共查询到20条相似文献,搜索用时 31 毫秒
1.
依据介质阻挡放电原理及低温等离子体转化有害气体的机理,设计了一套双介质阻挡放电型低温等离子体空气放电试验系统。研究了空气流量、激励电压峰峰值(VP‐P)及放电频率对空气放电特性及其产生的NO,NO2体积分数变化的影响,并采集了放电区域光谱信息。研究结果表明:当VP‐P、空气流量保持恒定时,NO,NO2的体积分数随放电频率的增大而逐渐减小;当放电频率、VP‐P保持恒定时,NO,NO2的体积分数均随空气流量的增大而逐渐减小;保持放电频率不变,VP‐P从13kV增大到28kV过程中,氮气发射特征谱线强度逐渐增大;保持VP‐P不变,放电频率从7kHz增大到11kHz过程中,氮气特征谱线强度逐渐减小。 相似文献
2.
J. Lucas M. A. Houghton I. G. Masheter 《International Journal of Automotive Technology》2012,13(6):853-860
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. 相似文献
3.
《JSAE Review》1995,16(1):21-25
The platinum ion-exchanged ZSM-5 zeolite catalyst (Pt-5), which reduces nitrogen oxides (NOx) in the presence of oxygen and hydrocarbons, was applied to actual diesel engine exhaust. Compared to the Cooper ion-exchanged ZSM-5 zeolite catalyst, the Pt-Z had higher NOx reduction efficiency, ηNOx = 33%, and lower activation temperature, 250°C, in normal engine operation. It was found that water in the exhaust gas did not apparently affect the NOx reduction, while the reduction efficiency was significantly affected by the aspect ratio of the catalyst reactor and by the shape of the catalyst, i.e. pellet or honeycomb. 相似文献
4.
Y. X. Shi Y. X. Cai X. H. Li Y. Y. Chen D. W. Ding W. Tang 《International Journal of Automotive Technology》2014,15(6):871-876
By using a self-designed non-thermal plasma (NTP) injection system, an experimental study of the regeneration of DPF was conducted at different temperatures, where oxygen as the gas source. The results revealed that PM can be decomposed to generate CO and CO2 by these active substances O3, O which was generated through the discharge reaction of NTP reactor. With the increasing of test temperature, the mass of C1 (C in CO) shows a overall downward trend while the mass of C2 (C in CO2) and C12 (C1 and C2) increase firstly and then decrease. When the test temperature is 80°C, the backpressure of DPF decreases fastest and the regenerative effect is remarkable. DPF can be regenerated by NTP technology without any catalyst at a lower temperature. Compared with the traditional regeneration method, the NTP technology has its superiority. 相似文献
5.
This paper proposes a real-time empirical model of NOx emissions for diesel engines. The proposed model predicts the level of NOx emissions using an empirical model developed based on the thermal NO formation mechanism, the extended Zeldovich mechanism. Since it is difficult to consider the exact physical NO formation phenomena in real-time applications, the proposed algorithm adapts the key factors of the NO formation mechanism from the extended Zeldovich mechanism: temperature of the burned gas, concentration of the gas species, and combustion duration where NO is generated. These factors are considered in a prediction model as four parameters: exhaust gas recirculation rate (EGR rate), crank angle location of 50 % of mass fraction burned (MFB50), exhaust lambda value, and combustion acceleration. The proposed prediction model is validated with various steady engine experiments that showed a high linear correlation with the NOx emission measured by a NOx sensor. Furthermore, it is also validated for transient experiments. 相似文献
6.
为了分析柴油机燃用F-T柴油的燃烧波动特性,在增压中冷直喷柴油机上对燃用F-T柴油和0号柴油的中高转速和负荷工况进行了对比试验研究。研究表明:在同一工况下,与0号柴油相比,燃用F-T柴油的燃烧始点较早,燃烧压力峰值较低,压力波动幅值较小;对燃烧压力进行频谱分析可以看出,F-T柴油的燃烧压力波动一阶主频率小于0号柴油的主频率,两种燃料的一阶主频率均随转速的增加而增大,随着负荷的增加有降低的趋势,且负荷对F-T柴油的影响较0号柴油更加显著。从燃烧振动噪声源的角度考虑,燃用F-T柴油有利于降低柴油机的燃烧噪声和缸内燃烧时的爆发冲击载荷。 相似文献
7.
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 NOx 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. 相似文献
8.
S. J. Lee S. J. Jeong W. S. Kim C. B. Lee 《International Journal of Automotive Technology》2008,9(6):659-670
The use of a diesel particulate filter (DPF) in a diesel aftertreatment system has proven to be an effective and efficient
method for removing particulate matter (PM) in order to meet more stringent emission regulations without hurting engine performance.
