近年来,天然气汽车(natural gas vehicles,NGVs)尾气净化三效催化剂的研究主要集中在具有高分散性的负载型贵金属催化剂。利用金属有机骨架(MOFs)模板法制备了纳米结构的CeCoO_(x)(M)复合氧化物作为载体,并与传统溶胶-凝胶法(SG)制备的...近年来,天然气汽车(natural gas vehicles,NGVs)尾气净化三效催化剂的研究主要集中在具有高分散性的负载型贵金属催化剂。利用金属有机骨架(MOFs)模板法制备了纳米结构的CeCoO_(x)(M)复合氧化物作为载体,并与传统溶胶-凝胶法(SG)制备的铈钴氧化物比较,探究了贵金属Pd在2种催化剂载体上的分散状态及对其催化性能的影响。结果表明,以CeCo-MOFs材料为前驱体衍生制备的Pd/CeCoO_(x)(M)催化剂其CO、NO、CH4三效催化性能相比溶胶-凝胶法制备的相同组成Pd/CeCoO_(x)(SG)催化剂,相同转化率下催化温度低了约100℃,具有更高的低温活性。以CeCo-MOFs为前驱体衍生制备的铈钴复合氧化物晶体粒子更小,晶相结构均匀,具有更大的比表面积,促进了Pd组分分散状态的提高,也丰富了催化剂的氧空位和结构缺陷,显著提高了催化剂的低温三效催化性能。利用MOFs前驱体热分解得到的复合氧化物可以作为三效催化贵金属活性组分分散的良好材料。展开更多
Pd/YZ-Al2O3 （Y and Zr modified Al2O3, and hereafter, labelled as A1） catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared and characterized by X-ray photoelectron spectroscopy （XPS）, NO-temperature progra...Pd/YZ-Al2O3 （Y and Zr modified Al2O3, and hereafter, labelled as A1） catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared and characterized by X-ray photoelectron spectroscopy （XPS）, NO-temperature programmed desorption （NO-TPD）, Nz-adsorption/desorption （Branauer-Emmet-Teller BET method）, X-ray diffraction （XRD） and CO-chemisorption. Catalytic activities for CH4, CO and NO conversion were tested in a gas mixture simulated the emissions from natural gas vehicles （NGVs） operated under stoichiometric conditions. The results indicated that all catalysts exhibited excellent catalytic performances for CH4 and CO oxidation and the promoting effect of CeO2 or La2O3 was significant for NO conversion. XPS results showed that the electron density around Pd was increased by CeO2 and/or La2O3, the binding energy of Pd 3d decreased as the order： Pd/Al 〉 Pd/Ce/Al 〉 Pd/La/Al 〉 Pd/CeLa/Al. The electron-rich Pd showed Rh-like catalytic properties which exhibited good activity for the reduction of NO. NO-TPD results showed that the addition of CeO2 and/or La2O3 increased NO adsorption on surface, and promoted the conversion of NO.展开更多
Accurate predictions of Shock Waves and Boundary Layer Interaction(SWBLI)and strong Shock Waves and Wake Vortices Interaction(SWWVI)in a highly-loaded turbine propose challenges to the currently widely used Reynolds-A...Accurate predictions of Shock Waves and Boundary Layer Interaction(SWBLI)and strong Shock Waves and Wake Vortices Interaction(SWWVI)in a highly-loaded turbine propose challenges to the currently widely used Reynolds-Averaged Navier-Stokes(RANS)model.In this work,the SWBLI and the SWWVI in a highly-loaded Nozzle Guide Vane(NGV)are studied using a hybrid RANS/LES strategy.The Turbulence Kinetic Energy(TKE)budget and the Proper Orthogonal Decomposition(POD)method are used to analyze flow mechanisms.Results show that this hybrid RANS/LES method can obtain detailed flow structures for flow mechanisms analysis.Strong shock waves induce boundary layer separation,while the presence of a separation bubble can in turn lead to a Mach reflection phenomenon.The shock waves cause trailing-edge vortices to break clearly,and the wakes,in turn,can change the shocks intensity and direction.Furthermore,the Entropy Generation Rate(EGR)is used to analyze the irreversible loss.It turns out that the SWWVI can reduce the flow field loss.There are several weak shock waves in the NGV flow field,which can increase the irreversible loss.This work offers flow mechanisms analysis and presents the EGR distribution in SWBLI and SWWVI areas in a transonic turbine blade.展开更多
In modern gas turbines,the High Pressure Turbine(HPT)is exposed to an extreme thermal environment due to the burned gases leaving the combustor.The burned gases are characterized by flow and temperature distortions th...In modern gas turbines,the High Pressure Turbine(HPT)is exposed to an extreme thermal environment due to the burned gases leaving the combustor.The burned gases are characterized by flow and temperature distortions that effect the aerodynamics and heat transfer of the turbine.The purpose of this paper is to investigate numerically the effect of the intensity of the swirling flow combined with the temperature non-uniformity‘‘Hot-Streak"(H-S)on the aerothermal performances of a HPT Nozzle Guide Vane(NGV).The investigations are conducted on the solid untwisted