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A comprehensive measurement and investigation of the cellularization of methanol/hydrogen flame is important for the thorough understanding of the transition of turbulent flame. In this work, a constant volume combustion bomb with schlieren photography technology is used to study the flame evolution of methanol/hydrogen fuel. By investigating the flames smooth laminar flame to a certain degree of cellular flame, the effect of hydrogen addition on the cellular instability of the hydrogen/methanol spherical flame is revealed. The experiments were conducted with different hydrogen mixing ratios (0%–80%) at different equivalence ratios (0.8–1.5) under a series of initial temperature (375 K–450 K) and pressure (1.0 bar–3.0 bar). The results showed that the process of flame cellular instability advanced in general as the hydrogen mixing ratio increased. The promoting effect of hydrogen addition was more significant in lean flames. The cellularization in lean flames was dominated by the instability of thermal diffusion, while that in the rich flames was dominated by the hydrodynamic instability. The initial pressure impacts the flame cellar instability mainly through the hydrodynamic instability.

This paper proposes a novel and efficient preparation method for copper-steel bimetallic materials. A transition welding wire for copper-steel gradient connections was designed, and then gas metal arc welding (GMAW) additive manufacturing processes were explored. The effects of the process and material on the microstructure, interface characteristics, and mechanical properties of copper-steel bimetallic materials were systematically studied. The results show that copper-steel bimetallic thin-walled parts can be well formed, which confirms the possibility of the arc additive manufacturing of copper-steel bimetallic parts. With the direct deposition of silicon bronze on the surface of low-alloy steel, the melting unmixed zone (MUZ) appears at the bonding interface of low-alloy steel and silicon bronze, which is prone to produce microcracks, leading to fracture failure of the joint. However, with the addition of the Cu-Ni interlayer, the Fe, Ni, and Cu elements in the bronze interface between the low-alloy steel and silicon were continuously diffused, which improved the nonuniformity of the Fe-rich phase in silicon bronze matrix, and realized the gradient connection at the welding joint. Comparing the tensile properties and microhardness of the joints, it can be found that the tensile strength of the low-alloy steel/Cu-Ni/silicon bronze joint was 66.36 pct higher than that of the alloy steel/silicon bronze joint, which can reach approximately 345.2 MPa and shows a typical ductile fracture mechanism. Additionally, the microhardness of the transition zone in the low-alloy steel/Cu-Ni/silicon bronze joint was more uniform.

The present paper dealt with characterizing microstructure and mechanical properties of the dissimilar weldment between stainless steel and copper obtained by gas metal arc welding using HS201 filler material. The results showed that the copper/weld interface was free of any defects, while the stainless steel/weld interface consisted of a melted unmixed zone with inhomogeneous distribution of composition. The weld showed a hybrid microstructure, which contained significant amount of steel globules and dendrites with different sizes. The hardness distribution of the weld was inhomogeneous, and an obvious reduction in microhardness of the heat-affected zone of copper was observed compared to that of the base metal of copper. Furthermore, all tensile specimens fractured at the heat-affected zone of copper, and the average tensile strength of welded joint reached 209.5 MPa.

The effects of hydrogen addition on laminar premixed methanol–air flames were studied both experimentally and numerically. To achieve this, a constant volume chamber (CVC) and the premix code in CHEMKIN were used. During the experiments, the equivalence ratios (ϕ) and hydrogen mole fractions ( X h ) were set to 0.6 to 1.8 and 0%–100%, respectively. In addition, initial environmental conditions were set to 375 K and 1 atm. The results indicate that the laminar flame speed (LFS) and burning velocity (LBV) both increase when more hydrogen is added into the methanol–air mixtures. For premixed methanol–air flames, the Markstein length ( L b ) decreases monotonically with an increase in the equivalence ratio; however, when the hydrogen fraction is greater than 40%, an increasing trend in the Markstein length is presented as the mixtures move toward the fuel-rich side. The variation in Markstein length is non-monotonic with the hydrogen fraction. A kinetics analysis indicates that methanol is mainly consumed by the dehydrogenation reaction caused from the impact of the active free radicals (OH and H). Reactions involving active free radicals and light intermediate species have the highest sensitivity and contribute the most to the propagation of a laminar flame. Therefore, the promotion effect of hydrogen additive is due to an enhancement in the radical pooling of H, OH, and O. The chain branching reaction R5 (O2 + H = O + OH) is essential for the geometric growth of free radicals. In addition, the amount of formaldehyde decreases owing to the hydrogen blending.

