含氧燃料成分对柴油机排放特性影响的试验研究

将占体积比80%柴油分别与20%乙醇、20%生物柴油以及同时与10%乙醇和10%生物柴油组合成的混合燃料,在增压中冷柴油机上进行实验,分析比较其排放特性。结果表明,随着含氧燃料中乙醇比例的增大,发动机排放的HC和CO升高,碳烟降低,NOX则差别不大。

Preparation and Flame Retardancy of Polyurethane/POSS Nanocomposites

Polyurethane/polyhedral oligomeric sisesquioxane （PU/POSS） nanocomposites were syn- thesized via polymerization utilizing the compatibility between POSS nanopartieles and 4J-diphenyl methylene diisocyanate. Scanning electron microscope images and Fourier transform infrared spectra revealed that POSS nanoparticles were dispersed in PU matrix. Thermal gravimetric analysis was employed to investigate the thermal decomposition be- havior of PU/POSS nanocomposites at elevated temperatures. Then fire performance was evaluated by limiting oxygen index, underwriters laboratories 94 testing and char residue morphology. These results showed that the addition of POSS promoted the formation of char residues which were covered on the surface of polymer composites, leading to the ira-provement of thermal stability and flame retardancy.

Carbon supported IrM(M= Fe,Ni,Co) alloy nanoparticles for the catalysis of hydrogen oxidation in acidic and alkaline medium

We studied the alloying effect in lr-based alloys on the catalysis of the hydrogen oxidation reaction （HOP,） in both acidic and alkaline medium. IrFe, lrNi and IrCo alloy catalysts with nanoparticle size of 〈S nm were obtained by our solvent-vaporization plus hydrogen reduction method. The second metal played an important role in tuning the crystal structure and surface electronic structure of the Ir-based alloy catalyst. Among the lrFe, IrCo and lrNi alloy catalysts, Ni induced a mid-sized contrac- tion of the lr lattice, and gave the best HOR activity in both acidic and alkaline medium. In acidic medium, the weakening of the Ir-Had interaction caused by the electronic effect of M （M = Fe, Ni, Co） alloying is responsible for the enhancement of HOR activity. The oxophilic effect of the catalytic metal surface, which affects OHad adsorption and desorption and surface Had coverage, has a large impact on the HOR activity in the case of alkaline medium,

Highly efficient Nb2O5 catalyst for aldol condensation of biomass-derived carbonyl molecules to fuel precursors

Aldol condensation is of significant importance for the production of fuel precursors from biomass- derived chemicals and has received increasing attention. Here we report a Nb2O5 catalyst with excellent activity and stability in the aldol condensation of biomass-derived carbonyl molecules. It is found that in the aldol condensation of furfural with 4-heptanone, Nb2O5 has obviously superior activity, which is not only better than that of other common solid acid catalysts (ZrO2 and Al2O3), more importantly, but also better than that of solid base catalysts (MgO, CaO, and magnesium- aluminum hydrotalcite). The detailed characterizations by N2 sorption/desorption, NH3-TPD, Py-FTIR and DRIFTS study of acetone adsorption reveal that Nb2O5 has a strong ability to activate the C=O bond in carbonyl molecules, which helps to generate a metal enolate intermediate and undergo the nucleophilic addition to form a new C–C bond. Furthermore, the applicability of Nb2O5 to aldol condensation is extended to other biomass-derived carbonyl molecules and high yields of target fuel precursors are obtained. Finally, a multifunctional Pd/Nb2O5 catalyst is prepared and successfully used in the one-pot synthesis of liquid alkanes from biomass-derived carbonyl molecules by combining the aldol condensation with the sequential hydrodeoxygenation.

Efficient Thickness of Solid Oxide Fuel Cell Composite Electrode

The efficient thickness of a composite electrode for solid oxide fuel cells was directly calculated by developing a physical model taking into account of the charge transfer process, the oxygen ion and electron transportation, and the microstructure characteristics of the electrode. The efficient thickness, which is defined as the electrode thickness corresponding to the minimum electrode polarization resistance, is formulated as a function of charge transfer resistivity, effective resistivity to ion and electron transport, and three-phase boundary length per unit volume. The model prediction is compared with the experimental reports to check the validity. Simulation is performed to show the effect of microstructure, intrinsic material properties, and electrode reaction mechanism on the efficient thickness. The results suggest that when an electrode is fabricated, its thickness should be controlled regarding its composition, particle size of its components, the intrinsic ionic and electronic conductivities,and its reaction mechanisms as well as the expected operation temperatures. The sensitivity of electrode polarization resistance to its thickness is also discussed.

