空燃比波动对压缩天然气发动机TWC甲烷起燃特性的影响
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摘要
针对压缩天然气(Compressed natural gas,CNG)发动机专用三元催化器(Three way catalyst,TWC)中空燃比波动影响甲烷起燃特性的重要因素,以小样试验为基础建立数值模型,考虑空燃比波动对甲烷起燃特性进行仿真计算,探究空燃比波动的振幅、浓燃占空比和波动中心的影响因素及规律。结果表明:在空燃比波动的一定范围内,空燃比波动振幅的增大会降低甲烷的起燃温度(T_(50))和完全转化温度(T_(90));空燃比波动的浓燃占空比越大,会使催化器内部的载体轴向平均温度升高,有利于甲烷水蒸气重整反应,相对降低甲烷的T_(50)和T_(90);空燃比波动的中心由偏稀变为偏浓,可以促进甲烷起燃;CNG发动机专用TWC工作在微浓的进气条件下有助于甲烷的起燃。
The light-off performance of methane of special Three-Way Catalytic converter(TWC)for Compressed Natural Gas(CNG)engine is significantly impacted by the A/F ratio fluctuation.Based on sample test data,a TWC model is established considering the A/F ratio.The effects of the amplitude,duty cycle and fluctuation center of A/F ratio on the light-off performance of methane are analyzed.The results show that greater amplitude would reduce the light-off temperature(T_(50))and complete conversion temperature(T_(90))of methane.Longer duty cycle of rich gas composition would cause smaller T_(50) and T_(90) because of higher mean axial temperature of substrate,which could promote the methane steam reforming and reaction.The fluctuation center from lean to rich would promote thelight-off performance of methane,and the greater the amplitude the stronger this effect.The rich gas composition could contribute to the light-off performance of methane based on the results of the duty cycle and the fluctuation center.
The light-off performance of methane of special Three-Way Catalytic converter(TWC)for Compressed Natural Gas(CNG)engine is significantly impacted by the A/F ratio fluctuation.Based on sample test data,a TWC model is established considering the A/F ratio.The effects of the amplitude,duty cycle and fluctuation center of A/F ratio on the light-off performance of methane are analyzed.The results show that greater amplitude would reduce the light-off temperature(T_(50))and complete conversion temperature(T_(90))of methane.Longer duty cycle of rich gas composition would cause smaller T_(50) and T_(90) because of higher mean axial temperature of substrate,which could promote the methane steam reforming and reaction.The fluctuation center from lean to rich would promote thelight-off performance of methane,and the greater the amplitude the stronger this effect.The rich gas composition could contribute to the light-off performance of methane based on the results of the duty cycle and the fluctuation center.
引文
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[16]冯国胜,李孟良,李军,等.车用催化剂评价系统开发[J].天津大学学报,2007,40(12):1481-1484.Feng Guo-sheng,Li Meng-liang,Li Jun,et al.Development of automotive catalyst evaluation system[J].Journal of Tianjin University,2007,40(12):1481-1484.
[17]Fujimoto K,Avalos-Borja M,Iglesia E,et al.Structure and reactivity of PdOx/ZrO2,catalysts for methane oxidation at low temperatures[J].Journal of Catalysis,1998,179(2):431-442.
[18]Mónica García-Diéguez,Ya-Huei Cathy Chin,Enrique Iglesia.Catalytic reactions of dioxygen with ethane and methane on platinum clusters:Mechanistic connections,site requirements,and consequences of chemisorbed oxygen[J].Journal of Catalysis,2012,285(1):260-272.
[19]环境保护部.HJ689-2014城市车辆用柴油发动机排气污染物排放限值及测量方法(WHTC工况法)[M].北京:中国环境科学出版社,2014.
[2]张强,李娜,李国祥.天然气发动机三效催化剂[J].山东大学学报:工学版,2010,40(4):121-124.Zhang Qiang,Li Na,Li Guo-xiang.Three way catalyst for CNG engine[J].Journal of Shangdong University(Engineering and Technology Edition),2010,40(4):121-124.
[3]尚鸿燕,胡伟,王云,等.理论空燃比天然气汽车尾气中H2O和O2对CH4与NO反应的影响[J].物理化学学报,2015,31(4):750-756.Shang Hong-yan,Hu Wei,Wang Yun,et al.Effects of H2O and O2on the reaction of NO reduction by CH4under stoichiometric natural gas vehicles[J].Acta Physico-Chimica Sinica,2015,31(4):750-756.
