Modelling soot formation in a premixed flame using an aromatic-site soot model and an improved oxidation rate

2009 ◽  
Vol 32 (1) ◽  
pp. 639-646 ◽  
Author(s):  
Matthew S. Celnik ◽  
Markus Sander ◽  
Abhijeet Raj ◽  
Richard H. West ◽  
Markus Kraft
Keyword(s):  
Oxidation Rate ◽  
Soot Formation ◽  
Premixed Flame ◽  
Soot Model

Application of a Phenomenological Soot Model for Diesel Engine Combustion

2008 ◽  
Author(s):  
Xiaobei Cheng ◽  
Hongling Jv ◽  
Yifeng Wu
Keyword(s):  
Diesel Engine ◽  
Chemical Reactions ◽  
Oxidation Rate ◽  
Soot Formation ◽  
Soot Oxidation ◽  
Soot Concentration ◽  
Engine Operation ◽  
Soot Particles ◽  
Turbulent Eddies ◽  
Soot Model

The application of the improved CFD code for the simulation of combustion and emission formation in a high-speed diesel engine has been presented and discussed. The soot concentration transport equation is found and solved together with all other flow equations. A slip correction factor is introduced into this equation. In turbulent combustion, the soot particles are contained within the turbulent eddies, and burnt up swiftly with the dissipation of these eddies in the soot oxidation zone. However, the chemical reactions always process except the dissipation of turbulent eddies and the intermixing of soot particles and turbulent eddies. The soot oxidation rate should be controlled simultaneity by the chemical reactions rate and the dissipation rate of turbulent eddies. A hybrid particle turbulent transport controlled rate and soot oxidation rate model is present in this paper and Soot formation and oxidation processes have been modeled according to this model. A reasonable agreement of the measured and computed data of in-cylinder pressure, soot, and NO emissions for different engine operation conditions has been made. The precision of simulated soot concentration is improved compare with the commonly Hiroyasu—Nagel—Strickland (HNS) soot model.

scholarly journals Modeling study of soot formation and oxidation in DI diesel engine using an improved soot model

2014 ◽  
Vol 62 (2) ◽  
pp. 303-312 ◽  
Author(s):  
Xiaobei Cheng ◽  
Liang Chen ◽  
Guang Hong ◽  
Fangqin Yan ◽  
Shijun Dong
Keyword(s):  
Diesel Engine ◽  
Soot Formation ◽  
Di Diesel Engine ◽  
Soot Model ◽  
Modeling Study

scholarly journals Investigating the Effects of Chemical Mechanism on Soot Formation Under High-Pressure Fuel Pyrolysis

2021 ◽  
Vol 7 ◽  
Author(s):  
Nick J. Killingsworth ◽  
Tuan M. Nguyen ◽  
Carter Brown ◽  
Goutham Kukkadapu ◽  
Julien Manin
Keyword(s):  
High Pressure ◽  
Soot Formation ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Chemical Mechanism ◽  
Navier Stokes ◽  
Chemical Mechanisms ◽  
Constant Volume Combustion Chamber ◽  
Fuel Pyrolysis ◽  
Soot Model

We performed Computational Fluid Dynamics (CFD) simulations using a Reynolds-Averaged Navier-Stokes (RANS) turbulence model of high-pressure spray pyrolysis with a detailed chemical kinetic mechanism encompassing pyrolysis of n-dodecane and formation of polycyclic aromatic hydrocarbons. We compare the results using the detailed mechanism and those found using several different reduced chemical mechanisms to experiments carried out in an optically accessible, high-pressure, constant-volume combustion chamber. Three different soot models implemented in the CONVERGE CFD software are used: an empirical soot model, a method of moments, and a discrete sectional method. There is a large variation in the prediction of the soot between different combinations of chemical mechanisms and soot model. Furthermore, the amount of soot produced from all models is substantially less than experimental measurements. All of this indicates that there is still substantial work that needs to be done to arrive at simulations that can be relied on to accurately predict soot formation.

Influence of Post-Injection Parameters on Soot Formation and Oxidation in a Common-Rail-Diesel Engine Using Multi-Color-Pyrometry

2012 ◽  
Author(s):  
Christophe Barro ◽  
Frédéric Tschanz ◽  
Peter Obrecht ◽  
Konstantinos Boulouchos
Keyword(s):  
Oxidation Rate ◽  
Time Window ◽  
Soot Formation ◽  
General Rule ◽  
Soot Oxidation ◽  
Lower Amount ◽  
Post Injection ◽  
Heat Addition ◽  
Underlying Mechanisms ◽  
A Minor

