Microcrystal Structure and C/O Element Occurrence State of Diesel PM by Non-Thermal Plasma Oxidation at Different Reaction Temperatures

Lu Yirui,Shi Yunxi,Cai Yi-xi,Fan Runlin,Zhu Lei,Zhu Kan 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.6

To reveal the effect of reaction temperature on the reduction of diesel particulate matter (PM) by non-thermal plasma (NTP) using oxygen as a gas source. The changes in the microcrystalline structure and the elemental state of PM before and after NTP oxidation at different temperatures were explored by Raman and X-ray photoelectron spectroscopy. After NTP oxidation, the disorder in the PM microcrystal structure and the amorphous carbon structure was reduced. The full width at half maximum (FWHM) of the D1 and D3 peaks decreased, and the FWHM of the G peak increased slightly. During the oxidation of PM, the carbon microcrystals grew and became restructured, and the graphitization of PM increased. After NTP oxidation, the content of O in PM increased as the reaction temperature increased, resulting in a gradual change in the binding form of O with C from C-O to C=O. The ability of temperature rise to promote the oxidation activity of NTP was gradually weakened for the thermal decomposition of NTP active substances. The microcrystalline structure and the occurrence state of C and O of PM changed with reaction temperature, indicating that the oxidizability of NTP on PM differed at different reaction temperatures.

Effect of non-thermal plasma injection flow rate on diesel particulate filter regeneration at room temperature

Chen Xulong,Shi Yunxi,Cai Yi-xi,Xie Junfeng,Yang Yinqin,Hou Daolong,Fan Yongsheng 한국탄소학회 2024 Carbon Letters Vol.34 No.3

For the regeneration of diesel particulate filters (DPF) using non-thermal plasma (NTP), both cost-effectiveness and regeneration efficiency should be raised. This study compared and contrasted the physicochemical characteristics of carbon black and engine particulate matter (PM). After carbon black was put into the DPF, an experimental setup for the oxidation of PM using NTP was created. The findings showed that carbon black and PM samples had comparable oxidation traits, micro-nanostructures, and C/O elemental ratios. O3, the main active species in NTP, was susceptible to heat breakdown, and the rate of decomposition of O3 increases with increasing temperature. The removal effectiveness of carbon black first improved and subsequently declined with an increase in the NTP injection flow rate during offline DPF regeneration using NTP at room temperature. A relatively high carbon black removal efficiency of 85.1% was achieved at an NTP injection flow rate of 30 L/min.

CARBON DEPOSIT INCINERATION DURING ENGINE FLAMEOUT USING NON-THERMAL PLASMA INJECTION

Xiaoyu Pu,Yixi Cai,Yunxi Shi,Jing Wang,Linbo Gu,Jing Tian,Runlin Fan 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.3

−In order to investigate the influence of initial regeneration temperatures on diesel particulate filter (DPF) regeneration, an experimental study of DPF regeneration was implemented using a dielectric barrier discharge (DBD) reactor, aided by exhaust waste heat after engine flameout. DPF trapping characteristics and carbon deposit mass were discussed to facilitate further data analysis and calculation. DPF regeneration was then investigated by comparison analysis of deposit removal mass, backpressure drop, and internal temperature change. The results revealed that a large amount of particulate matter (PM) was deposited in DPF with a high filtration efficiency of about 90 %. The deposit removal rate and percentage drop of the backpressure both maximized at the initial temperature of 100 oC. During DPF regeneration, the sharp rise of internal temperature indicated vigorous PM incineration and high CO2 emission. The results successfully demonstrated DPF regeneration using non-thermal plasma injection during engine flameout, and prominent heat durability was achieved in this method.

EFFECT OF POLYOXYMETHYLENE DIMETHYL ETHERS/DIESEL BLENDS ON FUEL PROPERTIES AND PARTICULATE MATTER OXIDATION ACTIVITY OF A LIGHT-DUTY DIESEL ENGINE

Jing Tian,Yixi Cai,Yunxi Shi,Yingxin Cui,Runlin Fan 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.2

Polyoxymethylene dimethyl ethers (PODE) was blended in diesel at volume ratios of 0 %, 10 %, 20 %, and 30 % (denoted as P0, P10, P20, and P30). The experimental study was carried on an unmodified YD480Q diesel engine. An engine exhaust particle sizer was introduced to analyze the particulate matter (PM) concentration and particle size distribution of diesel engine emission. The evaporation-oxidation characteristics of the PODE/diesel blends and the effect of the fuel blends on the oxidative activity of PM were investigated by thermogravimetric analysis and Arrhenius theorem. The results showed that blending PODE in diesel improved the evaporation-oxidation characteristics of the fuel and decreased the apparent activation energy of the fuel blends. PODE played a positive role in reducing PM emissions. The particle total number concentration of P30 decreased 28.29 ~ 66.60 % and the particle total volume density decreased 54.16 ~ 80.06 % compared to diesel. The particle size distribution shifted to a smaller particle size as the PODE blending ratio was increased. The mass fraction of the volatile substances (VS) increased and the mass fraction of the dry soot (DS) decreased by employing PODE as a diesel additive. Also, the oxidation activity of VS increased as the PODE blending ratio was increased. The oxidation activity of DS climbed to the peak when the PODE blending ratio was 20 % and then decreased.

