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As an innovative propulsion technique, laser augmented chemical propulsion (LACP) seems superior to the traditional ones. However, the corresponding combustion theories have still to be ascertained for LACP. Burning rate of 5-aminotetrazole (5-ATZ) propellant has been studied by testing pressed samples under different combustor pressures and laser powers. Based on micro computed tomography (MicroCT), an advanced thickness-over-time (TOT) method to characterize the regression of the produced non-planar burning surface is established. Because of a shell structure covering the combustion surface, the burning rate of the implemented 5-ATZ propellant is not constant during laser ablation. Resorting to functional fitting, a new law of non-constant burning including the effect of the observed unique burning surface structures is proposed. Accordingly, applicable combustion conditions of 5-ATZ based propellants have been preliminarily speculated for future research activities.

Improving the thermal decomposition performance of hexanitrohexaazaisowurtzitane (CL-20) by appropriate methods is helpful to promote the combustion performance of CL-20-based solid propellants. In this study, we synthesized a sandwich structure of CL-20 and nanoporous carbon scaffolds film (NCS) and emphatically studied the thermal decomposition performance of the composite structure. Thermogravimetric analysis and differential scanning calorimetry were used to measure the thermal decomposition process of the composite structure. The kinetic parameters of thermal decomposition were calculated by the thermal dynamic analysis software AKTS. These results showed that the thermal decomposition performance of the sandwich structure of CL-20 and NCS was better than CL-20. Among the tested samples, NCS with a pore size of 15 nm had the best catalytic activity for the thermal decomposition of CL-20. Moreover, the thermal decomposition curve of the composite structure at the heating rate of 1 K/min was deconvoluted by mathematical method to study the thermal decomposition process. And a possible catalytic mechanism was proposed. The excellent thermal decomposition performance is due to the sandwich structure enhances the interface reaction of CL-20 and NCS. This work may promote the extensive use of CL-20 in the field of solid rocket propellant.

The monolithic foamed propellants with high densities were prepared by casting and two-step foaming processes. Glycidyl azide polymer (GAP) and isocyanate were used as the binder system and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, CL-20) was employed as the energetic component. The newly designed formulation containing 60 % CL-20 produced a force constant of 1077 J/g and low flame temperature of 2817 K. Two foamed propellants with densities of 1.32 g/cm3 and 1.53 g/cm3 were fabricated by a confined foaming process and examined by closed bomb tests. The results revealed that porosity significantly affects burning performance. A size effect on combustion behaviors was observed for the foamed propellant with 5.56 % porosity, and a double-hump progressive dynamic vivacity curve was obtained. At last, the 30 mm gun test was carried out to demonstrate the interior ballistic performance, and the muzzle velocity increased by 120 m/s at the same maximum chamber pressure when monolithic propellant was added in the charge.

The main purpose of this study is to analyse the effects of oxy hydrogen (HHO) along with the Moringa oleifera biodiesel blend on engine performance, combustion and emission characteristics. HHO gases were generated using the typical electrolysis process using the potassium hydroxide solution. The experiments were performed under various engine loads of 25%, 50%, 75%, and 100% in a constant speed engine. Biodiesel from the M. oleifera was prepared by the transesterification process. Further, the procured biodiesel blends mixed with neat diesel at the concentration of 20% (B20) and 40% (B40). In addition to above, the HHO gas flow rate to the engine chamber maintained at the flow rate of 0.5 L-1. The use of the 20% and 40% blends with HHO reported less BTE compared to the neat diesel. However, B20 reported marginal rise in the BTE due to the addition of the HHO gas. On the other hand, addition of HHO gas to the blends significantly dropped the brake specific fuel consumption. With regard to the emissions, addition of the biodiesel blends reduced the concentration of the CO, HC, and CO2. Nevertheless, no reduction reported in the formation of the NO. However, adding the HHO to the biodiesel reduced the average NOx by 6%, which is a substantial effect. Overall, HHO enriching biodiesel blends are the potential replacement for the existing fossil fuels for its superior fuel properties compared to the conventional diesel.

Boron is a very promising and highly attractive fuel because of high calorific value. However, the practical applications in explosives and propellants of boron have been limited by long ignition delay time and low combustion efficiency. Herein, nano-Al and graphene fluoride (GF) as surface activated materials are employed to coat boron (B) particles to improve ignition and combustion performance. The reaction heat of nano-Al coated B/KNO3 and GF coated B/KNO3 are 1116.83 J/g and 862.69 J/g, respectively, which are higher than that of pure B/KNO3 (823.39 J/g). The ignition delay time of B/KNO3 could be reduced through nano-Al coating. The shortest ignition delay time is only 75 ms for B coated with nano-Al of 8 wt%, which is much shorter than that of pure B/KNO3 (109 ms). However, the ignition delay time of B/KNO3 coated with GF has been increased from 109 to 187 ms. B coated with GF and nano-Al shown significantly influence on the pressure output and flame structure of B/KNO3. Furthermore, the effects of B/O ratios on the pressure output and ignition delay time have been further fully studied. For B/KNO3 coated with nano-Al and GF, the highest pressures are 88 KPa and 59 KPa for B/O ratio of 4:6, and the minimum ignition delay time are 94 ms and 148 ms for B/O ratio of 7:3. Based on the above results, the reaction process of boron coated with GF and nano-Al has been proposed to understand combustion mechanism.

Ethanol and palm oil biodiesel blended with diesel fuel have the potential to reduce greenhouse gas emissions, such as carbon dioxide (CO2), and can gradually decrease dependence on fossil fuels. However, the combustion products from these fuels, such as oxides of nitrogen (NOx), total hydrocarbons (THC) and particulate matter (PM), require to be examined and any beneficial or detrimental effect to the environment needs to be assessed. This study investigates the hydrocarbon selective catalyst reduction (HC-SCR) activities by the effect of combustion using renewable fuels (biodiesel-ethanol-diesel) blends and the effect of hydrogen addition to the catalyst, with the various diesel engine operating conditions. Lower values rate of heat released were recorded as the ethanol fraction increases, resulting in trade-off where, lower NOx was produced while greater concentration of carbon monoxide (CO) and THC was measured in the exhaust. Consequently, increasing the THC/NOx promoting the NOx reduction activity (up to 43%). Additionally, the HC-SCR performance was greatly heightened when hydrogen was added into the catalyst and able to improve the NOx reduction activity up to 73%. The experiment demonstrated plausible alternatives to improve the HC-SCR performance through the aids from fuel blends and hydrogen addition.

