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In this study, mixed fuel droplets of ethyl alcohol and biodiesel with different volumes or ratios were prepared and the related expansion, injection and micro-explosion phenomena were investigated...

The ignition, injection, and micro-explosion characteristics of aviation fuel (RP-3)/ethanol mixed droplets and biodiesel/ethanol mixed droplets at different proportions under high temperature conditions (420 °C) were compared using an experimental setup. A device for measuring small droplet volumes was designed using an infusion set and different types of needles, and a corresponding equation was established. Mixed droplets suspended on high-temperature resistance nichrome wire with a diameter of 0.2 mm were heated by sending them to a position approximately 2 mm from the forklift preheating plug using a moving rail. SLR and high-speed cameras were used to observe the flame structure as well as the injection and micro-explosion of the mixed droplets during combustion, respectively. Expansion, injection, and micro-explosion were observed in the biodiesel/ethanol mixed droplet experiments when the biodiesel content was 60%. Although the micro-explosion of mixed droplets of aviation fuel/ethanol was not observed, expansion and ejection of the droplets were observed. Image Pro-plus software was used to calculate the diameters at different times in the combustion cycle of the droplets. Through this analysis, the occurrence of micro-explosion was described, and a model for the calculation of micro-explosion strength was established.

This study investigated the combustion characteristics and kinetics of sewage sludge (SS), wheat straw (WS) and their blends using thermogravimetric analysis, under air condition. Combustion characteristic parameters of SS blended with 5%–50% WS was enhanced, especially revealed by an increase in comprehensive combustion index. A significant synergetic interaction was found in high temperature region through experiments. When proportion of WS was 50%, the synergetic interaction was strongest. And the catalytic effect of alkali metal oxides in WS ash on the combustion of SS residues at high temperature region had a strong effect on synergetic interaction. Metal oxides circulated in different oxide forms to transport oxygen to carbon surface, leading to catalytic effect. Activation energy was evaluated by two isoconversional method: Flynn-Wall-Ozawa and Vyazovkin method. The lowest average activation energies of the blends were obtained at 50% wheat straw blending ratio (89.29 kJ/mol by FWO and 87.48 kJ/mol by V, respectively). The thermodynamic parameters (Gibbs free energy, Entropy and Enthalpy) were also obtained. And two master plots methods were utilized to determine the appropriate fit kinetic model of combustion which can be described by Avarami-Erofeve (A2).

This study aimed at understanding the effects of co-flow condition on lift-off characteristics of the propane jet flame. A co-flow burner system was used to provide free jet condition, air co-flow condition and vitiated co-flow condition. In vitiated co-flow, methane was the co-flow fuel, and the co-flow equivalence ratios of methane/air mixtures changed from 0.5 to 0.7. On the basis of the results, the flame issuing into air-co-flow showed a higher lift-off height compared to the flame not issuing into a co-flow (i.e. free jet condition), with a faster increment rate simultaneously. In the vitiated co-flow condition, a conversion of lift-off height changing tendency was observed with the increment of flow rate and equivalence ratio of the co-flow. As the cases remained the same equivalence ratio, the cases with lower co-flow rates showed higher lift-off heights in the early combustion period. The lift-off height increased with the equivalence ratio in the cases with low co-flow rate, however, it decreased at high co-flow rate. It could be observed in the captured images that the ignition process was accelerated with the increment of equivalence ratio and co-flow rate.

The catalytic efficiency of CeO2 carriers and the catalytic properties of palladium (Pd) nanocrystals loaded on different morphology CeO2 carrier were studied for lean methane (CH4) combustion. The catalytic activity of simple CeO2 carriers was ranked in the order of rod-CeO2(r-CeO2) > cube-CeO2(c-CeO2) > octahedral-CeO2(o-CeO2). After the Pd species was loaded on CeO2, 90% of CH4 was converted at 348 °C catalyzed by Pd/octahedral-CeO2 (Pd/o-CeO2) with (1 1 1) crystal faces, which had much higher catalytic activity comparing with Pd loaded on c-CeO2 with (1 0 0) crystal faces and r-CeO2 with (1 1 0) and (1 0 0) crystal faces. The results of XRD, HRTEM, EDS, H2-TPR, XPS and elemental mapping showed that the Pd species in the form of Pd0 and PdO were highly dispersed on surface of all CeO2 carriers. Most importantly, quasi In-situ XPS results convinced that Ce3+/Ce4+ ion pairs played an important role in the catalytic combustion of low-concentration methane by adsorbing or releasing oxygen. Compared with r-CeO2 and c-CeO2, the concentration of Ce3+ on the surface of o-CeO2 carrier was greatly increased when the Pd species were present, which indirectly reflected that the concentration of oxygen vacancies on the carrier surface also increased. Consequently, the high catalytic activity of Pd/o-CeO2 is not only related to the high dispersion of Pd0 and PdO species on the surface of the catalyst, but also closely related to the synergistic interaction between Pd species and (1 1 1) specific faces of o-CeO2 exposing.

