光电三极管在研究推进剂燃烧转爆轰行为中的应用

用探针法研究 DDT管中高能推进剂的燃烧波和爆轰波的传播特性 ,因各种因素的影响难以得到满意的结果 ,用光电三极管代替电离探针可得到相对理想的结果     

Packing Configurations of PBX‐9501 Cylinders to Reduce the Probability of a Deflagration to Detonation Transition (DDT)

The detonation of hundreds of explosive devices from either a transportation or storage accident is an extremely dangerous event. This paper focuses on identifying ways of packing/storing arrays of explosive cylinders that will reduce the probability of a Deflagration to Detonation Transition (DDT). The Uintah Computational Framework was utilized to predict the conditions necessary for a large scale DDT to occur. The results showed that the arrangement of the explosive cylinders and the number of devices packed in a “box” greatly effects the probability of a detonation.     

填料型预碳化塔的数学模型与模拟 ‘

硕酸化反应为一典型的连串、可逆放热反应,液膜内的快反应与液相本体的慢反应相互耦合,共同决定着ＣＯ２的化学吸收速率。本文在以往工作的基础上,通过对碳化机理和动力学的全面分析,建立了填料型预碳化塔的数学模型。对有关工业过程进行了模拟,指出了影响填料行为的关键因素并提出了相应的改进措施。     

Effect of Microwave Energy on Vacuum Drying Kinetics of Alginate-Starch Gel

Microwave energy drying under vacuum was investigated for alginate-starch hydrogel. Drying was conducted using 2450 MHz microwave energy at 25 mm Hg absolute pressure and different power levels; e.g., 300, 500, 700, 900, and 1100 watts. Drying was continued until final moisture content of the sample reached less than 1% wet basis. Moisture loss during drying was measured at 3-min intervals. Drying kinetics were used to describe both macroscopic and microscopic mechanisms of heat and mass transfer. Experimental drying kinetic data were fitted to a mathematical model. Experimental drying data points were fitted to an empirical model equation.     

Effect of Microwave Energy on Vacuum Drying Kinetics of Alginate-Starch Gel

Microwave energy drying under vacuum was investigated for alginate-starch hydrogel. Drying was conducted using 2450 MHz microwave energy at 25 mm Hg absolute pressure and different power levels; e.g., 300, 500, 700, 900, and 1100 watts. Drying was continued until final moisture content of the sample reached less than 1% wet basis. Moisture loss during drying was measured at 3-min intervals. Drying kinetics were used to describe both macroscopic and microscopic mechanisms of heat and mass transfer. Experimental drying kinetic data were fitted to a mathematical model. Experimental drying data points were fitted to an empirical model equation.     

爆轰火焰在管道阻火器内的传播与淬熄特性

在水平封闭的直管中,采用自主研制的阻爆实验系统(包括传感器系统、配气系统、数据采集系统、点火系统等)对不同活性预混气体爆轰火焰在波纹管道阻火器内的传播与淬熄过程进行了实验研究。结果显示当可燃气体接近当量浓度时(丙烷4.2%、乙烯6.6%、氢气28.5%,均为体积分数),预混气体从点燃到火焰淬熄过程历时非常短,总体可分为4个阶段,缓慢燃烧阶段、快速燃烧阶段、加速燃烧阶段和超压振荡阶段。丙烷-空气、乙烯-空气预混气体在D=80 mm的管道阻火器中,爆炸压力峰值较高。当管道直径增加至400 mm时,爆炸压力峰值逐渐降低,其中乙烯-空气预混气体的爆炸压力峰值仅为3 MPa左右;氢气-空气预混气体的爆炸压力峰值随管径的增加呈递增趋势。对爆轰速度的研究结果表明,丙烷-空气、乙烯-空气预混气体爆轰速度数值相差不大,丙烷-空气预混气体甚至稍高些;而氢气-空气的爆轰速度数值较高。而且随着管径的增加,管壁热损失增大及其阻力因素等原因影响使预混气体爆轰速度趋向平稳。最后,从经典传热学理论出发,推导出了阻火单元厚度与爆轰火焰速度之间的关系。并结合实验数据,提出了爆轰安全阻火速度的计算方法,为工业装置阻火器的设计和选型提供更为准确的参考依据。     

