scholarly journals Effects of aromatic on soot characteristics of aviation fuel surrogates in diffusion flames

2015 ◽  
Vol 18 (4) ◽  
pp. 55-64
Author(s):  
Thong Duc Hong ◽  
Osamu Fujita
Keyword(s):  
Diffusion Flames ◽  
Soot Formation ◽  
Linear Functions ◽  
Aviation Fuel ◽  
Light Extinction ◽  
Flame Height ◽  
Aircraft Engines ◽  
Mass Consumption ◽  
Function Of Two Variables ◽  
Fuel Surrogates

Co-annular smoke-free laminar diffusion wick-fed flames of dodecane and its blended with various amounts of propylbenzene of 10, 20, 25 vol.% have been used to study soot formation characteristics. Dodecane and propylbenzene are selected as the surrogates for paraffin class and aromatic class of aviation fuel. A light extinction method is adopted to determine the total soot volume (TSV) as a function of flame height (Hf) and fuel mass consumption rate (FMCR). An empirical model has been built to predict soot formation of dodecane and propylbenzene (Do/PB) mixtures as the function of two variables of FMCR and concentration of propylbenzenet (%PB). TSVs of Do/PB mixtures increase with increasing Hf, FMCR and %PB. The effect of Hf, FMCR and %PB on soot formation are respectively expressed as the quadratic, power law and linear functions. The result of current work creates a database for optimizing the trade-off impacts of aromatic in aviation fuel. This information is of high importance when blending aromatic to bioparaffins, which is produced from triglycerides and fatty acids in the vegetable by hydrotreating process, for using as a fuel in aircraft engines.

Synergistic Effect of Soot Formation in Ethylene/Propane Co-Flow Diffusion Flames at Elevated Pressures

2021 ◽  
Author(s):  
Dongsheng Zheng ◽  
Xin Hui ◽  
Xin Xue ◽  
Weitao Liu
Keyword(s):  
Synergistic Effect ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Total Carbon ◽  
Light Extinction ◽  
Flame Height ◽  
Carbon Mass

Abstract The synergistic effect of soot formation refers to the interaction between different fuels during soot forming processes, which results in higher soot formation than any individual fuels. The present study experimentally investigates the synergistic effect of soot formation in co-flow diffusion flames of propane/ethylene fuel mixtures. The total carbon mass flow rate of the propane/ethylene mixture was kept constant at 0.5 mg/s, and the propane carbon ratio (RC) was defined as the ratio of carbon mass flow rate of propane to the total carbon mass flow rate. The laser-induced incandescence (LII) and light extinction (LE) techniques were applied to measure the soot volume fractions (SVF) at pressures of 0.1–0.5 MPa. The results showed strong synergistic effect in propane/ethylene mixtures at atmospheric conditions; however, increasing pressure weakens the synergistic effect. The LII intensity contours showed that the soot formation zone extends when synergistic effect occurs at RC = 0.1 and 0.2 for 0.1 and 0.3 Mpa. The normalized peak SVF showed that synergistic effect monotonically becomes weak with increasing pressure from 0.1 to 0.3 Mpa; meanwhile, the it still stayed strong at 0.2 Mpa when using normalized maximum soot yield, and then turned to be weaker as pressure increases. Further comparison analysis of the SVF profiles between RC = 0 and 0.1 revealed that the synergistic effect occurs at the two-wing area of the sooty flame at low axial flame height, and then gradually becomes stronger with increasing axial flame height in the soot zone for 0.1–0.3 Mpa. To illustrate the pressure effects on synergistic soot formation, numerical analysis in homogeneous closed reactor was conducted and it was found that The PAHs formation competition between C3H3 pathway and HACA mechanism results in the different soot formation phenomenon of ethylene/propane flames.

Soot Formation With Light Extinction and Grayscale Extraction Methods Applied to Ethanol-Gasoline Blends Laminar Flame

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Shengli Wei ◽  
Jie Chen ◽  
Rui Xu ◽  
Tongyuan Ding ◽  
Xiqian Zhao
Keyword(s):  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Laminar Flame ◽  
Flame Structure ◽  
Extraction Methods ◽  
Light Extinction ◽  
Flame Height ◽  
Laminar Diffusion Flames ◽  
Mass Flowrate

Abstract In this paper, the two-dimensional parallel light extinction method was carried out to study the soot formation in laminar diffusion flames of four different ethanol-gasoline blends, of which ethanol volume fractions ranging from 0% up to 100% (E0, E20, E80, and E100). The flame images were processed synthetically via matlab to accurately calculate the flame height. In addition, the flame structure was redefined as three zones to observe the soot formation. The results indicate that the flame height changes with the variation of gas volume flowrate and fuel mass flowrate during the experiment. In terms of soot formation, as the volume fraction of ethanol increases, the proportion of soot forming zone decreases, while the area of blue flame zone grows. Simultaneously, the transition zone accounts for about 21% of the total flame area, which has no significant change with the increase of ethanol volume fraction.

