The Study On Droplet Combustion Behavior With Soot Model Under Electric Field

Liquid fuel is sprayed into the cylinder of the internal combustion engine, turbine orjet engine combustion to produce heat. Increased energy crisis and reducing emissionsof particulate matter emissions in recent years to protect the environmental awareness,prompting researchers to adopt new technology to improve the efficiency of thecombustion of fossil fuels, including a deep understanding of the physical process ofsingle droplet combustion is improved injection combustion characteristics of theinternal combustion engine energy utilization efficiency of the basic.In droplet combustion process soot has a very important influence, wherein theparticles of the radiation effects are significant direct impact on the droplet combustionflame temperature and the evaporation rate of the surface of the droplet, in addition, dueto the soot particles in the flame generation, strongly affect the diffusion of the flame inthe other gaseous components, especially the diffusion rate of the fuel vapor with anoxidizing agent, both of which directly determines the spatial position of the flame front,the distance between the surface of the droplet and flame front has played a very crucialrole during droplet evaporation, and therefore become very necessary and urgent tocarry out the study of soot particle model, from the soot particle nucleation, growth andcoagulation process to establish a set of semi-empirical soot particles model, comparedwith the available experimental results, verification of the accuracy of the model of thissoot particles, to effectively predict the flame temperature, the soot volume fraction andthe soot particle mean size, and by changing the oxygen-containing environment andtemperature conditions, to accurately predict the spatial distribution of soot volumefraction.In order to improve the droplet fuel combustion efficiency, and effectively controlthe generation of soot particles, this dissertation presents a new technology to achievethis goal, the applied electric field through the interaction of the free ions in the appliedelectric field in the flame, from experimental measured perspective, due to the buoyancyeffect, in droplet combustion flame morphology becomes a symmetrical flame, insteadof spherically symmetric under microgravity conditions, the use of electric force can beeffectively controlled the n-decane droplet combustion, from the flame morphology, theburning rate and soot generation parameters to illustrate the role of the external electric field on droplet combustion, and attain some important experimental Phenomenon, theanalysis showed that "ionic wind" is the important role in the applied electric field, butwe also need to consider the role of the anionic ion wind generated, so as to reasonablyexplain the flame morphology and combustion rate constant by the influence of theapplied electric field. In addition, the soot particles in the flame impact on the dropletcombustion is very significant, and under the action of an electric field to accelerate theoxidation of the soot particles, the reduction in soot particles resulting in a reduction ofthe external radiation heat exchange, resulting in a reduction in burn rate constant.Finally, this dissertation system studies comparing the combustion characteristics ofdifferent types of fuel droplets in the electric field, and the type and quantity of free ionsin the flame is not the same due to the different types of fuel combustion, and thereforesubject to the applied electric field are not consistent, in this thesis, propanol, n-decaneand diesel oil as experimental droplets fuel, three different fuel combustion processshowed the biggest difference is flame soot formation characteristics, the flamemorphology, the combustion rate and the soot generation showing certain experimentalrule with the applied electric field, for three different types of fuel droplets, regardlessof the direction of the electric field with the natural convection of the same direction orthe opposite, as the voltage between the plates increases, LII radiation intensity weredecreasing trend, indicating that the concentration of soot particles is reduced with theincrease of the voltage between the plates.