The application prospect and challenge of the alternative methanol fuel in the internal combustion engine.

In the context of global carbon neutrality, the internal combustion engines aim to further reduce the carbon emission and improve the fuel economy for the transportation sector. Methanol is treated as a renewable, reliability, and applicability energy, which also shows some superior physicochemical properties compared to the traditional fossil fuels. However, some challenges such as cold start issue, low fuel economy, high unregulated emissions need to address before the methanol widely applies in the engines. This article comprehensively reviews the physicochemical properties and production processes of the methanol, the cold start issue of the methanol engine, and emission and combustion characteristics of the methanol engine for evaluating its potential effect of emission reduction and energy saving in the transportation sector. In addition, different optimization strategies and advanced technologies are proposed and comprehensively discussed in this paper for addressing the issues of the cold start, combustion and emissions of the methanol engines in the real application. Finally, the conclusions and prospects of the methanol engine are presented for promoting its application in the transportation sector and further reducing the carbon emission in the near future, thereby achieving the carbon peak and carbon neutrality in the China.

Isovalent electronic systems B+13 and BeB12: structural interchange of GM and TS.

Fluxional Wankel motor molecules have received considerable attention in recent years in both chemistry and nanoscience. Based on extensive first-principles theory calculations, we present herein the smallest neutral quasi-planar alkaline-earth metal-doped Wankel motor complex Cs BeB12 (BeB2@B10), which is isovalent with C2v B+13 (B3@B10+). The global minimum (GM) Cs BeB12 (1) and transition state (TS) Cs BeB12 (2) correspond to the C2v TS (4) and C2v GM (3) of B+13, respectively. Molecular dynamics simulations show that, with ten equivalent GMs and ten equivalent TSs intervals, the B10 outer ring in BeB12 (1/2) overcomes the rotational energy barrier to rotate almost freely around the BeB2 triangular core above 800 K in a rotation angle of 36° in each step. Detailed bonding analyses indicate that, in addition to the ten localized periphery B-B bonds, both Cs BeB12 (1) and Cs BeB12 (2) possess three delocalized bonding systems over the molecular framework satisfying the (4n+2) Hückel rule, making the neutral complex 2σ + π triply aromatic in nature and highly stable in thermodynamics.

Parallel perturbation analysis of combustion cycle-to-cycle variations and emissions characteristics in a natural gas spark ignition engine with comparison to consecutive cycle method.

Severe combustion cycle-to-cycle variations (CCVs) in spark ignition (SI) engines significantly increase partial or incomplete combustion cycles, which may result in combustion instability or even misfire under extreme conditions, thereby seriously affecting the engine performance and increasing the unburned hydrocarbon and carbon monoxide emissions. In this study, the consecutive cycle method (CCM) and parallel perturbation method (PPM) are utilized to simulate the CCVs in a natural-gas (NG) SI engine. Specifically, 25 consecutive and concurrent cycles of the SI engine are simulated, and simulation results are compared with the experimental data. Further, the factors affecting the CCVs and exhaust emissions in the NG SI engine are verified by analyzing the low-pressure (LP) and high-pressure (HP) cycles. The results indicate that the simulated in-cylinder pressures of the NG SI engine based on PPM are basically in agreement with the experimental in-cylinder pressure distribution range, which suggests that the PPM can effectively predict the CCVs in NG SI engines. Furthermore, the required wall clock time for the simulation of CCVs is greatly reduced from 1 to 2 months (using CCM) to 2-3 days by using the PPM, which makes it particularly suitable for the industrial applications. Besides, the velocity field of the HP cycle is obviously stronger than that of the LP cycle. During the early stage of flame development, the flame area and volume of LP and HP cycles do not show much difference. However, the flame front surface-volume ratio of the HP cycle is larger than that of the LP cycle at 15 CA after the spark timing. Furthermore, the emissions formation and oxidation of the NG SI engine are strongly depended on the HP and LP cycles due to the combustion rate and flame propagation in the cylinder.

Effects of inhalation frequency on inhalation/exposure dose of hazardous nanoparticles and toxic gases during cigarette smoking.

In this study, we measured the pollutants generations during cigarette smoking under various inhalation frequency experiment scenarios by a self-developed smoking machine. Some concepts, the effective inhaled amount and exposure amount were proposed to quantitatively estimate emission rates. Important findings include: For interval 1 s, 2 s, 3 s, 4 s and 9 s (called from 1 s to 9 s herein), effective inhaled nano-scale PN (particle number) per cigarette was 8.43E+09 #, 7.24E+09 #, 5.74E+ 09 #, 3.82E+09 # and 1.15E+09 #, it decreased linearly with interval time; exposure amount of PN in side stream smoke was 1.06E+10 #, 1.2E+10 #, 1.48E+10 #, 1.84E+10 # and 8.74E+10 #, it increased with interval time. For toxic gases, all pollutants decreased with interval time in main stream smoke. In side stream smoke, NOx and CO firstly increased with interval time and then decreased (with the highest value at 3 s interval time), while HC always increased with interval time. So, this study is useful to understand the relationship between pollution and smoking habit.

Quantitative detection, sources exploration and reduction of in-cabin benzene series hazards of electric buses through climate chamber experiments.

