Novel Oxygen Storage Components Promoted Palladium Catalysts for Emission Control in Natural Gas Powered Engines

A three-way catalyst comprised novel oxygen storage components for emission control in natural gas powered engines was prepared. The addition of novel oxygen storage components to the Pd/γ-Al2O3 catalysts resulted in improved activities of the fresh and aged catalyst by lowering the light-off temperature for methane in natural gas engines exhaust.

Exhaust Cleaning with Dielectric Barrier Discharge

To clean the exhaust emissions as one of the most important tasks in pollution control, a study on the treatment of engine emissions with discharge assistance was reported. A DBD plasma source shaped in grid and cylinder was examined in different engine operational modes to reduce the NOx content of diesel engine exhaust. The composition of the exhaust gases and chemical reactions initiated by the discharge were analyzed. The discharge frequency had a crucial impact on the device＇s performance and gas treatment. The voltages applied to the discharge gap could alter the chemical reactions occurring in the treated gases, which were indicated by the NO to NO2 ratio. The operation of the system was studied at frequencies ranging from 400 Hz to 16 kHz.

Tuning energy transfer efficiency in quantum dots mixture by controling donor/acceptor ratio

Improving the emission performance of colloidal quantum dots(QDs)is of paramount importance for their applications on light-emitting diodes(LEDs),displays and lasers.A highly promising approach is to tune the carrier recombination channels and lifetime by exploiting the energy transfer process.However,to achieve this precise emission optimization,quantitative modulation on energy transfer efficiency is highly desirable but still challenging.Here,we demonstrate a convenient approach to realize tunable energy transfer efficiency by forming QDs mixture with controllable donor/acceptor(D/A)ratio.With the mixing ratio ranging from 16/1 to 1/16,the energy transfer efficiency could be effectively tuned from near zero to~70%.For the high mixing ratio of 16/1,acceptors obtain adequate energy supplied by closely surrounding donors,leading to~2.4-fold PL enhancement.While for the low mixing ratio,the ultrafast and efficient energy extraction process directly suppresses the multi-exciton and Auger recombination in the donor,bringing about a higher threshold.The facile modulation of emission performance by controllably designed mixing ratio and quantitatively tunable energy transfer efficiency will facilitate QD-based optoelectronic and photovoltaic applications.

COMPOSITIVE EMISSION CONTROL SYSTEM OF GASOLINE VEHICLE

The working principle of a kind of compositive emission control system is inquired into, which includes exhaust heater, secondary air supplement, exhaust gas recirculation （EGR）, thermal reactor and catalytic converter, etc. The purification effect of CO, HC and NOx emission of the gasoline spark ignite （S.I.） engine is studied. The entire vehicle driving cycle tests based on the national emission standard and a series of the gasoline engine-testing bench tests including full load characteristic experiment, load characteristic experiment and idle speed experiment are done. The results show that the system has a very good emission control effect to CO, HC and NOx of gasoline engine. The construction of the system is very simple and can be mounted on the exhaust pipe conveniently without any alteration of the vehicle-use gasoline engine.

Impact of binary blends of biodiesels on fuel quality,engine performance and emission characteristics

The incessant pressure of energy requirements by the growing global populace has led to the exploration of unconventional methods to produce renewable and sustainable fuels.Among these,biodiesel is most suited to the present needs of eco-friendly standards to keep the atmosphere free from residual emissions.Various fuel-modification methods were developed over a couple of decades to make biodiesel suitable for diesel engines.In the present research,Jatropha curcas biodiesel and waste-cooking-oil(WCO)biodiesel were used to craft a unique binary blend to obtain desirable fuel properties and operational suitability for the diesel engine.The blend with 80% WCO biodiesel and 20% J.curcas biodiesel,which had the most suitable fuel properties,was tested on a four-stroke single-cylinder vertical diesel engine.The emissions and operational parameters were analysed and compared with diesel.The results of the study indicated that engine emissions for binary blend,carbon monoxide and unburnt hydrocarbon emissions were highly reduced,and carbon dioxide and nitrogen oxide(NO_(x))emissions increased relative to diesel.At full load,NO_(x) emission was found to be 51.32% higher than that from diesel and 3.8% lower than that from WCO biodiesel.Engine performance showed that for the binary blend,at full load,the brake-specific fuel consumption was 396.82 g/kWh,which was 15.26% higher,and the brake thermal efficiency was 22.7%,which was 2.74% lower than regular diesel fuel.The present study suggests that the binary blend of J.curcas biodiesel and WCO biodiesel can be a promising approach towards advancements in the fuel properties of biodiesels.