Disclosed herein is a Pd(II)-catalyzed C(sp3)–H/P–H oxidative cross-coupling reaction between 8-methylquinolines with H-phosphonates or diarylphosphine oxides via chelation-assisted C(sp3)–H bond activation. The protocol exhibits a relatively broad functional-group tolerance and exclusive chemo- and regioselectivity. Furthermore, detailed mechanistic studies support the proposed reaction pathway.

It is a common sense that diesel engines produce worse soot emission than gasoline engines, even though gasoline direct injection also brings about terrible sooting tendency. However, reports showed that diesel emits less soot than gasoline in laminar diffusion flames, which implies that soot emission is a combined effect of multiple factors, such as the combustion mode, physical properties of the fuel, and also fuel chemistry. This work, thus, conducted numerical calculations in laminar co-flow diffusion flames of fuels with different negative temperature coefficient (NTC) behaviors in an order of n-heptane > iso-octane > toluene to solely evaluate the chemical effect, especially the role of low-temperature combustion on soot formation. 2-Dimensional simulations were carried out to obtain the soot distributions, and 0-dimensional simulations were performed to analyze the chemical kinetics of polycyclic aromatic hydrocarbon (PAH) formation and low-temperature reaction sensitivities. The grids of the 2-D model converged at 80(r) × 196(z), and the boundary conditions of both models were set to eliminate the influence of physical factors as much as possible. The results showed that there were three main reactions associated to the formation of aromatic hydrocarbons A1 at the first-stage combustion in the n-heptane flame and the iso-octane flame, in which the reaction of C7H15 + O2 = C7H15O2 enhances the NTC behavior. The first two reaction pathways generated larger molecular hydrocarbons and were unfavorable by A1 formation and therefore inhabit the PAH formation, and 49.8% of C7H16 reacted through the large molecular pathways, while the percentage for C8H18, with weaker NTC behavior, was only 37%. Toluene with even weaker NTC behavior showed no low-temperature oxidation. Therefore, in a more general case, fuels with stronger NTC behavior smoke less, and this conclusion could be promising potential to reduce soot emission in future.

Acetone–Butanol–Ethanol (ABE), as an alternative for butanol, can be used either in neat form or in blends with fossil fuels. Yet the flame characteristics of ABE blending gasolines have not been reported to date. To explore the effects of ABE addition on the laminar flame speed of gasoline, the spherical propagating flames of ABE, gasoline (represented by toluene reference fuel, TRF), as well as ABE-TRF mixture were measured at an initial condition of 1 bar, 400 K, and an equivalence ranging from 0.8 to 1.6. The results indicated that with an addition of 20% ABE fuel, the laminar flame speeds of ABE-TRF flame showed apparent increments at stoichiometric and ϕ = 1.2 flames. The normalized increment of laminar burning velocity I v raised monotonically with the increase of equivalence ratio. The three ABE-TRF mixtures showed small increment of laminar burning velocity than TRF flame in the order of u n . ABE 20631 u n . ABE 20361 u n . ABE 20163 , suggesting a suppressing effect of acetone addition on the mixture burning velocity of ABE-TRF mixtures. ABE fuel with more alcohol contents extended the range of stable flame while acetone addition diminished the flame diffusional thermal stability. The kinetic analysis showed that the rate-limiting reactions shifted from heavier molecular reactions to lighter ones by blending the ABE fuel into TRF, as well as the rate of production (ROP) of OH radical increased by 5.5%. The sensitivity reactions for rich ABE-TRF flames are also more dependent on light fractions compared to lean flames.