scholarly journals Experimental Investigation of Oxygen Addition to Fuel on Soot Formation in Laminar Coflow Diffusion Flames of Ethylene and Propane

2006 ◽  
Author(s):  
Fengshan Liu ◽  
Kevin A. Thomson ◽  
Gregory J. Smallwood
Keyword(s):  
Flow Rate ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Soot Volume Fraction ◽  
Oxygen Flow Rate ◽  
Flame Height ◽  
Fuel Flow Rate ◽  
Fuel Flow ◽  
Oxygen Addition

Investigation of the effect of oxygen addition to fuel on the visible flame appearance and soot formation characteristics of laminar diffusion flames is important to gain comprehensive understanding of gas-phase combustion chemistry and its interaction with soot chemistry. This paper reports experimental results of oxygen addition to fuel on the visible flame height and soot volume fraction distributions in axisymmetric coflow laminar ethylene and propane diffusion flames at atmospheric flames. The carbon flow rate was maintained constant in all the experiments. Although many experimental studies have been conducted in the literature in this topic, the present investigation aimed at providing spatially resolved soot volume fraction distributions over the entire range of oxygen addition from no oxygen addition up to the point of flashback while keeping the carbon mass flow rate constant. The level of oxygen added to fuel right before flashback is about 45% (the percentage of oxygen addition is always by volume in this study) of the fuel flow rate in the ethylene flame and 300% of the fuel flow rate in the propane flame. As the added oxygen amount to ethylene increases, the visible flame height first increases. When the added oxygen flow rate is about 13% of the fuel flow rate, the flame becomes smoking, i.e., soot escapes from the flame tip. When the oxygen flow rate reaches about 42% of the fuel flow rate, the flame stops smoking. When oxygen was added to propane, the visible flame height linearly decreases with increasing the amount of oxygen. These very different effects of oxygen addition to ethylene and propane indicate that oxygen plays a drastically different role in the chemical pathways leading to soot formation in ethylene and propane flames. Distributions of soot volume fractions in these flames were measured using a 2D light attenuation technique coupled with the Abel inversion. The present study provides valuable experimental data for validating soot models.

Pressure Dependence of Soot Formation in Diffusion Flames

2008 ◽  
Author(s):  
Hyun I. Joo ◽  
O¨mer L. Gu¨lder
Keyword(s):  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Strong Dependence ◽  
Soot Volume Fraction ◽  
Flame Height ◽  
Maximum Temperature ◽  
Cross Sectional ◽  
Spatially Resolved ◽  
Pressure Peak

The effects of pressure on soot formation and the structure of the temperature field were studied in co-flow methane-air laminar diffusion flames over a wide pressure range, from atmospheric to 6 MPa (60 atm) in a high-pressure combustion chamber. The selected fuel mass flow rates provided diffusion flames in which the soot was completely oxidized within the visible flame envelope and the flame was stable at all pressures considered. The spatially resolved soot volume fraction and soot temperature were measured by spectral soot emission as a function of pressure. The visible (luminous) flame height remained almost unchanged, about 9 mm, from 1 to 10 MPa, whereas it increased considerably from atmospheric to 1 MPa. Between 1 MPa and 6 MPa, the cross-sectional area of the flame (measured from the radius defined by either the maximum soot or maximum temperature annuli) showed an inverse dependence on pressure. Peak soot concentrations showed a strong dependence on pressure from 1 MPa to 4 MPa; however this dependence got relatively weaker between 4 MPa and 6 MPa.

Detailed Kinetic Modeling of Soot-Particle and Key-Precursor Formation in Laminar Premixed and Counterflow Diffusion Flames of Fossil Fuel Surrogates

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Ali Salavati-Zadeh ◽  
Vahid Esfahanian ◽  
Asghar Afshari
Keyword(s):  
Soot Particle ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Combustion Process ◽  
Reaction Model ◽  
Engine Fuel ◽  
Temperature Oxidation ◽  
Ignition Delay Times ◽  
Soot Precursors ◽  
Fuel Surrogates

This study reports a chemical kinetics soot model for combustion of engine-relevant fuels. The scheme accounts for both low- and high-temperature oxidation, considering their crucial role in engine combustion process. The mechanism is validated against several ignition delay times and laminar burning velocities data sets for single and mixtures of hydrocarbons. To assess the mechanism ability to predict soot precursors, formation of aromatic and aliphatic species with critical effects on soot formation is investigated for several laminar premixed and diffusion flames. The model includes soot particle inception, surface growth, coagulation, and aggregation based on the method of moments. The performance of the model is evaluated by predicting the amount of produced soot during heavy alkanes and aromatic species mixtures pyrolysis. The results are encouraging, proving this methodology to be a suitable tool to simulate the all-round combustion features of engine fuel surrogates by a single reaction model.

scholarly journals Effect of the Preheated Oxidizer Temperature on Soot Formation and Flame Structure in Turbulent Methane-Air Diffusion Flames at 1 and 3 atm: A CFD Investigation