NGV annular cascade developed in NASA Lewis Research Center.Four swirl intensities(|S_(n)|=0,0.1,0.25 and 0.5),two swirl orientations(positive and negative)and two hot-streaks(rounded and radial)at the NGV inlet are considered.The simulations are done by solving the Reynolds Averaged Navier-Stokes(RANS)equations using ANSYS-CFX software.The results show that the H-S with swirl undergoes twisting following the orientation of the swirl.The H-S twist is aggressive under positive swirl compared to the negative swirl case.The inlet swirl generates a new secondary flow structure,so called Swirl Vortex(SV),which induces more aerodynamic losses.The aerodynamic efficiency under negative swirl found to be higher than that under positive swirl.The maximum temperature on the vane surface is controlled by the radial transport of the SV towards the endwalls.展开更多
This paper introduces and analyzes Korea＇s NGV （natural gas vehicles） policy for soot-free bus fleet which intends to promote CNG （compressed natural gas） bus in metropolitan area for the reduction of air polluti...This paper introduces and analyzes Korea＇s NGV （natural gas vehicles） policy for soot-free bus fleet which intends to promote CNG （compressed natural gas） bus in metropolitan area for the reduction of air pollution from road sector. At the early stage, Korean goverrmaent established various supporting policy systems to encourage public transportation companies to purchase CNG buses as a means to replace diesel buses. It was evaluated as very successful with making net economic benefit of CNG bus promotion policy. During the 2nd stage, Korean government implemented CNG hybrid bus promotion policy to further reduce both air pollution and greenhouse gas. Now, a new social demand for the vehicles is zero-emission vehicles. The author asserts that current FCEV （fuel cell electric vehicle） should be considered as an alternative to zero-emission vehicles in Korea and suggests policy recommendation for the promotion of FCEV by referring the current CNG bus promotion policy in public transportation sector.展开更多
荷兰设计工作室we make carpets其实并不制作地毯,至少他们制作的不是大家印象中的那种地毯。这个设计三人组将自己的作品放在地板上,利用塑料叉、厨房清洁海绵、火柴和气球等生活中常见的材料进行设计,他们打造的独特地毯目前正在墨尔...荷兰设计工作室we make carpets其实并不制作地毯,至少他们制作的不是大家印象中的那种地毯。这个设计三人组将自己的作品放在地板上,利用塑料叉、厨房清洁海绵、火柴和气球等生活中常见的材料进行设计,他们打造的独特地毯目前正在墨尔本NGV儿童艺廊的＂hands on（亲自动手）＂展览上展出。展开更多
文摘近年来,天然气汽车(natural gas vehicles,NGVs)尾气净化三效催化剂的研究主要集中在具有高分散性的负载型贵金属催化剂。利用金属有机骨架(MOFs)模板法制备了纳米结构的CeCoO_(x)(M)复合氧化物作为载体,并与传统溶胶-凝胶法(SG)制备的铈钴氧化物比较,探究了贵金属Pd在2种催化剂载体上的分散状态及对其催化性能的影响。结果表明,以CeCo-MOFs材料为前驱体衍生制备的Pd/CeCoO_(x)(M)催化剂其CO、NO、CH4三效催化性能相比溶胶-凝胶法制备的相同组成Pd/CeCoO_(x)(SG)催化剂,相同转化率下催化温度低了约100℃,具有更高的低温活性。以CeCo-MOFs为前驱体衍生制备的铈钴复合氧化物晶体粒子更小,晶相结构均匀,具有更大的比表面积,促进了Pd组分分散状态的提高,也丰富了催化剂的氧空位和结构缺陷,显著提高了催化剂的低温三效催化性能。利用MOFs前驱体热分解得到的复合氧化物可以作为三效催化贵金属活性组分分散的良好材料。
基金supported by the Key Program of National Natural Science Foundation of China (20333030)the National High Technology Research and Development Program of China (863 Program, No. 2006AA06Z347)the National Natural Science Foundation of China (No. 20773090)
文摘Pd/YZ-Al2O3 （Y and Zr modified Al2O3, and hereafter, labelled as A1） catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared and characterized by X-ray photoelectron spectroscopy （XPS）, NO-temperature programmed desorption （NO-TPD）, Nz-adsorption/desorption （Branauer-Emmet-Teller BET method）, X-ray diffraction （XRD） and CO-chemisorption. Catalytic activities for CH4, CO and NO conversion were tested in a gas mixture simulated the emissions from natural gas vehicles （NGVs） operated under stoichiometric conditions. The results indicated that all catalysts exhibited excellent catalytic performances for CH4 and CO oxidation and the promoting effect of CeO2 or La2O3 was significant for NO conversion. XPS results showed that the electron density around Pd was increased by CeO2 and/or La2O3, the binding energy of Pd 3d decreased as the order： Pd/Al 〉 Pd/Ce/Al 〉 Pd/La/Al 〉 Pd/CeLa/Al. The electron-rich Pd showed Rh-like catalytic properties which exhibited good activity for the reduction of NO. NO-TPD results showed that the addition of CeO2 and/or La2O3 increased NO adsorption on surface, and promoted the conversion of NO.