Optical characterization of nano-sized organic carbon particles emitted from a small gasoline engine

The nano-sized organic carbon （NOC） particles emitted from a small gasoline engine were characterized using various ex situ optical techniques to assess their hazardous impact. The exhaust gas was sampled iso-kinetically by a quartz probe and passed through de-ionized water to gather the hydrophilic car- bonaceous particulates as hydrosol. The hydrodynamic diameter of the particles ranged between 1.7 and 3.6 nm at no load, with a mean diameter of 2.4 nm. The particle size in the engine exhaust was found to increase at higher loads, which is attributed to coagulation of the particles. The chemical structure of the particles was analyzed using UV-vis and infra-red spectroscopy. Both the band gap energy and oscillator strength data evaluated from the UV-vis absorbance showed that the NOC particles contained polyaromatic hydrocarbon structures with three to five aromatic rings. Infra-red spectroscopy analysis further confirmed the presence of aliphatic and carbonyl functionalities in the aromatic structures of the particles. The fine size of the particles, their high number concentration for the type of the engine under study and their structural features, make the particles extremely hazardous for environment and health.

A Brief Account of Domestic Vehicle Diesel Engines and Their Emission Control

Ⅰ. Briefing domestic vehicle diesel engines Before the 1970s, domestic vehicle diesel engines were mainly applied to heavy vehicles, while medium and light vehicles were powered chiefly with gasoline engines.

Impact of diesel emission fluid soaking on the performance of Cu-zeolite catalysts for diesel NH3-SCR systems

Diesel emission fluid （DEF） soaking and urea deposits on selective catalytic reduction （SCR） catalysts are critical issues for real diesel engine NH3-SCR systems. To investigate the impact of DEF soaking and urea deposits on SCR catalyst performance, fresh Cu-zeolite catalyst samples were drilled from a full-size SCR catalyst. Those samples were impregnated with DEF solutions and subsequently hydrothermally treated to simulate DEF soaking and urea deposits on real SCR catalysts during diesel engine operations. Their SCR performance was then evaluated in a flow reactor with a four-step test protocol. Test results show that the DEF soaking leached some Cu from the SCR catalysts and slightly reduced their Cu loadings. The loss of Cu and associated metal sites on the catalysts weakened their catalytic oxidation abilities and caused lower NO/NI-I3 oxidation and lower high-temperature N20 selectivity. Lower Cu loading also made the catalysts less active to the decomposition of surface ammonium nitrates and decreased low-temperature N20 selectivity. Cu loss during DEF impregnation released more acid sites on the surface of the catalysts and increased their acidities, and more NH3 was able to be adsorbed and involved in SCR reactions at medium and high temperatures. Due to lower NH3 oxidation and higher NH3 storage, the DEF-impregnated SCR catalyst samples showed higher NOx conversion above 400 ℃ compared with the non-soaked one. The negative impact of urea deposits during DEF impregnation was not clearly observed, because the high-temperature hydrothermal treatment helped to remove the urea deposits.

Hyperbolic metamaterials: fusing artificial structures to natural 2D materials

Optical metamaterials have presented an innovative method of manipulating light.Hyperbolic metamaterials have an extremely high anisotropy with a hyperbolic dispersion relation.They are able to support high-k modes and exhibit a high density of states which produce distinctive properties that have been exploited in various applications,such as super-resolution imaging,negative refraction,and enhanced emission control.Here,state-of-the-art hyperbolic metamaterials are reviewed,starting from the fundamental principles to applications of artificially structured hyperbolic media to suggest ways to fuse natural two-dimensional hyperbolic materials.The review concludes by indicating the current challenges and our vision for future applications of hyperbolic metamaterials.