The effect of a sweet orange peel oil additive on fuel blends of low-octane gasoline was investigated. The additive contains limonene, β-myrcene, eugenol, and triacetin, which have characteristics resembling gasoline but with advantages in terms of molecular structure that can increase RON and produce a homogeneous mixture. The additive changed the molecular behaviors influencing the physicochemical properties of the fuel blends. The experiments were conducted using fuel blends with additive fractions of 0%–75% (v/v). The fuel blends were mixed manually in 50-ml volumes in closed beaker glasses under STP conditions. The physicochemical properties were then measured to evaluate the chemical molecular structure compositions, viscosities, densities, heating values, and RONs of the blends, to determine the effect of the fuel additive on engines. The results show that the additive compounds were able to change the molecular behaviors of the fuel blends. The fuel blends produced 50 hydrocarbon compounds from 32 pure gasoline hydrocarbon compounds, which influenced the physical properties of the blends. The viscosities, beyond the lowest value at approximately 1.8 cSt, exhibited an increasing pattern compared to the viscosity of base gasoline fuel. The density and heating values tended to increase, even though there were fluctuating values due to intramolecular force movement and differences in molecular dipoles in the fuel blends. The RONs of the fuel blends, with additive fractions of 1%, 5%, 10%, 25%, 50%, and 75%, increased to 88.2, 91.5, 92.1, 95.7, 103.9, and 120.45, respectively. The increase in RON was also affected by the additive components among the fuel-blend molecules, which reacted to form highly stable hydrocarbon molecules, particularly aromatic and branched hydrocarbons, that inhibited combustion at low temperatures. Therefore, sweet orange peel oil as an additive can improve the physicochemical properties of gasoline, and thus can be mixed with any commercial fuel, especially those with a low octane number. It can be used for engines that require standard physical and high-octane properties.

Adding hydrogen to the fuel can change the combustion characteristics and greatly improve the pollutants emission for the gas turbine. The numerical method was adopted to study the combustion process in a counter-flow combustor of a 100 kW micro gas turbine using methane doped by hydrogen and various distribution schemes of air flow. The combustion characteristics and pollutant emissions were explored to ascertain the influence of air distribution based on solving the validated models. It was shown that as the amount of premixed air increased in the swirling gas, the range of the recirculation region became larger and the range of the high-temperature zone in the combustion chamber gradually enlarged. When the amount of premixed air was 30%, the outlet temperature distribution of the combustor was excellent and the average temperature was 1172 K. Moreover, the concentration of NO X gradually increased and reached a maximum value of 23.46 ppm (@15% O 2 ) as the premixed air increased in the range of the ratio less than 40%. It was reduced to 0.717 ppm (@15% O 2 ) when the amount of premixed air increased to 50%. These findings may support the running of the micro gas turbine using the hybrid fuel of hydrogen and methane.

Carbon monoxide (CO) is primarily the result of incomplete combustion, which has important impacts on the atmospheric chemical cycle and climate. Improved quantitative characterization of long-term CO trends is important for both atmospheric modeling and the design and implementation of policies to efficiently control multiple pollutants. Due to the limitations of high time-resolution and high-quality long-term observational data, studies on long-term trends in the CO concentration in China are quite limited. In this study, the observational data of the concentration of CO in a rural site of Beijing during 2006–2018 was used to analyze the long-term trend in CO concentration in Beijing. The Theil-Sen method and the generalized additive model (GAM)-based method, were used to conduct the trend estimation analysis. We found that the concentration of CO at the Shangdianzi site showed a significant downward trend during 2006–2018, with a decline rate of 22.8 ± 5.1 ppbV per year. The declining trend in CO also showed phasic characteristics, with a fast decreasing rate during the period of 2006–2008, stable variations during the period of 2009–2013 and a continuous downward trend after 2013. The declining trend in the CO concentration in the south to west (S-W) sectors where the polluted air masses come from is more rapid than that in the sectors where the clean air masses come from. The declining trend in the CO concentration implies the improved combustion efficiency and the successful air pollution control policies in Beijing and the surrounding area.

The process of starting the rotating detonation engine initially filled with air in low outer pressure conditions was studied. Such engines can be used for bringing satellites into the Earth orbit. A three-dimensional numerical simulation of an engine combustion chamber with a rotating detonation wave of a cylindrical type with an internal body fed by a hydrogen-oxygen mixture or an acetylene-oxygen mixture was performed. The influence of the lengths of the combustion chamber channel on the stability of the detonation wave and thrust characteristics was considered. An author's computer code was used in simulations, the code was based on a model of multicomponent gas dynamics with chemical transformations and turbulence. The code was tested by comparing it with experiments and analytical solutions for simple cases. To describe the kinetics of acetylene combustion, a simplified chemical scheme of interaction of 10 components was used, without “heavy” radical species: [C2H2, CO, CO2, H2, O2, H2O, OH, O, H, N2]. The influence of the chosen kinetic mechanism in case of hydrogen-oxygen mixture on the simulation results was studied. Various modes of the process in the detonation engine were obtained, including those with a stable detonation wave.

Gasification of biomass is an industrial process utilized to produce product gas that can be used in electrical power generation with internal combustion engines. However, there remain huge challenges with regards to tar and other pollutants, thus their removal before further use is necessary. Non-thermal plasma method can be considered as a novel and efficient way for treatment of tar from product gas. In this work, a laboratory-scale, reverse vortex flow gliding arc plasma reactor was developed and tested for the removal of tar model compound using naphthalene as surrogate. Effects of total gas feed rate in the range of 20–60 L/min, applied voltage in the range of 50–220 V, hence, power input in the range of 300–460 W with initial naphthalene concentration of 610 ± 50 mg/m3 on removal and energy input were investigated. It was found the tar removal efficiency increased with increasing applied voltage. Maximum naphthalene removal efficiency of 85% was achieved at applied high voltage of 15 kV and specific energy input of 0.13 kWh/m3 with energy utilization efficiency of about 4.60 g/kWh. From the findings, non-thermal plasma technology appeared to offer great potential in the removal of biomass tar from gasification. The technology may be promising for possible application to real biomass tar cracking and upgrading of product gas from gasification.

This paper presents how the combustion performance of nano-sized aluminum (nAl) powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.

An effective strategy involving a suitable carrier is needed to improve the dispersion, combustion and catalytic performances of catalyst nanoparticles. Herein, a Bi2WO6/g-C3N4 composite employing g-C3N4 as the catalyst carrier was prepared by a one-step in situ hydrothermal method, which was used as the combustion catalyst of solid propellants. The catalyst’s structure, morphology and its catalytic decomposition of several energetic materials were characterized by a series of analyses. The optimal ratio of g-C3N4 and Bi2WO6 was systematically determined. The results demonstrate that Bi2WO6/g-C3N4 (4:6) composite can diminish the decomposition temperatures of ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) and cyclotrimethylenetrinitramine+nitrocellulose (RDX+NC) by 25.0, 5.2, 24.0 and 1.2 (4.9) °C, and reduce their apparent activation energy by 59.5, 116.7, 11.6 kJ·mol-1, respectively. Moreover, the laser ignition tests indicate that Bi2WO6/g-C3N4 can effectively promote the ignition performance of RDX and RDX+NC. A possible mechanism of Bi2WO6/g-C3N4 on AP was proposed. The g-C3N4 catalyst carrier is superior to GO carrier due to its low cost, simple synthesis process, improved combustion and catalytic performances, as well as abundant N content. These make it have broad engineering application prospects in solid propulsion and several other energetic materials.

