Rocket Engine with Continuous Detonation Combustion of the Natural Gas–Oxygen Propellant System

In a demonstrator of a detonation rocket engine (DRE) using the natural gas–oxygen propellant system, a high (270 s) specific impulse at sea level at a low (32 atm) mean combustor pressure was experimentally obtained for the first time. Comparison of these characteristics with the respective ones (263 s and 61 atm) of the well-known Russian RD 170-A liquid-propellant rocket engine using deflagration combustion of the kerosene–oxygen propellant system showed that the specific impulse at sea level in the DRE is close to that in the deflagration-combustion engine but is produced at half as high a mean combustor pressure. This indicates that the energy efficiency of detonation combustion exceeds that of deflagration combustion, and that there is room to improve the weight–size characteristics of the turbopump unit in the DRE.     

Rocket Engine with Continuous Film Detonation of Liquid Fuel

It was experimentally proven for the first time that it is possible to perform continuous detonation combustion of a film of a liquid fuel in the annular combustor of a demonstrator of a liquid-fuel detonation rocket engine. Firing tests revealed a near-limit mode of longitudinally pulsating film detonation and modes of continuous spinning film detonation with one and two detonation waves circulating within the annular gap of the combustor.     

Magnesium boride sintered as high-energy fuel

Boron was chosen as fuel owing to its excellent thermodynamic values for combustion. The difficulty of the boron in combustion is the formation of a surface oxide layer, which postpones the combustion process, reducing the performance of the rocket engine. In this paper, magnesium boride was sintered as high-energy fuel as a substitute for boron. The combustion heat and efficiency of magnesium boride and boron were determined using oxygen bomb calorimeter. The combustion characteristics of magnesium boride were investigated by thermal analysis, chemical analysis, XRD, and EDS. Results show that the combustion performance of magnesium boride are better than that of amorphous boron in oxygenated environments. The evaporation of magnesium in magnesium boride combustion process prevent the formation of a closed oxide layer, leading to higher combustion efficiency.     

Borides and vitreous compounds sintered as high-energy fuels

Boron was chosen as fuel in view of its excellent thermodynamic values for combustion, as compared to traditional fuels. The problem of the boron in combustion is the formation of a surface layer of oxide, which delays the ignition process, reducing the performance of the rocket engine. This paper presents a high-energy fuel for rocket engines. It is composed of sintered boron (borides and carbides and vitreous compounds) with a reducing chemical agent. Borides and boron carbide were prepared since the combustion heat of the latter is similar to that of the amorphous boron (in: K.K. Kuo (Ed.), Boron-Based Solid Propellant and Solid Fuel, Vol. 427, CRC Press, Boca Raton, FL, 1993). Several chemical reducing elements were used, such as aluminum, magnesium, and coke. As the raw material for boron, different compounds were used: amorphous boron, boric acid and boron oxide.     

循环流化床燃煤过程NO、N2O和SO2的排放行为研究

在30kW循环流化床装置上进行了中国西部三种煤的燃烧实验，考查了燃烧温度、空气分级、空气过剩系数、固体颗粒循环料率和煤种等因素对NO、N2O、SO2污染物排放的影响。结果表明，强化空气分级可显著降低高挥发分煤种NO的生成量，但对N2O影响不大；增加空气过剩系数同时增加了NO与N2O的排放；增加固体循环料率显著降低NO生成量，但N2O排放略有增加；高阶煤燃烧生成较多N2O，低阶煤生成较多NO。燃烧温度1120K、过剩空气系数1.25下约85%燃料中N转化为N。实验范围内改变操作参数不影响SO2与CO排放量。     

RDF流化床燃烧过程NOx生成比较研究

随着中国经济的迅速发展和城市化进程的加快,由此带来的负作用凸现：各种资源的消耗不断增加;同时这种传统的高消耗、低产出、高污染的经济发展带来的环境污染也非常严重。据不完全统计,2003年中国城市生活垃圾总量为1．9亿t,并以每年8％～10％的速度递增,对垃圾进行简单填埋、焚烧不但污染土壤和地下水,     