Encapsulation of a nickel Salen complex in nanozeolite LTA as a carbon paste electrode modifier for electrocatalytic oxidation of hydrazine

A nickel salen complex was encapsulated in the supercages of nanozeolite NaA,LTA(linde type A)structure,using the flexible ligand method.The electrochemical behavior and electrocatalytic activity of a carbon paste electrode(CPE)modified with Ni(II)‐Salen‐A(Ni(II)‐SalenA/CPE)for hydrazine oxidation in0.1mol/L NaOH solution were investigated by cyclic voltammetry,chronoamperometry,and chronocoulometry.First,organic‐template‐free synthesis of nanozeolite LTA was performed and the obtained material was characterized by various techniques.The average particle size of the LTA crystals was estimated to be56.1and72nm by X‐ray diffraction and particle size analysis,respectively.The electron transfer coefficient was found to be0.64and the catalytic rate constant for oxidation of hydrazine at the redox sites of Ni(II)‐SalenA/CPE was found to be1.03×105cm3/(mol·s).Investigation of the electrocatalytic mechanism suggested that oxidation of hydrazine occurred through reaction with Ni3+(Salen)O(OH)and also direct electrooxidation.The anodic peak currents revealed a linear dependence on the square root of the scan rate,indicating a diffusion‐controlled process,and the diffusion coefficient of hydrazine was found to be1.18×10?7cm2/s.The results indicated that Ni(II)‐SalenA/CPE displays good electrocatalytic activity toward hydrazine oxidation owing to the porous structure of nanozeolite LTA and the Ni(II)‐Salen complex.Finally,the general reaction mechanism for the electrooxidation of hydrazine on Ni(II)‐SalenA/CPE in alkaline solution involves the transfer of four electrons,in which the first electron transfer reaction acts as the rate‐limiting step followed by a three‐electron process to generate environmentally friendly nitrogen and water as final products.

Ferroelectric solid solution Li1-xTa1-xWxO3 as potential photocatalysts in microbial fuel cells:Effect of the W content

Microbial fuel cells(MFCs)are bio-electrochemical systems that can directly convert the chemical energy contained in an effluent into bioelectricity by the action of microorganisms.The performance of these devices is heavily impacted by the choice of the material that forms the cathode.This work focuses on the assessment of ferroelectric and photocatalytic materials as a new class of non-precious catalysts for MFC cathode construction.A series of cathodes based on mixed oxide solid solution of LiTaO_3with WO_3formulated as Li_(1-x)Ta_(1-x)W_xO_3(x=0,0.10,0.20 and0.25),were prepared and investigated in MFCs.The catalyst phases were synthesized,identified and characterized by DRX,PSD,MET and UV–Vis absorption spectroscopy.The cathodes were tested as photoelectrocatalysts in the presence and in the absence of visible light in devices fed with industrial wastewater.The results revealed that the catalytic activity of the cathodes strongly depends on the ratio of substitution of W^(6+)in the LiTaO_3matrix.The maximum power densities generated by the MFC working with this series of cathodes increased from60.45 mW·m^(-3)for x=0.00(LiTaO_3)to 107.2 mW·m^(-3)for x=0.10,showing that insertion of W^(6+)in the tantalate matrix can improve the photocatalytic activity of this material.Moreover,MFCs operating under optimal conditions were capable of reducing the load of chemical oxygen demand by 79%(COD_(initial)=1030 mg·L^(-1)).