One of the favorable PM regeneration technologies is the NO2-assisted regeneration method due to the capability of continuous regeneration of PM under a much lower temperature than that
of thermal regeneration. In the present study, the thermal behavior of the monolith during regeneration and the conversion
efficiency of NO2 from NO with an integrated exhaust system of a diesel oxidation catalyst (DOC) and DPF have been predicted by one-channel
numerical simulation. The simulation results of the DOC, DPF, and integrated DOC-DPF models are compared with experimental
data to verify the accuracy of the present model for the integrated DOC and DPF modeling. The effects of catalyst loading
inside the DOC and the volume ratio between the DOC and DPF on the pressure drop, the conversion efficiency, and the oxidation
rate of PM, have been numerically investigated. The results indicate that the case of the volume ratio of ‘DOC/DPF=1.5’ within
the same diameter of both monoliths produced close to the maximum conversion efficiency and oxidation rate of PM. Under the
engine operating condition of 175 kW at 2200 rpm, 100% load with a displacement of 8.1, approximately 55 g/ft3 of catalyst (Pt) loading inside the DOC with the active Pt surface of 5.3 m2/gpt was enough to maximize the conversion efficiency and oxidation rate of PM. 相似文献
9.
Joonsoo Han Junho Lee Youngtaig Oh Gyubaek Cho Hongsuk Kim 《International Journal of Automotive Technology》2017,18(6):951-957
Urea-SCR systems have been widely used in diesel vehicles according to the strengthened NOx (Nitrogen Oxides) emission standard. The NOx removal efficiencies of the latest well optimized urea-SCR system are above 90 % at moderate exhaust gas temperature of 250 ~ 450 °C. However, a large amount of NOx is emitted from diesel vehicles at cold start or urban driving conditions, when the exhaust gas temperature is not high enough for SCR catalyst activation. Although many researchs have been stuied to improve NOx conversion efficiency at these low temperature conditions, it is still one of important technical issues. In this study, the effect of UWS injection at low exhaust gas temperature conditions is studied. This study uses a 3.4 L diesel engine equipped with a commertial urea SCR system. As a result, it is found that about 5 % of NOx removal efficiency is improved in the NRTC test when UWS injection starts at the SCR inlet temperature of 150 °C compared to 200 °C. It is also found that urea deposits can be formed on the wall of exhaust pipe, when the local wall temperature is lower than temperature of urea decomposition. 相似文献
10.
Tae Joong Wang 《International Journal of Automotive Technology》2018,19(6):941-947
In this study, the effect of hydrothermal aging over a commercial diesel oxidation catalyst (DOC) on deterioration in nitrogen dioxide (NO2) production activity has been experimentally investigated based on a micro-reactor DOC experiment. Through this experimental result, the NO2 to nitrogen oxides (NOx) ratio at DOC outlet has been mathematically expressed as a function of DOC temperature according to various aging conditions. The current study reveals that the catalyst aging temperature is a more dominant factor than the aging duration in terms of the decrease in NO2 production performance through DOC. The DOC sample hydrothermally aged for 25 h at 750 °C has displayed the lowest NO2 to NOx ratio compared to the samples aged for 25 ~ 100 h at 650 °C. Also, in this study, the impact of hydrothermal aging of a DOC on the selective catalytic reduction (SCR) efficiency in a ‘DOC + SCR’ aftertreatment system was predicted by using transient SCR simulations. To validate the SCR simulation, this study has conducted a dynamometer test of a non-road heavy-duty diesel engine with employing a commercial ‘DOC + SCR’ system on the exhaust line. The current study has quantitatively estimated the effect of the variation in NO2 to NOx ratio due to the hydrothermal aging of DOC on the NOx removal efficiency of SCR. 相似文献
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双燃料发动机性能与排放的试验研究 总被引:3,自引:0,他引:3
研究了双燃料发动机与原柴油机动力性、经济性、排放性的不同及供油提前角对双燃料发动机性能的影响。台架试验结果表明,双燃料发动机没有出现排温升高和功率损失现象;常用的中等功率天然气掺烧率达75%左右;NO排放比原机降低,在中、大功率时双燃料发动机的烟度排放比原机有大幅度下降,相当于原机的20%左右。 相似文献
14.
