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In order to explore the influence of different temperature and oxygen concentration on the combustion and micro-explosion of BD60R10E30 droplets (the ratio of biodiesel, aviation fuel and ethanol was 60:10:30), a set of volume measuring device was designed, and the volume of BD60R10E30 droplets with 1.34 μL was obtained by using this device, and a multi-parameter tube furnace experimental system was established. By adjusting the parameters of temperature and oxygen concentration, the experimental phenomena such as droplet ignition, expansion and micro-explosion were found, and the shape and boundary of discrete flame were firstly observed in mixed fuel. The modified micro-explosion intensity calculation model was established, and the micro-explosion intensity of mixed droplets under different conditions was calculated, and the reasons for the difference of micro-explosion intensity were analyzed. In addition, the concept of volume burning rate of micro-droplets was put forward, and the volume burning rate model based on micro-explosion intensity was established. The average volume burning rate of BD60R10E30 droplets under different micro-explosion intensity conditions was calculated by combining the micro-explosion intensity model with the volume burning rate model. • The combustion condition of aero-engine in different flight phases is analyzed. •Oxygen concentration and temperature can affect BD60 R10E30 droplets micro-explosion. •A new equation for calculating the micro-explosion intensity is established. • The droplet burning rate was calculated by combining the micro-explosion model. [ABSTRACT FROM AUTHOR]

The ignition and combustion characteristics of anthracite-rice husk (AC-RH) and bituminous coal-rice husk (BC-RH) pellets were investigated in a vertical heating tube furnace under different experimental condition, for gas temperature (873 K–1073 K) and under air and different oxygen concentration (21–70%) in CO 2 /O 2 atmosphere. The investigation of the ignition and combustion characteristics focused on ignition mechanism, ignition delay, ignition temperature and combustion process. AC-RH pellets had two ignition mechanism in CO2/O2 atmosphere: homogeneous ignition of volatile and heterogeneous ignition of char. Heterogeneous ignition region decreased while homogeneous ignition increased as rice husk blending ratio increased in oxygen concentration-gas temperature plane. Only homogeneous ignition was observed when rice husk blending ratio was 30%. As for BC-RH pellets, only homogeneous ignition occurred in all experimental conditions. The effect of the rice husk blending on the anthracite was more pronounced than the bituminous coal for ignition mechanism. As oxygen concentration increased, a significant reduction in ignition delay and ignition temperature was observed at low rice husk blending ratio and low gas temperature. but at 1073 K, high oxidizer temperature weakened the effect of biomass blending and oxygen concentration on ignition delay and ignition temperature. Meanwhile, at 20% and 30% rice husk blending ratio, it also weakened the effect of oxygen concentration and oxidizer temperature on ignition delay and ignition temperature. In contrast, blending ratio had a more significant effect on ignition behavior. The replacement of N 2 by CO 2 at the same oxygen concentration contributed to an increase in ignition delay time and internal ignition temperature, which suppressed the ignition behavior. Different ignition mechanisms corresponded to different combustion processes. • The ignition and combustion behavior of coal-biomass blend pellet was investigated. • The critical condition of the transition for ignition mechanism was found. • The effect of Tg, O2% and BRH on ignition delay and temperature was discussed. • The effect of RH blending on anthracite was pronounced than bituminous coal. [ABSTRACT FROM AUTHOR]

Summary: This study applied the artificial neural networks (ANNs) model to the thermal data obtained by suspension ignition and combustion experiment of single peanut shells (PS, millimeter scale) pellet under O2/CO2 atmosphere. ANN11 was the best ANN model for predicting the relevant parameters of PS combustion. The coincidence between ANN prediction data and experimental data was over 99%. Two modes of biomass pellet ignition were observed: homogeneous ignition of volatiles and hetero‐homogeneous ignition of volatiles and char simultaneously. The ignition mode was transformed from homogeneous ignition to hetero‐homogeneous ignition when oxygen concentration was 50%. In addition, it was observed that ignition at the bottom emerged first, and then the upper end was ignited, finally generating an envelope flame. This phenomenon occurred when gas flow temperature exceeded 873 K or the oxygen concentration was greater than 50%. The reduction of ignition delay time and internal ignition temperature from 21% to 50% oxygen concentration was more intense than that of 50% to 100% oxygen concentration. Increasing oxygen concentration or temperature resulted in a shorter, brighter, and more stable volatile flame of biomass pellets, which reduced volatile burnout time. Nevertheless, the impact of gas flow rate on biomass combustion was intricate and irregular. [ABSTRACT FROM AUTHOR]

Abstract 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). Highlights • TG analysis of co-combustion between sewage sludge and wheat straw was studied. • Blending wheat straw improved the thermal behavior of sewage sludge combustion. • Synergetic interaction was found at high temperature in positive manner. • The minimum average activation energy was obtained by blending 50% wheat straw. [ABSTRACT FROM AUTHOR]

The combustion behavior and gas product characteristics of coal gangue (CG) and peanut shell (PS) in air atmosphere were studied by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). Artificial neural network (ANN) method was used to establish the optimal prediction model of CG and PS co-combustion. The heating rate of TG-FTIR experiment was set to 10 °C/min, 20 °C/min and 30 °C/min. The mass fractions of PS in the experimental samples were 0%, 25%, 50%, 75% and 100%. Some functional groups in the gas products were detected by Fourier transform infrared spectrometer. Moreover, the apparent activation energy (E) was calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The activation energies of CG and PS mixture combustion are significantly lower than that of pure substance. ANN models have been established to predict the relationship between mass loss and experimental conditions. By comparing errors and correlation coefficients, it is found that the ANN20 model is optimal. Image 1 • First study on application of ANN model to co-combustion of CG and PS. • The predicted data of ANN were in good agreement with the experimental results. • The gas products of co-combustion were detected. • Activation energy was estimated from the KAS and FWO methods. • ANN20 is the best model for predicting CG and PS combustion. [ABSTRACT FROM AUTHOR]