Acetone–Butanol–Ethanol (ABE), as a clean and economical alternative transportation fuel, its component ratio has been reported to have a significant impact on spray combustion characteristics. To fundamentally clarify the interactions between components in ABE, the laminar flame speeds (LFS) and stretch effect of ABE mixtures with component ratios (6:3:1, 3:6:1, 1:6:3) and their individual components under a wide range of equivalence ratios (0.8–1.6) at 1 bar, 400 K, were measured, and the chemical kinetics were further analyzed. The results indicate that the LFSs of the three pure fuels follow the order of ethanol > n-butanol > acetone, while ethanol only propagates marginally faster than n-butanol. The LFSs of the three ternary mixtures distribute in between that of the ethanol and acetone. In addition, their LFSs follow the order of ABE631 < ABE361 < ABE163. The comparison among all the tested fuels shows that the addition of ethanol or n-butanol improves burning velocity, while acetone suppresses it....

Kink deformation is uncommonly observed in Ti-35V-15Cr-0.3Si-0.1C beta titanium alloy deformed at 5 × 10 3 s −1 . Band structures have formed on the deformed samples. Electron back scattered diffraction analyses prove those band structures are kink bands rather than commonly reported twins in beta alloys with high niobium. The kink bands are classified into three categories since the intragranular misorientation axis analyses reveal that three lattice rotation axes (Taylor axes) exist among the kink bands. The three Taylor axes are [ 1 1 0 ] , [ 5 4 1 ] , [ 12 1 ] and the corresponding three slip mode of the dislocation kink model are ( 112 ) [ 11 1 ] , ( 123 ) [ 11 1 ] , ( 101 ) [ 1 1 1 ] respectively. It is demonstrated that the selection of the slip mode in a kink bands is dominated by the loading axis. A slip system would have the priority to be selected as the slip mode of the kink deformation if the loading axis is close to the normal direction of the slip plane and the perpendicular direction of the slip direction.

The epitaxial growth behaviors of equiaxed primary α phase (α p ) at different cooling rates (150–0.15 °C/s) in a near α titanium alloy Ti60 were studied by optical micrograph, back scattered electron (BSE) images, high-resolution electron backscatter diffraction technique (EBSD) and electron probe microanalysis (EPMA). Microstructural observations indicated that the size of α p significantly increased with decreasing cooling rate. The rim-α phase observed by BSE image, which formed at the periphery of α p during cooling and has an identical crystallographic orientation to the interior region of α p analyzed by Kikuchi diffraction patterns, is considered to be evidence of epitaxial growth of α p . EBSD analysis also showed that α p preferentially grew extending for a distance along the β/β boundary resulting in extension-α phase from α p . The EPMA confirmed that contrast difference in BSE image within α p is caused by the difference in composition. The further microanalysis of local composition indicated that epitaxial growth during continuous cooling is mainly controlled by the diffusional redistribution of aluminum and molybdenum atoms between α p and β matrix. On this basis, the sizes of α p were theoretically calculated after continuous cooling based on a diffusion-controlled model, and model predictions showed good agreement with experimental measurements.

The present study is to systematically investigate the role of titanium carbides on microstructural evolution of a burn resistant titanium alloy Ti-35V-15Cr-0.3Si-0.1C, especially on DRX and its kinetics under different deforming conditions during hot compression. First, a particle stimulated nucleation (PSN) phenomenon is found responsible for the pervasive dynamic recrystallization (DRX) in the material, in which DRX grains (or subgrains) prefer to form in the vicinity of titanium carbides (TiCx). And the morphology and distribution of TiCx can be altered by processing, which means the number of potential nuclei and the resultant recrystallization may be controlled by controlling the working process. Second, it is found that DRX fraction and DRX (sub) grain size are all deforming parameters (deformation temperature, strain and strain rate) dependent, and DRX kinetics is investigated by quantitative metallography analysis. The kinetics for DRX initiated by PSN in the present material follows the Avrami equation, which is consistent with the conventional DRX kinetics. The difference for this alloy is that only a small critical strain ( Z d 2.95 = e 24.58 . At last, by a billet cogging experiment, it is confirmed that multi-directional deformation can fully break down coarse TiCx and promote PSN, leading to a fine and homogeneous microstructure.

