Planar laser-induced fluorescence imaging of flame heat release rate

Paul, Phillip H.; Najm, Habib N.

doi:10.1016/s0082-0784(98)80388-3

Cited by 236 publications

(101 citation statements)

References 19 publications

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“…It is worthwhile to consider the location of the region of OH and CH 2 O in ξ -space with relation to the HRR profile. As discussed earlier, the pixel-by-pixel product of OH-PLIF and CH 2 O-PLIF is an experimental marker for HRR, used in gaseous [33][34][35] and liquid [36] fuel configurations. The relationship between the overlap of OH and CH 2 O and HRR regions will be discussed in Section 3.4.…”

Section: Counterflow Flame Structurementioning

confidence: 99%

“…Since preheat and dilution have been shown to alter the heat release characteristics [2,3,6,12], it is essential to investigate the effect of hot product dilution on heat release rate profiles and therefore explore possibilities of experimental markers used to map them. In particular, the experimental technique of using the product of OH-and CH 2 O-PLIF signals is conventionally used as a marker of heat release for both gaseous [33][34][35] and, more recently, liquid fuels [36]. This method would be valid as an experimental HRR marker only if laminar flame calculations show that the overlap of OH and CH 2 O mimics the local reaction zone.…”

Section: Introductionmentioning

confidence: 99%

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Simulations of laminar non-premixed flames of kerosene with hot combustion products as oxidiser

Sidey

Giusti

Mastorakos

2016

Combustion Theory and Modelling

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The effects of hot combustion product dilution in a pressurised kerosene-burning system at gas turbine conditions were investigated with laminar counterflow flame simulations. Hot combustion products from a lean (φ = 0.6) premixed flame were used as an oxidiser with kerosene surrogate as fuel in a non-premixed counterflow flame at 5, 7, 9 and 11 bar. Kerosene-hot product flames, referred to as 'MILD', exhibit a flame structure similar to that of kerosene-air flames, referred to as 'conventional', at low strain rates. The Heat Release Rate (HRR) of both conventional and MILD flames reflects the pyrolysis of the primary and intermediate fuels on the rich side of the reaction zone. Positive HRR and OH regions in mixture fraction space are of similar width to conventional kerosene flames, suggesting that MILD flames are thin fronts. MILD flames do not exhibit typical extinction behaviour, but gradually transition to a mixing solution at very high rates of strain (above A = 160, 000 s −1 for all pressures). This is in agreement with literature that suggests heavily preheated and diluted flames have a monotonic S-shaped curve. Despite these differences in comparison with kerosene-air flames, MILD flames follow typical trends as a function of both strain and pressure. Further still, the peak locations of the overlap of OH and CH 2 O mass fractions in comparison with the peak HRR indicate that the pixel-by-pixel product of OH-and CH 2 O-PLIF signals is a valid experimental marker for non-premixed kerosene MILD and conventional flames.

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Section: Counterflow Flame Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulations of laminar non-premixed flames of kerosene with hot combustion products as oxidiser

Sidey

Giusti

Mastorakos

2016

Combustion Theory and Modelling

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“…OH is not a good marker for flame front imaging and this is the cause of current controversial results: Laser-induced fluorescence of OH is one of the most commonly used flame front markers. Although a recent experimental effort implied that OH is not as good as the product of OH and CH 2 O as an indicator of heat release rate (Paul and Najm, 1998), it is adequate to mark the flame front location (Gü lder et al, 2000). 2.…”

Section: ö L Gü Lder and G J Smallwoodmentioning

confidence: 99%

Flame Surface Densities in Premixed Combustion at Medium to High Turbulence Intensities

