Characteristics of turbulent n-heptane jet flames in a hot and diluted coflow

Ye, Jingjing; Medwell, Paul R.; Evans, Michael J.; Dally, Bassam B.

doi:10.1016/j.combustflame.2017.05.027

Cited by 42 publications

(88 citation statements)

References 92 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Particle seeding must be ensured in the both the jet and hot coflow streams to ensure even and unbiased measurements in the mixing region. This requirement to seed particles into the coflow has restricted velocity measurements in JHC burners which generate hot and diluted coflows on porous bed burners (Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Ye et al, 2017Ye et al, , 2018Evans et al, 2019b;Kruse et al, 2019). Particle image velocimetry is a planar technique using Mie scattering from particles illuminated by a pair of pulsed lasers separated by a known time interval.…”

Section: Velocity-field Measurementsmentioning

confidence: 99%

“…Fundamental studies of these flames have not only provided significant insight into autoignition processes, but have been used to generate extensive datasets in simplified configurations for validating turbulence-chemistry interaction models for numerical modeling of combustion systems. Fundamental studies of laminar and turbulent jet flames issuing into high temperature, low oxygen environments have been undertaken in jet in hot coflow (JHC) burners (Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Oldenhof et al, 2010Oldenhof et al, , 2011Oldenhof et al, 2012;Medwell and Dally, 2012a;Sepman et al, 2013;Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Evans et al, 2017bEvans et al, , 2019aKruse et al, 2019), hot cross-flow burners (Sidey and Mastorakos, 2017), vitiated coflow burners (VCBs) (Cabra et al, 2002(Cabra et al, , 2005Gordon et al, 2008Gordon et al, , 2009Macfarlane et al, 2018Macfarlane et al, , 2019Ramachandran et al, 2019), and partially premixed jet burners (PPJBs) (Dunn et al, 2007a;Dunn et al, 2009), as have spray flames in hot coflow burners (Correia Rodrigues et al, 2015a,b;Wang et al, 2019b). In each case, fresh fuel issues from a jet into a stream of hot gas generated by lean premixed flames, resulting in 15% O 2 (by vol.).…”

Section: Introductionmentioning

confidence: 99%

“…Such improved understanding these transitions-and the structure of the upstream flames leading to their formation-may be achieved through targeted laser-diagnostics studies and subsequently validated, complementary numerical modeling. The high fidelity data that laser diagnostics can provide allows for the detailed study of reactive structures across the broad range of spatial and temporal scales in different optically-accessible JHC burners and reactors (Plessing et al, 1998;Cabra et al, 2002Cabra et al, , 2005Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Gordon et al, 2008Gordon et al, , 2009Oldenhof et al, 2010Oldenhof et al, , 2011Oldenhof et al, 2012;Medwell and Dally, 2012a;Sepman et al, 2013;Sorrentino et al, 2015Sorrentino et al, , 2016Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Evans et al, 2017bEvans et al, , 2019aSidey and Mastorakos, 2017;Macfarlane et al, 2018Macfarlane et al, , 2019Kruse et al, 2019;Ramachandran et al, 2019). Laser diagnostics a provide means to investigate the small-scale and distributed reaction zones in macroscopically-near-homogeneous MILD combustion conditions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Evans

Medwell

2019

Front. Mech. Eng.

Self Cite

View full text Add to dashboard Cite

There is a wealth of existing experimental data of flames collected using laser diagnostics. The primary objective of this review is to provide context and guidance in interpreting these laser diagnostic data. This educational piece is intended to benefit those new to laser diagnostics or with specialization in other facets of combustion science, such as computational modeling. This review focuses on laser-diagnostics in the context of the commonly used canonical jet-in-hot-coflow (JHC) burner, although the content is applicable to a wide variety of configurations including, but not restricted to, simple jet, bluff body, swirling and stratified flames. The JHC burner configuration has been used for fundamental studies of moderate or intense low oxygen dilution (MILD) combustion, autoignition and flame stabilization in hot environments. These environments emulate sequential combustion or exhaust gas recirculation. The JHC configuration has been applied in several burners for parametric studies of MILD combustion, flame reaction zone structure, behavior of fuels covering a significant range of chemical complexity, and the collection of data for numerical model validation. Studies of unconfined JHC burners using gaseous fuels have employed point-based Rayleigh-Raman or two-dimensional Rayleigh scattering measurements for the temperature field. While the former also provides simultaneous measurements of major species concentrations, the latter has often been used in conjunction with planar laser-induced fluorescence (PLIF) to simultaneously provide quantitative or qualitative measurements of radical and intermediary species. These established scattering-based thermography techniques are not, however, effective in droplet or particle laden flows, or in confined burners with significant background scattering. Techniques including coherent anti-Stokes Raman scattering (CARS) and non-linear excitation regime two-line atomic fluorescence (NTLAF) have, however, been successfully demonstrated in both sooting and spray flames. This review gives an overview of diagnostics techniques undertaken in canonical burners, with the intention of providing an introduction to laser-based measurements in combustion. The efficacy, applicability and accuracy of the experimental techniques are also discussed, with examples from studies of flames in JHC burners. Finally, current and future directions for studies of flames using the JHC configuration including spray flames and studies and elevated pressures are summarized.

