铝/乙醇基纳米浆体燃料的着火燃烧特性研究

为了明确纳米铝粉从低浓度到高浓度变化对液体碳氢燃料着火燃烧特性的影响,采用液滴悬挂法研究了不同温度下(700~800℃)乙醇液滴和添加不同浓度(2.5wt%, 10wt%, 15wt%和20wt%)纳米铝粉的铝/乙醇基纳米浆体燃料液滴的着火燃烧特性。利用高速摄影系统捕捉了液滴整个燃烧过程,分析了其液滴寿命。通过热电偶对液滴附近气相温度的测量,获得了其着火性能参数。结果表明,添加纳米铝粉可以改善乙醇液滴的着火性能。不同铝粉浓度改善效果不同,低浓度时效果较好,着火延迟时间显著缩短,点火温度明显降低。随温度升高,乙醇及添加纳米铝粉的铝/乙醇基纳米浆体燃料液滴着火延迟时间及着火温度均明显降低。纳米铝粉(S2)对乙醇(S1)着火延迟时间和液滴寿命的降幅在750℃最大,其降幅分别达42.20%和18.43%。纳米铝粉(S3)着火温度降低,其最大降低幅度也出现在750℃,相对于乙醇(S1)降低幅度达28.57%。一定铝粉浓度范围内,液滴微爆炸程度和微爆炸时长随铝粉浓度升高而增大,但铝粉浓度超过10wt%后趋势变得平稳。     

Analysis of cyclic combustion of solid fuels

The cyclic nature of coal particles combustion results from the movement of loose material in the flow contour of the circulating fluidized bed (CFB): the combustion chamber, the cyclone, the downcomer.The experimental results proved that the cyclic change of the oxygen concentration around coal particles, led to the vital change of both mechanism and combustion kinetics. The mathematical model of the process of coal combustion has been scientifically described whose original concept is based on the allowance for cyclic changes of concentrations of oxygen around the char particle. It enables the prognosis for change of the surface and the centre temperatures and a mass loss of the char particles during the cyclic combustion. It allows to appoint mass-rate of combustion of a char particle in the above conditions.     

Novel solid hypergolic fuels for hybrid propellants

A new class of compounds, viz., monothiocarbohydrazones, have been found to be hypergolic with anhydrous and red fuming nitric acids. A study of the ignition delays of the various thiocarbohydrazonenitric acid systems as a function of particle size and fuel/oxidizer ratio reveals no significant effect by these parameters. The observed ignition delays have been explained in terms of the chemical reactivity and structure of these compounds.     

Oxygen carriers for chemical looping combustion of solid fuels

A thermal analyzer-differential scanning calorimeter-mass spectrometer (TG-DSC-MS) was used to study oxygen carriers (OC) for their potential use for the application of chemical looping combustion (CLC) to solid fuels. Reaction rates, changes in reaction rates with repeated oxidation-reductions, exothermic heats during oxidation, and the effect of changing reduction gas compositions were studied. Oxidation rates were greater than reduction rates and reaction rates were reproducible through multiple oxidation-reduction cycles except where agglomeration occurred with powders. Iron oxide (Fe₂O₃ powder) and iron-based catalysts were found suitable for CLC of solid fuels having rapid reduction rates which increased with higher reducing gas concentrations. Fe₂O₃ powder was used to oxidize a high carbon coal char in an inert gas removing 88% of the carbon from the char. Other properties such as cost and durability indicated iron oxide OCs potential use for CLC of solid fuels.     

Pyrolysis kinetics and combustion characteristics of waste recovered fuels

Alternative fuels, such as biomass and refuse derived fuels tend to play an increasingly important role in the European energy industry. Co-firing fuels derived from non-hazardous waste streams have the potential of covering a significant part of the future demand on co-incineration capacities, which is expected to increase due to the implementation of the 2000/76 EC landfill Directive. However, their combustion behaviour has not yet been fully investigated, because of the difficulty to define representative fuel characteristics simulating accurately all the fuel fractions. In the present study, refuse derived fuel behaviour was investigated by thermogravimetry under pyrolysis and combustion conditions. A non-isothermal thermogravimetric analyser (TA Q600) operated at ambient pressure was used for both the pyrolysis and combustion experiments. The devolatilisation of the waste samples was investigated at a temperature range of 30-1000 °C with the constant heating rate of 20 °C/min and for particle sizes between 150 and 250 μm. Combustion tests were realized under the same heating conditions. The independent parallel, first order, reactions model was elaborated for the kinetic analysis of the pyrolysis results. The thermal degradation of the refuse derived fuel samples was modeled assuming four parallel reactions corresponding to the devolatilisation of cellulose, hemicellulose, lignin and plastics. Increased activation energies were calculated for the plastics fraction. Lignin presented the lowest contribution in the pyrolysis of the samples. Slightly increased combustion reactivities were found for the waste fuel samples compared to lignite. It is concluded that waste recovered fuels can be used in existing combustion facilities either alone or in combination with coal and future investigations should focus on the operational behaviour of large-scale facilities when exploiting these waste species.     