[4]胡明江,王忠.La0.7Sr0.3Mn1-xCoxO3-δ催化剂降低天然气发动机尾气排放的研究[J].环境科学学报,2014,34(4):835-842.Hu Ming-jiang,Wang Zhong.Effects on emissions of natural gas engine with La0.7Sr0.3 Mn1-xCox O3-δcatalysts[J].Journal of Environmental Science,2014,34(4):835-842.
[5]王勇,孙冬野,漆正刚.基于排放目标的汽油车闭环燃油控制优化[J].汽车工程,2016,38(10):1169-1176.Wang Yong,Sun Dong-ye,Qi Zheng-gang.Optimization of closed-loop fuel control of gasoline vehicle for emission target[J].Automotive Engineering,2016,38(10):1169-1176.
[6]Xi Y Z,Ottinger N,Liu Z G.Development of a lab reactor system for the evaluation of aftertreatment catalysts for stoichiometric natural gas engines[C]∥SAE Paper,2017-01-0999.
[7]Djamela Bounechada,Gianpiero Groppi,Pio Forzatti,et al.Effect of periodic lean/rich switch on methane conversion over a Ce-Zr promoted Pd-Rh/Al2O3catalyst in the exhausts of natural gas vehicles[J].Applied Catalysis B:Environmental,2012,119-120:91-99.
[8]Sheedeh Fouladvand, Magnus Skoglundh, PerAnders Carlsson.Unsteady-state operation of supported platinum catalysts for high conversion of methane[J].Chemical Engineering Journal,2016,292:321-325.
[9]Effendy M,Wardhono E Y.Determination of model kinetics for forced unsteady state operation of catalytic CH4 oxidation[C]∥MATEC Web of Conferences,Istanbul,Turkey,2016,60:03001.
[10]李俊,王建昕,肖建华,等.闭环控制系统空燃比波动对三效催化剂活性的影响[J].汽车工程,2000,22(2):134-138.Li Jun,Wang Jian-xin,Xiao Jian-hua,et al.Effect of A/F ratio fluctuation of closed-loop system on TWC[J].Automotive Engineering,2000,22(2):134-138.
[11]李俊,王建昕,肖建华.空燃比对三效催化剂起燃特性的影响[J].汽车技术,2000(10):15-16,24.Li Jun,Wang Jian-xin,Xiao Jian-hua.Effects of air/fuel ratio on the incipient combustion performance of three way catalyst[J].Automobile Technology,2000(10):15-16,24.
[12]董团结,王建昕,庄人隽,等.三效催化转化器与电控汽油机匹配的研究[J].内燃机学报,2001,19(6):573-577.Dong Tuan-jie,Wang Jian-xin,Zhuang Ren-juan,et al.Research on the matching of TWC and electronic gasoline engine[J].Journal of Internal Combustion Engine,2001,19(6):573-577.
[13]于秀敏,董伟,嵇全喜.直喷汽油机催化器快速起燃的试验研究[J].汽车工程,2011,33(10):865-868.Yu Xiu-min,Dong Wei,Ji Quan-xi.An experimental study on the fast light off of catalytic converter in a gasoline direct injection engine[J].Automotive Engineering,2011,33(10):865-868.
[14]Shang Hong-yan,Wang Yun,Cui Ya-juan,et al.Catalytic performance of Pt-Rh/CeZrYLa+LaAl with stoichiometric natural gas vehicles emissions[J].Chinese Journal of Catalysis,2015(3):290-298.
[15]Wang Yun,Shang Hong-yan,Xu Hai-di,et al.Effects of ZnO content on the performance of Pd/Zr0.5Al0.5O1.75 catalysts used in lean-burn natural gas vehicles[J].Chinese Journal of Catalysis,2014(7):1157-1165.
[16]冯国胜,李孟良,李军,等.车用催化剂评价系统开发[J].天津大学学报,2007,40(12):1481-1484.Feng Guo-sheng,Li Meng-liang,Li Jun,et al.Development of automotive catalyst evaluation system[J].Journal of Tianjin University,2007,40(12):1481-1484.
[17]Fujimoto K,Avalos-Borja M,Iglesia E,et al.Structure and reactivity of PdOx/ZrO2,catalysts for methane oxidation at low temperatures[J].Journal of Catalysis,1998,179(2):431-442.
[18]Mónica García-Diéguez,Ya-Huei Cathy Chin,Enrique Iglesia.Catalytic reactions of dioxygen with ethane and methane on platinum clusters:Mechanistic connections,site requirements,and consequences of chemisorbed oxygen[J].Journal of Catalysis,2012,285(1):260-272.
[19]环境保护部.HJ689-2014城市车辆用柴油发动机排气污染物排放限值及测量方法(WHTC工况法)[M].北京:中国环境科学出版社,2014.