预混气体爆轰胞格结构定性仿真建模*

预混气体的爆轰波具有典型的胞格结构,主要用烟熏技术记录下爆轰波在管道中由横波、入射波和马赫杆交合的三波点运动轨迹。胞格宽度λ作为胞格的特征长度,爆轰的胞格尺寸也是判断可燃混合气体最基本的特征参数,基于胞格尺寸,爆轰的其他动态参数,如临界管径、爆轰极限和直接起爆的临界能量等都可以通过联立爆轰胞格尺寸得到。爆轰胞格结构在研究预混气体爆轰波传播特性方面意义重大,不同初始条件对胞格尺寸都会产生一定的影响,本文通过定性与定量相结合的建模方式研究分析爆轰胞格尺寸与初始条件的关系,根据与实验数据的定量比较,验证定性仿真的正确性和可行性。     

初始条件影响气体非稳定爆轰波在弯管中传播特性的实验研究

对丙烷 氧气 空气的预混气体非稳定爆轰波通过圆形截面弯管时传播特性包括弯管角度以及预混气体的初始浓度和初始压力的影响因素进行了初步的实验研究 .结果表明 ,初始条件对可燃气体非稳定爆轰波经过弯管时爆轰参数有很大影响 .随着弯管角度的增加 ,弯管后非稳定爆轰波强度先增加后减小 ,弯管前非稳定爆轰波强度变化很小 ;随着预混气体的初始浓度和初始压力的增加 ,弯管前后非稳定爆轰波强度增加 .这一实验研究结果对安全使用管道阻火器具有重要的实际意义     

初始条件对管道内爆轰波传播特性影响研究

实验研究了C_2H_2+2.5O_2+nAr气体爆轰波传播特性随初始条件变化规律。采用光电二极管测量爆轰波传播速度,烟迹法记录爆轰波胞格结构。结果表明:随初始压力降低,爆轰波在管道内出现稳态式、快速波动式、失效式传播模式。稳态式传播时爆轰速度局部波动小于平均速度的5%,初始压力对爆轰速度几乎无影响;快速波动式传播时爆轰速度局部波动增大,平均速度发生衰减,衰减幅度随初始压力降低而增大。随Ar稀释浓度增加,爆轰速度逐渐减小,且Ar稀释浓度对爆轰速度的影响显著。胞格尺寸随初始压力的降低而增大;稳态气体胞格结构规整;而非稳态气体胞格结构杂乱。     

甲烷预混气螺旋爆轰的定量不稳定性研究

针对CH4这种特别气体,对其实验结果运用数字化处理方法研究CH4稳定性.在内径50.8 mm圆形管道内获得CH4+2O2预混气在不同初始压力条件下的胞格爆轰结果并使用烟膜记录,且测得的平均爆轰速度数据与CJ爆轰速度接近,在初始压力高于5 kPa时爆轰可稳定传播.烟膜上形成的三波点轨迹十分不规则.为减少人为误差,使用改进后的数字化处理烟膜图像的技术方法,从烟膜轨迹中得出柱状图及自相关函数结果,发现CH4+2O2是一种爆轰十分不稳定的气体,并给出CH4+2O2预混气的爆轰胞格尺寸及差距,结果显示人为测量结果偏大而数字化处理方法更为准确.这种方法能计算CH4+2O2预混气胞格尺寸及不稳定度,完善了定量化预混气不稳定程度的方法.     

初始压力对狭缝内爆轰传播特性影响的实验研究

在高度H=1 mm,宽度W=20 mm的狭缝内,实验研究了不同初始压力(P_0=10~40 k Pa)下化学恰当比的C_2H_4/O_2预混气的爆轰传播特性。采用烟迹法记录爆轰胞格结构,同时采用高速摄影捕捉火焰面。实验结果表明,随着初始压力降低,爆轰波的化学反应诱导区距离增大,壁面条件(如摩擦、导热)的影响增强,导致火焰传播的速度震荡加剧,爆轰波传播从多头模式向单头模式过渡,并可出现多次起爆或者熄爆等复杂现象。此外,稳定自持传播爆轰波的速度亏损会随初始压力降低而增大,但详细规律还需进一步研究。     