show abstract

Section: Velocity-field Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Evans

Medwell

2019

Front. Mech. Eng.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Since auto-ignition is a complex process which occurs on short time scales and is very sensitive to thermal, mixing, and flow boundary conditions, experimental studies in technical systems with detailed diagnostics remain challenging. One option to study auto-ignition in a well-controlled environment with technical relevance and well-documented and reproducible boundary conditions are "Jet-in-Hot-Coflow" burners, which gained significant research interest in recent years [1][2][3][4][5][6][7][8]. In this configuration, (cold) fuel is injected into the hot exhaust gas of a lean hydrogen/air-flame, mimicking the mixing process of recirculated combustion products with fresh gas in GT combustors with recirculation.…”

Section: Introductionmentioning

confidence: 99%

“…In this configuration, (cold) fuel is injected into the hot exhaust gas of a lean hydrogen/air-flame, mimicking the mixing process of recirculated combustion products with fresh gas in GT combustors with recirculation. While several previous studies focused on methane or methane/hydrogen mixtures [1][2][3][4]9], only a few studies with heavier fuels such as ethylene [5,6,10], n-heptane [8], DME [7,11], or propane in laminar [12] and turbulent [11,13] environments exist. Additionally, previous studies have mainly focused on steady-state jet flames [1][2][3][4][5], while only a few studies on the formation mechanism of auto-ignition kernels exist [6,[14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of the auto-ignition of a transient propane Jet-in-Hot-Coflow

Arndt

Papageorge

Fuest

et al. 2019

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

Auto-ignition is a complex process which is extremely sensitive to boundary conditions such as local temperature, mixture or strain rate and occurs on very short timescales. Therefore, measurement techniques with high spatio-temporal resolution have to be applied to test cases with well-defined boundary conditions in order to generate high-quality validation data for numerical simulations. In the current paper, the auto-ignition of a transient propane jet-in-hot coflow was studied with high-speed OH* chemiluminescence imaging and high-speed Rayleigh scattering for the simultaneous determination of mixture fraction, mixture temperature and scalar dissipation rate immediately prior to the onset of auto-ignition. A variation of the coflow temperature showed a pronounced temperature dependence of the auto-ignition location and time, and the temperature sensitivity was higher than for a comparable methane test case from the literature. This is explained by the lower sensitivity of propane ignition delay times to the local strain rate in comparison to methane. The Rayleigh measurements however showed that the formation mechanism of auto-ignition kernels is similar for propane and methane. Ignition kernels were found to form upstream of bulges of the inflowing jet at locations with locally low scalar dissipation rate.

show abstract

Flame Self-interaction and Flow Topology in Turbulent Homogeneous Mixture n-Heptane MILD Combustion

Abo-Amsha

Chakraborty

2023

Flow Turbulence Combust

View full text Add to dashboard Cite

Moderate or Intense Low-oxygen Dilution (MILD) combustion has potential to achieve both high energy efficiency and ultra-low emissions. This analysis adopts the critical point theory to characterise the Flame-Self Interaction (FSI) events and flow topologies in turbulent, homogeneous mixture, n-Heptane MILD combustion using Direct Numerical Simulations (DNS) with reduced chemical mechanism. The local flame geometry has also been categorised using the mean and Gauss curvatures. It was found that the Tunnel Formation (TF) and Tunnel Closure (TC) topologies are the most probable FSI events at all values of the reaction progress variable c, while the Unburned Pocket (UP) and Burned Pocket (BP) topologies were mostly present towards the unburned and burned mixtures of the flame, respectively. Moreover, increasing the turbulence intensity did not result in any significant changes in the distribution of FSI events. Investigation of the flow topology distribution showed that the features associated with non-zero dilatation rate did not exist in the MILD cases considered. This is a consequence of the negligible thermal expansion effect due to the small temperature rise in MILD combustion cases. Increasing the dilution factor caused a reduction in the frequency of FSI events for all c levels. The distributions of flame self-interaction events in homogeneous mixture MILD combustion have been found to be significantly different from previously reported distributions for conventional turbulent premixed combustion.

show abstract

Characteristics of turbulent n-heptane jet flames in a hot and diluted coflow

Cited by 42 publications

References 92 publications

Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Experimental investigation of the auto-ignition of a transient propane Jet-in-Hot-Coflow

Flame Self-interaction and Flow Topology in Turbulent Homogeneous Mixture n-Heptane MILD Combustion

Contact Info

Product

Resources

About