柴油添加剂和微粒捕集器的协同性分析与研究

柴油添加剂可以降低发动机燃烧室内的碳烟生成,而微粒捕集器则能有效控制柴油机尾气中微粒排放。对柴油添加剂种类、微粒捕集器过滤体材料和微粒捕集器的再生方法分别作了介绍,并着重对柴油添加剂促进微粒捕集器再生的机理和存在的问题进行了分析和研究。     

燃用F-T柴油颗粒相多环芳香烃的排放特性

在满足国Ⅲ排放的高压共轨柴油机上,对比分析了燃用F-T柴油和国Ⅲ柴油时,发动机尾气中颗粒相多环芳香烃的排放特性,结果表明,在低、中、高3种转速的负荷特性下,柴油机燃用F-T柴油时,颗粒相总多环芳香烃比排放量为0.01～0.10,μg/(kW.h),与国Ⅲ柴油的比排放量0.04～0.42,μg/(kW.h)相比,有大幅下降,且比排放量随着负荷的增大呈降低趋势.两种燃料排放的颗粒相多环芳香烃中三环的菲及四环的荧蒽和芘含量最多,三者之和占总多环芳香烃的80%以上.此外,F-T柴油菲的比排放量在所有试验工况均低于国Ⅲ柴油;F-T柴油荧蒽和芘的比排放量除在中等转速的中、高负荷略高于国Ⅲ柴油外,其余工况均低于国Ⅲ柴油.     

生物柴油对直喷式柴油机燃烧和排放的影响

列举了生物柴油的基本物化特性。介绍了生物柴油对直喷式柴油机燃烧和排放的影响。相比普通柴油,燃用生物柴油可以减少CO、CO_2、SO_2、HC、微粒以及碳烟的排放且不会影响柴油机工作性能。采用EGR、乳化油、多次喷射及微粒捕捉器等措施可以进一步降低使用生物柴油的微粒和NOx排放。生物柴油作为一种可再生的替代能源,以其良好的环境效应受到越来越多的关注。     

掺混含氧燃料对柴油机氧化催化器+催化型柴油机颗粒捕集器氧化及再生特性的影响

为了研究掺烧含氧燃料对柴油机排放及柴油机氧化催化器(DOC)耦合催化型柴油机颗粒捕集器(CDPF)后处理系统低温氧化特性与再生特性的影响,基于一台4缸高压共轨柴油机,选取国五柴油、15%生物柴油-柴油(D85B15)、15%正戊醇-柴油(D85P15)、20%正戊醇-柴油(D80P20)作为燃料,在1 900m海拔环境下进行了试验。研究表明:在外特性工况下,与柴油相比,燃用D85B15和D85P15的柴油机动力性略有下降,燃用D85P15的柴油机有效热效率最高。燃用D85B15的NO_x排放略低于柴油,最高降低3.33%;而D85P15的NO_x排放有所增加,最高增加2.85%。在低负荷工况下燃用国五柴油时DOC+CDPF对CO的转化效率明显高于燃用D80P20时,2 000r/min时燃用柴油时CO转化效率高达96.8%,而D80P20只有36.9%。低速高负荷工况下燃用国五柴油与D80P20时,DOC对排气温度的提升作用均比较明显,平均提升41.8℃和42.5℃。燃用D80P20时DOC+CDPF压差升高较慢,压差最高比燃用国五柴油低6kPa,DOC后端平均温度比燃用国五柴油高10℃。柴油机燃用D80P20在高负荷尤其是低转速高负荷时可有效降低颗粒物排放,降低DOC+CDPF压差。     

餐饮废油基生物柴油对柴油机有害排放特性的影响

在一台电控共轨增压中冷柴油机台架上，燃用纯柴油以及分别掺混10%、20%、30%餐饮废油制生物柴油的柴油/生物柴油混合燃料，研究生物柴油对柴油机燃烧及排放特性的影响。结果表明:生物柴油使发动机的预喷放热率略微下降，主喷放热率有所升高，缸压峰值随掺混比例的增大略有降低；燃用生物柴油使发动机的NO_x排放有所上升，HC排放略有下降，CO排放变化不大；低转速下核模态颗粒排放略微增加，积聚态颗粒数有所减少，高转速下核模态和积聚态颗粒数都减少；掺混生物柴油会增加发动机排气颗粒物的氧化活性，使得最大氧化速率温度降低，活化能降低；掺混生物柴油能够降低颗粒相多环芳烃的质量比排放。     

