电加热金属载体催化剂对汽油机冷起动阶段排放性能的影响

采用电加热金属载体催化剂(EHC),研究了加热电压、加热时间以及贵金属涂敷量对汽油发动机冷起动排放性能的影响.试验结果表明:EHC载体热容小,升温快,THC、CO和NOx的转化效率比陶瓷载体高;加热电压越大,EHC加热功率越大,直接影响THC、CO和NOx的转化效率;EHC加热一定时长后,继续增加加热时间,不一定能达到减排效果;通过EHC的应用,能够减少三元催化器50％的贵金属用量.     

矿用防爆柴油机DOC减排装置的研发

针对目前矿用防爆柴油机尾气中CO、HC排量高,严重危害矿下工作人员身体健康的现状。为此,我们利用柴油氧化催化剂(DOC)成功研发了一种适于矿用防爆柴油机的DOC减排装置,该装置对尾气中CO的转化率高达95%以上,HC的转化率也高达80%以上,且使用寿命长,具有很好的经济环保价值,适于在矿用防爆柴油机车上推广使用。     

摩托车尾气净化技术现状及发展趋势

控制摩托车排气的净化技术是一项以催化转化为核心的综合设计和匹配优化工程,金属载体上载工艺是摩托车催化转化技术的核心,也是制备金属载体催化剂的关键工艺。经试验证明,新工艺既保证了催化剂组份抗热冲击和机械冲击能力,也具有良好的CO、HC和NOx三元净化性能。     

催化剂涂覆量对POC降低柴油机排放的影响

在1台4缸柴油机上进行了POC催化剂涂覆量对柴油机污染物排放量影响的试验研究,分析了POC催化剂涂覆量对HC,CO,PM和烟度的影响规律。结果表明,催化剂涂覆量为0.706×10-3 g/cm3时对HC和CO均有较高的转化效率,分别为58.4%和72.5%;涂覆催化剂后,POC对PM的氧化率和捕集率随POC前温度的变化呈现相似的规律,最高捕集率与氧化率均出现在230℃左右,分别为73.2%和30.1%。     

国内外摩托车基础技术综述(2)

(上接2002年第8期) 4 环保技术 4.1 尾气后处理技术 尾气后处理技术主要有以下几种应用形式: 二元催化转化器:利用附着在金属(或陶瓷)载体上的氧化型催化剂的催化作用,将尾气中的HC和CO氧化成H2O和CO2,从而降低排放,但对NOx的净化效果甚微.该技术在国内应用已比较成熟,许多在城市销售的摩托车都装有该装置.     

柴油机微粒排放控制技术

由于柴油机具有较好的燃油经济性、耐久性和气体排放物较少等优点,因此近年来车用柴油机得到了较大的发展。车用柴油机的销售量现在已占欧洲市场的18％以上,在亚洲市场也呈不断增长趋势。展望到2000年,世界柴油车比重将占汽车总量的20％。柴油机排放中有害成份主要有CO、HC、NO_x和微粒,但HC、CO排放较少,     

共轨柴油机燃烧纯生物柴油的试验研究

对一台国产涡轮增压直喷柴油机燃烧0#柴油和纯生物柴油的动力性、燃油经济性和排放性能进行对比试验研究。试验结果表明,在柴油机不进行任何调整的情况下,燃烧纯生物柴油会降低其动力性和燃油经济性,但可大幅度改善CO、HC和PM的排放性能。     

汽车污染排放物的测量

汽车排放的污染物主要是一氧化碳(CO)、碳氢化合物(HC)、氮氧化合物(NOx)及炭烟等。在相同工况下汽油机排放的CO、HC和NOx的排放量比柴油机大，因此目前国家标准中对汽油机主要限制CO、HC和NOx的排放量。而柴油机由于其燃烧时混合气形成的时间非常短，在空气不足或混合气不均匀的情况下主要是产生炭烟污染，因此排放标准中主要限制柴油机排气的烟度。     

车用柴油机微粒排放法规与控制技术

1柴油机排气微粒的危害性 柴油机具有良好的燃油经济性、动力性、耐久性和排放性等优点,汽车柴油化已成为国际潮流.与汽油机相比,柴油机有害气体HC、CO的排放量相当低,柴油机的CO排放大约只有汽油机的1/10,柴油机的NOx排放量和汽油机处于同一数量级,但柴油机微粒排放约为汽油机的30～80倍.因此,微粒排放已经是制约柴油车发展的最主要因素之一.     