EFFECTS OF RESIDUAL ASH ON DPF CAPTURE AND REGENERATION

Yingxin Cui,Yixi Cai,Runlin Fan,Yunxi Shi,Linbo Gu,Xiaoyu Pu,Jing Tian 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.5

To study the effects of residual ash on the capture and regeneration of a diesel particulate filter (DPF), repeated capture and complete regeneration experiments were conducted. An engine exhaust particulate sizer was used to measure the particle size distribution of diesel in the front and back of DPF. Discrepancies in the size distribution of the particulate matter in repeated trapping tests were analyzed. To achieve complete DPF regeneration, a DPF regeneration system using nonthermal plasma technology was established. The regeneration carbon removal mass and peak temperatures of DPF internal measuring points were monitored to evaluate the effect of regeneration. The mechanism explaining the influence of residual ash on DPF capture and regeneration was thoroughly investigated. Results indicate that the DPF trapping efficiencies of the nuclear-mode particles and ultrafine particles have significant improvements with the increase quantity of residual ash, from 90 % and 96.01 % to 94.17 % and 97.27 %, respectively. The exhaust backpressure of the DPF rises from 9.41 kPa to 11.24 kPa. Heat transfer in the DPF is improved with ash, and the peak temperatures of the measuring points accordingly increase. By comparing the regeneration trials, the elapsed time for complete regeneration and time difference for reaching the peak temperature between adjacent reaction interfaces are extended with increased quantity of ash. The carbon removal mass rises by 34.00 %.

Effect of Aged Lubricating Oil on the Regeneration of Diesel Particulate Filters and Ash Physical Characteristics with Non-Thermal Plasma Technology

Zhao Nan,Cai Yi-xi,Shi Yunxi,Wang Weikai,Ni Sijia 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.5

The objective of this study was to evaluate the effects of lubricating oil age on the generation of diesel particulate filters (DPF) by non-thermal plasma (NTP) technology and to characterize the physical properties of ash. The regeneration status was evaluated by the concentration of regeneration products and regeneration temperature. The compositional and morphological characteristics of ash were analyzed by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Compared with DPF@L-fresh, the internal regeneration temperature was reduced in DPF@L-age. The unit removal time of carbon was 39.23 min/g for DPF@L-fresh but was reduced to 34.87 min/g for DPF@L-age, which indicated that the efficiency of NTP regeneration increased. Shorter regeneration time and lower airflow resistance caused by NTP technology aided the formation of a unique chain-type ash with the structure of a hollow column. Several fine particles that had formed by the condensation of volatiles were distributed on the ash surface of the aged lubricant, and the ash clusters were loosely combined. TEM images revealed that ash was mostly composed of a crystal structure, that the ash dimension of aged lubricant decreased, and that the adhesion between ash particulates was weak.

Experimental Investigation of Ozone Decomposition in Diesel Particulate Filter Regeneration with Non-Thermal Plasma Technology

Wang Weikai,Cai Yi-xi,Shi Yunxi,Wang Jing,Zhao Nan,Ji Liang 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.4

A non-thermal plasma (NTP) reactor was used to generate ozone for diesel particulate filter (DPF) regeneration. The kinetic mechanism of ozone thermal decomposition reaction is explored, and the effect of temperature on the change of ozone concentration is analyzed. The changes of the internal temperature and the concentration of regeneration products such as CO2 and CO during the regeneration under constant temperature and non-constant temperature conditions are then studied and the influence of different regeneration environments on the regeneration is analyzed in combination with the decomposition law of ozone. In the non-constant temperature condition, DPF surface temperature changes significantly with time. The results show that when using an NTP reactor to generate ozone, the activation energy of the decomposition reaction is 2.80755 × 104 J/mol and the law of thermal decomposition reaction can be described as 190.76 . /. During DPF regeneration, the overall regeneration rate and ozone utilization rate in the nonconstant temperature environment are higher than in the constant temperature environment and the temperature change (delta-T) peak rises with the increase of PM deposition. The regeneration with NTP under non-constant thermal condition is an effective way to improve the efficiency of DPF regeneration.