低温等离子木质钙钛矿柴油机尾气净化器设计与试验

Non-thermal plasma-woody perovskite purifier for diesel engine exhaust

为有效提高低温等离子体(non-thermal plasma,NTP)协同木质钙钛矿型催化剂净化柴油机尾气的效能,首先,设计了以刚玉管和木质钙钛矿型催化剂为介质的介质阻挡放电反应器(dielectric barrier discharge,DBD),建立了DBD反应器的二维仿真模型,采用COMSOL软件等离子体模块计算DBD反应器不同参数条件下活性物种的数密度,通过分析得出较优的反应器内部参数;其次,设计了低温等离子木质钙钛矿柴油机尾气净化器总体结构,建立了基于压力损失的数值模型,分析不同DBD布置形式对排气背压的影响;最后,搭建发动机台架以对该净化器的净化性能进行试验验证。研究结果表明:当净化器输入电压为15 kV,填充率为30%,DBD并联个数为20,反应器长度为0.16 m时,尾气净化器的排气背压满足国标要求,可实现碳烟颗粒物(particulate matter,PM)、NO_x、CO和HC的同时净化。当发动机转速为2 600 r/min、发动机负荷为50%时,净化器对PM、NO_x、CO和HC的净化效率分别为92%、64%、72%和61%。该研究结果可为NTP协同催化在净化汽车尾气净化领域的应用提供理论参考。

Woody perovskite-type catalysts are the sorts of porous catalysts with biomass morphology,in order to achieve the simultaneous purification of PM,NOx,CO,and HC.Among them,the ratio of adsorbed oxygen(Oads)/lattice oxygen(Olatt)of perovskite-type catalysts can be improved to avoid the collapse and aggregation of perovskite-type catalysts.The reason was attributed to the presence of a large number of high-energy electrons,active particles,and active heavy particles in non-thermal plasma(NTP).In addition,the NTP can outstandingly improve the specific surface area and porosity of catalysts.The NTP can enhance the four-way purification performance of PM,NOx,CO,and HC emitted by automobile exhausts over woody perovskite-type catalysts.Dielectric barrier discharge(DBD)can generate the NTP under atmospheric pressure conditions,indicating the broad application prospects in environmental protection and material processing.This study aims to enhance the performance of NTP synergistic woody perovskite-type catalysts,in order to purify the diesel engine exhaust.Firstly,a DBD reactor was designed,of which the corundum tubes and woody perovskite-type catalysts were used as the discharge medium.A two-dimensional simulation model was established for the DBD reactor.The plasma module of COMSOL software was employed to calculate the number density of active species under different parameter conditions of the reactor.After that,the optimal internal parameters of the reactor were obtained.Secondly,the overall mechanical structure of the non-thermal plasma-woody perovskite purifier was designed for the diesel engine exhaust.A numerical model was established to analyze the impact of different DBD arrangements on exhaust back pressure using pressure loss.Lastly,a test bench of the diesel engine was set to verify the purification performance of the purifier.According to the relevant regulations of automotive testing,the D2(5 loads operating at rated speed)test cycle was selected from the ISO 8187 international standard,in order to test and verify the purifier.The model calculation indicated that when the input voltage of the exhaust purifier was 15 kV,the filling rate was 30%,the number density of active particles in the reactor reached the maximum,with an electron density of 1016/m3,the electron energy distribution in the reactor ranged from 101.1 to 101.5 eV,and the number densities of N2+,-CO,and-N2 reached 1018/m3,the number densities of-O reached 1013/m3,respectively.Once the number of DBD parallel connections was 20,and the DBD reactor length was 0.16 m,the exhaust back pressure of the purifier was 996.3 Pa.The experimental results showed that the exhaust back pressure of the purifier fully met the national standard requirements,in order to achieve the simultaneous purification of PM,NOx,CO,and HC.Furthermore,the purification efficiencies of the purifier reached 92%,64%,72%,and 61%,respectively,when the engine speed was 2600 r/min and the load was 50%.Once the purifier was used for no more than 75 h,the exhaust back pressure of the purifier was less than 3 kPa.Correlation analysis of experimental data revealed that the PM,CO and HC were promoted to reduce NOx,thus leading to the oxidation of PM,CO,and HC.The finding can provide the theoretical reference for synergistic catalysis in the field of automotive exhaust purification.