康明斯公司满足排放法规的柴油机技术--《全国柴油车污染防冶研讨会》之二

柴油机排放污染物中有害成份主要有CO、HC、NOX及PM等,与同等功率汽油机相比,虽柴油机HC、CO排放较少,但NOX与PM排放较多,柴油机微粒排放约是汽油机30～80倍.在柴油机整个使用寿命期内的排放污染物中,PM和NOX分别占22%和21%.NOX主要是NO和NO2,NO是一种无色、无味的气体.     

Heat exchanger/catalytic system for reducing the exhaust emissions from diesel engines

A system has been researched over the past 3 years for reducing the exhaust pollutants from diesel engines for light commercial vehicles. The system researched achieves Euro 6 standards for reduction of polluting gases (CO, HC, PM, NO). It consists of 4 main sections: 1. A heater and heat exchanger (HE); 2. A CO/HC oxidising catalyst (D°C); 3. Pt catalyst on a diesel particulate filter (DPF); 4. A NO reducing reaction (SCR) within the DPF. The system operates as follows. The exhaust gas contains oxidising gases, namely both O₂ and NO₂. The levels of CO and HC are oxidised by O₂ to CO₂ for temperatures above 200°C. Carbon (PM) is oxidised to CO₂ by NO₂ but requires a temperature above 250°C. The operating exhaust temperature of 300°C is ideal for the removal of NO by using the Pt catalyst and the CO generated within the DPF. The heater is required to be able to raise the exhaust temperature at any time to 300°C in order to optimise the performance of the system, since diesel engine exhaust temperatures vary between 160°C (slow speeds) to 350°C (high speeds). Considerable heat is required (??3 kW) to maintain the exhaust gas for a 2l engine at 300°C for engine idle conditions. Therefore a heat exchanger is required to re-circulate the input heat and thereby reduce the maximum power consumption to a maximum of 500W over the engine full operating test cycle. This energy is supplied by the engine battery and alternator. Experimental results have been obtained for the exhaust from a Kubota diesel engine and the reductions in exhaust emissions of 83% (CO/ HC), 58% (NOx) and 99% (PM) were obtained. The PM was continuously cleaned so that there was no build up of back pressure.     

Parametric study of the main parameters influencing the catalytic efficiency of a diesel oxidation catalyst: Parameters influencing the efficiency of a diesel catalyst

This work studies the impact of five parameters: CO and HC engine-out emissions, space velocity, average value and profile of exhaust temperature, on Diesel CO and HC tail-pipe emissions. The first part of this work is conducted on a reactor and shows that both HC and CO light-off temperature increases with CO and HC input concentration. CO and HC initial concentration influence the adsorption/desorption capacities of HC only at high temperatures. Space velocity also influences CO and HC conversion efficiency. The second part of this work studies the impact of different combinations of HC and CO engine-out emissions on CO and HC conversion and tail-pipe emissions in the case of New European Driving Cycle. This part proposes that a Diesel oxidation catalyst must be mainly studied at the Urban Part of NEDC, as the CO and HC conversions are very high at the extra-urban part of NEDC. CO and HC conversion efficiencies are also dependent on exhaust temperature and catalytic volume. In the case of two different profiles of exhaust temperature with the same average temperature, CO and HC conversion efficiency is lower in the case of the smoother profile.     

分子筛型SCR对车用柴油机排放改善的试验研究

商用车柴油机多采用DOC+SCR的后处理系统来满足国Ⅳ、国Ⅴ排放标准的要求,而不同类型SCR的催化特性对最终污染物排放影响也不同。试验获取了一支铜基分子筛型SCR,基于1台2.8L柴油机和一支钒基SCR,运行了车用柴油机稳态循环(ESC)和瞬态排放循环(ETC),研究并分析了其对柴油机污染物的减排特性。结果表明,相较于钒基SCR,运行ETC循环时分子筛型SCR对发动机NOx和PM排放的减排效率分别提升19%和33%;分子筛型SCR对NOx的低温转化效率更高,且由于对排气流量不敏感,在高空速工况下其转化效率显著高于钒基SCR;分子筛型SCR对颗粒物个数的减排效率弱于钒基SCR,达7%以上,容易将大质量颗粒物分解为小质量颗粒物;两种SCR均对CO和HC具有一定的减排效果,减排率可达20%左右。     