Fuel effects on diffusion flames at elevated pressures

This study addresses the influence of elevated pressures up to 1.6 MPa on the flame geometry and the flickering behavior of laminar diffusion flames and particular attention has been paid to the effect of fuel variability. It has been observed that the flame properties are very sensitive to the fuel type and pressure. The shape of the flame was observed to change dramatically with pressure. When the pressure increases, the visible flame diameter decreases. The height of a flame increases first with pressure and then reduces with the further increase of pressure. The cross-sectional area of the flame (A_cs) shows an average inverse dependence on pressure to the power of n (A_cs ∝ P⁻ⁿ), where n = 0.8 ± 0.2 for ethylene flame, n = 0.5 ± 0.1 for methane flame and n = 0.6 ± 0.1 for propane flame. It was observed that the region of stable combustion was markedly reduced as pressure was increased. High speed imaging and power spectra of the flame chemiluminescence reveal that an ethylene flame flickers with at least three dominant modes, each with corresponding harmonics at elevated pressures. In contrast methane flames flicker with one dominant frequency and as many as six harmonic modes at elevated pressures.     

大型马蹄焰玻璃熔窑火焰空间气体动力学特征数值模拟研究

在本文的马蹄焰玻璃熔窑火焰空间气体动力学数值模拟中,关联了火焰空间的几何构型,小炉火焰出口速度,下倾角度等等基本因素.数值模拟结果显示马蹄焰流股特性上述几个要素密切相关.为适应池窑内玻璃液熔制工艺要求,在熔窑规模增加中强化纵长方向的扩张,则给马蹄焰的燃烧过程组织带来极大困难.对于窄长的窑型,入射火焰流股远程动力减弱,马蹄焰回转不够流畅;若增加火焰流股的远程动力,则火焰流股近程覆盖力减弱.若增加火焰流股入射速度同时增加小炉下倾角,则虽然火焰的近程覆盖力增加,但火焰流股受到阻滞,远程动力减弱.     

A NEW APPROACH FOR THE CLASSIFICATION AND ENUMERATION OF UNIQUE REACTION ROUTES AND UNIQUE OVERALL REACTIONS IN MULTIPLE CHEMICAL REACTION SYSTEMS

The methodology of response reactions (RERs) introduced earlier from thermodynamic and kinetic considerations is used in this work to develop a new algorithm for the classification and enumeration of unique/direct reaction routes (RRs) and overall reactions (ORs). According to the RERs approach, a unique set of both RRs and ORs may be generated starting from any conceivable set of linearly independent RRs and ORs. In particular, the direct ORs may be most conveniently enumerated starting from the formula matrix of the terminal species (reactants and products), i.e., without any relation to the elementary reactions comprising the detailed mechanism. Depending on the type of ORs produced by the RRs one can distinguish between two distinct types of direct RRs. Namely, one option is to define a direct RR by specifying the intermediate species that need to be eliminated. This type of RR is referred to as Milner RRs. The other option is to require the direct RRs to produce RERs, thus resulting in RRs referred to as Happel-Sellers RRs.     

Photocatalytic oxidation of butyraldehyde over titania in air: By-product identification and reaction pathways

In this study, gas phase photocatalytic oxidation (PCO) of n-butyraldehyde was carried out in a packed-bed reactor (titania supported on an inert packing). An on-line system consisting of two collection columns (one glass bead and one activated carbon) and a GC/MS was used for by-product identification. Various temperature levels (50, 90, 115, 170, 270, 320°C) were used in the by-product desorption from the activated carbon column. The oxidation yielded carbon dioxide as the end product. The by-products revealed many reaction pathways of the photocatalytic process. The major by-products (propionaldehyde, 1-propanol, ethanol, and acetaldehyde) were believed to undergo a C-C bond cleavage followed by hydrolysis. Secondary by-products (propyl formate, di-n-propyl ether, and 3-heptene) were caused by esterification, dehydration, and reductive coupling. Aldol condensation of the vapor phase aldehydes on TiO 2 surfaces followed by cyclization may be partially responsible for the formation of some minor by-products such as ethylbenzene.     

