Validation of leading point concept in RANS simulations of highly turbulent lean syngas-air flames with well-pronounced diffusional-thermal effects

Verma, Salman; Monnier, Florian; Lipatnikov, Andrei

doi:10.1016/j.ijhydene.2021.01.022

Cited by 13 publications

(5 citation statements)

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“…From this perspective, the leading-point concept, which highlights a strong increase in the mean local consumption velocity near the leading edges of the discussed flames (Kuznetsov & Sabelnikov 1990; Lipatnikov & Chomiak 2005; Verma et al. 2021), appears to be the best tool available today, at least for predicting . Other approaches that could be invoked to address the influence of on the mean local consumption velocity were not addressed in the present work, but could be explored in future studies.…”

Section: Discussionmentioning

confidence: 99%

“…Accordingly, a fuel consumption rate pre-computed for the critically strained laminar premixed flame can directly be used as an input parameter for numerical simulations of turbulent combustion of mixtures characterized by a low (Verma et al. 2021).…”

Section: Discussionmentioning

confidence: 99%

“…2011, 2013, 2015; Zhang et al. 2018) and to quantitatively predict measured results using Reynolds-averaged Navier–Stokes computations (Karpov, Lipatnikov & Zimont 1996 a ; Verma, Monnier & Lipatnikov 2021). The method was also supported in a DNS study (Lee et al.…”

Section: Background and Research Goalsmentioning

confidence: 99%

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Displacement speed, flame surface density and burning rate in highly turbulent premixed flames characterized by low Lewis numbers

et al. 2023

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Direct numerical simulation data obtained from four pairs of turbulent, lean hydrogen–air, complex-chemistry flames are analysed to explore the influence of molecular diffusion on flame surface density, displacement speed $S_d$ and the flame surface density transport equation terms. Each pair involves (i) a flame where mixture-averaged molecular diffusivities are adopted and Lewis number $Le$ is significantly less than unity and (ii) an equidiffusive flame where all molecular diffusivities are set equal to molecular heat diffusivity of the mixture and $Le=1$ , with other things being equal. Reported results show that significantly higher turbulent burning rates simulated in the former flames result mainly from an increase in the local fuel consumption rate, whereas an increase in flame surface area plays a secondary role, especially in more intense turbulence. The rate increase stems from (i) an increase in the peak local fuel consumption rate and (ii) an increase in a width of a zone where the rate is significant. The latter phenomenon is of more importance in richer flames and both phenomena are most pronounced in the vicinity of the flame leading edges, thus indicating a crucial role played by the leading edge of a premixed turbulent flame in its propagation. Moreover, mean displacement speed differs significantly from the laminar flame speed even in the equidiffusive flames, varies substantially across flame brush and may be negative at the leading edges of highly turbulent flames.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Displacement speed, flame surface density and burning rate in highly turbulent premixed flames characterized by low Lewis numbers

et al. 2023

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“…The 𝑘 − 𝜀 turbulence model due to its suitable accuracy and low computational cost has been a popular model for simulating reacting flows (which are inherently expensive). This model has been used in numerous reacting flow simulations in various geometries and has produced reliable results, some of which can be observed in references (Giuffrida et al 2020, Berni et al 2021, Verma et al 2021, Aleiferis et al 2021, Bordoloi et al 2021and Ong et al 2021. In this model, the Reynolds stresses can be related to turbulent viscosity as follows:…”

Section: Governing Equationsmentioning

confidence: 99%

Computational Investigation of Effects of Side-Injection Geometry on Thrust-Vectoring Performance in a Fuel-Injected Dual Throat Nozzle

