogeneously.

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Section: High-speed Imaging Experimentsmentioning

confidence: 60%

Section: Ignition Delay Time Measurementsmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shock tube studies of ethanol preignition

Figueroa-Labastida

Badra

Elbaz

et al. 2018

Combustion and Flame

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“…Shock tubes are ideal laboratory devices for producing controlled hightemperature and pressure conditions that exist inside gas turbines. Measurements were performed in a stainless-steel, heated, double-diaphragm shock tube with an inner diameter of 14 cm, located at the University of Central Florida, which has been described in our prior work [3,[12][13][14][20][21][22]. The driver and driven sections of the shock tube are separated by a polycarbonate diaphragm 0.381 mm thick which suddenly ruptures to create a normal shock wave which shock heats the test mixture.…”

Section: Methodsmentioning

confidence: 99%

Shock Tube Demonstration of Acousto-Optically Modulated Quantum Cascade Laser as a Broadband, Time-Resolved Combustion Diagnostic

Loparo

Ahmed

Vasu

et al. 2018

Journal of Energy Resources Technology

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We provide the first demonstration of an acousto-optically modulated quantum cascade laser (AOM QCL) system as a diagnostic for combustion by measuring nitric oxide (NO), a highly regulated emission produced in gas turbines. The system provides time-resolved broadband spectral measurements of the present gas species via a single line of sight measurement, offering advantages over widely used narrowband absorption spectroscopy (e.g., the potential for simultaneous multispecies measurements using a single laser) and considerably faster (>15 kHz rates and potentially up to MHz) than sampling techniques, which employ fourier transform infrared (FTIR) or GC/MS. The developed AOM QCL system yields fast tunable output covering a spectral range of 1725–1930 cm−1 with a linewidth of 10–15 cm−1. For the demonstration experiment, the AOM QCL system has been used to obtain time-resolved spectral measurements of NO formation during the shock heating of mixture of a 10% nitrous oxide (N2O) in a balance of argon over a temperature range of 1245–2517 K and a pressure range of 3.6–5.8 atm. Results were in good agreement with chemical kinetic simulations. The system shows revolutionary promise for making simultaneous time-resolved measurements of multiple species concentrations and temperature with a single line of sight measurement.

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Influence of the double bond position in combustion chemistry of methyl butene isomers: A shock tube and laser absorption study

Arafin

Laich

Ninnemann

et al. 2020

Int J of Chemical Kinetics

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Shock tube experiments have been carried out on 2-methyl-1-butene (2M1B), 2-methyl-2-butene (2M2B), and 3-methyl-1-butene (3M1B)-the three isomers of methyl butene compound. Carbon monoxide (CO) time-histories and ignition delay times are obtained behind reflected shockwaves over the temperature range of 1350-1630 K and pressures of 8.3-10.5 atm with stoichiometric mixtures of 0.075% fuel in O 2 /Ar. Comparative ignition study reveals that 3M1B ignites significantly faster than the other two isomers, while 2M1B dissociates earlier but ignites later than 2M2B. Possible mechanisms for this behavior are discussed with ignition delay time sensitivity and reaction path analysis. In addition, timeresolved CO measurements are compared with three different reaction mechanisms from the literature. Sensitivity analyses have been carried out to identify important reactions that need attention to accurately predict the chemistry of these isomers. Further investigation into the rates of unimolecular fuel decomposition reactions and C 3 H 3 + O 2 = CH 2 CO + HCO reaction are suggested based on the current investigation.

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New insights into the shock tube ignition of H2/O2 at low to moderate temperatures using high-speed end-wall imaging

Cited by 71 publications

References 58 publications

Shock tube studies of ethanol preignition

Shock tube studies of ethanol preignition

Shock Tube Demonstration of Acousto-Optically Modulated Quantum Cascade Laser as a Broadband, Time-Resolved Combustion Diagnostic

Influence of the double bond position in combustion chemistry of methyl butene isomers: A shock tube and laser absorption study

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