国-Ⅲ柴油机生物柴油颗粒排放特性研究

以柴油机颗粒物粒径分布特性为研究重点,在国-Ⅲ高压共轨柴油机上针对不同混合比的生物柴油与柴油混合燃料的颗粒物排放特性进行了研究.试验结果表明,共轨柴油机的颗粒物数量排放一般为双态分布(核态和聚集态),基本以50 nm为分界线.随着负荷的增加,颗粒粒径分布由单态分布转化为双态分布.这是由于排气中的SO2被催化器氧化为SO3后,进一步形成了微小的硫酸颗粒.在2 000 r/min的高低负荷,生物柴油混合燃料的颗粒粒径分布存在明显的不同.试验结果表明,燃料硫含量对柴油机核态颗粒的形成具有直接的影响.而生物柴油混合燃料内部舍氧,可明显降低聚集态颗粒排放数量.聚集态计算颗粒质量可有效反映舍氧燃料对碳烟的氧化作用,也间接表明了柴油机聚集态颗粒以碳烟为主.     

DOC+DPF对生物柴油发动机排气颗粒理化特性的影响

以某型高压共轨柴油机为研究对象,研究试验样机燃用BD20混合燃料时,DOC+DPF后处理装置对其排气颗粒理化特性的影响.结果表明:外特性工况下,试验样机连接DOC+DPF后,聚集态颗粒数量浓度降幅最高达99.4%,,而核态颗粒数量浓度降幅不如聚集态颗粒.随试验样机转速上升,DOC+DPF的捕集效率呈上升趋势.此外,试验样机连接DOC+DPF后,多环芳烃(polycyclic aromatic hydrocarbons,PAH)排放质量下降91.5%,,所检测的19种PAH组分中,有17种组分排放质量减少,DOC+DPF可使PAH等效毒性下降93.9%,.     

天然气合成油对高压共轨柴油机燃烧及微粒排放粒度分布的影响

针对高压共轨增压中冷柴油机燃用不同GTL添加比例的GTL/柴油混合燃料,试验研究了不同工况下微粒排放粒度分布特征,分析了GTL添加比例对燃烧及微粒排放粒度分布的影响。研究结果表明:与石化柴油相比,燃用GTL/柴油混合燃料能够降低排气烟度,但当GTL添加体积比超过20%后,排气烟度的改善趋势减缓,高负荷工况更明显。随着GTL添加比例增加,预混合燃烧放热率峰值及缸内压力升高率峰值降低,峰值相位提前,扩散燃烧放热率峰值变化不大。发动机燃用GTL燃料时的微粒数量浓度呈双峰对数分布,核态微粒数量浓度峰值在25%负荷时达到最大值,随着负荷增加峰值降低且逐渐向大粒径方向移动;积聚态微粒峰值随着负荷增加而升高。对于不同GTL添加比例的混合燃料,在中等转速工况,随着GTL添加比例增加,总微粒及积聚态微粒数量浓度增加,核态微粒数量变化不大;高转速工况,燃用G20混合燃料总微粒及核态微粒数量最少,增大GTL添加比例则核态微粒及积聚态数量均有所增加。     

BTL/柴油混合燃料对柴油机瞬态工况微粒粒度分布的影响

试验研究了不同添加比例的生物柴油(BTL)混合燃料对高压共轨柴油机瞬变工况下微粒排放的影响,分析了不同瞬变率工况下微粒粒度分布特征,揭示了燃料理化特性对柴油机瞬态工况微粒排放粒度分布的影响规律。研究结果表明:瞬态工况下石化柴油、生物柴油燃料微粒粒数排放均呈双峰结构,核态微粒峰值在10nm附近,积聚态微粒峰值在60nm附近;石化柴油燃料微粒排放以大粒径积聚态微粒为主,占微粒总数的55%以上;BTL燃料微粒排放以小粒径核态微粒为主,占微粒总数的96%以上。随着工况瞬变率的减小,BTL燃料、石化柴油微粒平均数量排放均逐渐减少,BTL燃料下降更明显;石化柴油核态微粒排放受瞬变率的影响较为显著,BTL燃料受瞬变率的影响不明显。对于不同添加比例的生物柴油混合燃料,在小瞬变率工况,微粒排放数量随添加比例的增加缓慢上升;在中等瞬变率工况,添加比小于30%时微粒排放数量基本不增加,但核态微粒所占比例略有上升;在高瞬变率工况,添加比例大于10%时微粒排放数量大幅度上升。     