© 2021 Hydrogen Energy Publications LLCIn the present study, the pure ammonia combustion in a model combustor is performed to seek ammonia-fueled applications. To this aim, effects of the oxygen enrichment with an oxygen concentration of 100% in the oxidizer on flame characteristics, temperature profiles and NO profiles during the ammonia combustion were evaluated in terms of excess air/oxygen coefficients. Furthermore, in order to better understand the effect of an oxygen of 100% usage under the oxy-ammonia combustion conditions, the air-ammonia combustion has been studied as well and their results are compared and discussed each other. According to the results predicted, the oxidizer with an oxygen content of %100 provides better flame stability in the case of pure ammonia combustion. The most stable flame for oxy-ammonia combustion can be achieved when the excess oxygen coefficient is 1.0 or 1.2. Furthermore, the minimum NO levels emerge under the fuel-rich condition. Temperature and NO emissions decrease considerably under the air-ammonia combustion. However, except the fuel-rich conditions, flame stabilities are not satisfactory due to ammonia's flame speed under the air-ammonia combustion. Moreover, the air-ammonia combustion under the fuel-rich condition seems as a good option for obtaining the lowest NO levels. On the other hand, the oxy-enrichment condition is thought as a promising method for pure ammonia combustion provided that NO emissions should be optimized by using NO reduction methods.

Although energy densities of lithium-ion batteries (LIBs) continue to increase, safety problems such as fires and explosions have significantly hindered their large-scale applications. Conventional wisdom tells us the fire of LIBs largely originated from the flammable liquid carbonate solvents, and thus the research on additives with properties of suppressing “liquid-type fire” is the way to fabricate nonflammable batteries. However, the outcome has been proven to be inferior. Here, we carefully examined the evolution of battery fire under thermal abuse condition and found that the “jet fire” caused by flammable gases inside batteries is critical for the fire hazard, and the research effort should be redirected to search proper additives with “gaseous-type fire” suppressing properties. Unfortunately, conventional “gaseous-type fire suppressant” shows poor compatibility with battery electrolytes. Thus, we rationally designed a new kind of supramolecular electrolyte, where the molecules of “gaseous-type fire suppressant” and “SEI&CEI improver” are self-assembled together by intermolecular interactions. Due to this design, the supramolecular electrolyte produces improved cycling stability of Li metal anode and high voltage LiCoO2 cathode (up to 4.4 V). More importantly, it sharply decreases the self-extinguish time of carbonate electrolyte from ∼100 s/g to ∼0 s/g, which is unprecedented and can effectively suppress the “jet fire”, thus preventing the further combustion of commercial pouch cell during thermal runaway. Our work is providing the criteria required to overcome this challenge via supramolecular engineering of the electrolyte, which provides a new way to tune electrolyte functions and may bring numerous new possibilities.

Facile strategy enabling the fabrication of carbon dots (CDs) with favorable performance useful for various applications is highly desirable. Here, we report the fabrication of highly fluorescent carbon dots (CDs) towards sensitive metal ion detection, brightly fluorescent printing pattern, as well as green flame retardants for synthetic polymeric materials. CDs are synthesized by solvothermal treatment of polypropylene carbonate (PPC) with ethylenediamine, and the quantum yield of CDs could increase from 30 to 86% by further adding trace of citric acid. The abundant functional groups on the surface of CDs allow CDs well incorporated into polymers to form CD-loaded polystyrene (PS) microspheres, which are employed to construct fluorescent supraballs via triphase microfluidic technique and used as “inks” for uniform fluorescent patterns. Interestingly, the resultant CDs show good flame retardancy for highly flammable polymeric foams and fibers. The CDs surpass previously reported flame-retardant additives, to show excellent combustion resistance that the addition of 20 wt% CDs causes 75% decrease in the peak of heat release rate (P-HRR) for polyurethane (PU) foams. Significantly, a molecular dynamics simulation process for PU/CDs combustion is constructed. This work may spur the preparation and application of high-performance carbon-based nanomaterials.

Biodiesel is composed of various types of methyl ester compounds with different concentrations. The role of unsaturation degree was observed through single-molecule droplet combustion from three fatty acid methyl ester compounds. This research was conducted under normal gravity at ambient temperature and atmospheric pressure. Analysis of droplet combustion characteristics was observed along the heating, evaporation, ignition, and combustion stages. The cis configuration and allyl groups in unsaturated molecules related to different unsaturation degrees affect the droplet combustion process. Allyl and bis-allyl groups play an important role in accelerating hydrogen atom abstraction due to the weaker bond dissociation energy of the C H bond adjacent to the carbon double bond. The lower energy gap in unsaturated molecules is prone to electron excitation. Increasing the unsaturation degree resulted in shorter ignition delay and burning duration but higher droplet temperature, burning rate constant, specific power output, and flame dimensions. Soot particles formed above the flame tip on the unsaturated molecules gave a higher flame dimension. A high concentration of linoleic methyl ester in biodiesel fuel is recommended due to of high power output. However, the soot formation at a higher level of unsaturation degree should be considered.

In the present study, the ratio of reducing to oxidizing (F/O) elements as an indicator for maximum oxygen interference during the solution combustion synthesis (SCS) process of ZnO particles was determined using simple mathematical calculations. The obtained result was called special point (S.P). To interpret the role of S.P in the SCS reactions, ZnO particles were synthesized in the presence of citric acid, hexamine, hydrazine, and urea with various F/O values (0.75, 1, 1.25). The correlations between the S.P, physicochemical properties of the synthesized ZnO powders, and density functional theory (DFT) predictions were investigated. X-ray diffraction results, band-gap values, oxygen vacancy data, DFT results, and S.P points demonstrated the direct relation of these parameters. According to the S.P idea, it can be affirmed that the structural defects, particle size, optical band-gap (Eg = 3.06), the color of the products, the magnetic properties (0.2 emu/g), and the antibacterial inhibitory (15.625 µg/mL) of the synthesized particles were controlled via the interference of O2 during the synthesis process. In fact, the S.P investigation was suggested that the reaction rate of the combustion synthesis process could regulate the properties of ZnO particles.

This study reports the impacts of dual fuel mixtures on the theoretical performance characteristics of a spark ignition engine (SIE). The effects of addition of liquefied hydrogen, methane, butane, propane (additive fuels) into gasoline, iso-octane, benzene, toluene, hexane, ethanol and methanol fuels (primary fuels) on the variation of power, indicated mean effective pressure (IMEP), thermal efficiency, exergy efficiency, were examined by using a combustion model. The fuel additives were ranged from 10 to 50% by mass. The results exhibited that the ratios of hydrogen, methane, butane, propane noticeably affect the performance of the engine. The maximum increase ratio of power is 82.59% with 50% of toluene ratio and its maximum decrease ratio is 10.84% with 50% of methanol ratio in hydrogen mixtures. The maximum increase ratio of thermal efficiency and exergy efficiency are observed as 26.75% and 32.23% with the combustion of benzene-hydrogen mixtures. The maximum decrease ratio of thermal efficiency is 29.71% with the combustion of 50% of methanol ratio and it is 21.95% for the exergy efficieny with the combustion of 50% of ethanol ratio in hydrogen mixtures. The power, IMEP, thermal efficiency and exergy efficiency of primary fuels demonstrate different variation characteristics with respect to type and ratio of additive fuels.