基金supported by the National Natural Science Foundation of China(No.51876098).
文摘Accurate predictions of Shock Waves and Boundary Layer Interaction(SWBLI)and strong Shock Waves and Wake Vortices Interaction(SWWVI)in a highly-loaded turbine propose challenges to the currently widely used Reynolds-Averaged Navier-Stokes(RANS)model.In this work,the SWBLI and the SWWVI in a highly-loaded Nozzle Guide Vane(NGV)are studied using a hybrid RANS/LES strategy.The Turbulence Kinetic Energy(TKE)budget and the Proper Orthogonal Decomposition(POD)method are used to analyze flow mechanisms.Results show that this hybrid RANS/LES method can obtain detailed flow structures for flow mechanisms analysis.Strong shock waves induce boundary layer separation,while the presence of a separation bubble can in turn lead to a Mach reflection phenomenon.The shock waves cause trailing-edge vortices to break clearly,and the wakes,in turn,can change the shocks intensity and direction.Furthermore,the Entropy Generation Rate(EGR)is used to analyze the irreversible loss.It turns out that the SWWVI can reduce the flow field loss.There are several weak shock waves in the NGV flow field,which can increase the irreversible loss.This work offers flow mechanisms analysis and presents the EGR distribution in SWBLI and SWWVI areas in a transonic turbine blade.
文摘In modern gas turbines,the High Pressure Turbine(HPT)is exposed to an extreme thermal environment due to the burned gases leaving the combustor.The burned gases are characterized by flow and temperature distortions that effect the aerodynamics and heat transfer of the turbine.The purpose of this paper is to investigate numerically the effect of the intensity of the swirling flow combined with the temperature non-uniformity‘‘Hot-Streak"(H-S)on the aerothermal performances of a HPT Nozzle Guide Vane(NGV).The investigations are conducted on the solid untwisted NGV annular cascade developed in NASA Lewis Research Center.Four swirl intensities(|S_(n)|=0,0.1,0.25 and 0.5),two swirl orientations(positive and negative)and two hot-streaks(rounded and radial)at the NGV inlet are considered.The simulations are done by solving the Reynolds Averaged Navier-Stokes(RANS)equations using ANSYS-CFX software.The results show that the H-S with swirl undergoes twisting following the orientation of the swirl.The H-S twist is aggressive under positive swirl compared to the negative swirl case.The inlet swirl generates a new secondary flow structure,so called Swirl Vortex(SV),which induces more aerodynamic losses.The aerodynamic efficiency under negative swirl found to be higher than that under positive swirl.The maximum temperature on the vane surface is controlled by the radial transport of the SV towards the endwalls.
文摘This paper introduces and analyzes Korea＇s NGV （natural gas vehicles） policy for soot-free bus fleet which intends to promote CNG （compressed natural gas） bus in metropolitan area for the reduction of air pollution from road sector. At the early stage, Korean goverrmaent established various supporting policy systems to encourage public transportation companies to purchase CNG buses as a means to replace diesel buses. It was evaluated as very successful with making net economic benefit of CNG bus promotion policy. During the 2nd stage, Korean government implemented CNG hybrid bus promotion policy to further reduce both air pollution and greenhouse gas. Now, a new social demand for the vehicles is zero-emission vehicles. The author asserts that current FCEV （fuel cell electric vehicle） should be considered as an alternative to zero-emission vehicles in Korea and suggests policy recommendation for the promotion of FCEV by referring the current CNG bus promotion policy in public transportation sector.