The emission trade-off between soot and NOx is an issue of major concern in automotive diesel applications. Measures need to be taken both on the engine and on the aftertreatment sides in order to optimize the engine emissions while maintaining the highest possible efficiency. It is known that post injections have a potential for exhaust soot reduction without any significant influence in the NOx emissions. However, an accurate and general rule of how to parameterize a post injection such that it provides a maximum reduction of soot emissions does not exist. Moreover, the underlying mechanisms are not understood in detail. The experimental investigation presented here provides insight into the fundamental mechanisms of soot formation and reduction due to post injections under different turbulence and reaction kinetic conditions. In parallel to the measurement of soot elementary carbon in the exhaust (using a Photo Acoustic Soot Sensor), the in-cylinder soot formation and oxidation process have been investigated with an Optical Light Probe (OLP). This sensor provides crank angle resolved information about the in-cylinder soot evolution. The experiments confirm conclusions of earlier works that soot reduction due to a post injection is mainly based on two reasons: increased turbulence (from the post injection) during soot oxidation and lower soot formation due to lower amount of fuel in the main combustion at similar load conditions. A third effect of heat addition during the soot oxidation, which was often mentioned in the literature, could not be confirmed. In addition, the experiments show that variations of turbulence (from swirl) and reaction kinetics have a minor influence on the diffusion controlled heat release rate. However, the time phasing of the soot evolution is highly influenced by these variations with only small changes in the peak soot concentration. It is shown that the soot reduction of a post injection depends on the timing. More precisely, the soot reduction capability of a post injection decreases rapidly as soon as its timing is late in the soot oxidation phase. The soot oxidation rate can only be improved by increased turbulence and heat addition from the post injection in a time window before the in-cylinder soot peak occurs. Depending on EGR and swirl level, a maximum dwell time can be defined after which the post injection effect becomes counterproductive with respect to the soot oxidation rate.

Numerical Simulation of the Effect of Magnetic Fields on Soot Formation in Laminar Non-Premixed Flames

2021 ◽  
Author(s):  
Edison E. Chukwuemeka ◽  
Ingmar M. Schoegl
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Volume Fraction ◽  
Soot Formation ◽  
Premixed Flames ◽  
Premixed Flame ◽  
Pollutant Emissions ◽  
Chemical Mechanism ◽  
Computational Domain ◽  
The Magnetic Field

Abstract Characteristics of non-premixed flames such as flame height and lift-off height are affected by the presence of magnetic fields due to the paramagnetic properties of some combustion species. However, it is unknown whether magnetic fields can be used to reduce the emission of pollutants in non-premixed flames. In general, pollutant emissions are reduced in combustion systems if the mixing of combustion species is enhanced during the process. Since paramagnetic combustion species such as O2, O, OH, HO2, etc have a preferential motion direction in the presence of magnetic fields, there is a potential to harness this effect of mixing by imposing a magnetic field on the flame. This study seeks to provide some insights on the effect of magnetic field on pollutants generated in a laminar non-premixed flame numerically. The non-premixed flame is simulated using a detailed chemical mechanism for propane-air combustion and a modified Moss-Brookes soot model. To simulate the effect of magnetism on the paramagnetic chemical species, the species paramagnetic susceptibility is computed using the Curie relation. The non-premixed flame is placed at three different locations within the magnetic field. The computation predicted that the amount of average pollutants reduction is dependent on the location of the flames within the magnetic fields with respect to magnetic gradients. The mass weighted average of the soot volume fraction over the computational domain decreased when the non-premixed flame is located at certain locations within the magnetic field of the solenoid with respect to the absence of the magnetic fields, but increases in other locations.

scholarly journals Experimental and computational investigation of temperature effects on soot mechanisms

2014 ◽  
Vol 79 (7) ◽  
pp. 881-895 ◽  
Author(s):  
Xiaojie Bi ◽  
Maoyu Xiao ◽  
Xinqi Qiao ◽  
Chia-Fon Lee ◽  
Liu Yu
Keyword(s):  
Ambient Temperature ◽  
Soot Formation ◽  
Oxidation Mechanism ◽  
Soot Oxidation ◽  
Ambient Temperatures ◽  
Operation Conditions ◽  
Constant Volume Chamber ◽  
Soot Mass ◽  
Soot Measurement ◽  
Soot Model

Effects of initial ambient temperatures on combustion and soot emission characteristics of diesel fuel were investigated through experiment conducted in optical constant volume chamber and simulation using phenomenological soot model. There are four difference initial ambient temperatures adopted in our research: 1000 K, 900 K, 800 K and 700 K. In order to obtain a better prediction of soot behavior, phenomenological soot model was revised to take into account the soot oxidation feedback on soot number density and good agreement was observed in the comparison of soot measurement and prediction. Results indicated that ignition delay prolonged with the decrease of initial ambient temperature. The heat release rate demonstrated the transition from mixing controlled combustion at high ambient temperature to premixed combustion mode at low ambient temperature. At lower ambient temperature, soot formation and oxidation mechanism were both suppressed. But finally soot mass concentration reduced with decreasing initial ambient temperature. Although the drop in ambient temperature did not cool the mean in-cylinder temperature during the combustion, it did shrink the total area of local high equivalence ratio, in which soot usually generated fast. At 700 K initial ambient temperature, soot emissions were almost negligible, which indicates that sootless combustion might be achieved at super low initial temperature operation conditions.