This paper reviews several important preparation methods, and several kinds of MnO2 composites, which is efficient in formaldehyde catalytic oxidation. The preparation of MnO2 composites discussed in this article refer to sol–gel method, rheological phase reaction method, micro-emulsion method, chemical coprecipitation method, solid-phase synthesis and template method. After a presentation of methods for the preparation of MnO2, a review of the performance on formaldehyde catalytic oxidation over (I) manganese oxides; (II) metal–MnO2 oxide composites; (III) graphene–MnO2 composites is provided. The mechanisms for catalytic oxidation of HCHO over MnO2 composites, future directions and potential hotspots are also discussed to facilitate understanding.

Proxies based on glycerol dialkyl glycerol tetraethers (GDGTs), a suite of membrane lipids occurring ubiquitously in soils, have generated increasing interest in quantitative paleo-environmental reconstruction. Hot and dry climates are likely to have occurred in the geological past; however, the limitations and applicability of these proxies to hot and dry environments are still unknown. In this study, we analyzed the GDGT distribution in the Turpan (TRP) basin of China, where the highest soil temperature can be approximately 70°C, and the mean annual precipitation (MAP) is 15.3 mm. We compared GDGT-based proxies among TRP soils, Nanyang (NY) soils, and Kunming (KM) soils; these three sites exhibit similar mean annual air temperature (MAAT) albeit contrasting temperature seasonality and MAP. Archaeal isoprenoidal GDGTs (isoGDGTs) dominate over bacterial branched GDGTs (brGDGTs) in most TRP soils; this is a characteristic GDGT distribution pattern for soils from dry regions globally. Another feature is the anomalously high GDGT-0/crenarchaeol ratio, which is generally attributed to the contribution of anaerobic methanogenic archaea by previous studies; however, these anaerobic archaea are unlikely to be highly abundant in the dry TRP soils, indicating that certain uncultured halophilic Euryarchaeota are likely to produce a significant amount of GDGT-0 that finally results in a high GDGT-0/Cren ratio. The changes in the salinity of the TRP soils appear to be an important factor affecting the MBT’5ME and the relative abundance of 6- vs. 5-methyl pentamethylated brGDGTs (IRIIa’). This is likely to introduce certain scatters in the correlations between MBT’5ME and MAAT and that between IRIIa’ and pH determined at the global scale. A comparison of the MBT’5ME-inferred temperature between TRP, NY, and KM soils does not indicate a significant bias toward summer temperature, indicating that brGDGT paleothermometers in soils could reflect the MAAT.

This work aimed to figure out the liftoff characteristics of ethylene and ethane, which are both promising fuels in the new energy era for flames in coflow. A free jet condition, air coflow...

In this work, NiCo2O4 with a hierarchical porous flower-like structure was fabricated and used as catalyst support for Pd nanoparticles. The NiCo2O4 was composed of porous nanoplates without overlapping, and the Pd nanoparticles were uniformly distributed on these nanoplates. Pd–NiCo2O4 with the Pd loading of 2.0 wt% showed extremely high activity and stability, methane (1.0% CH4/Air) can be totally oxidized at 330 °C and the T90 is 309 °C, which is much lower than that of pure NiCo2O4 (T90 = 405 °C). At wet condition with the presence of 10 vol% water vapor, the catalytic activity was still acceptable with the T90 of 366 °C, and no activity decrease or permanent damage for the catalyst was observed after 35 h reaction, showing high stability. A series of techniques including TEM, SEM, XRD, H2-TPR, BET and especially quasi in situ XPS combined with in situ MS were used to characterize the catalysts and investigate the catalysis mechanism. Two pathways of CHO evolution were proved by the quasi in situ XPS and in situ MS results: OCHO intermediate dehydrogenation pathway at lower temperature and CO oxidation pathway of CHO at higher temperature.

Combustion behaviors and carbon monoxide emission characteristics of four kinds of coals and their blends, which were shaped into pellets, were investigated in a drop-tube furnace with vari...

The methylation index (MBT or MBT′) of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils along altitudinal transects of some mountains, e.g. Mount (Mt.) Shennongjia and Mt. Gongga, exhibited no correlation with altitude or mean annual air temperature (MAT) alone. However, a significant correlation between MBT′, cyclization ratio (CBT) of brGDGTs and MAT for each transect could still be found. To investigate the reason, we reanalyzed the brGDGTs in soils from Mt. Shennongjia using an improved liquid chromatography method and examined whether the newly described 6-methyl brGDGTs were the main cause of the large scatter in the correlation between MBT′ and MAT. In contrast to MBT′, the MBT′5ME, based on 5-methyl brGDGTs alone, correlated significantly with MAT (R2 0.89, p