低配比GTL柴油和生物柴油的燃烧颗粒排放特性

以一台电控高压共轨柴油机为样机,研究了柴油机分别燃用低配比天然气合成油(GTL柴油)、低配比生物柴油混合燃料的颗粒排放特性。所用燃料分别为纯柴油、GTL柴油体积掺混比为10%的燃料(G10)、生物柴油体积掺混比10%的燃料(B10)。研究了该机燃用这三种燃料的烟度、颗粒数量及粒径分布特性。研究结果表明:柴油机燃用G10燃料、B10燃料的排气烟度均低于纯柴油,B10燃料的排气烟度低于G10燃料;柴油燃用三种燃料的排气颗粒数量大多呈明显的单峰或者双峰对数分布。B10燃料的核态颗粒数量在各工况下均为最高,G10燃料在各负荷下全粒径范围内聚集态颗粒与核态颗粒的数量几乎均为最低。随负荷增加,柴油机颗粒总数量呈总体上升趋势。各工况下,柴油机燃用B10燃料的颗粒总数量最高,G10燃料的颗粒总数量最低,核态颗粒数量的差异在其中占主导地位。     

Investigation of foreign particles in polycrystalline silicon using infrared microscopy

The presence of SiC and SiNO particles in as-grown polycrystalline silicon has been investigated using infrared (IR) microscopy. These foreign particles were also characterized using electron beam induced current measurements, and scanning electron microscopy together with energy dispersive spectrum analyses. These performance-degrading inclusions were found to be distributed throughout the bulk of the material and varied in size from several microns to about 20 μm. In addition to the observation of the foreign particles, the feasibility of using IR microscopy as a characterization tool was also demonstrated.     

Particulate emissions from laser ignited and spark ignited hydrogen fueled engines

Exponentially increasing energy demand and stricter emission legislations have motivated researchers to explore alternative fuels and advanced engine technologies, which are more efficient and environment friendly. In last two decades, hydrogen has emerged as promising alternative fuel for internal combustion (IC) engines and vehicles. For gaseous fuels, laser ignition (LI) has emerged as a novel ignition technique due to its superior characteristics, leading to improved combustion, engine performance and emission characteristics. Numerous advantages of LI system such as flexibility of plasma location, lower NO_x emissions and capability of igniting ultra-lean fuel–air mixture makes LI system superior compared to conventional spark ignition (SI) system. This study experimentally compares particulate emissions from hydrogen fueled engine ignited by LI and SI systems. Experiments were performed in a constant speed engine prototype, which was suitably modified to operate on gaseous fuels using both LI as well as SI systems. Particulate were characterized using engine exhaust particle sizer (EEPS) spectrometer. Results showed that LI engine resulted in relatively higher particulate number concentration as well as particulate mass compared to SI engine. In both ignition systems, particulate emissions increased with increasing engine load however rate of increase was relatively higher in LI system. Relatively larger count mean diameter (CMD) of particulate emitted from SI engine compared to LI engine was another important observation. This showed emission of relatively smaller particles in larger numbers from LI engine, compared to baseline SI engine.     

肝癌介入治疗若干问题探讨

试验测定了粒子尺寸对流化床热处理炉的流动性能、升温能力的影响，推荐了适用于不同工艺过程的粒子优选方案，以降低流体床的气耗和能耗。     

超细颗粒在碰撞凝并作用下的尺寸分布变化

对于燃烧过程中生成的超细颗粒，其自身的布朗运动引起的细颗粒之间的碰撞以及与较大颗粒之间的碰撞是改变其尺寸分布的主要因素．基于矩方法，对颗粒的初始分布作出一个合理的正态对数分布假设，研究了超细颗粒在碰撞凝并作用下的颗粒尺寸分布的变化情况．并将所得到的结果与仅仅考虑细颗粒之问碰撞的结果进行对比．数值结果表明，在同时考虑两种碰撞时，布朗凝并碰撞的自保持特性发生了一定的变化；与仅仅考虑细颗粒之间的碰撞凝并时相比，颗粒初始的不均匀程度对最终的颗粒分布的影响增强，成为一个必须考虑的因素．     