Urea-SCR system optimization with various combinations of mixer types and decomposition pipe lengths
Y. S. Cho S. W. Lee W. C. Choi Y. B. Yoon 《International Journal of Automotive Technology》2014,15(5):723-731
The demand for NOx after-treatment system has increased dramatically due to the stricter NOx emission regulations for diesel vehicles. The urea-SCR system is one of the NOx after-treatment methods found to be quite effective to meet the regulation requirement enforced by various authorities including the Euro-6. In order to develop an effective urea-SCR system, it is critical to establish an even distribution of reductant over the catalyst surface since this favorable distribution can increase reduction reaction and in turn, improve NOx conversion efficiencies. In the current study, a number of design variations of the urea-SCR system which included two mixer types and three decomposition pipe lengths, were evaluated systematically using CFD analysis and experimental measurements. The purpose of the CFD analysis was to estimate the distribution of reductant within the urea-SCR system with a specific configuration and the purpose of the engine emission test was to measure the amount of NOx reduction, respectively. The results from the systematic analysis revealed the relation between the reductant distribution over the SCR and the performance of the NOx reduction. 相似文献
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为提高柴油机节能减排的效果,简要分析了多次喷射形式及其作用,依据车辆在不同路况运行,确定了车辆对应的6种柴油机典型工况。提出了基于工况排放值约束的多次喷射分配方法,采用工况排放分摊率确定典型工况的排放限值,进行喷射次数和变化喷射组合寻优,最后结合4JB1高压共轨柴油机台架试验,以氮氧化物和烟度为衡量参数,兼顾燃油消耗率的变化,分析不同喷射组合对柴油机排放的影响。结果表明:怠速工况和中速大负荷工况宜用2次喷射,低速小负荷工况和中速中负荷工况宜用3次喷射,中速小负荷工况宜用4次喷射,高速大负荷工况宜用1次喷射,说明基于工况排放值约束的多次喷射分配方法是有效的。 相似文献
17.
Jaegu Kang Sanghyun Chu Jeongwoo Lee Gyujin Kim Kyoungdoug Min 《International Journal of Automotive Technology》2018,19(1):27-35
In this research, the effects of three operating parameters (Diesel injection timing, propane ratio, and exhaust gas recirculation (EGR) rates) in a diesel-propane dual fuel combustion were investigated. The characteristics of dual-fuel combustion were analyzed by engine parameters, such as emission levels (Nitrogen oxides (NOx) and particulate matter (PM)), gross indicated thermal efficiency (GIE) and gross IMEP Coefficient of Variance (CoV). Based on the results, improving operating strategies of the four main operating points were conducted for dual-fuel PCCI combustion with restrictions on the emissions and the maximum pressure rise rate. The NOx emission was restricted to below 0.21 g/kWh in terms of the indicated specific NOx (ISNOx), PM was restricted to under 0.2 FSN, and the maximum pressure rise rate (MPRR) was restricted to 10 bar/deg. Dual-fuel PCI combustion can be available with low NOx, PM emission and the maximum pressure rise rate in relatively low load condition. However, exceeding of PM and MPRR regulation was occurred in high load condition, therefore, design of optimal piston shape for early diesel injection and modification of hardware optimizing for dual-fuel combustion should be taken into consideration. 相似文献
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Zhong Chang Liu Xing Yuan Jing Tian Yong Qiang Han Kai Bo Yu Peng Kun Teng 《International Journal of Automotive Technology》2018,19(5):783-794
The object of this paper is to reduce soot emissions under typical 5s transient conditions of constant speed and increasing torque. And effects of fuel injection timing on combustion and emissions parameters were experimentally and numerically studied in a regulated two-stage turbocharged diesel engine with a turbine bypass valve (TBV). The test results indicated that: the smaller TBV opening could improve deterioration of smoke emissions and BSFC at medium and heavy loads. Afterward, the full-stage injection timing (FSIT) strategies (delaying injection timing during the entire transient process) could reduce soot and NOX emissions simultaneously. However, when TBV opening became larger, smoke emissions and BSFC were deteriorated gradually. Moreover, the sectional-stage injection timing (SSIT) strategies (advancing injection timing from 10 % load to a preset load and delaying injection timing from the preset load to 100 % load) could markedly reduce soot emissions by 75.8 % with TBV opening 20 %; the degradation of fuel consumption could be effectively suppressed. Finally, coupling the SSIT strategies with the TBV control strategies could significantly improve the transient performance. 相似文献
20.
Particulate matter in diesel engine exhaust, particularly nano-particles, can cause serious human health problems including
diseases such as lung cancer. Because diesel nano-particle issues are of global concern, regulations on particulate matter
emissions specify that not only the weight of particulate matter emitted but also the concentration of nanoparticles must
be controlled. This study aimed to determine the effects on nano-particle and PM emissions from a diesel engine when applying
a urea-SCR system for NOx reduction. We found that PM weight increases by approximately 90% when urea is injected in ND-13 mode over the emission without
urea injection. Additionally, PM weight increases as the NH3/NOx mole ratio is increased at 250 °C. In SEM scans of the collected PM, spherical particles were observed during urea injection,
with sizes of approximately 200 nm to 1 μm. This study was designed to determine the conditions under which nano-particles
and PM are formed in a urea-SCR system and to relate these conditions to particle size and shape via a quantitative analysis
in ND-13 mode. 相似文献