Multipoint ignition of an optically radiating transparent gas

Minsk. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 3, pp. 16–21, May–June, 1989.     

Ignition of a radiating gas by an incandescent surface

Conclusions The fundamental regularities of ignition of a radiating and absorbing gas by an incandescent surface are examined. In the case of an optically thin medium characteristic for high-temperature ignition, the problem is solved in the traditional stationary and nonstationary formulations [8]. It is shown that radiant heat transfer plays an essential part in the gas ignition process, in particular, the process can be accelerated and retarded in an optically thin gas medium because of radiant heat exchange. The case of an optically dense gasl _kb/l _o corresponds to radiant heat conduction, and therefore, does not result in a change in the ignition time but only to an increase in the scale of the lengthl _o. For intermediate values ofl _kb/l _o the dependence of on parameters governing the energetics of radiant heat transfer is complex in nature and can only be analyzed numerically in each specific case. The development of a suitable model of radiation heat exchange is the fundamental difficulty here.Minsk. Translated from Fizika Goreniya i Vzryva, Vol. 26, No. 1, pp. 15–21, January–February, 1990.     

Ignition of a gas suspension in a cavity with heated radiating walls

Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 26, No. 5, pp. 20–24, September–October, 1990.     

Effect of nonequilibrium absorption on gas transport in heterogeneous systems

A mathematical model is suggested for nonequilibrium gas absorption by a condensed medium through a free surface or a membrane. Surface reactions describe by first-and second-order rate equations are taken into account. Gas transport through membranes and nonequilibrium gas sorption by liquids through a membrane are considered by way of examples. The effect of the sorption rate can be accounted for by introducing an efficient permeability of the gas-liquid interface.     

Flow improver additives for gas condensate

This paper describes synthesis and evaluation of polymeric additives for improving the flow properties of gas condensate. The additives were prepared by the free-radical initiated polymerization of methacryl esters with styrene and acrylic or methacrylic acid. Polymerization was performed by initiator azo-bis isobutyronitrile in toluene or xylene at 80 °C. The influence of additives structure, composition and molar weight, as well as gas condensate properties on its flow properties was studied. Gas condensate samples from the fields of Kalinovac, Stari Gradac and Molve located in the northern Croatia were used for evaluation of the prepared additives. It was found that the additives efficiency was considerably influenced by their properties and by condensate n-paraffin content and distribution.     

堇青石的红外辐射特性

堇青石是一种硅酸盐矿物，因其具有优良的红外辐射特性、较高的热稳定性和化学稳定性等优点而成为一种重要的红外辐射材料。分析了改善堇青石材料红外性能的几个主要途径：适当减小原料的粒度、合理选择堇青石合成方法、在堇青石基质中添加适量过渡金属氧化物、选取适宜的堇青石烧结温度等。介绍了堇青石在红外辐射导电陶瓷、红外泡沫陶瓷、高温红外辐射涂料和常温红外辐射涂料中的应用，展示了堇青石作为红外材料的发展前景。     

Numerical analysis of the flow around a system of bodies behind the shock wave

The incidence of a shock wave on a system of cylinders and spheres is numerically simulated. Flow regimes around a system of bodies are described, and a parametric analysis of the examined phenomenon is performed. Based on numerous computations, a chart of flow regimes is composed, which includes flow patterns with an individual shock wave and with a collective shock wave, depending on the free-stream Mach number and on the distance between the bodies.     

障碍物间危险气体泄漏扩散的二维数值模拟

建立了一套基于κ-ε湍流模型的数值模拟方法,该方法适用于模拟可燃性气体、毒性气体等危险气体意外泄漏扩散时的湍流风场情况和危险气体的浓度分布情况。将数值模拟结果与风洞试验数据进行比较的结果表明,所建立的方法在模拟障碍物间危险气体泄漏扩散方面具有一定的有效性。     

障碍物附近可燃性气体泄漏扩散的三维数值模拟

建立了一套适用于求解可燃性气体意外泄漏扩散时,可燃性气体浓度分布的三维数值模拟方法。对设置有障碍物的可燃性气体扩散风洞实验进行数值模拟,并将数值模拟结果与风洞实验数据进行比较。数值计算结果与风洞实验数据吻合得很好,两者浓度分布的趋势基本一致。数值模拟结果在一定程度上反映出可燃性气体扩散的浓度分布情况以及障碍物附近的气流和湍流情况,证明所建立的三维数值模拟方法在模拟障碍物附近可燃性气体泄漏扩散方面具有一定的有效性。     