Mathematical Modeling of Aluminum Diboride Combustion in an Air Flow

A mathematical model and the results of calculating the ignition and combustion of energetic condensed systems based on mono- and polydispersed aluminum diboride particles in air flows in constant-cross-section channels are reported. The kinetic characteristics of the transformations that separate aluminum diboride particles formed by gasification of energetic condensed systems undergo in a high-temperature oxidizing medium were determined using the dependences of the ignition induction period and combustion time on the air temperature and diameter and initial temperature of the particles. These dependences, in turn, were calculated using the model of parallel chemical reactions. The range of combustion conditions corresponding to the initial air temperatures from 300 to 2000 K and Mach numbers in the channel from 0.1 to 1.5 was considered. The influence of the aluminum diboride particle size and of the rate and initial temperature of the air flow on the combustion efficiency was demonstrated. The relationships between the combustion completeness factor of aluminum diboride particles at various initial parameters of the air flow and gasification products of energetic condensed systems at various fuel mixture equivalence ratios, corresponding to the diffusion and kinetic combustion, were determined. The conditions of the transition between the diffusion and kinetic control modes were found.

     

Demonstrator of continuous-detonation air-breathing ramjet: Wind tunnel data

First experimental investigations were carried out into the detonation combustion of hydrogen in a demonstrator of an original-design air-breathing ramjet while blowing with an air flow at Mach 4 to 8 in an impulse wind tunnel, and for the first time under these conditions, continuous spin and longitudinal pulsed modes of detonation combustion of hydrogen in an annular combustor were detected.     

Wind Tunnel Testing of a Detonation Ramjet Model at Approach Air Stream Mach Number 5.7 and a Stagnation Temperature of 1500 K

The mode of continuous detonation combustion of hydrogen in the annular combustor of a model of a detonation air-breathing ramjet at the approach air stream Mach number 5.7 and a stagnation temperature of 1500 K was experimentally detected for the first time in a pulsed wind tunnel. The thrust and fuelbased specific impulse of the ramjet model were 1550 N and 3300 s, respectively.     

Electrodeposition of composite Ni–B coatings in a stirred heterogeneous system

The formation of composite electrochemical coatings of a nickel matrix with boron microparticles was investigated. Electrolytical nickel–boron layers were deposited on a paraffin-impregnated graphite electrode in a stirred heterogeneous system formed by a Watts-type nickel plating bath and dispersed boron powder particles. The polarisation behaviour of the composite plating bath as a function of the boron particle loading was examined. The effect of deposition conditions, as well as of the amount of boron powder in the plating bath on the boron content in the composite Ni–B coatings, was examined. The composite coating structure was established using scanning electron microscopy and light optical microscopy. The distribution of boron particles in the composite deposits was investigated by dynamic secondary ion mass spectrometry. The boron particles content was determined gravimetrically. The obtained results suggest that the content of incorporated boron particles increases with an increasing amount of boron in the plating bath. The potentiodynamic deposition method is demonstrated to be more suitable for production of composite coatings with a high content of boron particles than the potentiostatic one. Homogeneous distribution of boron particles in the nickel matrix without coagulation or sedimentation was associated with the electrochemical fabrication method in stirred heterogeneous systems.     

废木料焚烧炉燃烧过程的数值模拟

采用数值模拟方法研究了废木料焚烧炉的流动与燃烧状况，以预见不同条件下废木料燃烧与污染物的排放。应用RNG k-ε双方程模型联合几率分布函数（pdf）的组分输运方程，结合颗粒轨道模型对废木料焚烧炉进行数值模拟，计算结果揭示了各种燃烧条件下，燃烧室内的速度场和温度场分布及CO等浓度分布。仅供一次风的情况下，二燃室出口温度高，CO燃烬效果较差；在合适的二次风供给的情况下，总的过量空气系数较小，对燃烧效果改善明显。     

Ignition and combustion characteristics of compound of magnesium and boron

Compound of magnesium and boron (MB) is promising to be the ideal substitute of amorphous boron which is usually used as the raw material of boron-based fuel-rich propellants. In this study, the physical characteristics of MB and amorphous boron were studied by the scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. The thermal reaction characteristics and the ignition and combustion characteristics were investigated through TG/DSC experiments and laser ignition experiments. The experimental results show that the MB particle is much more regular than amorphous boron, which favors for the preparation of boron-based fuel-rich propellants. Magnesium exists in the form of elementary substance, and boron oxide is produced during the preparation of MB which results in the longer ignition delay time of MB. The content of magnesium and the pressure have effects on the MB combustion performance. Although the combustion of magnesium can provide much heat for the combustion of boron, MB with moderate content of magnesium shows the best combustion performance. On the contrast, the ignition delay time of MB is independent on the content of magnesium and the pressure.     