Gülder

Smallwood

2007

Combustion Science and Technology

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The surface densities of flame fronts in turbulent premixed propane= air flames were determined experimentally. The instantaneous flame fronts were visualized using laser induced fluorescence (LIF) of OH on two Bunsen type burners of 11.2 and 22.4 mm diameters. Nondimensional turbulence intensity, u 0 =S L , was varied from 0.84 to 15, and the Reynolds number, based on the integral length scale, varied from 34 to 467. These flames are in the flamelet combustion regime as defined by the most recent turbulent premixed combustion diagrams. From 100 to 800 images were recorded for each experimental condition. Flame surface densities were obtained from the instantaneous maps of the progress variable, which is zero in the reactants and unity in the products. These flame surface densities were corrected for the mean direction cosines of the flame fronts, which had a typical value of 0.69 for the Bunsen flames. In the non-dimensional turbulence intensity range of up to 15, it was found that the maximum flame surface density and the integrated flame surface density across the flame brush do not show any significant dependence on turbulence intensity. This was discussed in the framework of a flame surface density-based turbulent premixed flame propagation closure model.

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“…The product of OH and CH 2 O by simultaneous LIF images was firstly reported by Paul and Najm (1998) as a good indicator for laminar flames. It was also adopted in the study of the lean premixed turbulent flames (Balachandran et al 2005).…”

Section: Introductionmentioning

confidence: 88%

A study on heat release rate indicator in the auto-igniting droplets using direct numerical simulation

Chen

2016

JTST

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Local heat release rate is one of the most concerned parameters in the combustion processes. However, this parameter is hard to be measured directly in the experiments. Therefore local heat release rate indicators have been sought and evaluated, and many works focus on the study in the gaseous laminar or turbulent premixed flames. The motivation of this work is to explore and validate heat release rate indicators for auto-igniting n-heptane droplets. To this end, direct numerical simulation (DNS) is performed with a detailed chemical reacting mechanism. Results show that the product of mass fractions of OH and CH 2 O is a proper indicator when the local auto-ignition prevails and the temperature rises quickly. The elementary reactions involved are analyzed, which shed light on the construction and performance of heat release rate indicators. Some new definitions of the indicators are proposed and evaluated. The proportional relationship between the indicator and the actual local heat release rate is determined. The heat release associated with different combustion regimes are distinguished, which reveals the dominant role of premixed flames in the droplets auto-ignition processes. Currently, most of the reported HRIs are for gaseous laminar and turbulent premixed flames. Their validity and performance in the two-phase combustion or in higher hydrocarbons flames need be evaluated. More importantly, the mechanism of what makes it a proper HRI or how to find a good HRI has not been investigated systematically. The quantitative relationship between the indicator and the actual local heat release rate is not yet determined in the turbulent studies. This paper aims to make a contribution to the above issues by numerical simulation. Direct numerical simulation (DNS) is performed to study the HRIs for the auto-igniting n-heptane droplets distributed in the hot vitiated flow.DNS is believed to resolve the turbulence completely, and it has been extended to the study of two-phase combustion. Auto-ignition of the liquid droplets in hot circumstance is one interested topic of DNS (Baba and Kurose 2008;Fujita et al. 2013;Kitano et al. 2013). The specific methods include two dimensional (2D) DNS coupled with the detailed reacting mechanism (Wang and Rutland 2007;Yoo et al. 2009;Wang and Rutland 2005) and 3D DNS coupled with the simplified reacting mechanism (Wang et al. 2012;Schroll et al. 2009;Wang et al. 2014). The effects of the relevant parameters, e.g. the overall equivalence ratio, the droplet diameter and its distribution, the initial gas temperature, pressure on ignition delay time were examined Rutland 2005, 2007;Im et al. 1998). So far, 3D DNS coupled with the detailed reacting mechanism (Borghesi et al. 2013) is rare due to huge requirement of calculation resources. Meanwhile, DNS also favors to the optimization of the related models in gaseous or two-phase combustion simulation. For instance, the droplets evaporation model coupled with the detailed chemical reacting mechanism is a concerned issue. Recently...

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Planar laser-induced fluorescence imaging of flame heat release rate

Cited by 236 publications

References 19 publications

Simulations of laminar non-premixed flames of kerosene with hot combustion products as oxidiser

Simulations of laminar non-premixed flames of kerosene with hot combustion products as oxidiser

Flame Surface Densities in Premixed Combustion at Medium to High Turbulence Intensities

A study on heat release rate indicator in the auto-igniting droplets using direct numerical simulation

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