High-quality and deeply excavated PtPdNi nanocubes as efficient catalysts toward oxygen reduction reaction

The oxygen reduction reaction(ORR)on the cathode of a polymer electrolyte fuel cell requires the use of a catalyst based on Pt,one of the most expensive metals on the earth.A number of strategies,including optimization of a different metal into the core,have been investigated to enhance the activity of a Pt-based catalyst and thus reduce the loading of Pt.By dedicating to compounding high catalytic activity Pt_(2.7)Pd_(0.3)Ni concave cubic with high index crystal face,the paper shows that concave structures can offer more active site and high level of catalytic activity and if mixed with other metal,decrease the proportion of Pt and improve its mass activity.The paper also makes an exploration into the theory and conditions behind the formation of Pt_(2.7)Pd_(0.3)Ni concave cubic structure,and investigates the difference it demonstrates by modifying the reactive conditions.The results of the oxygen reduction performance of the electrochemical test are as follows:the concave cube-shaped Pt-Pd-Ni catalyst has a mass activity of 1.28 A mg_(Pt)^(–1) at 0.9 V,its highest mass activity is 8.20 times that of commercial Pt/C,and its specific activity is 8.68 times of that commercial Pt/C.And the Pt-Pd-Ni ternary nanocage has excellent structural invariance.After the stability test,there is no obvious structural change and performance degradation in the nanostructure.

UO2-BeO Composite Fuel Thermal Property and Performance Modeling

An enhanced thermal conductivity UO2-BeO composite nuclear fuel was studied. A methodology to generate ANSYS （an engineering simulation software） FEM （finite element method） thermal models of enhanced thermal conductivity oxide nuclear fuels was developed. The results showed significant increase in the fuel thermal conductivities and have good agreement with the measured ones. Thus BeO is one of the promising candidates for fabricating two-phase high thermal conductivity ceramic nuclear fuels with UO2. The reactor performance analysis showed that the decrease in centerline temperature was 250-350 K depending on different fabrication methods for the UO2-BeO composite fuel, and thus we can improve nuclear reactors＇ performance and safety, and high-level radioactive waste generation for the existing and next generation nuclear reactors.

Possibility of Using Ni-Co Alloy As Catalyst for Oxygen Electrode of Fuel Cell

In recent years, the scale of use of fuel cells （FCs） has been increasing continuously. One of the essential elements that affect their work is a catalyst. Precious metals （mainly platinum） are known for their high efficiency as FC catalysts. However, their high cost holds back the FCs from application on a large scale. Therefore, catalysts that do not contain precious metals are sought. Studies are focused mainly on the search for fuel electrode catalysts, but for the efficiency of FCs also the oxygen electrode catalyst is of great significance. The paper presents an analysis of the possibilitiesof using Ni-Co alloy as a catalyst for the oxygen electrode of the FC.

Synthesis/design optimization of SOFC-PEM hybrid system under uncertainty

Solid oxide fuel cell–proton exchange membrane(SOFC–PEM) hybrid system is being foreseen as a valuable alternative for power generation. As this hybrid system is a conceptual design, many uncertainties involving input values should be considered at the early stage of process optimization. We present in this paper a generalized framework of multi-objective optimization under uncertainty for the synthesis/design optimization of the SOFC–PEM hybrid system. The framework is based on geometric, economic and electrochemical models and focuses on evaluating the effect of uncertainty in operating parameters on three conflicting objectives: electricity efficiency, SOFC current density and capital cost of system. The multi-objective optimization provides solutions in the form of a Pareto surface, with a range of possible synthesis/design solutions and a logical procedure for searching the global optimum solution for decision maker. Comparing the stochastic and deterministic Pareto surfaces of different objectives, we conclude that the objectives are considerably influenced by uncertainties because the two trade-off surfaces are different.

Research on Thermal Properties of Nomex Fiber and Nomex/Viscose Blended Fabric

Based on the analysis of the properties of Nomex 450 and Nomex 462,the thermal properties of Nomex 462/Lenzing Viscose Flame retardent(FR)blending materials were analyzed.It was discovered through burning test and Thermal Gravity(TG)analysis that the blended material was superior in thermal behaviors to the material made from either Nomex or Viscose FR filament,when the ratio of Nomex and Lenzing Viscose FR reached 80∶20,and excellent thermal properties were achieved with the value of Limiting Oxygen Index(LOI)up to 36.1%.Blending Nomex and Viscose FR filaments may be recommended for better fire retardant property of related fabric.