Combustion measurement of thermoacoustic oscillating flames by diode-laser absorption spectroscopy sensors

Diode-laser absorption spectroscopy has been applied to a swirl-stabilized turbulent combustor to detect high frequency combustion oscillation and combustion state related to combustion noise. Two diode-laser absorption spectroscopy techniques of scanned-wavelength method and fixed-wavelength method are adopted. In the scanned-wavelength method, fluctuations of temperature and H₂O mole fraction up to 1 kHz are detected. Two dominant peak frequencies of power spectra of these fluctuations, which are about 125 Hz and 140 Hz, coincide with those of pressure fluctuation in the combustor. In the case of control by secondary fuel injection, the energy at peak frequency of temperature and H₂O mole fraction decreases in accordance with noise reduction. Similar to the combustion noise, temperature fluctuation shows a minimal value at the appropriate frequency of secondary fuel injection. By analysing transmitted signals, the fixed-wavelength method provides power spectra similar to those obtained by the scanned-wavelength method. The advantage of the fixed-wavelength method is capability of detection of high frequency combustion oscillation more than 1 kHz. These results prove that the diode-laser absorption spectroscopy has great applicability as sensors for the combustion measurement of thermoacoustic oscillating flames and active control of turbulent combustion.     

Development and testing of granular catalysts for combustors of regenerative gas turbine plants

Two types of granular catalysts for effective methane combustion in combustors of gas turbine plants (GTPs) were developed: (1) catalysts based on noble metals with a low Pd content (1–2 wt %), characterized by a low methane ignition temperature, and (2) catalysts based on manganese oxides and hexaaluminates, which have an increased thermal stability. The methane oxidation kinetics was investigated, and combustion in the catalyst chamber of the GTP was simulated. For optimizing the combustion technology, the following two-step process using a combined catalytic package is suggested. The inlet zone of the combustor is filled with a highly active Pd catalyst, which initiates methane oxidation and ensures that the temperature at the exit of this zone is the initial temperature of methane combustion. This takes place in the next zone, which is filled with an oxide catalyst tolerant to high temperatures. The pilot testing of the catalysts was carried out in a model catalytic combustor. The results are in satisfactory agreement with calculated data. Long-term tests indicate the high stability of the catalysts. The Pd catalyst was demonstrated to retain its high activity and to provide an ignition temperature of 240°C. The initial activity of the hexaaluminate-based catalysts remains unchanged after tests at 930°C. The use of a combined charge of the palladium (7–15%) and manganese (85–93%) catalysts in the model GTP combustor allows a high natural gas combustion efficiency to be achieved at a low level of hazardous emissions (NO _x , 0–1 ppm; CO, 1–3 ppm; hydrocarbons, 3–10 ppm).     

Thermal reaction characteristics of the boron used in the fuel-rich propellant

High pressure DSC and simultaneous TG/DSC were used to study the different kinds of boron that was used in the fuel-rich propellant and the amorphous boron in different gases and different pressure. Also, some of the samples before the experiment and after the experiment were analyzed by the SEM. The results show that: (1) there is a big exothermic peak between 550 °C and 850 °C for all the samples because the combustion heat of boron is very high, and the exothermic peak appears in advance when the pressure or the oxygen concentration increases. (2) Although the reaction process of all the samples with air or oxygen could be divided into five stages, the reaction characteristics are different from each other. Especially, amorphous boron is much more active than the boron used in the fuel-rich propellant. (3) The exothermic peak at about 700 °C appears in advance, and the percentage conversion of boron decreases when the content of magnesium increases and boron–magnesium compound is used as the raw materials. (4) Some samples start to lose their mass for the sake of the evaporation of the (BO)_n.     