Direct numerical simulations of mass transfer in square microchannels for liquid-liquid slug flow

Microreactors for the development of liquid-liquid processes are promising technologies since they are supposed to offer an enhancement of mass transfer compared to conventional devices due to the increase in the surface/volume ratio. But impact of the laminar flow should be negative and the effect is still to be evaluated. The present work focuses on the study of mass transfer in microchannels by means of 2D direct numerical simulations. We investigated liquid-liquid slug flow systems in square channel of depth. The droplet velocity ranges from 0.0015-0.25 m/s and the ratio between the channel depth and the droplet length varies between 0.4 and 11.2. Droplet side volumetric mass transfer coefficients were identified from concentration field computations and the evolution of these coefficients as a function of the flow parameters and the channel size is discussed. This study reveals that mass transfer is strongly influenced by the flow structure inside the droplet. Moreover, it shows that the confinement of the droplets due to the channel size leads to an enhancement of mass transfer compared to cases where the droplets are not constrained by the walls.     

Mathematical Modeling and Simulation of Drying Using Two Industrial Concurrent and Countercurrent Rotary Dryers for Ammonium Nitrate

Drying of ammonium nitrate (AN) is accomplished in the Shiraz Petrochemical Complex (SPC) using a concurrent rotary dryer following a countercurrent rotary dryer. A mathematical model for these rotary dryers including heat and mass transfer was developed. The model was checked against industrial-scale data, which showed a good agreement. The average absolute deviation of the simulation results compared to the industrial data for the concurrent dryer was 4.0% for solids moisture, 1.3% for solids temperature, and 1.8% for air temperature and for the countercurrent dryer it was 9.0% for the solids moisture, 2.0% for solids temperature, and 4.6% for air temperature. These simulation results reveal that for outlet solid moisture, inlet AN moisture, and air temperature as well as the outlet temperature of product, the inlet solid and air temperature have major effects for both concurrent and countercurrent flow.     

Experimental study and simulation of vibrated fluidized bed drying

The paper addresses numerical simulation for the case of convective drying of seeds (fine-grained materials) in a vibrated fluidized bed, analyzing agreement between the numerical results and the results of corresponding experimental investigation. In the simulation model of unsteady simultaneous one-dimensional heat and mass transfer between gas phase and dried material during drying process it is assumed that the gas-solid interface is at thermodynamic equilibrium, while the drying rate (evaporated moisture flux) of the specific product is calculated by applying the concept of a “drying coefficient”. Mixing of the particles in the case of vibrated fluidized bed is taken into account by means of the diffusion term in the differential equations, using an effective particle diffusion coefficient. Model validation was done on the basis of the experimental data obtained with narrow fraction of poppy seeds characterized by mean equivalent particle diameter (d_S,d = 0.75 mm), re-wetted with required (calculated) amount of water up to the initial moisture content (X₀ = 0.54) for all experiments. Comparison of the drying kinetics, both experimental and numerical, has shown that higher gas (drying agent) temperatures, as well as velocities (flow-rates), induce faster drying. This effect is more pronounced for deeper beds, because of the larger amount of wet material to be dried using the same drying agent capacity. Bed temperature differences along the bed height, being significant inside the packed bed, are almost negligible in the vibrated fluidized bed, for the same drying conditions, due to mixing of particles. Residence time is shorter in the case of a vibrated fluidized bed drying compared to a packed bed drying.     

Experimental studies of the role of chemical kinetics in turbulent flames

Flames of di-t-butyl-peroxide (DTBP) decomposition in a 0.376DTBP + 1.0N₂ mixture are studied in laminar and turbulent media. The observed values of unstretched laminar burning velocity are in reasonable agreement with the value obtained from the Zel’dovich-Semenov-Frank-Kamenetsky theory. Turbulent explosions in this particular mixture are characterized by a number of features that are believed to be common for all developing turbulent flames and have relevance to spark-ignition engine combustion of lean mixtures. Flame propagation is unsteady and is characterized by a mass burning rate that increases in time. The rate of the flame acceleration varies from one explosion to another. If the burning rate is related to the average flame radius, however, it exhibits much smaller variations. This phenomenon bears a striking resemblance to cycle-to-cycle variations in a spark-ignition engine. Comparisons of the present results with mixtures of significantly different composition, chemical kinetics, and exothermicity, but with similar laminar flame speed and Lewis number show that the data obtained in closed-volume explosions are in good agreement if the unsteady character of the flame is taken into account. The differences in details of the kinetic mechanisms and thermochemistry appear to be responsible for the flame behaviour only near the limit of extinction by turbulence. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 4, pp. 43–52, July–August, 2009.     