Mechanism of particulate reduction in heavy fuel oil combustion

A residual fuel oil, neat and with four different additives, was tested using three experimental devices: a very fast pyrolyser of fuel droplets which produced cenospheres; a thermogravimetric analyser which gave information on the reactivity of the cenospheres; and a 1.16 MW boiler. The additives did not modify cenosphere production in the pyrolyser, but changed their reactivity. This reactivity change was in accordance with particulate reduction in the boiler and with the retention of the metal additive in the cenospheres. The retention of the metal depended on the nature of the organic part of the additive.     

The combustion of droplets of liquid fuels and biomass particles

Studies have been made of the combustion of droplets of liquid hydrocarbons, including kerosene and Diesel fuels, biofuels such as FAME and the alcohols, especially ethanol and n-butanol, and of pulverised solid biomass materials such as pine wood and Miscanthus which burn in an analogous fashion. Information is given on the burning rates of both the liquids and the solids and data given on soot formation yields for the different fuels. The mechanism of soot formation is discussed in relation to (1) volatile liquid fuels such as n-heptane, alcohols and aviation fuels, (2) liquid fuels having higher aromatic levels such as Diesel fuels, and (3) biomass particle combustion.     

Radiative combustion of pyrolyzing fuel in a cylindrical combustor

Investigation on ignition and flame propagation of pyrolyzing fuel in a cylindrical combustor is accomplished. The pyrolyzing fuel of cylindrical shape is concentrically located in a combustor sustained at high temperature. Due to gravity, the buoyancy motion is inevitably incurred in the combustor and this affects the flame initiation and propagation behavior. The radiative heat transfer due to absorption gas plays an important role since it absorbs and emits radiative energy. Numerical studies have been performed over various parameters relevant to gas radiation as well as overheat ratios. The ignition criterion is decided on experimental basis. For the case of relatively small overheat ratio, the gas absorption reduces the flow intensity by the far-reaching effect of radiation. Visible blue flame hence does not evolve. For a high overheat ratio, the strong visible blue flame is generated and self-propagates. The gas radiation makes the considerable effect on ignition delay and flame thickness as well as thermal and reactive nature of visible blue flame.     

Solution combustion synthesis of ZnO powders using mixture of fuels in closed system

Single phase ZnO powders with wurtzite structure were synthesized by solution combustion method using various amounts of mixed glycine-citric acid fuel in the presence (open system) and absence (closed system) of air oxygen. Phase evolution, microstructure and optical properties were investigated by thermal analysis, X-ray diffractometry, electron microscopy and Raman, photoluminescence (PL) and diffuse reflectance spectrometry techniques. Rapid combustion reaction in closed system led to weak crystallinity, as confirmed by deep-level emissions in PL spectra. Larger spherical particles (~200?nm) were synthesized in open system at ? =?1. The as-combusted ZnO powders in closed system exhibited higher photocatalytic activity under ultraviolet irradiation, due to their higher adsorption capacity of methylene blue on ZnO surface. Photodegradation rate increased with the increase of fuel content in as-combusted ZnO powders produced by open route as a result of the reduction of particle size and band gap energy.     

不同石化燃料燃烧烟尘的来源辨识

利用固相微萃取-气质联用(SPME-GC-MS)技术,对汽油、柴油、聚苯乙烯、ABS 4种石化燃料进行燃烧烟尘的特征组分分析,对其特征组分谱图中的保留时间进行归纳总结.对获得的20×35的数学矩阵,进行了主成分分析,得到了3个主成分,其累计率达到了92％,表明主成分所组成的二维数学坐标以及三维坐标系能较好地将不同比例的...     

Optical studies of spray development and combustion of water-in-diesel emulsion and microemulsion fuels

Physical properties, spray behaviour and combustion characteristics of a water-in-diesel emulsion, a water-in-diesel microemulsion and a conventional diesel fuel were investigated. The size of the drops, in the water-containing fuels, was measured by NMR diffusometry. Spray development and combustion were studied by optical methods in an optically accessed combustion vessel at conditions similar to those in a diesel engine. High speed shadowgraphs were employed to measure break-up, droplets penetration, vapour penetration and start of combustion. Combustion duration, flame temperature and relative soot concentration were determined by emission-based methods. Differences in spray behaviour suggest an enhanced atomisation for the water-containing fuels compared to regular diesel fuel. Moreover, reduced soot concentrations and flame temperature with increased combustion duration were noticed for the water-in-diesel fuels than for the regular diesel fuel.     

