Efficiencies of low-momentum jet diffusion flames in crosswinds

Johnson, Matthew R.; Kostiuk, Larry W.

doi:10.1016/s0010-2180(00)00151-6

Cited by 101 publications

(75 citation statements)

References 14 publications

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“…9. As shown in Figure 9 (a), the results indicate a negative linear correlation of the combustion efficiency with u cf , which is consistent with the experimental observations [44]. This trend implies a decrease in flare efficiency with an increase in values of u cf .…”

Section: Combustion Efficiencysupporting

confidence: 89%

“…The significance of these geometric transformations in reducing the efficiency characteristics of the flame is well documented [12,44]. The main flow feature on the leeside of the release pipe is caused by the reduced pressure within the recirculation vortices in the downwash wake region.…”

Section: Influence Of Flow Conditionsmentioning

confidence: 99%

“…Flare performance is usually determined in terms of the combustion efficiency or carbon conversion efficiency ( t ), which is defined [44] as:…”

Section: Combustion Efficiencymentioning

confidence: 99%

“…Flame ionization detectors are used for CH4 measurements and nondispersive infrared analyzers are used for CO2 and CO. All of the analyzers employed have an uncertainty of 1% of their full-scale reading. Therefore an estimated error in the conversion efficiency is less than approximately 0.6% [37][38]44].…”

Section: Combustion Efficiencymentioning

confidence: 99%

“…Previous experimental studies have established that the efficiency of flare combustion has a strong dependence on the cross-flow velocity [7,44]. Therefore in the following, the capability of the three turbulence models to capture this dependency is examined.…”

Section: Combustion Efficiencymentioning

confidence: 99%

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CFD predictions of wake-stabilised jet flames in a cross-flow

Lawal¹,

Fairweather²,

Gogolek³

et al. 2013

Energy

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This study describes an investigation into predicting the major flow properties in wake-stabilised jet flames in a cross flow of air using first-and second-order turbulence models, applied within a Reynolds-averaged Navier-Stokes (RANS) modelling framework. Standard and re-normalisation group (RNG) versions of the k-turbulence model were employed at the first-order level and the results compared with a secondmoment closure, or Reynolds stress model (RSM). The combustion process was modelled using the laminar flamelet approach together with a thermal radiation model using the discrete ordinate method. The ability of the various turbulence models to reproduce experimentally established flame appearance, profiles of velocity and turbulence intensity, as well as the combustion efficiency of such flames is reported. The results show that all the turbulence models predict similar velocity profiles over the majority of the flow domain considered, except in the wake region, where the predictions of the RSM and RNG k-models are in closer agreement with experimental data. In contrast, the standard k-model over-predicts the peak turbulence intensity. Also, it is found that the RSM provides superior predictions of the planar recirculation and flame zones attached to the release pipe in the wake region. 1.IntroductionA large quantity of oil field associated gas, and waste hydrocarbons from the process industry, is flared globally each year. With the predicted increase in oil production in the next decades, a significant increase in flaring is expected [1,2]. However, flare operations can result in the formation of pollutants such as unburned hydrocarbons, CO, NO x and noise and the effect of a cross-flow of wind can be significant. In order to minimise these effects, a detailed understanding of the flow features and structures of these non-premixed jet flames in a cross-flow (JFICF) is necessary. Depending on the value of the jetto-cross-flow momentum flux ratio, R= j u j 2 / cf u cf 2 , where j , cf and u j , u cf are the density and velocity of the fuel jet and the cross-flow, respectively, the flow features that arise in the JFICF have an important influence on the flame's combustion characteristics.For flares operating at low values of R, typically R ≤ 1.0, the flame is either seated on the flare stack or stabilised in its wake [3]. The latter case is also known as a wake-stabilised flare which belongs to a flow regime where the flame is severely bent-over by the cross-flow and has high turbulence intensities in the near-field [4]. This category of flare is commonly found in offshore crude oil production facilities.The three main flow features in the wake-stabilised flare include: a counter-rotating vortex pair (CVP)[5], coherent structures around the upper surface of the jet [3] and the planar recirculation zone in the wake of the stack [6]. The latter zone is part of the low-pressure region where a secondary flame is attached to the release pipe, as shown in Fig. 1, and the vortex dynamics and mixing in this ...

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Section: Combustion Efficiencysupporting

confidence: 89%

Section: Influence Of Flow Conditionsmentioning

confidence: 99%

“…Flare performance is usually determined in terms of the combustion efficiency or carbon conversion efficiency ( t ), which is defined [44] as:…”

Section: Combustion Efficiencymentioning

confidence: 99%

Section: Combustion Efficiencymentioning

confidence: 99%

Section: Combustion Efficiencymentioning

confidence: 99%