In this study, hot workability of Ti–35V–15Cr–0.3Si–0.1C alloy is investigated in the temperature range of 900–1150°C and strain rate range of 0.01–10 s− 1 using processing maps. In the maps, the stability domain displays the feature of dynamic recrystallisation and dynamic recovery. The fraction of recrystallisation in this alloy is much larger than that in other β-Ti alloys, which can be attributed to the effect of titanium carbides by a ‘particle stimulated nucleation’ mechanism. Higher temperature and lower strain rate are helpful for breaking down the carbides and improving the workability. However, deforming >1100°C would result in grain coarsening. In instability domain, the occurrence of flow localisation, shear bands and cracking is discussed. The optimised processing window is in 1050–1100°C /0.01–0.1 s− 1.

A special recrystallization mechanism called ‘particle stimulated nucleation’ (PSN) is found responsible for the pervasive discontinuous dynamic recrystallization (DDRX) in the burn resistant β-stablized Ti–35V–15Cr–0.3Si–0.1C alloy. This might be the first time that PSN is found in titanium alloys. PSN mechanism is studied by transmission electron microscopy (TEM) and Electron Back Scattered Diffraction (EBSD) techniques. Local strain incompatibility between the matrix and the titanium carbides leads to high density of dislocation in the particle deformation zone (PDZ), which provides the ideal sites for PSN. Recrystallized grains produced by PSN is randomly oriented and the microtexture gets weaker as the fraction of DRX increases.

Compressed natural gas-Diesel dual-fuel combustion mode, the partial replacement of diesel fuel with cleaner fuel, is one of the most important strategies to achieve clean efficient combustion. However, low substitutions conditions face unstable combustion and high emission issues. Thus, the current work investigated the effect of hydrogen blending in natural gas on the combustion and soot emission characteristics experimentally in an optical engine. An optical diagnosis study of its performance, combustion flame development, and soot concentration distribution was conducted at various hydrogen volume rates (0%, 30%) and main injection timing (13°CA BTDC, 10°CA BTDC, 5°CA BTDC). In-cylinder flame images were captured by a high-speed camera and further processed to obtain flame characteristics as well as soot distributions. The results showed that the effect of hydrogen blending is mainly reflected in a change of ignition delay period and more ignition points at the initial combustion stage which improves combustion stability. When hydrogen is added, flame propagation speeds up, the flame distribution is more extensive especially in the first stage combustion, the heat release rate and pressure rise rate increase accordingly. Besides, soot emissions considerably decreased in the central region of the cylinder, especially during the first stages of combustion. When the injection advance angle is large, adding hydrogen results in the ignition delay period is extended, more premixed flames appear, and the maximum pressure increases. When that is small, adding hydrogen shortens the ignition delay period, but the poor diesel atomization results in diffusion combustion.

A protocol has been established for oxygen-mediated amidoselenation and amidotelluration of alkenes under mild conditions. This method provides a simple route to a series of structurally diverse β-amido selenides and β-amido tellurides in moderate to high yields. The wide substrate scope, good functional group tolerance, ease of large-scale preparation and potential for product derivatization make this reaction attractive for the synthesis of nitrogen-, selenium- and tellurium-containing molecules.

Acetone-butanol-ethanol mixture (ABE) is being studied as an alternative fuel because it not only preserves the advantages of oxygenated fuels, but also lowers the cost of fuel recovery for butanol during fermentation. The previous experimental study on spray and flame lift-off length for diesel with 20% addition of ABE mixture, shows a shorter and narrower spray and a much longer flame lift-off length compared to those of neat diesel, which leads to considerably less soot emission level of ABE20. In this study, a detailed mechanism capable of predicting the ignition delay for ABE as well as ABE-diesel blends is implemented to the KIVA-3V program to simulate the spray dynamics and lift-off length inside the constant volume chamber. The presented model is able to capture the trends with regard to ignition delay, combustion duration and peak pressure. The overall predictivity for ABE20 is better than that of D100. Spray penetration and the lift-off length for both fuels are simulated and the numerical definition for lift-off length is discussed. It is found that the threshold temperature to define lift-off length can be uniform under different ambient temperatures, but varies with respect to oxygen concentration. The simulations also agree with the measurements in predicting the lift-off length decreases as temperature and oxygen concentration increases. Finally, the simulation sooting tendency is presented to show that, due to the improved spray and combustion process of ABE-diesel blend, the soot emission level is much less than conventional diesel fuel.