Lately, attention to combustion synthesis has been encouraged owing to being cost-effective, rapid, and produces samples with low crystallite sizes and/or different morphology. So, in this paper, for the first time, ZnO nanoparticles were facilely fabricated utilizing the combustion procedure using L-arginine, L-valine, and L-alanine as organic fuels. Besides, the fabricated ZnO samples were recognized using different tools such as FT-IR, XRD, FE-SEM, HR-TEM, and UV–Vis. The XRD patterns show that the mean crystallite size of ZnO samples, which were fabricated operating L-arginine, L-valine, and L-alanine fuels, is 25.24, 31.11, and 35.65 nm, respectively. The HR-TEM images approved that the ZnO samples, which were fabricated operating L-arginine, L-valine, and L-alanine fuels, are composed of irregular, hexagonal, and sphere shapes with an average diameter of 22.46, 34.57, and 40.29 nm, respectively. The EDX patterns display peaks at 1.0 and 8.6 KeV for Zn. Also, there are peaks at 0.6 KeV for O. The values of the energy gap for the ZnO samples, which were fabricated operating L-arginine, L-valine, and L-alanine fuels, are 3.30, 2.88, and 2.63 eV, respectively. The photocatalytic degradation process is an important water treatment method due to its effectiveness in producing hydroxyl free radicals which able to degrade numerous dyes. So, the fabricated ZnO samples were examined for the photocatalytic degradation of methylene blue dye along with biological activity against some strains of bacteria. Furthermore, the maximum percent of degradation of 50 mL of 10 mg/L methylene blue dye under UV irradiations is 54.69, 41.34, and 30.76% after 90 min exploiting the ZnO samples which were fabricated operating L-arginine, L-valine, and L-alanine fuels, respectively. Also, % degradation of methylene blue dye under UV irradiations in the presence of hydrogen peroxide is 100% after 70 min using the ZnO sample which was fabricated operating L-arginine fuel. Moreover, the fabricated ZnO products show high bactericidal activity against Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Additionally, the fabricated ZnO products show moderate bactericidal activity against Bacillus cereus and Salmonella typhimurium.

CdO nanoparticles (CdO NPs) were synthesized utilizing urea-assisted auto-combustion (AC) and microwave combustion (MC) methods. The structural, thermal, optical, morphological, and compositional analysis of the prepared samples were investigated after they were heat treated at 350 °C. The impact of heat treatment and the method of synthesis on their physicochemical properties were investigated. XRD was used to determine the phase, crystallite size, and lattice constant of CdO NPs. The modification of the phase and crystallite size of CdO NPs indicates the impact of the heat treatment and synthesis process. The annealing process raises the crystallite size from 28 nm to 45 nm for the auto combustion approach and from 24 nm to 40 nm for the microwave combustion method. Under heat treatment, the energy band gaps of CdO NPs from auto combustion method and microwave combustion method samples were determined to be 2.09 eV and 1.65 eV, respectively. The surface morphology of CdO NPs was documented by SEM, indicating that the particle's morphology was modified by the synthesis procedure. The nanoscale range of the particles is confirmed by TEM micrographs of annealed CdO NPs, which is closely matched with the crystallite size derived from XRD. TG-DTA was used to examine the thermal characteristics of annealed CdO NPs.

Oxyfuel combustion is a promising technology to produce CO2 rich effluents. Nevertheless, storage as well as valorization steps require to increase the purity of these CO2 rich effluents due to the presence of CO and NOx produced during combustion process. In view of development of transition metal-based catalyst for this application, cobalt and/or copper derived hydrotalcite materials were used as precursor of oxide catalyst for NO-CO abatement in a gas stream similar to those obtained when an oxyfuel combustion is performed. Hydrotalcite precursors and catalysts were characterized by several techniques. The best catalytic performances for the NO-CO abatement are obtained with cobalt-aluminum mixed oxide catalyst. The impact of water was also investigated and following trends were obtained: (i) a decrease in activity for NO oxidation while no modification was observed for CO oxidation; (ii) a shift towards higher temperature for NO reduction while maintaining the same yield; (iii) an improved stability of the catalyst with time on stream.

NOx and toluene have been identified as the dominant air pollutants in solid wasted combustion, and it is of great importance to remove these two pollutants simultaneously. Here, we found that Mn/CeO2 and Mn/TiO2 exhibited a bifunctional property in both NO reduction and toluene oxidation, and both of which could achieve 80% of conversion rate in NO reduction and toluene oxidation processes. However, the activity of both Mn/CeO2 and Mn/TiO2 decreased in simultaneous removal of NOx and toluene compared with separate NOx reduction and toluene oxidation. This indicates that there is a mutual inhibition between NOx reduction and toluene oxidation in simultaneous removal process over Mn-based catalysts, attributing to the competitive adsorption and utilization of active oxygen. In detail, the adsorption of toluene occupied the Lewis acid sites and restrained the NH3 adsorption. Meanwhile, the competitive utilization of active oxygen by NH3/NOx inhibited toluene oxidation to CO2 by active oxygen species as the reaction between NH3/NOx and active oxygen species would occur more easily.

The article presents the results of mathematical modeling of the initial stage of the combustion of wood and coal particles in conditions corresponding to the combustion chambers of boiler units of thermal power plants. A hypothesis is formulated that describes the sequestration of anthropogenic sulfur oxides (SOx) under the conditions of combustion of mixed fuels based on coal and wood as a result of the interaction of water vapors (formed during the evaporation of interporeal and adsorbed biomass moisture) with SOx with the formation of sulfuric (H2SO4) acid vapors. When these vapors of sulfuric acid H2SO4 interact with iron oxides of the mineral part of the coal. To test the formulated hypothesis, a new mathematical model has been developed for the processes of co-ignition and combustion of wood and coal particles under high-temperature heating conditions. The mathematical model of the ignition process developed by the authors differs from the known ones (published in leading international scientific periodicals on the combustion of solid fuels) by a detailed description of a complex of gas-phase and heterogeneous thermochemical reactions occurring both in the boundary layer of fuel particles and in their porous structure. The mathematical model of the combustion process of wood-coal fuel particles developed by the authors is currently the most detailed in describing the thermophysical, thermochemical and aeromechanical processes occurring both in the fuel particles and in their small vicinity. Multistage kinetic schemes for the oxidation of the main volatile components (methane ‒ CH4, carbon monoxide ‒ CO, hydrogen ‒ H2), as well as the formation of sulfur oxides by means of oxidation of hydrogen sulphide (H2S), released as a result of pyrolysis of the organic part of coal, have been adopted. Based on the results of numerical modeling, the possibility of intensifying the processes of sequestration of sulfur oxides by moistening the wood component of the fuel mixture has been established. It is shown that water vapor can act as an agent adsorbing anthropogenic sulfur oxides, transforming the latter into sulfuric acid vapor, respectively. In turn, the vapors H2SO4 and HNO- 3 can be relatively easily captured by means of condensation. It has been established that for effective SOx capture during co-combustion of coal and biomass, the moisture content of the latter must be at least 5% by weight. The research provides grounds for the conclusion about the possibility of environmentally efficient combustion of coal in the composition of wood-coal fuel composites.