气泡周围流场的PIV测定和浓度场研究

针对单乙醇胺水溶液吸收二氧化碳过程,采用粒子成像测速仪(PIV)对气泡周围的流场进行了测定,流场围绕气泡的对称轴呈对称分布.对速度场实验数据进行拟合,得到了泡顶对称轴上径向速度的分布方程.另外,采用实时激光全息干涉系统对不同液体流速下单乙醇胺吸收二氧化碳的传质过程进行了研究,通过CCD摄像机采集并记录下不同时刻的全息干涉条纹图.由干涉条纹图和浓度-折射率标准曲线,计算出传质达到稳态时气泡周围液相侧近界面浓度分布,近界面浓度及浓度边界层厚度.浓度分布呈指数衰减趋势,且浓度边界层厚度远远小于速度边界层厚度;随着液体流速的增加,气泡周围液相侧浓度边界层厚度和近界面浓度均减小.结合速度分布方程和对流扩散方程,推导出单乙醇胺水溶液吸收二氧化碳过程液相侧浓度分布模型.     

气液两相流水平绕流柱体的动态压降特性

压降是气液两相流绕流柱体时包含丰富流动信息的重要参数,对于压降的研究密切关系到两相流动系统的设计和运行.以空气和水为实验介质在泡状流、塞状流、弹状流和环状流四种流型下,研究了气液两相流水平绕流梯形柱体的动态压降特性.结果表明:泡状流和塞状流的动态压降有较稳定的波动,其时均值主要取决于液相流量;弹状流的动态压降变化剧烈,其时均值随两相雷诺数的分布比较均匀;环状流的动态压降变化比较平缓,其时均值随两相雷诺数的增加呈近似线性递增;在四种不同流型下,时均动态压降系数随两相雷诺数的增加都呈线性递减.这一结果为分析气液两相流绕流柱体的流动特性提供了有益的借鉴.     

环形超声速喷管内天然气流场特性

依据角动量守恒原理设计了一种用于天然气脱水的环形超声速喷管,建立了相应的物理和数学模型,并采用RNG κ-ε湍流模型对喷管内天然气流场特性进行了数值计算.结果表明,天然气进入环形超声速喷管后发生膨胀降温,在喷管出口处马赫数可达1.85,温度低达-70℃,天然气经旋流叶片产生旋流,离心加速度最大可达640 000g,在低...     

导流锥式超声速旋流分离装置流动特性

采用二维轴对称模型,以理想空气为介质对超声速旋流分离装置内的流场特性进行了数值模拟。同时搭建实验平台,对小压比条件下影响流场特性和分离性能的结构和操作参数进行了研究。研究结果表明:进出口压比为1.4同时排液通道外壁张角小于12°时,超声速喷管扩张段内在面积比达1.27的情形下仍不存在气动激波,同时对扩张段内存在激波产生的情况进行分析,得出其原因为在排液口内产生反向压缩波,并向喷管上游移动。通过实验研究得出,压比为1.4,面积比为1.27时超声速旋流分离器分离效率最高,达到20.5%。     

Ignition of porous bodies under conditions of counterflow nonstationary filtration of a gas

An analytical method for calculating the time characteristics of ignition of a porous body with outflow of an inert gas from the sample (counterflow nonstationary filtration) is developed employing the wave theory of ignition and an averaging technique using a certain weighting function. Numerical calculations confirmed the validity of the main assumptions of the theory on the stagewise nature of the ignition process and the wave mechanism of heating of the material. Complete qualitative and good quantitative agreement between conclusions of an approximate analysis and numerical results is shown. The error in determining the times of establishment of zero gradient and disturbance of temperature equilibrium does not exceed 50%. It is established that the equations of isothermal filtration are adequate for describing the process of gas escape from a porous body during ignition. It is shown that the gas mass flow can be calculated using a quasistationary approach. The region of applicability of the model of a semiinfinite body in ignition problems with counterflow nonstationary filtration of gases is determined. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 31–40, July–August, 2000.