In this study, a large-scale in-cabin benzene series hazard detection is firstly performed on 20 electric buses by a full-scale climate chamber. The sources of BTEX are analyzed deeply by parts detection, and a series of effective measures are performed to reduce BTEX. Firstly, the in-cabin BTEX pollution with considerations of a series of parameters, such as interior configuration, environment temperature, vehicle age, and ventilation mode, is analyzed. The result shows that: 1) The VOCs concentrations decrease with vehicle age, higher configuration level and better ventilation system (particularly, fresh wind mode reduce VOCs fastly), while increases with environment temperature; 2) BTEX in bus cabins occupy approximatively 70.1% of TVOC, thus the BTEX overproof is the main culprit which causes VOCs to exceed standard. Then, measurements on components/materials VOCs releases were performed in a small climate chamber to discriminate key species and their sources. Xylene released from glues materials is found as a key species that causes BTEX/VOC to exceed limitation. Lastly, some measures, such as optimizations of materials selection and manufacturing crafts, are adopted to improve in-cabin pollution, and positive effects are obtained. For example, ethylbenzene and xylene released from HL 125 (a polyurethane adhesive) decrease by 2456% and 1930% respectively after improvement. And in-cabin xylene and TVOC decrease by 2274% and 222%, respectively, and all of them are lower than limitation value.

Dispersion behaviors of exhaust gases and nanoparticle of a passenger vehicle under simulated traffic light driving pattern.

In the present study, the flow structure and pollutants dispersions were investigated by experiment and simulation on a typical passenger vehicle under simulated traffic light driving pattern. Some important findings were achieved: 1) gaseous pollutants diffuse drastically during first 0.3-0.6 m distance depending on wind velocity, at 1.25 m/s wind speed which is the similar level of exhaust gas, the pollutant concentration rises suddenly at ~0.6 m because exhaust plume is twisted by bottom gas flow, and a low velocity zone is produced; 2) as wind speed increases, the vehicle-induced turbulence is more and more important on pollutant dispersion pattern than exhaust plume dynamics. For instance, at 1.25 m/s and 4.17 m/s wind speeds, pollutants decrease to zero at ~1.6 m behind tail pipe, but at 0 m/s condition, pollutant relative fraction is still at ~0.12 level even at very long distance; 3) solid particle has larger attenuation rate than gaseous pollutants, only after ~0.6 m the particle number (PN) and diameter are very close to background values. Solid particle can diffuse to farther distance in vehicle transverse direction, when a car passes through the pedestrians with a 3 m distance, pedestrians expose to 2.6-3 times higher PN relative to atmosphere with diameters of 28-33 nm, this is very hazardous for human health; 4) exhaust pollutants disperse difficultly when followed by a car with a commonly waiting distance. At free dispersion scenario only behind ~0.6 m, PN decreases to 5800 #/cm3 (background value), but in-cabin PN of the following car (behind 0.8 m) rises to 3.5 × 104 #/cm3 (even after 2-3 times decay through ventilation system). This study provides implications for future studies on transport planning.

Sequencing of pT5282-CTXM, p13190-KPC and p30860-NR, and comparative genomics analysis of IncX8 plasmids.

This study proposes a replicon-based scheme for typing IncX plasmids into nine separately clustering subgroups, including IncX1α, IncX1ß and IncX2-8. The complete nucleotide sequences of three IncX8 plasmids, namely pT5282-CTXM and p30860-NR from Enterobacter cloacae and p13190-KPC from Klebsiella pneumoniae, were determined and were compared with two other previously sequenced IncX8 plasmids (pCAV1043-58 and pCAV1741-16). These five plasmids possessed conserved IncX8 backbones with limited genetic variation with respect to gene content and organisation, and each of them carried one or three accessory modules that harboured resistance markers and metabolic gene clusters as well as transposons, insertion sequence (IS)-based transposition units and miniature inverted repeat transposable elements (MITEs), indicating that the relatively small IncX8 backbones were able to integrate various foreign genetic contents. The resistance genes blaCTX-M-3 and blaTEM-1 (ß-lactam resistance), blaKPC-2 (carbapenem resistance) and ΔblaTEM-1, and tet(A) (tetracycline resistance) and mph(E) (macrolide resistance) were found in pT5282-CTXM, p13190-KPC and pCAV1741-16, respectively, whilst p30860-NR and pCAV1043-58 carried no resistance genes. The data presented here provide an insight into the diversification and evolution history of IncX8 plasmids.

Comparative genomics of type 1 IncC plasmids from China.

AIM: This study dealt with genomic characterization of type 1 IncC resistance plasmids, capable of spreading across taxonomic borders, from China. MATERIALS & METHODS: p112298-tetA was sequenced and compared with type 1 IncC reference plasmid pR148 and two available sequenced type 1 IncC plasmids pHS36-NDM and pVAS3-1 from China. RESULTS: These plasmids contained one or more exogenous resistance islands, which included the ARI-A islands, the ARI-B islands, the ISEcp1-blaCMY units and the bla KPC-2 region and were inserted at various sites in the IncC backbone and thus represented three distinct lineages. CONCLUSION: Complex rearrangement and homologous recombination events have occurred during evolution of p112298-tetA, making it significantly differ modularly from the other three plasmids with respect to both plasmid backbone and exogenous resistance regions.