2022

JAFM

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Dual-throat Nozzle (DTN) is known as one of the most effective approaches of fluidic thrust-vectoring. It is gradually flourishing into a promising technology to implement supersonic and hypersonic thrust-vector control in aircrafts. The main objective of the present study is numerical investigation of the effects of secondary injection geometry on the performance of a fuel-injected planar dual throat thrust-vectoring nozzle. The main contributions of the study is to consider slot and circular geometries as injector cross-sections for injecting four different fuels; moreover, the impact of center-to-center distance of injection holes for circular injector is examined. Three-dimensional compressible reacting simulations have been conducted in order to resolve the flowfield in a dual throat nozzle with pressure ratio of 4.0. Favre-averaged momentum, energy and species equations are solved along with the standard k − ε model for the turbulence closure, and the eddy dissipation model (EDM) for the combustion modelling. Second-order upwind numerical scheme is employed to discretize and solve governing equations. Different assessment parameters such as discharge coefficient, thrust ratio, thrust-vector angle and thrust-vectoring efficiency are invoked to analyze the nozzle performance. Computationally predicted data are agreed well with experimental measurements of previous studies. Results reveal that a maximum vector angle of 17.1 degrees is achieved via slot injection of methane fuel at a secondary injection rate equal to 9% of primary flow rate. Slot injection is performing better in terms of discharge coefficient, thrust-vector angle and thrust-vectoring efficiency, whereas circular injection provides higher thrust ratio. At 2% secondary injection for methane fuel, vector angle and vectoring efficiency obtained by slot injector is 8% and 34% higher than the circular injector, respectively. Findings suggest that light fuels offer higher thrust ratio, vector angle and vectoring efficiency, while heavy fuels have better discharge coefficient. Increasing center-to-center distance of injector holes improves thrust ratio, while having a negative effect on discharge coefficient, vector angle and vectoring efficiency. A comparison between fuel injectant of current study and inert injectant in the previous studies indicates that fuel reaction could exhibit substantial positive effects on vectoring performance. Secondary-to-primary momentum flux ratio is found to play a crucial role in nozzle performance.

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“…This fact is one of the reasons for the change in the mechanism of the generation of pulsations during the combustion of hydrogen in comparison with the combustion of methane, as will be considered below. It is important to note that the change in these values (Ka and Da) affects the results of calculations of existing mechanisms [32,33]. Therefore, to predict the operation of engines on hydrogen fuel, new or modified turbulent combustion models should be used, as, for example, shown in [34].…”

Section: Flame Size and Formmentioning

confidence: 99%

Physical and Chemical Features of Hydrogen Combustion and their Influence on the Characteristics of Gas Turbine Combustion Chambers

Zubrilin¹,

Кузнецов²,

Tsapenkov³

et al. 2022

Preprint

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Hydrogen plays a key role in the transition to a carbon-free economy. One of the areas of hydrogen use is the substitution of hydrocarbon fuel in gas turbine engines and power plants. This review article discusses the features of hydrogen combustion and their influence on the characteristics of combustion chambers in comparison with methane. The paper presents both the results of a study of pure hydrogen or methane and methane-hydrogen mixtures with different hydrogen content. Among the main features, it is worth noting a smaller ignition delay time and higher laminar flame speed with a shift in its maximum value to a rich mixture, which significantly affects on flashback inside burners premixer, especially at elevated air temperatures. Another feature is the increased temperature of the flame, which can lead to an increase in the rate of nitrogen oxides formation. However, wider combustion concentration ranges contribute to the stable combustion of hydrogen at temperatures lower than those of methane. Along with this, it was shown that even at the same adiabatic temperature, more nitrogen oxides are formed in a hydrogen flame than in a methane flame, which indicates an additional mechanism for NOx formation in addition to the Zeldovich mechanism. The article also summarizes some of the results of a study on the effect of hydrogen on the occurrence of thermoacoustic instability, which depends on the initial nature of pulsations during methane combustion. The presented data will be useful both to engineers who are engaged in solving the problems of designing hydrogen combustion devices, and to scientists in this field of study.

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Validation of leading point concept in RANS simulations of highly turbulent lean syngas-air flames with well-pronounced diffusional-thermal effects

Cited by 13 publications

References 78 publications

Displacement speed, flame surface density and burning rate in highly turbulent premixed flames characterized by low Lewis numbers

Displacement speed, flame surface density and burning rate in highly turbulent premixed flames characterized by low Lewis numbers

Computational Investigation of Effects of Side-Injection Geometry on Thrust-Vectoring Performance in a Fuel-Injected Dual Throat Nozzle

Physical and Chemical Features of Hydrogen Combustion and their Influence on the Characteristics of Gas Turbine Combustion Chambers

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