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3671
Author(s):  
Subrat Garnayak ◽  
Subhankar Mohapatra ◽  
Sukanta K. Dash ◽  
Bok Jik Lee ◽  
V. Mahendra Reddy
Keyword(s):  
Mole Fraction ◽  
Air Temperature ◽  
Reaction Rate ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Flame Structure ◽  
Soot Volume Fraction ◽  
Computational Domain ◽  
Pressure Elevation

This article presents the results of computations on pilot-based turbulent methane/air co-flow diffusion flames under the influence of the preheated oxidizer temperature ranging from 293 to 723 K at two operating pressures of 1 and 3 atm. The focus is on investigating the soot formation and flame structure under the influence of both the preheated air and combustor pressure. The computations were conducted in a 2D axisymmetric computational domain by solving the Favre averaged governing equation using the finite volume-based CFD code Ansys Fluent 19.2. A steady laminar flamelet model in combination with GRI Mech 3.0 was considered for combustion modeling. A semi-empirical acetylene-based soot model proposed by Brookes and Moss was adopted to predict soot. A careful validation was initially carried out with the measurements by Brookes and Moss at 1 and 3 atm with the temperature of both fuel and air at 290 K before carrying out further simulation using preheated air. The results by the present computation demonstrated that the flame peak temperature increased with air temperature for both 1 and 3 atm, while it reduced with pressure elevation. The OH mole fraction, signifying reaction rate, increased with a rise in the oxidizer temperature at the two operating pressures of 1 and 3 atm. However, a reduced value of OH mole fraction was observed at 3 atm when compared with 1 atm. The soot volume fraction increased with air temperature as well as pressure. The reaction rate by soot surface growth, soot mass-nucleation, and soot-oxidation rate increased with an increase in both air temperature and pressure. Finally, the fuel consumption rate showed a decreasing trend with air temperature and an increasing trend with pressure elevation.

Soot formation in ducted turbulent diffusion flames

AIAA Journal ◽  
1991 ◽  
Vol 29 (6) ◽  
pp. 932-935 ◽  
Author(s):  
T. Neill ◽  
I. M. Kennedy
Keyword(s):  
Turbulent Diffusion ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Turbulent Diffusion Flames

The influence of nitrogen and hydrogen addition/dilution on soot formation in coflow ethylene/air diffusion flames

Fuel ◽  
2022 ◽  
Vol 309 ◽  
pp. 122244
Author(s):  
Andisheh Khanehzar ◽  
Francisco Cepeda ◽  
Seth B. Dworkin
Keyword(s):  
Diffusion Flames ◽  
Soot Formation ◽  
Hydrogen Addition ◽  
Air Diffusion

Analytical Formulation-Based Soot Modelling in Ethylene Laminar Jet Diffusion Flames

2021 ◽  
Author(s):  
Amit Makhija ◽  
Krishna Sesha Giri
Keyword(s):  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Soot Volume Fraction ◽  
Smoke Point ◽  
Computational Time ◽  
Detailed Model ◽  
Conservation Equations ◽  
Oxidation Rates

Abstract Soot volume fraction predictions through simulations carried out on OpenFOAM® are reported in diffusion flames with ethylene fuel. A single-step global reaction mechanism for gas-phase species with an infinitely fast chemistry assumption is employed. Traditionally soot formation includes inception, nucleation, agglomeration, growth, and oxidation processes, and the individual rates are solved to determine soot levels. However, in the present work, the detailed model is replaced with the soot formation and oxidation rates, defined as analytical functions of mixture fraction and temperature, where the net soot formation rate can be defined as the sum of individual soot formation and oxidation rates. The soot formation/oxidation rates are modelled as surface area-independent processes. The flame is modelled by solving conservation equations for continuity, momentum, total energy, and species mass fractions. Additionally, separate conservation equations are solved to compute the mixture fraction and soot mass fraction consisting of source terms that are identical and account for the mixture fraction consumption/production due to soot. As a consequence, computational time can be reduced drastically. This is a quantitative approach that gives the principal soot formation regions depending on the combination of local mixture fraction and temperature. The implemented model is based on the smoke point height, an empirical method to predict the sooting propensity based on fuel stoichiometry. The model predicts better soot volume fraction in buoyant diffusion flames. It was also observed that the optimal fuel constants to evaluate soot formation rates for different fuels change with fuel stoichiometry. However, soot oxidation strictly occurs in a particular region in the flame; hence, they are independent of fuel. The numerical results are compared with the experimental measurements, showing an excellent agreement for the velocity and temperature. Qualitative agreements are observed for the soot volume fraction predictions. A close agreement was obtained in smoke point prediction for the overventilated flame. An established theory through simulations was also observed, which states that the amount of soot production is proportional to the fuel flow rate. Further validations underscore the predictive capabilities. Model improvements are also reported with better predictions of soot volume fractions through modifications to the model constants based on mixture fraction range.

Sign in / Sign up

Export Citation Format

Share Document