A combined numerical and experimental investigation of the different chemical effects of H2 (CE-H2) on soot formation was conducted by applying the reactive molecular dynamics simulation (ReaxFF MD) and the pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) diagnostic technique. In addition, the detailed chemical reaction pathway for the different CE-H2 was explored in the combustion of methane (CH4) and ethylene (C2H4) fuels. It was found that both the experimental and numerical results reflected the evolution of polycyclic aromatic hydrocarbons (PAHs) and initial soot particles and the different CE-H2 on PAHs/soot formation. The primary reason for the different CE-H2 was that the hydrogen addition led to the production of a large number of hydrogen atoms, which promoted acetylene (C2H2) formation during the methane combustion through the chemical reactions C2H5 + H ↔ C2H4 + H2 and C2H4 + H ↔ C2H3 + H2, but inhibited acetylene formation during the ethylene combustion through the chemical reaction C2H3 ↔ C2H2 + H. The hydrogen addition only increased the number of 6-membered rings in the largest PAH/soot particle of methane combustion but decreased the numbers of all ringed compounds in the largest PAH/soot particle of ethylene combustion. Moreover, the CE-H2 promoted methane pyrolysis but inhibited ethylene pyrolysis.

The outstanding advantages of methanol such as low pollutant emissions of nitrogen oxides (NOx) and carbon monoxide (CO) make it a promising clean-burning fuel. Despite, the latent heat of vaporization of methanol is 3.70 times that of gasoline, the low heating value of methanol is one of the most critical barriers to its effective utilization in industrial applications. Thus, the methanol burner needs to be effectively designed to determine the desired combustion characteristics and the optimal design of this type of clean burner. Hence, this study presents a computational fluid dynamic analysis on the combustion characteristics of a methanol swirling burner with two layers of swirling blades. A particular focus of this study is emphasized on the effects of different swirling blade angles (45°+45°, 60°+60°, and 45°+60°) and various equivalence ratios (0.5, 0.75, 1.0, 1.25, and 1.75) on the combustion characteristics and pollutants formation of the swirl burner. The velocity and temperature profiles, combustion characteristics, and concentrations of major combustion species are analyzed in detail. The results show that the blade angle arrangement of 45°+60° exhibits the best combustion characteristics in comparison with the other blade angle arrangements. It is also found that the BA3 with an equivalent ratio in the range of 1.0~1.25 shows the best performance in the emissions of NOx and CO compared with other combinations of swirling blade arrangements and equivalence ratios. More specifically, the optimal equivalence ratio ranges from 1.0 to 1.25 at which the NOx and CO emissions are measured to be 27.0 and 11.0 mg/m3, respectively.

Since the early years of the 21st century, the whole world has faced two very urgent problems: the depletion of fossil energy sources and climate change due to environmental pollution. Among the solutions sought, 2,5-Dimethylfuran (DMF) emerged as a promising solution. DMF is a 2nd generation biofuel capable of mass production from biomass. There have been many studies confirming that DMF is a potential alternative fuel for traditional fuels (gasoline and diesel) in internal combustion engines, contributing to solving the problem of energy security and environmental pollution. However, in order to apply DMF in practice, more comprehensive studies are needed. Not out of the above trend, this paper analyzes and discusses in detail the characteristics of DMF's combustible laminar flame and its instability under different initial conditions. The evaluation results show that the flame characteristics of DMF are similar to those of gasoline, although the burning rate of DMF is much higher than that of gasoline. This shows that DMF can become a potential alternative fuel in internal combustion engines.

Ozone (O3) was introduced into the intake air to control the ignition in a gasoline compression ignition (GCI) engine. An early fuel injection at −68 °CA ATDC was adopted to mix the fuel with the reactive O-radicals decomposed from the O3, before the reduction of the O-radicals due to their recombination would take place. The second injection was implemented near top dead center to optimize the profile of the heat release rate. The engine experiments were performed around the indicated mean effective pressure (IMEP) of 0.67 MPa with a primary reference fuel, octane number 90 (PRF90), maintaining the 15% intake oxygen concentration with the EGR. The quantity of the first injection, the second injection timing as well as the ozone concentration were changed as experimental parameters. The results showed that the GCI operation with the ozone addition makes it possible to reduce the maximum pressure rise rate while attaining high thermal efficiency, compared to that without the ozone. Appropriate combinations of the ozone concentration and the first injection quantity achieve low smoke and NOx emissions. Further, the ozone-assisted GCI operation was compared with conventional diesel operation. The results showed that the indicated thermal efficiency of the ozone-assisted GCI combustion is slightly lower than that of the conventional diesel combustion, but that GCI assisted with ozone is highly advantageous to the smoke and NOx emissions.

3,3,3-trifluoropropene (R1243zf or HFO-1243zf) has low global warming potential, which is expected to be an excellent alternative to hydrofluorocarbon refrigerants in air conditioning and refrigeration systems, but its flammability hinders the practical applications. This paper reports the experimental results of the flammability inhibition effects of carbon dioxide (R744), 1,1,1,2,3,3,3-heptafluoropropane (R227ea), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) on R1243zf. The measured critical suppression ratios decrease in the order: R744 (3.1) > R134a (1.42) >R125 (0.68)> R227ea (0.58), which are also predicted by group contribution method. The flammability limit range of R1243zf was estimated as per three methods, and the closest estimation values to tested data was obtained by using the Jones’ method (the stoichiometric concentration for combustion method). Finally, the mechanisms of flammability inhibition effect differences of R744, R227ea, R125, and R134a on R1243zf were analyzed, from the views of the combustibles or oxidants dilution, combustibles and oxidants isolation, and/or free radical production and consumption. A hydrofluorocarbon flame retardant that has the big F/H ratio and produces much free radical CF3 during its thermal decomposition, exhibits the good flammability inhibition efficiency to R1243zf.

The preparation of four kinds of α-, β-, γ-, and δ-type MnO2 with distinct crystal phases and tunnel structures were achieved and applied for 1,2-dichloroethane (1,2-DCE) catalytic combustion. The redox ability and acidity of MnO2 as well as the corresponding reaction mechanism were studied by means of various surface-sensitive techniques, including TPR, TPD, OIE, XPS, in situ DRIFTS together with DFT calculation. The catalytic activities in 1,2-DCE combustion illustrated that γ-MnO2 displayed the most superior activity with the maximum HCl yield of 95% and CO2 yield of 92%, due to its abundant oxygen vacancies on surface, easy formation of active oxygen species, and strong acidity that readily reacted with the adsorbed reactant to form HCl, which reflects the synergies of redox property and acidity. However, the strong Mn-Cl bonding associated with high valent Mn4+ and scarcity of acidic sites in β- and δ-MnO2 hinder the HCl elimination process, even leading to undesirable chlorine deposition associated with series of the polychlorinated byproducts including 1,1,2-C2H3Cl3 and CCl4 via Cl substitution process. A mechanism for 1,2-DCE combustion involving dehydrochlorination via the C-Cl bonds cleavage at acidic sites as well as excess polychlorination by Cl2 over relatively oxidative sample was accordingly proposed.