Composite Cathode Based on Redox-Reversible Nb2TiO7 for Direct High-Temperature Steam Electrolysis

Ni/YSZ fuel electrodes can only operate under strongly reducing conditions for steam elec- trolysis in an oxide-ion-conducting solid oxide electrolyzer （SOE）. In atmosphere with a low content of H2 or without H2, cathodes based on redox-reversible Nb2TiO7 provide a promising alternative. The reversible changes between oxidized Nb2TiO7 and reduced Nbl.33Tio.6704 samples are systematically investigated after redox-cycling tests. The conductivities of Nb2TiO7 and reduced Nb1.33Tio.6704 are studied as a function of temperature and oxygen partial pressure and correlated with the electrochemical properties of the composite electrodes in a symmetric cell and SOE at 830 ℃. Steam electrolysis is then performed using an oxide-ion-conducting SOE based on a Nb1.33Ti0.6704 composite fuel electrode at 830 ℃. The current-voltage and impedance spectroscopy tests demonstrate that the reduction and activation of the fuel electrode is the main process at low voltage; however, the steam electrolysis dominates the entire process at high voltages. The Faradic efficiencies of steam electrolysis reach 98.9% when 3%H2O/Ar/4%H2 is introduced to the fuel electrode and 89% for that with introduction of 3%H2O/Ar.

Process Flow Model of Combined High Temperature Fuel Cell Operated with Mixture of Methane and Hydrogen

One of the main challenges of biogas and syngas use as fuel in hybrid solid oxide fuel cell （SOFC） cycles is the variable nature of their composition, which may cause significant changes in plant performance. On the other hand, hydrogen is one of the main components in some types of gasified biomass and syngas. Therefore, it is vital to investigate the influences of hydrogen fraction in inlet fuel on the cycle performance. In this work, a steady-state simulation of a hybrid tubular SOFC-gas turbine （GT） cycle is first presented with two configurations： system with and without anode exhaust recirculation. Then, the results of the model when fueled by syngas, biofuel, and gasified biomass are analyzed, and significant dependency of system operational parameters on the inlet fuel composition are investigated. The analysis of impacts of hydrogen concentration in the inlet fuel on the performance of a hybrid tubular SOFC and gas turbine cycle was carried out. The simulation results were considered when the system was fueled by pure methane as a reference case. Then, the performance of the hybrid SOFC-GT system when methane was partially replaced by H2 from a concentration of 0% to 95% with an increment of 5% at each step was investigated. The system performance was monitored by investigating parameters like temperature and flow rate of streams in different locations of the cycle; SOFC and system thermal efficiency; SOFC, GT, and cycle net and specific work; air to fuel ratio; as well as air and fuel mass flow rate. The results of the sensitivity analysis demonstrate that hydrogen concentration has significant effects on the system operational parameters, such as efficiency and specific work.

Fabrication and characterization of Ba Ce_(0.8)Y_(0.2)O_(2.9)-Ce_(0.85)Sm_(0.15)O_(1.925) composite electrolytes for IT-SOFCs

The Ba Ce0.8Y0.2O2.9-Ce0.85Sm0.15O1.925 composite electrolytes were prepared with Ba Ce0.8Y0.2O2.9(BCY) and Ce0.85Sm0.15O1.925(SDC). The SDC and BCY powders were mixed in the weight ratio of 95:5, 85:15, and 75:25, respectively(named as BS95, BS85, and BS75). Because of the composite effect between the SDC and BCY phases, the BS95 and BS85 exhibit improved conductivity compared with the pure SDC and BCY. The conductivity of BS95 is higher than that of BS85, indicating that the composite effect of BS95 is greater than that of BS85. Nevertheless, the composite effect in BS75 does not exist. Hence, we conclude that the composite effect in the BCY-SDC composites will decrease with the increase of the amount of BCY and even disappear when the amount of BCY exceeds a certain value. In our case, the optimum composition of the composite electrolyte is 95 wt% SDC and 5 wt% BCY. The BS95 has the highest conductivity(σ1t=0.07808 S cm-1, at 800 °C) and the fuel cell based on the BS95 shows the best performance(the maximum power density reaches as high as 526 mw cm-2 at 750 °C). The encouraging results suggest that the BCY-SDC composites are the very promising electrolyte materials for IT-SOFCs.