The present study proposed a reduced mechanism for a fuel blend of toluene reference fuel (TRF, toluene/n-heptane) and n-butanol for modeling the combustion and soot formation processes of n-butanol/diesel blend fuel. A detailed reaction mechanism for n-butanol, consisting of 243 species and 1446 reactions, and a reduced TRF mechanism, containing 158 species and 468 reactions, were reduced separately and then combined to create a new TRF/n-butanol mechanism. The new TRF/n-butanol mechanism contained 107 species and 413 reactions. A multi-technique reduction methodology was used which included directed relation graph with error propagation and sensitivity analysis (DRGEPSA), unimportant reaction elimination, reaction pathway analysis, and sensitivity analysis. In addition, a reduced 12-step NOx mechanism was combined with the TRF/n-butanol mechanism to predict NOx emissions. The proposed mechanism was also coupled with a multi-step soot model to predict the combustion and soot formation processes. The proposed mechanism was validated using available ignition delay times, laminar flame speeds and species concentration profiles from shock tubes, flat flame burner and jet stirred reactors. Good agreements were found for the above comparisons and with results from detailed mechanisms. Furthermore, multi-dimensional CFD simulations were conducted by using the KIVA-3V R2 code coupled with the preconditioned Krylov method. The effects of exhaust gas recirculation (EGR), injection timing and blending ratio of n-butanol on combustion and NOx formation were analyzed and validated experimental data. The pressure, heat release rate, NOx, and soot emissions with respect to fuel blends, EGR rates and start of injection (SOI) timings agreed well with the experimental results. With increasing n-butanol content, both experimental and calculated soot emission decreased, demonstrating that butanol additive was capable of reducing soot emission compared to pure diesel. Both experiments and models revealed that soot emissions peak occurred at SOI close to TDC. The proposed mechanism can readily be used to predict the combustion and soot formation processes of butanol-diesel blends fuel in combustion CFD simulations.Copyright © 2015 by ASME

Oxidative stress is considered to be an important factor in producing lethal hepatocyte injury associated with nonalcoholic fatty liver disease (NAFLD). Glucose fluctuation, more pronounced in patients with diabetes, has been recognized as an even stronger oxidative stress inducer than the sustained hyperglycemia. Here, we investigated the role of glucose variability in the development of the NAFLD based on hepatocyte apoptosis and possible mechanisms. To achieve this goal we studied C57BL/6J mice that were maintained on a high fat diet (HFD) and injected with glucose (3 g/kg) twice daily to induce intermittent high glucose (IHG). We also studied hepatic L02 cells incubated with palmitic acid (PA) to induce steatosis. The following experimental groups were compared: normal glucose (NG), sustained high glucose (SHG) and IHG with or without PA. We found that, although hepatic enzyme levels and liver lipid deposition were comparable between HFD mice injected with glucose or saline, the glucose injected mice displayed marked hepatocyte apoptosis and inflammation, accompanied by increased lipid peroxide in liver.In vitro, in the presence of PA, IHG increased L02 cell apoptosis and oxidative stress and produced pronounced mitochondrial dysfunction relative to the NG and SHG groups. Furthermore, treatment with the mitochondrial permeability transition (MPT) inhibitor, cyclosporin A (1.5 μmol/l), prevented mitochondrial dysfunction, oxidative stress and hepatocyte apoptosis. Our data suggests that IHG under lipotoxicity might contribute to the development of NAFLD by increasing oxidative stress and hepatocyte apoptosis via MPT and its related mitochondrial dysfunction.