Study of ignition chemistry on turbulent premixed flames of n-heptane/air by using a reactor assisted turbulent slot burner

Windom, Bret; Won, Sang Hee; Reuter, Christopher B.; Jiang, Bo; Ju, Yiguang; Hammack, Stephen D.; Ombrello, Timothy; Carter, Campbell

doi:10.1016/j.combustflame.2016.02.031

Cited by 28 publications

(12 citation statements)

References 41 publications

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“…chemistry, and associated heat release can perturb the flame structure, especially under complex mixing scenarios used in modern gas turbine engines [34,35]. As such, the availability of reliable, verified chemical kinetic mechanisms for the pressures and temperatures prevalent in the premixing (autoignition) zone of gas turbines (initial pressures up to 50 bar, temperatures up to 1200 K) is essential to aid future turbine design.…”

Section: Introductionmentioning

confidence: 99%

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

Goldsborough

Hochgreb

Vanhove

et al. 2017

Progress in Energy and Combustion Science

187

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Rapid compression machines (RCMs) are widely-used to acquire experimental insights into fuel autoignition and pollutant formation chemistry, especially at conditions relevant to current and future combustion technologies. RCM studies emphasize important experimental regimes, characterized by lowto intermediate-temperatures (600-1200 K) and moderate to high pressures (5-80 bar). At these conditions, which are directly relevant to modern combustion schemes including low temperature combustion (LTC) for internal combustion engines and dry low emissions (DLE) for gas turbine engines, combustion chemistry exhibits complex and experimentally challenging behaviors such as the chemistry attributed to cool flame behavior and the negative temperature coefficient regime. Challenges for studying this regime include that experimental observations can be more sensitive to coupled physicalchemical processes leading to phenomena such as mixed deflagrative/autoignitive combustion. Experimental strategies which leverage the strengths of RCMs have been developed in recent years to make RCMs particularly well suited for elucidating LTC and DLE chemistry, as well as convolved physicalchemical processes. Specifically, this work presents a review of experimental and computational efforts applying RCMs to study autoignition phenomena, and the insights gained through these efforts. A brief history of RCM development is presented towards the steady improvement in design, characterization, instrumentation and data analysis. Novel experimental approaches and measurement techniques, coordinated with computational methods are described which have expanded the utility of RCMs beyond empirical studies of explosion limits to increasingly detailed understanding of autoignition chemistry and the role of physical-chemical interactions. Fundamental insight into the autoignition chemistry of specific fuels is described, demonstrating the extent of knowledge of low-temperature chemistry derived from RCM studies, from simple hydrocarbons to multi-component blends and full-boiling range fuels. Emerging needs and further opportunities are suggested, including investigations of under-explored fuels and the implementation of increasingly higher fidelity diagnostics.

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Section: Introductionmentioning

confidence: 99%

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

Goldsborough

Hochgreb

Vanhove

et al. 2017

Progress in Energy and Combustion Science

187

View full text Add to dashboard Cite

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“…These low-temperature cool flames have also been shown to be an important influence on engine knock [12] and can extend the lean flammability limit [13][14][15]. Even in continuous combustion systems such as gas turbines, the low-temperature chemistry can significantly modify the fuel composition, which in turn may affect the turbulent burning velocity [16,17] or stabilization mechanism [18,19] of the main flame and possibly contribute to phenomena such as lean blow off [20]. As a result, the low-temperature oxidation of hydrocarbon fuels has received much attention over the years [21].…”

Section: Introductionmentioning

confidence: 99%

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Reuter

Lee

Won

et al. 2017

Combustion and Flame

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The low-temperature oxidation of hydrocarbon fuels has received increasing attention as advanced engines seek to operate in less conventional combustion regimes. Large n-alkanes are a notable component of many real transportation fuels and possess strong reactivity in this important low-temperature range. These n-alkanes have been studied extensively in various canonical kinetic experiments but seldom in systems with strong coupling between lowtemperature chemistry, transport, and heat release. To address this issue, the present study investigates self-sustaining n-alkane cool diffusion flames in a counterflow burner. The extinction limits of both hot diffusion flames and cool diffusion flames are measured at atmospheric pressure for a range of n-alkanes from n-heptane to n-tetradecane. It is observed that while these fuels behave similarly for hot flames, the larger n-alkanes are substantially more reactive in the low-temperature cool flame regime. Moreover, ozone addition strongly enhances the low-temperature chemistry to the point where the differences in fuel reactivity are nearly suppressed.The experimental measurements are compared with numerical simulations employing both detailed and reduced chemical kinetic models of various sizes. Although the different kinetic models adequately predict the extinction limits of the hot flames, a large scatter is present in the model results for cool flames, and a general overprediction of the measured cool flame extinction limit is observed for all of the fuels studied. This implies that the cool flame heat release is not well agreed upon by the current chemical kinetic models, despite their capability to reproduce many homogeneous reactor experiments at low temperatures. Furthermore, it is observed that the cool flame heat release is spread over a substantial number of reactions involving large molecules, a trait that makes it particularly difficult to create reduced kinetic models that can accurately describe cool flame behavior. The results of this study suggest that the cool flame platform can provide crucial validation of the coupling between chemistry, transport, and heat release in flames at low temperatures. 2 3 4 5 6 7 8

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“…The Co-flow Axisymmetric Reactor-Assisted Turbulent (CARAT) burner, depicted in Figure 1, is a generational update to the Reactor-Assisted Turbulent Slot (RATS) burner 11,12 . Like the RATS burner, the CARAT burner is a Bunsen-type burner with an extended reactor section capable of controlling the pre-flame residence time and temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Gokalp 9 and Koliatis 10 studied premixed cool flames within reactors subject to various degrees of turbulence. Some of the authors' previous experiments 11,12 involved turbulent premixed flames that were strongly affected by low-temperature ignition, but no cool flame fronts were actually visible in those experiments. Recent numerical simulations have shown that cool flames can play an important role in the ignition [13][14][15] , stabilization 16 , and propagation 17 of turbulent flames.…”

Section: Introductionmentioning

confidence: 98%

Experimental Investigation of the Stabilization and Structure of Turbulent Cool Diffusion Flames

Reuter

Yehia

Won

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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Although recent studies of laminar cool flames have provided important advances in understanding the low-temperature chemistry of both hydrocarbons and oxygenates, there has been limited experimental insight into how interactions between turbulence and chemistry occur in cool flames. To address this, a new Co-flow Axisymmetric Reactor-Assisted Turbulent (CARAT) burner has been developed and characterized in this investigation for the purpose of directly studying turbulent cool flames. A methodology for establishing stable turbulent cool diffusion flames under well-defined conditions is proposed. The structure of dimethyl ether flames is examined using both formaldehyde planar laserinduced fluorescence and Rayleigh scattering. It is found that weak turbulence produces wrinkled turbulent cool flames in which fluctuations occur mainly on the fuel side of the flame. However, at increased levels of turbulence, large pockets of unburned reactants appear in the vicinity of the cool flame, and structural fluctuations extend to both sides of the flame. This study offers a well-defined experimental platform for the study of turbulence-chemistry interactions at low temperatures.

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Study of ignition chemistry on turbulent premixed flames of n-heptane/air by using a reactor assisted turbulent slot burner

Cited by 28 publications

References 41 publications

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Experimental Investigation of the Stabilization and Structure of Turbulent Cool Diffusion Flames

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