Comparison of HC species from diesel combustion modes and characterization of a heat-up doc formulation

This study summarizes engine speed and load effects on HC species emissions from premixed charge compression ignition (PCI) and conventional diesel combustion, and it evaluates diesel oxidation catalyst (DOC) formulations on a gas flow reactor for the purpose of diesel particulate filter regeneration or lean NO_x trap desulfation. HC emissions are sampled simultaneously by a Tedlar bag for light HC species and by a Tenax TA™ adsorption trap for semi-volatile HC species, and they are analyzed by gas chromatography with a flame ionization detector. The bulk temperature and residence time during combustion are key parameters that are important for understanding the effects of speed and load on engine-out HC emissions. The degree of post-flame oxidation is higher in PCI than in conventional combustion, and it is increased for PCI with a higher speed and load, as indicated by a lower fuel alkanes/THC ratio, a higher alkenes/fuel alkanes ratio, and a higher methane/THC ratio. Ethene and n-undecane are two representative HC species, and they are used as a surrogate mixture in the gas flow reactor to simulate PCI and conventional combustion with in-cylinder post fuel injection. Among the three DOC formulations tested, the catalyst with constituent precious metals of platinum and palladium (PtPd) showed the best light-off performance, followed by PtPd with an addition of cerium dioxide (PtPd+CeO₂), and platinum (Pt), regardless of exhaust compositions. Conventional combustion exhaust composition shows a lower light-off temperature than that of PCI, regardless of catalyst formulation.     

小型多缸柴油机气态排放的研究

改善排放是小缸径多缸柴油机当前发展的重要方向。在诸多影响因素中,取4种参数对气态排放量的影响进行了初步的试验研究。试验结果表明,喷油提前角、喷孔总面积、进水温度及进气密度对CO,HC,NO_x的排放量有明显的影响。     

废食用油代用燃料在柴油机上的试验研究

食用植物油是一种很有前途的代用燃料,它是利用植物的光合作用不断更新生产的一种能源。通过用废食用油制得的柴油机代用燃料,在小型高速柴油机上与0号柴油做了性能对比试验。试验结果表明,与燃用柴油相比,用废食用油作为代用燃料输出功率几乎相同(仅低2%),燃油消耗增加了6%~12%,排气温度降低了20℃,所排出的CO2降低了10%~15%,CO降低了10%~18%,HC降低了47%。     

轻型车燃用生物柴油瞬态工况排放特性的研究

通过对轻型车燃用生物柴油和0#柴油尾气排放的测量和分析，研究瞬态工况有害排放物模态特性。试验结果表明，与0#柴油相比，轻型车燃用生物柴油可显著改善冷启动过程的HC和CO排放，其HC、CO和PM比排放分别降低76．9％、45．7％和52．8％，但NOx比排放增加5．8％。燃料在燃烧转变为CO2和H2O释放出化学能的同时也将空气中的N2氧化成NOx，因而可用NOx／CO2来描述NOx排放随运行工况的变化规律。     

汽车燃油空气加热器燃烧排放控制研究

针对燃油空气加热器开机、关机排放污染严重的问题,提出通过改进点火系统和供油系统来降低排放。通过对比发现:采用全陶瓷点火后,开机过程的CO、HC浓度基本不变,但烟度不透光系数(OPAC)峰值降低,排烟持续时间缩短;改进供油系统后,关机过程的HC排量降到原来的30%,CO排量降到原来的3%,烟度OPAC值降为原来的28%,各排放持续时间均缩短。试验结果表明:采用全陶瓷点火和改进供油系统有效地降低了加热器的开机、关机排放污染。     

负载型贵金属催化剂对乙醇汽油车排放的净化研究

利用XRD,BET和H2-TPR等方法对制备的负载型催化剂Pt/CZ进行了表征。采用浆料球磨涂覆工艺制备了含铈锆固溶体的三效催化剂,并在模拟乙醇汽油车尾气条件下对其催化性能进行了评价。结果表明,三效催化剂有良好的CO,HC,NOx和CH3CHO同时净化的三效性能和低的起燃活性,有较高的活性,还有良好的抗高温性能。气氛中加入SO2后降低了催化剂活性。