soot volume fraction
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2021 ◽  
Vol 7 ◽  
Author(s):  
Juan J. Cruz ◽  
Ignacio Verdugo ◽  
Nicolás Gutiérrez-Cáceres ◽  
Felipe Escudero ◽  
Rodrigo Demarco ◽  
...  

The main characteristics of pool fire flames are flame height, air entrainment, pulsation of the flame, formation and properties of soot particles, mass burning rate, radiation feedback to the pool surface, and the amount of pollutants including soot released to the environment. In this type of buoyancy controlled flames, the soot content produced and their subsequent thermal radiation feedback to the pool surface are key to determine the self-sustainability of the flame, their mass burning rate and the heat release rate. The accurate characterization of these flames is an involved task, specially for modelers due to the difficulty of imposing adequate boundary conditions. For this reason, efforts are being made to design experimental campaigns with well-controlled conditions for their reliable repeatability, reproducibility and replicability. In this work, we characterized the production of soot in a surrogate pool fire. This is emulated by a bench-scale porous burner fueled with pure ethylene burning in still air. The flame stability was characterized with high temporal and spatial resolution by using a CMOS camera and a fast photodiode. The results show that the flame exhibit a time-varying propagation behavior with a periodic separation of the reactive zone. Soot volume fraction distributions were measured at nine locations along the flame centerline from 20 to 100 mm above the burner exit using the auto-compensating laser-induced incandescence (AC-LII) technique. The mean, standard deviation and probability density function of soot volume fraction were determined. Soot volume fraction presents an increasing tendency with the height above the burner, in spite of a local decrease at 90 mm which is approximately the position separating the lower and attached portion of the flame from the higher more intermittent one. The results of this work provide a valuable data set for validating soot production models in pool fire configurations.


Author(s):  
Felipe Escudero ◽  
Juan José Cruz ◽  
Fengshan Liu ◽  
Andrés Fuentes

Abstract This work presents a layer-peeling (LP) algorithm to correct the signal trapping effect in planar laser-induced incandescence (LII) measurements of soot volume fraction. The method is based on measurements of LII signals captured by an intensified CCD camera at a series of parallel planes across a diffusion flame. A method based on presumed function (PF) of soot volume fraction is also proposed for comparison. The presented methods are numerically tested based on synthetic LII signals emitted from a simulated axisymmetric laminar diffusion flame using the CoFlame code. Numerical results showed that the LP method is able to correct the signal trapping effect, even for fairly large optical thicknesses and in a wide range of detection wavelengths. The correction decreases the relative errors induced by neglecting the trapping effect considerably. The signal trapping effect correction is less important for the determination of integrated soot quantities such as radially integrated soot volume fraction or total soot loading. Planar LII measurements were carried out and calibrated in order to test the method experimentally in a coflow flame. The LP, PF and a simplified analytical (SA) model were compared. The results indicate that the differences in soot volume fraction of 1 ppm or about 15% are obtained in zones of maximum soot loading of 6.5 ppm when the trapping effect is accounted for. Also, the LP and SA methods were found computationally efficient and accurate compared to the PF method. Although the study was performed in a canonical laminar axisymmetric flame, the proposed method can be applied to any statistically steady 3D flame.