The current energy crisis and the escalating concern over pollution level necessitate the development of various low emission and clean technologies for efficient utilization of fossil fuels. These technologies offer the benefits of using fossil fuels continuously without harming the environment. Oxy fuel combustion technology is one of the promising low emission combustion technologies having an additional advantage of being a better retrofit option compared to other clean technologies. In the present study, the stability and flame characteristics of LPG flame in a tubular burner has been investigated with oxygen as the oxidizing gas and nitrogen or carbon dioxide as the balance gas. The experiments were conducted to study the effect of primary aeration and the effect of balance gas on the stability and flame characteristics of air and oxy flames. The experimental results from the preliminary experiments show that the flame height decreases with increase in primary aeration for both air and oxy cases and the premixed blue zone increases with primary aeration. The flames observed for oxy cases are dull and weak at all equivalence ratio (or primary aeration). The measured axial flame temperature indicated that the temperature of oxy flames is lower than that of the air flames for the same primary aeration. The data obtained from the stability tests show that the oxy flames can withstand relatively lower port velocity than its air counterpart. Therefore, the stable operating range of the given burner design is lower when CO2 is used as the balance gas. These differences in the stability and flame characteristics is attributed to the difference in the thermo physical properties like molar heat capacity, mass diffusivity and thermal conductivity of the balance gas CO2 and N2.

Ammonia (NH3) has recently received much attention as a promising future fuel for mobility and power generation. The use of ammonia as a fueling vector can help curb global warming by cutting CO2 emissions because it is a carbon-free fuel and a hydrogen carrier with a high percentage of hydrogen atoms per unit volume. Liquid ammonia contains a higher volumetric density of hydrogen than liquid hydrogen. The low reactivity of ammonia, however, hinders its direct usage as a combustible fuel. One feasible way to boost the reactivity of ammonia is to target a dual-fuel system comprising of ammonia and a suitable combustion promoter. In this work, combustion properties of ammonia were investigated by blending it with various proportions of dimethyl ether (DME) using a rapid compression machine (RCM) and a constant volume spherical reactor (CVSR) over a wide range of experimental conditions. DME is a highly reactive fuel that may be produced in a sustainable carbon cycle with a net zero-carbon emission. Ignition delay times (IDTs) of NH3/DME blends were measured over a temperature (T) range of 649–950 K, pressures (P) of 20 and 40 bar, equivalence ratios (Φ) of 0.5 and 1 for a range of DME mole fractions (χDME) of 0.05–0.5 in the blends. In addition, the laminar burning velocities of NH3/DME blends were measured at P = 1, 3 and 5 bar, Φ = 0.8 to Φ = 1.3 and T = 300 K for χDME ranging 0.18 to 0.47. Our results suggest that DME is a good ignition promoter, resulting in a significant shortening of IDTs and an increase of flame speeds of NH3. A detailed chemical model has been developed and validated against the experimental data. Overall, our kinetic model offered reasonable predictive capabilities capturing the experimental trends over a wide range of conditions. In the worst-case scenario, our model underpredicted IDTs by a factor of ∼2.5 while overpredicting laminar flame speed by ∼20%.

Moderate or intensive low-oxygen dilution (MILD) combustion is a novel combustion technology with high efficiency and low emissions. Few studies have been performed on the application of this technology for partial oxidation processes. In this research, a Computational Fluid Dynamics study for the effect of different parameters on the natural gas partial oxidation under MILD combustion conditions has been carried out. The combustion chamber was in the form of cylinder with a diameter of 300 mm and a length of 1500 mm. The effect of parameters such as different kinetic mechanisms, adding ethane and propane to methane (shale gas feed), adding steam to the feed and distance (interval) between methane and oxygen nozzles were investigated. Results showed that addition of ethane and propane to methane increased the mole fraction of CO and C2H2 so that, in the case of mixed methane with ethane and propane compared to the case of pure methane, an increase of 18.75% and 12.93% was observed for CO and C2H2, respectively. In addition, with increasing the percentage of steam in the inlet feed at a constant flow rate, methane conversion increased so that it in the case of 30% inlet steam was 77.17%, which showed 11% promotion compared to the pure methane case. Also, increasing the distance between the fuel and oxidizer nozzles led to an increase in the maximum temperature in the combustion chamber.

Cotton fibers mainly consist of cellulose biological macromolecule, and its exceedingly flammable nature has severely restricted its application in the fields requiring flame retardancy. To endow cotton fabric with excellent flame retardancy and superior durability, a high-efficiency durable flame retardant (THPO-P) with ammonium phosphate ester and phosphine oxide groups was synthesized and chemically bonded to cotton fabric through padding-baking method. THPO-P showed high flame-retardant efficiency, and the add-on of 5.9% was sufficient to prepare cotton fabric with self-extinguished feature. With the add-on of 19.9%, treated fabric possessed excellent fire safety and durability. The total heat release and peak heat release rate values reduced by 77.1% and 91.8% in contrast to pristine fabric, respectively. Its LOI value still reached up to 33.4% even after 50 laundering cycles, which was far beyond the flame-retardant standard. THPO-P played flame-retardant role by restraining the release of flammable volatiles, liberating nonflammable gases and promoting the char formation during combustion. The flame-retardant treatment deteriorated the tensile strength, whiteness and softness of cotton fabric.

Methane–oxygen burning is considered for many future rocket engines for practicality and cost reasons. As this combustion is slower than hydrogen–oxygen, flame ignition and stability may be more difficult to obtain. To address these questions, numerical simulation with realistic chemistry is appropriate. However the high pressure and turbulence intensity encountered in rocket engines enhance drastically the stiffness of methane oxy-combustion. In this work, Analytically Reduced Chemistry (ARC) is proposed for accurate chemistry description at a reasonable computational cost. An ARC scheme is specifically derived for typical rocket engine conditions. It is validated by comparison with its parent skeletal mechanism on a series of laminar flames. Then the numerical stiffness of chemistry is overcome with an original approach for time integration, allowing to run simulations close to the acoustic time step whatever the chemical stiffness. It is demonstrated on laminar cases that the flame structure is well preserved, and that numerical stability is ensured while decreasing significantly the computational cost. The performance of ARC with the fast time integration method is finally demonstrated in a 3D Large-Eddy Simulation of a lab-scale Liquid Rocket Engine combustion chamber, where a detailed flame analysis is conducted.