狭缝内C2H4/O2预混气的起爆与速度亏损

受限通道内的预混气起爆与传播受外界因素影响较大,如初始压力、通道尺寸等。通过自制不同高度的狭缝通道,考察了狭缝高度和初始压力对C_2H_4/O_2可燃预混气起爆特性及传播过程的影响。结果发现:改变初压和狭缝高度确实对预混气起爆有较大影响,尤其是狭缝高度的不断降低可能获得不同于常规管道的DDT特性;爆轰波的速度亏损同时与初压和狭缝高度有关,其值正比于H~(-0.8)P_0~(-0.5)。考虑到实验结果的局限性,后续还需进行多次重复实验,以获得更加准确的实验数据。     

管道内障碍物扰动对煤气爆炸特性影响的数值模拟

结合实验研究,采用迎风型WENO格式和两阶段化学反应模型就管道内障碍物对煤气/空气预混气体爆炸火焰的影响规律进行了数值研究,探讨了自管道右端面反射产生的压缩波与火焰传播的相互作用规律,得出了该反射波是造成火焰速度下降的原因.在此基础上,分析了障碍物对火焰的作用机理以及由此诱发的流场变化规律.结果表明,由于障碍物的加入,爆燃波发生多次反射,使得可燃混合气体得到充分压缩,温度和压力增加,化学反应速率提高,火焰强度得到加强.同时,从障碍物中传播出去的爆燃波经壁面反射后形成三波点,使得该处火焰速度升高,随着三波点的向前传播,由于能量的耗散,火焰速度逐渐下降.这些结论为爆炸场预估、防火防爆和爆轰推进中有效控制可燃气体的燃烧速率和火焰传播速度提供了重要的理论依据.     

甲烷煤尘爆轰参数计算及实验研究

为研究甲烷煤尘爆轰过程中气固两相耦合效应及量化关系.采用理论分析和实验的方法,计算了不同体积分数的甲烷、不同质量浓度的煤尘及甲烷煤尘混合物在燃烧、爆轰过程中爆压和爆速等重要参数.理论分析揭示了燃烧波、爆轰波的传播特征,爆炸实验验证了燃烧波和爆轰波传播规律.研究结果表明:甲烷的燃烧加速煤的热解,煤粉挥发份析出较快;初始阶段甲烷气体的反应速度快,压力上升速率快;煤在高温下快速热解出可燃气体,并发生闪燃;因此,甲烷煤尘混合物爆轰比单一的气相、固相爆轰的分析和测试困难的多.该研究成果对于煤矿安全生产防治抑爆技术等应用具有参考价值.     

预混火焰微小尺度燃烧传播机制研究

采用实验与数值模拟相结合的方法对预混气体火焰在平板狭缝中传播进行了研究,利用高速数字摄像系统对传播过程进行抓取。结果表明,当狭缝高度一定时,火焰的熄灭常数与临界火焰速度呈现的是近似直线关系。并对化学反应放热、壁面散热等与预混气体火焰传播与淬熄有关因子之间的内在联系进行分析,总结出预混气体火焰在平板狭缝中的传播与熄灭规律。对判断火焰在狭缝中是否淬熄提供参考,对选用阻火器及设计阻火芯提供一定的理论依据。     

初始压力对爆轰波在管道内传播的影响

建立爆轰管道研究不同初始压力下爆轰波在管道内传播规律.选用CH4+2O2气体,采用光纤探针测量爆轰波在管道内的传播速度,采用烟迹法记录爆轰波胞格结构.结果表明:爆轰波在管道内传播时出现5种不同传播模式,分别为稳态式、快速波动式、结巴式、驰振式与失效模式.在稳态传播模式下,爆轰波局部速度波动很小且平均速度接近理论爆轰CJ速度,并呈现多头胞格结构.随着初始压力的降低,爆轰波局部速度波动增加且其平均速度产生衰减.在驰振式爆轰解耦处,爆轰波胞格结构消失,过载爆轰时,重新形成胞格结构.进一步降低初始压力至爆轰失效时,则无胞格结构.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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