2021 ◽  
Author(s):  
Mingshan Sun ◽  
Zhiwen Gan

Abstract The current study analyzed the soot precursor of the n-butylbenzene found in diesel and kerosene in laminar flame, and integrated the corresponding poly-aromatic hydrocarbon (PAH) growth mechanism with the popular n-butylbenzene oxidation mechanisms to improve the soot formation prediction of n-butylbenzene. The size of soot precursor was determined by the fringe length in the core of soot particle since the nanostructure of the core of soot particle is similar with that of nascent soot particle formed by soot precursor nucleation. The geometric mean fringe length in core of soot particles was measured to be 0.67 nm approximating to the size of five-ringed PAH (A5). An A5 growth mechanism was added on a popular n-butylbenzene mechanism, and the combined mechanism was further reduced. After validation by the ignition delay time in literature, the combined mechanism was then validated by the primary particle diameter in laboratory and soot volume fraction of n-propylbenzene in literature. The calculated soot precursor concentration and PAH condensation rate of the combined mechanism are smaller than that of the base mechanism. The simulated primary soot particle diameter of proposed combined mechanism agrees well with the measure primary soot particle diameter. Comparing to the simulated soot volume fraction of base n-butylbenzene mechanism, the simulated soot volume fraction of proposed combined n-butylbenzene-A5 mechanism agrees well with the measure soot volume fraction of n-propylbenzene in literature. This study provides certain support for further investigation of soot formation of n-butylbenzene and its relative fuel like diesel and kerosene.


2021 ◽  
Vol 127 (11) ◽  
Author(s):  
Devashish Chorey ◽  
Matthias Koegl ◽  
Prasad Boggavarapu ◽  
Florian J. Bauer ◽  
Lars Zigan ◽  
...  

AbstractWe report the three-dimensional (3D) mapping of polycyclic aromatic hydrocarbons (PAHs), soot, and hydroxyl radicals (OH) in ethylene/air diffusion flames. A structured illumination-based frequency recognition algorithm for multiple exposures (FRAME) approach is combined with sample translation to intersect the flame in several two-dimensional planes. The FRAME technique has been used for recording a snapshot of multiple species on a single camera. It relies on extracting the amplitude of spatial modulation of two or more probed species encoded on a single sub-image. Here, the FRAME technique is first applied for simultaneous imaging of PAH by laser-induced fluorescence (PAH-LIF) and soot by laser-induced incandescence (LII). Sequentially, it is employed for simultaneous mapping of OH-LIF and soot-LII. The LII signal is converted to absolute soot volume fraction (fv) maps using a line-of-sight light extinction measurement. Finally, we have demonstrated the approach for layer-wise 2D imaging of soot volume fraction and averaged 3D mapping of multiple species.


2021 ◽  
pp. 317-326
Author(s):  
Jingwen Lu ◽  
Shuwei Zhang ◽  
Longhui Tan ◽  
Jianyi Lu

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5995
Author(s):  
Qianqian Mu ◽  
Fuwu Yan ◽  
Jizhou Zhang ◽  
Lei Xu ◽  
Yu Wang

Furanic biofuels have received increasing research interest over recent years, due to their potential in reducing greenhouse gas emissions and mitigating the production of harmful pollutants. Nevertheless, the heterocyclic structure in furans make them readily to produce soot, which requires an in-depth understanding. In this study, the sooting characteristic of several typical furanic biofuels, i.e., furan, 2-methylfuran (MF), and 2,5-dimethylfuran (DMF), were investigated in laminar counterflow flames. Combined laser-based soot measurements with numerical analysis were performed. Special focus was put on understanding how the fuel structure of furans could affect soot formation. The results show that furan has the lowest soot volume fraction, followed by DMF, while MF has the largest value. Kinetic analyses revealed that the decomposition of MF produces high amounts of C3 species, which are efficient benzene precursors. This may be the reason for the enhanced formation of polycyclic aromatic hydrocarbons (PAHs) and soot in MF flames, as compared to DMF and furan flames. The major objectives of this work are to: (1) understand the sooting behavior of furanic fuels in counterflow flames, (2) elucidate the fuel structure effects of furans on soot formation, and (3) provide database of quantitative soot concentration for model validation and refinements.