Experimental investigation of combustion characteristics and NOx formation of coal particles using laser induced breakdown spectroscopy

To study the mechanism of coal combustion and NO_x formation, the combustion of coal particles in different atmospheres (O₂/N₂, O₂/CO₂) with different O₂ concentrations was investigated using the CO₂ laser as a heat source. The spatial distribution of atoms and groups (e.g., H at 656.2 nm, O at 777.3 nm, CN at 388.3 nm) relating to the combustion flame were measured simultaneously using laser induced breakdown spectroscopy (LIBS). The residual energy was measured during the collection of LIBS spectra in the combustion process, which could be characterized the temperature profiles of combustion flame due to the positive correlation with temperature. The combustion stage could be clearly discriminated by the emission of H and CN, along with the flame temperature. The residual energy obtained in different atmospheres indicated that the impact of combustion atmosphere on flame temperature is greater in the char combustion stage rather than volatile combustion stage. It was determined from the temporal and spatial distribution of residual energy and CN intensity that a higher flame temperature leads to a higher concentration of CN. The correlation between the generation of CN and the NO_x formation was also investigated to show that the formation approaches of NO_x are similar in the O₂/CO₂ and O₂/N₂ atmospheres, while the fuel-N conversion paths are different between volatile combustion and char combustion stages. The measurement of temporal and spatial distributions of LIBS spectra with varying flame temperatures is significant in revealing the mechanism of coal-particle combustion and NO_x formation.     

Particle Movement Using Monte-Carlo Technique in a Gas Insulated Busduct of Various Designs

Due to the higher reliability and small ground space requirement, compressed GIS （gas insulated substation） has found extensive applications in urban areas and developing countries. The major parts of GIS is the gas insulated busducts, circuit breakers, isolators, etc.. The voltage withstand capability of SF6 （sulphur hexafluoride） busduct is strongly dependent on field perturbations such as those caused by conductor surface imperfections and by conducting particle contaminants which arise due to manufacturing process, mechanical vibrations, moving parts of system etc.. Contamination can create insulation problems at operating fields. An optimized design of GIS by varying the inner and outer diameter to 89 mm and 241 mm is considered for analysis and compared with a single phase enclosure with outer diameter as 152 mm and inner conductor diameter of 55 mm with aluminum and copper particles of size 10 mm in length and 0.25 mm in radius present on the enclosure. The results have been compared on the extent of particle movement for the same condition of the gas and particle geometry. Monte Carlo simulation is also carried out for determining the motion of particles in axial and radial directions. The random solid angle is changed from 1 to 0.5 degrees to take into account more smooth end profile of the particle. The simulation results have been presented and analyzed.     

关于测量内燃机缸内流场用示踪粒子的研究

本文论述了使用PIV测量技术时示踪粒子的选取原则和各种示踪粒子特性比较，并且详细介绍了一种由作者研制的带有Laskin喷头的新式粒子添加装置，经过试验证明效果比较理想。此种装置产生的液态粒子，最特殊的地方是其内部为空心。因此在相同的体积下，其质量比一般的示踪粒子要轻，很符合PIV拍摄。     

Thermo-mechanical aspects of the heterogeneous ignition of metals

During the heterogeneous oxidation of metallic particles in a gaseous oxidant, a film of oxide usually separates the metal and oxidant, with the reaction rate being governed to a great extent by the protective properties of the film. A theoretical and experimental study of the influence of the failure of the protective oxide film on the metal's heterogeneous ignition has been performed. The possible reasons for the fracture are analyzed; also the critical conditions of the oxide film are estimated. Experiments conducted with aluminum and titanium powders have shown that the fracture of the protective oxide film results in a significant increase in the metal's reactivity. The assumptions of a theoretical analysis are confirmed experimentally.     

Simple synthesis of Pt nanoparticles on noncovalent functional MWNT surfaces: Application in ethanol electrocatalysis

After the siloxane is polymerized on the nanotube surfaces, the carbon nanotube is embedded within the polysiloxane shell with a hydrophilic amino group situated outside. Platinum (Pt) nanoparticles were synthesised on as-produced noncovalent functional multi-walled carbon nanotubes (MWNTs) via electrostatic interactions. The structure and nature of the resulting Pt/MWNT composite were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic properties of the Pt/MWNT electrode for oxidation of ethanol have been investigated by cyclic voltammetry (CV), and excellent electrocatalytic activity can be observed.