Suppression Of Soot Formation Research Articles

Effects of the electric field on soot formation in combustion: A coupled charged particle PBE-CFD framework

In this article, a coupled PBE-CFD framework has been proposed to study counterflow non-premixed flames and soot formation under an external electric field. This framework integrates the population balance equation (PBE) for nanoparticle dynamics into an in-house CFD solver for the multicomponent reactive flows. Different electric properties have been considered in this model. An ion mechanism used in both fuel-rich and fuel-lean combustion is combined with a detailed chemistry for neutral gaseous species and small-size aromatics to retain the full chemistry. In order to model soot particles carrying charges and the movement of the reacting fluid medium in the electric field, a second PBE for the production and transport of charges on soot particles is introduced for the first time and incorporated into the original PBE for the number density of particles. Also, the electric force for the gas mixture is included in the momentum equations. The electric drift velocities for ions and soot particles are also considered in the transport equations of ions and the PBE of soot particles, respectively. The simulations have shown that the presence of the electric field modifies the stagnation plane of the counterflow flames and reduces the soot formation in both rich-fuel and lean-fuel conditions in agreement with experimental observations. The application of the soot particle charging model, accompanied by a proper electric correction factor on the nanoparticle processes of nucleation and surface growth, significantly improves the stability of the flame structure. The introduction of the electric correction factor reveals that the suppression of soot formation in an electric field is mainly caused by the inhibited chemical reactions of the PAH nucleation and particle surface growth, which is more important than the electric drift of the charged particles. Reducing the critical size of the particle charging process enhances the electric drift of nascent soot, thus lessening its subsequent evolution.

Thermodynamics of cementite layer formation

The formation of cementite layers upon carburization of iron is described by a thermodynamic approach assuming the establishment of an equilibrium within the carburizing gas atmosphere and between the solid and the gas. Based on that, the suppression of soot formation by adding ammonia to the gas, which has recently been reported in the literature as a kinetically determined surprising phenomenon, can be explained sufficiently well and, hence, proves to be a thermodynamically predictable effect.

Comparison of Soot Formation Characteristics between DME Diffusion Flame and the Partially Premixed Methane Flame

Experimental study of soot formation in DME jet diffusion flame was performed to investigate the influence of the oxygen contained in the molecular structure of DME. The amount of soot in the flame was measured using the transmitted light attenuation method, and was compared with that of the partial premixing methane flame under the high temperature and various surrounding oxygen conditions. The results showed that the amount of soot in the DME diffusion flame is much less than that of methane flame in most conditions, and the partially premixied methane flame of φ=7 that is substantially equal in equivalent ratio with DME diffusion flame generated 3-10 times as much soot as DME. This result suggests that the suppression of soot formation in DME flame is not due to the decrease of substantial equivalent ratio with contained oxygen, but attributed to the molecular structure of DME. The volume of the methane that is generated by primary pyrolysis of DME might have considerable influence on the generated soot amount.

The first half-million years of combustion research and today's burning problems

Publisher Summary This chapter reviews the history of combustion science and technology. The pioneering experiments in combustion research, some 600,000 years ago, were concerned with flame propagation rather than ignition. The initial ignition source was provided by nature in the form of the electrical discharge plasma of a thunderstorm or as volcanic lava, depending on location. The first half-million years of combustion research were characterized by the supposition that there are infinite reservoirs of fuel and repositories for products. The limitations to applying control by electric fields to practical combustion systems have been calculated for all three phases: removal from products, control of residence time in growth zones, and the removal of charged nuclei. The suppression of soot formation and its promotion can be greatly strengthened when electron emission is increased by a negative potential on the emitter and suppressed when electrons are prevented from escaping by the application of a positive field.