CSP分析方法在简化燃烧化学反应系统中的应用

基于计算奇异摄动(CSP)思想, 对甲烷/空气预混燃烧系统进行分析. CSP将反应空间分裂, 消除刚性; 将单点分析和全局分析相结合, 合理选择主要组分和稳态物质, 使用CSP的特征指数简化方程. 构建了针对甲烷/空气预混燃烧系统的总包15步反应机理, 并利用Sandia实验室的PREMIX软件包对该系统进行分析, 验证了简化机理的准确性, 证实了CSP分析方法在燃烧系统中应用的可靠性和优越性, 并为研究简化燃烧系统的分析提供了一种新的思路.     

Superhydrophobic cellulose nanocomposites

Superhydrophobic cellulose nanocomposites were prepared using a multi-step nanoengineering process. The combination of different techniques made it possible to construct novel features at the ensuing surface, characterized by both an increase in its roughness induced by amorphous silica particles and a reduction in its energy insured by perfluoro moieties, giving rise to water contact angles approaching 150 degrees . The modification calls upon an aqueous LbL system followed by siloxane hydrolysis, both conducted at room temperature in air. Each modification was followed by scanning electron microscopy (SEM) and atomic force microscope (AFM). These original cellulose-silica-silane composite materials open the way to further valorisations of a ubiquitous renewable resource in applications such as water repellence and self-cleaning.     

Source identification of lead-containing particles in the ambient air of the center of Shanghai by analyzing individual aerosol particles

Summary Single aerosol particles were analyzed in the ambient air of the center of Shanghai by scanning proton microprobe to obtain characteristic X-ray spectra (micro-PIXE) which were considered to be the fingerprints of these aerosol particles. The origin of the lead-containing particles was identified by the combination of the micro-PIXE spectra with pattern recognition technique. It was found that the most of the lead-containing particles were derived from vehicle exhaust, coal combustion and soil dust.     

Application of Plasma Fuel Reformer to an On-Board Diesel Burner

A conventional diesel burner has arisen several shortcomings, such a large supply of air for a stoichiometric combustion, and a long heat-up time to reach the light-off temperature of catalyst in a diesel after-treatment system. This study shows a promising potential of using a plasma reformer for staged diesel combustion with minimized air and fuel consumption, and increased the flame stability with low NOx emission. A working principle of a plasma fuel reformer for staged combustion is explained in detail by both visualizing the plasma-assisted flame and analyzing the gas products. The concentrations of H₂, CO, NOx and the unburned total hydrocarbons were measured by gas chromatography and a commercial gas analyzer. Considering the operating condition of diesel exhaust gas is too harsh to maintain a stable diesel flame with a conventional diesel burner, plasma fuel reformer has distinctive advantages in stable flame anchoring under the condition of low oxygen concentration and fast flow speed. The re-ignition and stable flame anchoring by entrapment of oxygen in exhaust gas is mainly attributed to the low ignition energy and high diffusion velocity of hydrogen molecule. From an economic point of view, plasma reformer is also the only technology which can use only 1/3–1/8 of the air required for the stoichiometric burning of a conventional diesel burner. A conventional burner was simulated and analyzed to consume up to 30 % more fuel compared to the plasma reformer with the staged combustion to get the same level of temperature elevation in a real diesel engine scale.     

The morphology of ceramic phases in BxC-SiC-Si infiltrated composites

The present communication is concerned with the effect of the carbon source on the morphology of reaction bonded boron carbide (B₄C). Molten silicon reacts strongly and rapidly with free carbon to form large, faceted, regular polygon-shaped SiC particles, usually embedded in residual silicon pools. In the absence of free carbon, the formation of SiC relies on carbon that originates from within the boron carbide particles. Examination of the reaction bonded boron carbide revealed a core-rim microstructure consisting of boron carbide particles surrounded by secondary boron carbide containing some dissolved silicon. This microstructure is generated as the outcome of a dissolution-precipitation process. In the course of the infiltration process molten Si dissolves some boron carbide until its saturation with B and C. Subsequently, precipitation of secondary boron carbide enriched with boron and silicon takes place. In parallel, elongated, strongly twinned, faceted SiC particles are generated by rapid growth along preferred crystallographic directions. This sequence of events is supported by X-ray diffraction and microcompositional analysis and well accounted for by the thermodynamic analysis of the ternary B-C-Si system.