The effects of magnesium/polytetrafluoroethylene (Mg/PTFE) pyrotechnic compositions on the coupled flow field and reignition mechanism are important aspects governing the performance and range of base bleed projectiles (BBPs). Owing to a decrease in pressure and temperature when the BBP leaves the muzzle, rapid depressurization occurs, which extinguishes the base bleed propellant. The Mg/PTFE pyrotechnic composition pressed in the igniter of the base bleed unit (BBU) provides additional energy to the BBU via a chemical reaction. Thus, the extinguished base bleed propellant is reignited under the effect of high-temperature combustion gas jets from the igniter. In this study, a numerical analysis is conducted to evaluate the effects of PTFE and Mg granularity as well as Mg/PTFE pyrotechnic compositions. Owing to the rapid depressurization, the temperature and pressure was found to decrease for different Mg/PTFE pyrotechnic compositions. However, the depressurization time increased as the PTFE granularity increased, the Mg granularity decreased, and the Mg content increased. When the pressure in the combustion chamber of the BBU decreased to the atmospheric pressure, the combustion gas jets from the igniter expand upstream (rather than downstream). However, these combustion gas jets exhibit different axial and radial expansion characteristics depending on the pyrotechnic compositions used. The results show that the reignition delay time, td, of the base bleed propellant was 377.608, 94.27, 387.243, 523.966, and 221.094 ms for cases A–E, respectively. Therefore, it was concluded that the Mg/PTFE pyrotechnic composition of case B was the most beneficial for the reignition of the base bleed propellant, with the earliest addition of energy and mass to the BBP.

The knock intensity (KI) evaluation is critical during fuel and engine development. In the current study, the effect on combustion knock was investigated in CI engine fueled with methanol-diesel-n-pentanol blends. MnP5, MnP10, MnP15, MnP20, and MnP25 fuel blends were used in the present investigation. The cylinder pressure data was used to evaluate in the knock intensity (KI). Further, combustion parameters like heat release rate, ignition delay and combustion duration were also presented in this study. As per the results, the KI values for MnP5 were found to be higher than diesel at all loads, whereas these values for MnP15 were observed to be lower than diesel at 25% and 50 % load.

Direct gaseous fuel injection in internal combustion engines is a potential strategy for improving in-cylinder combustion processes, performance and emissions outputs and, in the case of hydrogen, could facilitate a transition away from fossil fuel usage. Computational fluid dynamic studies are required to fully understand and optimise the combustion process, however, the fine grids required to adequately model the underexpanded gas jets which tend to result from direct injection make this a difficult and cumbersome task. In this paper the gaseous sphere injection (GSI) model, which utilises the Lagrangian discrete phase model to represent the injected gas jet, is further improved to account for the variation in the jet core length with better estimation due to total pressure ratio change. The improved GSI model is then validated against experimental hydrogen and methane underexpanded freestream jet studies, mixing in a direct injection hydrogen spark ignition engine and combustion in a pilot ignited direct injection methane compression ignition engine. The improved GSI model performs reasonably well across all cases examined which cover various pressure ratios, injector diameters, injection conditions and disparate gases (hydrogen and methane) while also allowing for relatively coarse meshes (cheaper computational cost) to be used when compared to those needed for fully resolved modelling of the gaseous injection process. The improved GSI model should allow for efficient and accurate investigation of direct injection gaseous fuelled engines.

Hybrid rocket propulsion can contribute to reduce launch costs by simplifying engine design and operation. Hypergolic propellants, i.e. igniting spontaneously and immediately upon contact between fuel and oxidizer, further simplify system integration by removing the need for an ignition system. Such hybrid engines could also replace currently popular hypergolic propulsion approaches based on extremely toxic and carcinogenic hydrazines. Here we present the first demonstration for the use of hypergolic metal-organic frameworks (HMOFs) as additives to trigger hypergolic ignition in conventional paraffin-based hybrid engine fuels. HMOFS are a recently introduced class of stable and safe hypergolic materials, used here as a platform to bring readily tunable ignition and combustion properties to hydrocarbon fuels. We present an experimental investigation of the ignition delay (ID, the time from first contact with an oxidizer to ignition) of blends of HMOFs with paraffin, using White Fuming Nitric Acid (WFNA) as the oxidizer. The majority of measured IDs are under 10 ms, significantly below the upper limit of 50 ms required for functional hypergolic propellant, and within the ultrafast ignition range. A theoretical analysis of the performance of HMOFs-containing fuels in a hybrid launcher engine scenario also reveals the effect of the HMOF mass fraction on the specific impulse (Isp) and density impulse (ρIsp). The use of HMOFs to produce paraffin-based hypergolic fuels results in a slight decrease of the Isp and ρIsp compared to that of pure paraffin, similar to the effect observed with Ammonia Borane (AB), a popular hypergolic additive. HMOFs however have a much higher thermal stability, allowing for convenient mixing with hot liquid paraffin, making the manufacturing processes simpler and safer compared to other hypergolic additives such as AB.

SiO2@3COFs@CuO and SiO2@3COFs@Fe2O3 are prepared in this study. Then SiO2 and its hybrids are incorporated into PS through solution blending method. The thermal stability, mechanical performance, combustion performance and smoke density of PS and its nanocomposite are investigated. The temperature at 5 wt% weight loss and the maximum weight loss rate of PS/SiO2@3COFs@ Fe2O3 (PS 4) under air are 15 and 14 °C higher than that of neat one, respectively. The glass-transition temperature of PS/SiO2@3COFs (PS 2) is 1.5 °C lower than that of PS, which can conclude that SiO2@3COFs contributes to impact strength of PS 0. The peak heat release rate (20.8%) and total heat release (14.0%) of PS 2 decreases further compared with that of PS 0. The smoke density of PS 4 is 23.1% lower than that of neat PS. The influence of SiO2 and its nano-hybrids on the pyrolysis and combustion of PS is investigated. Incorporation of SiO2 and its nano-hybrids shows little effect on pyrolysis process of PS. However, heat resistance of PS is enhanced obviously and thermal degradation rate of PS is also decreased through incorporation of SiO2 and its nano-hybrids. The gaseous pyrolysis products (aromatic compounds and alkenyl compounds) of PS and its nanocomposite also decrease.

The increasing energy demand and the need to reduce emissions have propelled the use of bioenergy and biofuels. Although carbon emissions can be significantly reduced using biofuels, an increase in the emissions of Nitrogen oxides (NOx) is inevitable. To address this issue, selective catalytic reduction (SCR) using ammonia (NH3) has played a significant role in curbing NOx emissions from the combustion of conventional and biofuels. The combustion usually occurs at low temperature (

Achieving higher energy storage and controllable energy release processes is the major research goal in solid propellants. Combustion catalysts are applied to modify the energy release behavior of solid propellants but at the expense of lowering the total energy density of the propellants owing to their non-energetic feature. Here, with ammonium perchlorate (AP) based propellant as proof-of-concept material, we demonstrate a reactive combustion catalyst strategy based on the clever use of the novel structure of Ti3C2 MXene, including appropriate reactivity, high energy storage, and large specific surface area. It is found that the Ti3C2 MXene could first react with AP as fuel, releasing large amount of heat and in-situ generating TiOx/C nanosheets. The resulting TiOx/C nanosheets can further catalyze the thermal decomposition of AP by accelerating both electron and proton transfer during AP decomposition. As expected, the Ti3C2 MXene not only improves the pyrolysis reaction kinetics of AP based composites, but also increases the energy output of the propellants. The development of reactive catalysts with excellent catalytic activity and increased energy release provides a new strategy for the design of solid propellants.

