Electric Field Control Of Soot Distribution And Accumulation In The Flame

In last 20 years, the research on the formation and control of combustion generated inhalable particles was conducted in more details. The state-of-art diagnostic processes provided better ways to do the on-line research. Soot is the most initial and important particle generated by combustion. However, it is important to note that no previous study has been reported on which a one dimensional flame is aligned normal to a uniform electric field. This has inhibited capacity to isolate the separate effects of the field and contributed to the lack at a quantitative study of the electrophoretic effect (without ionic wind) on soot particles. To meet these needs, the present research aims to investigate the effects of a uniform electric field on a series of one dimensional laminar premixed ethylene/air flames by using the state-of-art on-line diagnostic technologies (LII, LE and TSPD-TEM).The first aim is to find the uniform flame and electric field we need. Laser diagnostic technologies and thermophoretic sampling system were used to describe the uniformity of the soot distribution in the flames; and electric field was calculated to find the right set up scale to make it uniform.The second aim is to assess whether positively or negatively charged soot particles dominate in a flame. This was assessed by laser extinction, used to measure the variation of soot volume fraction due to the deposition under an electric field. It is found that more than 50% of charged soot particle in the flame are positive. The presence of electric field can affect the residence time of charged soot particles.The third aim is to measure the variation of soot volume fractions and particle morphology with change in the residence time induced by an electric field. Laser induced incandescence and thermophoretic sampling particles diagnostics were used. Drag force, electric force and thermopherotic force were calculated to provide a quantitative explanation for the experiment results. It is found that for the particles which smaller than 100 nm, drag force is the dominant force and the electric force can only change the fly direction of the soot; while for particles bigger than 100 nm (ususlly smaller than 200 nm in the flame), the number of charge will remarkably increase and the electric force will be the dominant force instead of drag force.The forth aim is to assess the effect on flame flicker of an applied electric field as a function of equivalence ratio. This was examined by determining the flickering points and the discharge points. The re-stabilization was found in a positive electric field, indicated the remarkable effect of the electric force.