scholarly journals An Improved Soot Formation Model for 3D Diesel Engine Simulations

2006 ◽  
Vol 129 (3) ◽  
pp. 877-884 ◽  
Author(s):  
Joan Boulanger ◽  
Fengshan Liu ◽  
W. Stuart Neill ◽  
Gregory J. Smallwood
Keyword(s):  
Diesel Engine ◽  
Soot Formation ◽  
Computing Time ◽  
Combustion Process ◽  
Computational Cost ◽  
Wall Region ◽  
Soot Particles ◽  
Engine Combustion ◽  
Near Wall ◽  
Soot Model

Soot formation phenomenon is far from being fully understood today and models available for simulation of soot in practical combustion devices remain of relatively limited success, despite significant progresses made over the last decade. The extremely high demand of computing time of detailed soot models make them unrealistic for simulation of multidimensional, transient, and turbulent diesel engine combustion. Hence, most of the investigations conducted in real configuration such as multidimensional diesel engines simulation utilize coarse modeling, the advantages of which are an easy implementation and low computational cost. In this study, a phenomenological three-equation soot model was developed for modeling soot formation in diesel engine combustion based on considerations of acceptable computational demand and a qualitative description of the main features of the physics of soot formation. The model was developed based on that of Tesner et al. and was implemented into the commercial STAR-CD™ CFD package. Application of this model was demonstrated in the modeling of soot formation in a single-cylinder research version of Caterpillar 3400 series diesel engine with exhaust gas recirculation (EGR). Numerical results show that the new soot formulation overcomes most of the drawbacks in the existing soot models dedicated to this kind of engineering task and demonstrates a robust and consistent behavior with experimental observation. Compared to the existing soot models for engine combustion modeling, some distinct features of the new soot model include: no soot is formed at low temperature, minimal model parameter adjustment for application to different fuels, and there is no need to prescribe the soot particle size. At the end of expansion, soot is predicted to exist in two separate regions in the cylinder: in the near wall region and in the center part of the cylinder. The existence of soot in the near wall region is a result of reduced soot oxidation rate through heat loss. They are the source of the biggest primary particles released at the end of the combustion process. The center part of the cylinder is populated by smaller soot particles, which are created since the early stages of the combustion process but also subject to intense oxidation. The qualitative effect of EGR is to increase the size of soot particles as well as their number density. This is linked to the lower in-cylinder temperature and a reduced amount of air.

A Comparative Performance Study of Soot Formation Models in Methane Elevated Pressure Non-Premixed Flames

2011 ◽  
Vol 110-116 ◽  
pp. 18-22 ◽  
Author(s):  
A. Yunardi ◽  
B. Elwina ◽  
Sylvia Novi ◽  
D. Wusnah ◽  
Bindar Yazid
Keyword(s):  
Experimental Data ◽  
Soot Formation ◽  
Elevated Pressure ◽  
Single Step ◽  
Performance Study ◽  
Ethylene Flame ◽  
Step Model ◽  
Radial Profiles ◽  
Dissipation Model ◽  
Soot Model

This paper presents results obtained from the application of a computational fluid dynamics (CFD) code Fluent 6.3 to modeling of elevated pressure methane non-premixed sooting flames. The study focuses on comparing the two soot models available in the code for the prediction of the soot level in the flames. A standard k-ε model and Eddy Dissipation model are utilized for the representation of flow field and combustion of the flame being investigated. For performance comparison study, a single step soot model of Khan and Greeves and two-step soot model proposed by Tesner are tested. The results of calculations are compared with experimental data of methane sooting flame taken from literature. The results of the study show that a combination of the standard k-ε turbulence model and eddy dissipation model is capable of producing reasonable predictions of temperature both in axial and radial profiles; although further downstream of the flame over-predicted temperature is evidence. With regard to soot model performance study, it shows that the two-step model clearly performed far better than the single-step model in predicting the soot level in ethylene flame at both axial and radial profiles. With a modification in the constant α of the soot formation equation, the two-step model was capable of producing prediction of soot level closer to experimental data. In contrast, the single-step soot model produced very poor results, leading to a significant under-prediction of soot levels in both flames. Although the Tesner’s soot model is simpler than the current available models, this model is still capable of providing reasonable agreement with experimental data, allowing its application for the purpose of design and operation of an industrial combustion system.

Sign in / Sign up

Export Citation Format

Share Document