2021 ◽  
Vol 7 ◽  
Author(s):  
Robert Schmitz ◽  
Mariano Sirignano ◽  
Christian Hasse ◽  
Federica Ferraro

Synthetic fuels, especially oxygenated fuels, which can be used as blending components, make it possible to modify the emission properties of conventional fossil fuels. Among oxygenated fuels, one promising candidate is oxymethylene ether-3 (OME3). In this work, the sooting propensity of ethylene (C2H4) blended with OME3 is numerically investigated on a series of laminar burner-stabilized premixed flames with increasing amounts of OME3, from pure ethylene to pure OME3. The numerical analysis is performed using the Conditional Quadrature Method of Moments combined with a detailed physico-chemical soot model. Two different equivalence ratios corresponding to a lightly and a highly sooting flame condition have been investigated. The study examines how different blending ratios of the two fuels affect soot particle formation and a correlation between OME3 blending ratio and corresponding soot reduction is established. The soot precursor species in the gas-phase are analyzed along with the soot volume fraction of small nanoparticles and large aggregates. Furthermore, the influence of the OME3 blending on the particle size distribution is studied applying the entropy maximization concept. The effect of increasing amounts of OME3 is found to be different for soot nanoparticles and larger aggregates. While OME3 blending significantly reduces the amount of larger aggregates, only large amounts of OME3, close to pure OME3, lead to a considerable suppression of nanoparticles formed throughout the flame. A linear correlation is identified between the OME3 content in the fuel and the reduction in the soot volume fraction of larger aggregates, while smaller blending ratios may lead to an increased number of nanoparticles for some positions in the flame for the richer flame condition.


2021 ◽  
Vol 7 ◽  
Author(s):  
Jiwei Zhou ◽  
Mengxiang Zhou ◽  
Liuhao Ma ◽  
Yu Wang

A cost-effective and straightforward light extinction method has been extensively used for measurement of soot volume fraction (SVF) in sooting flames. The traditional pointwise measurement with translation stage suffers from relatively time-consuming operation and low spatial resolution. In the current study, the planar light extinction method is processed by utilizing a CMOS camera to image the combustion field of counterflow diffusion flame (CDF) backlit with the lamp. Collimated and diffuse optical layouts were adopted to explore the feasibility. Investigations of beam-steering effects are presented and discussed through a combination of computational fluid dynamics (CFD) and ray tracing simulations. Measured SVF are compared to the well-validated laser-induced incandescence (LII) measurements. Current measurements show that the diffuse optical layout is feasible and robust to provide accurate and more efficient measurement of the SVF in CDF with superior spatial resolution (21.65 μm).


2021 ◽  
pp. 1-27
Author(s):  
Van Ga Bui ◽  
Thi Minh Tu Bui ◽  
Anh Tuan Hoang ◽  
Sandro Nizetic ◽  
Thanh Xuan Nguyen Thi ◽  
...  

Abstract The paper presents a comparative study on combustion and emissions of hydrogen-enriched biogas premixed charge in direct injection dual fuel (DIDF) engine and indirect injection dual fuel (IDIDF) engine. The results show that the IDIDF engine outperforms the DIDF engine in terms of higher indicative engine cycle work (Wi), lower emissions of CO, soot, and noise, but the disadvantage is higher NOx emission. Under the same fueling condition, the IDIDF engine's Wi is on average 6% higher than that of the DIDF engine, but the NOx concentration in the combustion products of the IDIDF engine is 1.5 times higher than that of the DIDF engine. The IDIDF engine creates the stratified mixture distribution with higher O2 concentration in the auxiliary combustion chamber, which is favorable for auto ignition and reduces the ignition delay. The biogas composition affects slightly CO, and soot emissions, but significantly affects NOx emission. When the methane composition in biogas increases from 60% to 80%, the soot volume fraction is approximately 0.1ppm in both types of combustion chambers; the CO concentration varies from 1.4-1.8%, meanwhile, the NOx concentration varies from 3000-5000ppm in the case of IDIDF engine and 2500-4500ppm in the case of DIDF engine. For both types of dual fuel engines, when engine speed increases, CO concentration, and the soot volume fraction increase, while Wi and NOx concentration decrease.


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