高温燃烧水解-电位滴定法测定固体生物质燃料中氯试验条件的确定

对高温燃烧水解-电位滴定法测定固体生物质燃料中氯的测定数据进行了统计分析,确定了其试验条件,按所定试验条件对测定结果进行了精密度（重复性限）评估。     

Products of combustion of mixtures of aluminum and tungsten nanopowders in air

It is experimentally found that intermediate products of combustion of mixtures of aluminum and tungsten nanopowders in air are aluminum nitrides, remainders of metallic tungsten and aluminum, complex oxides, and possibly tungsten nitrides. These products were obtained by terminating the combustion process when a temperature close to the maximum value is reached. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 59–65, July–August, 2007.     

Experimental analysis of the ignition front propagation of several biomass fuels in a fixed-bed combustor

Fixed-bed combustion in a tube reactor is a useful procedure to exploit a large variety of biomasses obtaining accurate in-bed data. In this paper, the ignition front propagation velocity is experimentally studied in a counter-current process for eight different biomass fuels with a wide range of origins, compositions and packing properties. Air mass flow rate is the main operative parameter and clearly distinguishes three stages of combustion (oxygen-limited, fuel limited and cooling by convection). The impact of the excess air ratio is also analyzed. This parameter confirmed that the maximum front velocity is achieved under sub-stoichiometric conditions, where the cooling effects of excessive air are minimized. Other variables with a major influence on the ignition front velocity are moisture and ash content. Finally, an uncertainty analysis is included to determine the accuracy of the entire measurement process.     

Combustion of a gasoline-hydrogen-air mixture in a reciprocating internal combustion engine cylinder and determining the optimum gasoline-hydrogen ratio

This paper reports results of an analysis of experimental data on the combustion of a gasoline-hydrogen-air mixture in a reciprocating internal combustion engine cylinder. The completeness of combustion of the mixture is shown to depend on the amount of hydrogen in the fuel mixture and the composition and physicochemical properties of the mixture. In particular, the conditions of addition of hydrogen to the gasoline-air mixture with active chemical action on the combustion process and the action of hydrogen as an additional fuel component are determined. A dimensionless universal relation is proposed that allows one to uniquely determine the initial composition of the fuel mixture (hydrogen to gasoline ratio) to accomplish combustion of the fuel mixture at the lean combustion limit. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 8–14, July–August, 2007.     

High-porosity TiAl foam by volume combustion synthesis

Preparation of high-porous TiAl foam by volume combustion synthesis (VCS) was investigated. It is shown that the optimum conditions for pore formation are attained when gas evolution coincides in time with melting of the reactants.      

水泥窑用固体替代燃料对比分析

本文针对目前水泥行业水泥窑用固体替代燃料,对工业边角料、生物质园林垃圾、废旧轮胎从各工业分析指标,相关燃烧特性等方面与煤粉展开相关对比分析。     

Pilot ignited premixed combustion of dimethyl ether in a turbodiesel engine

This paper describes combustion studies of dimethyl ether in a common rail turbodiesel engine wherein the dimethyl ether was fumigated into the intake air and the conventional diesel injection was used with the intention of igniting the premixed DME-air charge. This combustion process is referred to here as a “mixed mode” process and is similar in some respects to what is commonly referred to as “dual fuel” combustion. In contrast to “dual fuel” combustion, however, in which the gaseous fuel is often natural gas or biogas, in this process with DME the gaseous charge ignites largely independently of the diesel injection. The diesel injection was accomplished with a single, main injection. The engine was operated at a single speed and load. Gaseous and particulate emissions were monitored and heat release analysis was performed to examine how the fuels burn and the impact on emissions formation at various levels of substitution of diesel fuel with fumigated DME, at as high as 44% of the fuel energy from DME. Reductions in NO_x emissions and increases in particulate matter emissions are observed with DME fumigation. The increase in PM emissions is attributed to enrichment of the diesel fuel spray, due to displacement of intake oxygen by the fumigated DME, despite the widely observed soot suppressing effect of DME.     

Solid fuels in chemical-looping combustion using a NiO-based oxygen carrier

The feasibility of using three different solid fuels in chemical-looping combustion (CLC) has been investigated using NiO as oxygen carrier. A laboratory fluidized-bed reactor system for solid fuel was used, simulating a chemical-looping combustion system by exposing the sample to alternating reducing and oxidizing conditions. In each reducing phase 0.2 g of fuel was added to the reactor containing 20 g oxygen carrier. The experiments were performed at 970 °C. Compared to previously published results with other oxygen carriers the reactivity of the used Ni-particles was considerably lower for the high-sulphur fuel and higher for the low-sulphur fuel. Much more unconverted CO was released and the fuel conversion was much slower for high-sulphur fuel such as petroleum coke, suggesting that the nickel-based oxygen carrier was deactivated by the presence of sulphur. The NiO particles also showed good reactivity with methane and a syngas mixture of 50% H₂ and 50% CO. For all experiments the oxygen carrier showed good fluidizing properties without any signs of agglomeration.