Model Detonation of Solid Explosives by the Homogeneous Mechanism

A twophase detonation model of solid porous explosives, which takes into account the compression of solidstate particles and the presence of a solid component in detonation products, is developed. The homogeneous detonation mechanism based on the Arrheniustype reaction is studied. Detonation is initiated by the region of highpressure and hightemperature gases modeling the detonator explosion. A numerical experiment confirms that there exists an initiationpressure limit below which no homogeneous mechanism of detonation is active. The detonation wave has the leading front in which the explosive is precompacted and the gas in the porous volume is compressed up to a pressure of 100 GPa without any significant change in particle density. Then the gas compresses the particles themselves up to the pressure and temperature of the thermal explosion. As a result, the leading front is followed (after a certain delay) by a narrow reaction zone where detonation products are formed with a further increase in pressure.     

ABS阻燃性能的研究

总结了适用于ABS阻燃性能的各种阻燃剂,分析了它们的阻燃机理及阻燃效果。介绍了目前国内外在ABS阻燃方面的研究状况     

Effect of a nanosecond gas discharge on deflagration to detonation transition

The possibility of using a high-voltage nanosecond discharge to initiate gaseous detonation was shown experimentally. The experiments were performed with C₃H₈ + 5O₂ and C₃H₈/C₄H₁₀ + 5O₂ + xN₂ (x = 0–10) mixtures at an initial pressure of 0.15–0.6 atm. The discharge was initiated by a voltage pulse of duration ≈60 nsec and amplitude 4–70 kV; the energy input was 0.07–12 J. Under the conditions of the experiment, three flame propagation regimes were observed: slow combustion, transient detonation, and Chapman—Jouguet detonation. For the initiation of the C₃H₈+ 5O₂ mixture in a tube of diameter 140 mm, the length of the deflagration to detonation transition was 130 mm at an initial pressure of 0.3 atm and an initiation energy of 70 mJ. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 80–90, March–April, 2006.     

共轭爆轰模型及其数值解

按照CJ和ZND模型．在所有可能的终点状态中CJ面爆轰产物的熵最低．而且系统永远达不到热力学平衡态．不符合热力学基本定律。为克服这些缺点,取热力学平衡态作为爆轰过程终点,建立了一种新的共轭爆轰模型。在共轭爆轰模型中．阵面激发化学反应释放出的能量。使得爆轰产物粒子朝不同的方向运动。每一对分别向前和向后运动的粒子被称为共轭对。共轭对在做爆炸中产生并在膨胀中湮没。将此过程与爆轰波传播相关联．建立了共轭爆轰模型。它从守恒定律和热力学定律导出．没有类似于cJ似设之类的附加条件。共轭爆轰模型方程组封闭且有唯一解。对于理想气体,由该模型得出的爆轰参数与CJ-ZND模型相近。     

Calculation of the critical detonation diameter of explosive charges using data on their shock-wave initiation

This paper deals with the further development of the quantitative theory of critical detonation diameter that was earlier proposed by the author. According to this theory, to calculate the critical diameter, it is necessary to know the shock adiabat, detonation velocity, and the generalized kinetic characteristic of decomposition of a high-explosive (HE) charge under shock-wave compression. It is suggested that the generalized kinetic characteristic of decomposition of a HE can be found from an experimental dependence of the shock-wave amplitude on the distance the shock wave travels during shock-wave initiation of the HE charge. This approach allows one to calculate the critical detonation diameters of HE charges with sufficient accuracy. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 112–115, March–April, 2006.     

Spectral Investigation and Color Properties of Copper(I) Halides CuX (X=F,Cl, Br,I) in Pyrotechnic Combustion Flames

Four pyrotechnic compositions containing copper or its compounds and different halogens were tailored to produce the emitters copper(I) fluoride, CuF, copper(I) chloride, CuCl, copper(I) bromide, CuBr, and copper(I) iodide, CuI. The UV/Vis emission spectra of these compositions were measured and allow for the identification and assignment of the above species CuF, CuCl, CuBr, and CuI. Copper(I) fluoride is a poor emitter with a very narrow green band centered at λ=493 nm only. In contrast all the other copper(I) monohalides have extended band systems with boundaries ranging from about λ=400 to 540 nm. CuCl yields a blue chemiluminescence, whereas CuBr surprisingly gives a highly saturated (Σ=95 %) intense blue violet (λ_d=459 nm) emission. CuI displays an overall bluish green emission only due to more intense band systems λ>500 nm. The spectral properties of all the emitters and the color values of the emitters in the 1931‐CIE color diagram are presented.