Partially premixed combustion is one of the developing areas of combustion research that has the advantages of both premixed and diffusion mode of combustion. The present work involves a computational study on the stability and characteristics of partially premixed butane-air flames. The effect of operating parameters like fuel-air ratio, primary aeration, and the presence of co-flow and co-swirl on the stability and flame characteristics has been studied. The simulation results show that the height of the flame decreases with an increase in primary aeration and also in the presence of a co-swirl stream. It has also been found that the stability of flames increases with co-swirl air but deteriorates with the presence of the co-flow air. The flame temperature increases with primary aeration and it has been observed that the peak flame temperature shifts away from the burner mouth for lower primary aeration. It has been observed that the flame stability improves with co-swirl air which is attributed to the recirculation zone created due to the swirl motion which acts as a heat source. The poor stability in the presence of co-flow air is attributed to flame stretching and aerodynamic quenching of the stretched flame lets. The lift off velocity and the stable operating range increases with equivalence ratio and also with co-swirl air.

The Hydroxymethyl (•CH2OH) radical is an important intermediate species in both atmosphere and combustion reaction systems. The rate coefficients for •CH2OH + 3O2 and (CH2OH + 3O2 (+H2O) reactions were calculated using Rice−Ramsperger−Kassel−Marcus (RRKM)/master equation (ME) simulation and canonical variational transition state theory (CVT) between the temperature range of 200 to 1500 K based on the potential energy surface constructed using CCSD(T)//ωB97XD /6-311++G(3df,3pd). The results show that •CH2OH + 3O2 leads to form CH2O and HO2 in the temperature 1000K). When water molecule added to the reaction favored the formation of CH2O and HO2 in all the temperature. The calculated rate coefficient for the •CH2OH + 3O2 (2.8×10-11 cm3 molecule-1 s-1 at 298K) is in good agreement with the previous experimental values (~1×10-11 cm3 molecule-1 s-1 at 298K). The rate coefficients for the water-assisted reaction (2.4×10-16 cm3 molecule-1 s-1 at 1000K) is at least 3-4 order magnitude smaller than the water-free reaction (6.2×10-12 cm3 molecule-1 s-1 at 1000 K). This result is consistent with the similar types of reaction system. Our calculations also predict that the effect of a single water molecule favors the formation of CH2O in the combustion condition however, the water-free reaction favors the formation of CH2O in the atmospheric condition. The current study helps to understand how a single water molecule changes the reaction mechanism and chemical kinetic behaviour under atmospheric and combustion conditions.

The effect of fuel mixture and annealing temperature on the structural properties and electrochemical performance of Li1.20Mn0.52Ni0.20Co0.08O2 powders prepared by the combustion synthesis were studied. Different combinations of citric acid fuel and ammonium acetate along with post-temperature treatments could be used to control the product characteristics. Simultaneous thermal analyses and thermodynamic modelling were used to describe the combustion processes. The analysis of the XRD data and other reports showed that the synthesis method and chemical compositions of lithium-rich layered oxides (LLO) could influence their description either as a solid solution or a ‘composite’ structure. The annealing temperature greatly influenced the lattice parameters, unit cell volumes, crystallite sizes, and cationic disorder of the samples whilst the use of fuel mixture had little effect. Furthermore, the electrochemical performances of the cathode materials were studied and the relationship with the structural properties of the powder samples were analysed. The Li1.20Mn0.52Ni0.20Co0.08O2 powders synthesized with only citric acid fuel (100-T) displayed the best electrochemical performance compared with those produced using the fuel mixtures. The enhanced electrochemical performance of the 100-T cathodes was shown to be an integrative property of the highest values reported for their structural properties. The results show that citric acid assisted combustion and annealing temperature (mostly with pre-annealing) could be used to optimize the electrochemical performance of LLO cathode materials.

The main objective of this paper is to synthesize the energetic nanoparticles and blend with base fuel to study the fuel properties. Magnesium Oxide (MgO) is synthesized using combustion method EDTA as fuel and Magnesium Nitrate (Mg(NO3)2) as precursor. The obtained MgO nanoparticles have been subjected to various analytical techniques for characterization. The XRD pattern confirms the crystal structure of MgO which is composed of cubic phase of periclase. The MgO nanoparticles are blended with diesel fuel as base fuel by using ultra sonication method. The blended diesel fuel was used to study the fuel properties such as flash point, fire point and viscosity. It was found that the fuel properties have improved significantly compared to the base diesel fuel.

SiC porous ceramics (SPCs) are key functional medium materials, which are widely applied as porous burners. However, SPCs produced via the polyurethane sponge replica technique usually exhibit a randomly distributed cellular structure, leading to vulnerability and a low combustion efficiency for the porous burners. In this study, SPCs were structurally designed via novel 3D printed resin template technique; this endowed the SPCs with synergistically optimized strength and combustion characteristics. SPCs containing tetrakaidecahedron, octahedron and cubic cells were successfully prepared via SiC slurry coating and sintering in air. The cell parameters determined the strength and combustion properties of the SPCs. The SPCs containing cubic cells exhibited the largest strength and strain, because more struts were present parallel to the loading direction; this is more advantageous for stress bearing compared to those vertical to the loading direction. The tetrakaidecahedron cell facilitated the formation of a disturbance effect within the SPCs to a higher extent than the cubic and octahedron cells, thereby enhancing the heat exchange performance between the fluid and porous framework. Hence, the SPC with tetrakaidecahedron cells exhibited the best combustion properties, which resulted in the highest surface temperature and lowest pollution emission.

Diesel Particulate filters are considered one of the most efficient technologies to reduce particulate matter emitted by diesel engines. In this paper we study the development of catalytic ceramic papers based on Mn-Ce and their applications as soot particle filters in bench scale tests. Ceramic papers were prepared by a dual polyelectrolyte papermaking method and were impregnated with Mn and Ce precursors through a wet-spray procedure using a commercial fogger. Catalytic ceramic papers were tested as catalysts for the combustion of soot, which was obtained both from the burning of diesel fuel and directly from a bench test. In addition, the filtering capacity of catalytic ceramic papers was tested through opacity measurements by placing the ceramic papers in a suitable case at the end of the engine. Mn-Ce based catalysts were active in the soot combustion. The addition of citric acid considerably improved the catalytic performance of all the systems studied. This beneficial effect of citric acid is related to an improvement in the distribution of the catalytic material onto the ceramic fibers, being the mixed equimolar oxide Mn-Ce the most active catalyst.

Polycyclic aromatic hydrocarbons are lipophilic chemicals that are normally formed as by-products of fossil fuel combustion and residues of coal processing. They are ubiquitous as contaminants from petroleum and coal utilization and are of environmental and occupational health concern because of their toxic, mutagenic, and carcinogenic properties.