This paper investigates the ignition and combustion characteristics of cattle manure particles under different environmental conditions, and analyses the ash produced by combustion. The cattle manure particles were fixed in a vertical heating furnace, and a thermocouple and camera recorded the internal temperature and combustion process of the particles. The environmental temperature of the combustion chamber was set at 873, 973 and 1073 K, and the oxygen concentrations were 10–80%; the gas flow rate was set to 10, 20 and 30 L/min, respectively. The experimental results show that the effect of environmental temperature on the ignition and combustion of cattle manure particles is most obvious. Under most circumstances, the volatile matter begins to ignite before the particulate matter. As the environmental temperature and oxygen concentration increase, the condition of ignition and combustion were improved, and the internal ignition temperature, ignition delay and volatile combustion time were reduced. In addition, thermogravimetric experiments on powdered cattle manure were also carried out at four heating rates, and four peaks were presented in the derivative thermogravimetric (DTG) curve, corresponding to four different stages of cattle manure combustion. • Thermogravimetric experiment and particle combustion experiment were combined. • The ignition and combustion process of single cattle manure particles was detected. • The skeleton of the single particles remained intact during burning process. • The tendency of slagging and fouling of cattle manure ash is very low. [ABSTRACT FROM AUTHOR]

Highlights • Free jet condition, air co-flow condition and vitiated co-flow condition were generated to conduct a systematic study. • A conversion of lift-off height changing tendency was found in the combustion under the vitiated co-flow condition. • Effects of co-flow rate and co-flow equivalent ratio on propane lift-off jet flame in co-flow were investigated. Abstract 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. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of CeO 2 carriers and the catalytic properties of palladium (Pd) nanocrystals loaded on different morphology CeO 2 carrier were studied for lean methane (CH 4 ) combustion. The catalytic activity of simple CeO 2 carriers was ranked in the order of rod-CeO 2 (r-CeO 2 ) > cube-CeO 2 (c-CeO 2 ) > octahedral-CeO 2 (o-CeO 2 ). After the Pd species was loaded on CeO 2 , 90% of CH 4 was converted at 348 °C catalyzed by Pd/octahedral-CeO 2 (Pd/o-CeO 2 ) with (1 1 1) crystal faces, which had much higher catalytic activity comparing with Pd loaded on c-CeO 2 with (1 0 0) crystal faces and r-CeO 2 with (1 1 0) and (1 0 0) crystal faces. The results of XRD, HRTEM, EDS, H 2 -TPR, XPS and elemental mapping showed that the Pd species in the form of Pd 0 and PdO were highly dispersed on surface of all CeO 2 carriers. Most importantly, quasi In-situ XPS results convinced that Ce 3+ /Ce 4+ ion pairs played an important role in the catalytic combustion of low-concentration methane by adsorbing or releasing oxygen. Compared with r-CeO 2 and c-CeO 2 , the concentration of Ce 3+ on the surface of o-CeO 2 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-CeO 2 is not only related to the high dispersion of Pd 0 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-CeO 2 exposing. [ABSTRACT FROM AUTHOR]

Coal slime, a low-calorific-value fuel, is a by-product during coal washing, which can be disposed in quantity and fully utilized in circulating fluidized bed (CFB) boiler. This research paid attention to the ignition and combustion behaviors of single coal slime particles, which affect the normal combustion, operation stability and burning efficiency in circulating fluidized bed boiler. The ignition and combustion behaviors including ignition mechanism, ignition delay, ignition temperature and combustion process of single coal slime particles in a vertical heating tube furnace in CO 2 /O 2 atmosphere were researched under different operation condition parameters, for different gas temperatures ( T g  = 923, 1073, and 1173 K), gas flow rates ( V  = 0–20 L/min), and oxygen mole concentrations (O 2 % = 5–80%). Coal slime particle had three ignition mechanisms in CO 2 /O 2 atmosphere, namely, homogeneous ignition of volatiles at the windward and leeside of particle, heterogeneous ignition of char and heterogeneous ignition of coal. Only heterogeneous ignition of char and homogeneous ignition of volatiles at the windward of particle occurred in quiescent atmosphere. However, homogeneous ignition region decreased while heterogeneous ignition region increased gradually with the increasing flow rates in the oxygen concentration-gas temperature plane. Different ignition mechanisms were accompanied with various combustion processes. The combustion processes corresponding to heterogeneous ignition of char changed from flameless combustion to flaming combustion as oxygen concentration increased. Moreover, the critical oxygen concentration elevated from 30% to 50% with the increasing flow rate. The ignition temperatures and ignition delays decreased with the increasing gas temperature and oxygen concentration. As the flow rate increased, the trends became more obvious in medium-to-low oxygen concentrations. Compared with the ignition characteristics and combustion processes of coal slime particles in N 2 /O 2 atmosphere, those in CO 2 /O 2 atmosphere were suppressed due to the higher mole heat capacity and lower diffusion rate of oxygen molecule in CO 2 . [ABSTRACT FROM AUTHOR]