Physicochemical Properties Of Particles And Influencing Factors Of Purification Effect Under The Action Of INTP

As people pay more attention to environmental problems,diesel exhaust purification has become one of the important research directions of diesel engine development.Non-thermal plasma?NTP?technology is a research hotspot in the field of diesel engine after-treatment with the advantages of high conversion efficiency,simple device and no secondary pollution.The current researches mainly focus on the use of direct non-thermal plasma technology to purify diesel engine exhaust gas.There is less research on the use of indirect non-thermal plasma?INTP?technology to purify diesel particulate matter?PM?.In this paper,a test bench for diesel PM purification with INTP technology was set up.The experimental study of the physicochemical properties of particles and the influencing factors of purification effect under the action of INTP was carried out.The main research work is as follows:?1?In order to explore the influence of INTP technology on the physicochemical properties of particles,the PM was sampled for thermogravimetric analysis,and the variation of PM components and characteristic temperatures before and after the action of INTP were analyzed.The apparent activation energy of PM components before and after the action of INTP was calculated by Arrhenius method.A fourier transform infrared spectrometer and a scanning electron microscope were applied to investigate the changes of particle functional groups and surface morphology before and after the action of INTP under different diesel engine conditions.The results showed that the apparent activation energy of volatile matter in PM was lower than that of the solid carbon.After the action of INTP,the proportion of volatile components in the PM declined and the proportion of solid carbon increased.The characteristic temperatures and apparent activation energy of PM both decreased after the action of INTP,so INTP had the ability to make PM easier to be oxidized at a lower temperature and improve the oxidation activity of PM.After the action of INTP,the alkyl functional groups on the PM surface were reduced,and the oxygen-containing functional groups and aromatic rings were formed.The apparent morphology of particles became relatively smooth after the action of INTP.?2?In order to further explore the influence of INTP technology on soluble organic fraction?SOF?in PM,a microbalance was applied to measure particle mass before and after the action of INTP.Subsequently,the extraction samples were analyzed by gas chromatography-mass spectrometer.The influence of INTP technology on SOF components,carbon atoms,branched alkanes and oxygen-containing content were investigated.The results showed that after the action of INTP,particle mass was reduced in varying degrees under different loads.After the action of INTP,olefins,lipids and alcohols were formed in the SOF.The C11^C14 content with small carbon number and oxygen-containing content increased,the proportion of branched alkanes decreased.?3?The gas source flow rate of NTP injection system was optimized to investigate its effect on the particle purification via the action of INTP.The concentration and proportion of ultrafine particles,nuclear particles and aggregated particles were analyzed by using an engine exhaust particle sizer to measure the quantity concentration and mass concentration of PM under different gas source flow rates.The geometric mean particle size of PM quantity concentration and mass concentration before and after the action of INTP was calculated.The composition,characteristic temperatures and activation energy of particles under different gas source flow rates were analyzed by the thermogravimetric analyzer.The gas source flow rate of the NTP injection system had a great influence on the O₃concentration and output.Under different gas source flow rates,the PM quantity concentration and mass concentration both decreased and reached a nadir at 10 L/min gas source flow rate.The influence of gas source flow rate on the oxidation activity of volatile components was small,however gas source flow rate had a great effect on the oxidation activity of solid carbon.