BaF2替代BaO 对钡镓锗酸盐玻璃光学性质的影响

在摩尔分数组成x(BaO),r(Ga2O),r(GeO2)为0．20,0．15,0．65的玻璃中,分别以摩尔分数0．05,0．10．0．15和0．20的BaF2替代BaO,研究了氟化物对玻璃折射率和光吸收性质的影响。结果表明,在玻璃中加入氟化物．玻璃折射率和色散降低,玻璃的紫外吸收边向短波侧迁移,而红外吸收边无明显变化。不含氟化物的氧化物玻璃中含有大量的OH基．这些OH基在2．24μm、2．97μm和4．23μm附近引起光吸收．在含氟化物的玻璃中,2．24μm的吸收峰消失,而2．97μm和4．23μm附近的吸收大大减弱。讨论了各OH基吸收峰的起源,利用计算机技术对2．97μm附近的OH基吸收峰进行了高斯峰分离。玻璃在2．24μm的弱吸收可能来自H2O分子的一个伸缩模和两个振动模的结合(p 2ρ)．4．23μm吸收带是由与非桥O形成强氢键的OH基(T-OH…O^--T)伸缩振动引起,而中心位于2．7～3．2μm的OH吸收带为受不同程度氢键影响的OH基伸缩振动吸收．这些吸收带叠加导致OH吸收带出现非对称性加宽,吸收中心随玻璃中OH含量不同发生移动。     

正庚烷燃烧反应中间自由基的光谱测量

采用ICCD瞬态光谱探测系统和化学激波管,在点火温度1 408K,点火压力2.0atm,燃料摩尔分数1.0%,当量比1.0的条件下,拍摄了正庚烷燃烧过程中不同时刻的瞬态发射光谱,光谱曝光时间6μs,拍谱范围200～850nm。确认了在所拍光谱范围内主要是OH,CH和C2自由基的特征辐射光谱,表明小自由基OH,CH和C2是正庚烷燃烧过程中重要的反应中间产物。所拍时间分辨光谱显示,在正庚烷燃烧反应中,OH,CH和C2自由基一出现很快就达到其浓度峰值,但CH和C2自由基随着反应的进行迅速减少至消失,OH自由基持续的时间却长很多。实验结果为了解正庚烷燃烧反应微观过程和验证其燃烧反应机理提供了实验依据。     

H_2O和CO_2高温混合气体喷流红外辐射特性

利用数值仿真方法研究了H_2O和CO_2高温混合气体喷流的红外辐射特性。根据H_2O和CO_2两种气体的吸收特性,将红外波段划分为1.32~1.69μm、1.56~2.27μm、2.27~3.8μm、3.8~8.3μm和8.3~20μm五个波段。建立了基于某型发动机喷嘴的尾流红外辐射特性模型,并利用此模型分别研究了H_2O和CO_2高温混合气体喷流在这五个波段的辐射特性分布。仿真结果表明,喷流中H_2O含量越高,越有助于能量的扩散,因此喷流温度和辐射能量也越低;在高温喷流的辐射特性中,中波红外波段辐射能量最强,长波红外波段的最弱。     

高温高压下氮、氩对OH、O2辐射影响的光谱研究

 本文利用我们研制的棱镜谱仪探测技术研究了氢反应过程OH、O₂的激发辐射特性。研究表明，在高温高压下氩气、氮气减弱链式反应，降低OH辐射；但是，一定量的氩可以使O₂辐射加强。谱仪测量发现，O₂辐射迟于OH辐射，它直接证明了O₂在链中止后受激辐射。本文还观察了入射波激励和反射波激励下OH辐射强度及感应时间的变化过程。所用的光谱探测技术可用于冲击波激励或高速反应产生的高温高压激励辐射特性的研究。     

γ-Fe_2O_3中的氢含量

利用热中子透射法测定γ-Fe_2O_3的氢含量。利用差热分析、磁分析以及穆斯堡尔效应研究γ-Fe_2O_3的相变,实验结果表明在γ-Fe_2O_3结构中确实含有一定量的氢,当γ-Fe_2O_3结构中的阳离子空位被H~(1 ),Co~(2 ),Si~(4 ),P~(5 )等离子占据时,将有利于γ-Fe_2O_3晶体结构的稳定,从而使γ-Fe_2O_3转变为α-Fe_2O_3的相变温度有所提高。     

水溶液中Ca(OH)2粒径分布研究

本文利用激光粒度分析仪研究了石灰产地、石灰尺寸和液固质量百分比对石灰水合所得浆液中Ca(OH)2粒径的影响.结果显示,石灰尺寸和液固质量百分比对浆液中Ca(OH)2粒径分布影响较小,而产地对粒径有一定影响.将平均粒径为5μm的分析纯Ca(OH)2粉末制备成浆液,其粒径增大到13μm,表明Ca(OH)2在水中发生团聚.因此,单纯依靠改变制备条件或石灰来源,对于减小Ca(OH)2的粒径作用不大,必须采用其它措施如添加分散剂来减轻团聚并减小粒径.     

红外光谱的二硫化碳火焰光谱辐射特性研究

近年来,化工领域对二硫化碳需求日益增多,而二硫化碳具有易燃易爆等特点。在生产过程中易发生火灾事故,危害性极大,易造成经济损失和人员伤亡。在火灾事故危害研究中,火焰光谱研究极有必要。因为火焰光谱中含有大量信息,包括火焰温度、燃烧组分、各个波段的热辐射强度等信息。以二硫化碳燃料为研究对象,搭建了火焰光谱测试平台,主要由VSR红外光谱仪、伸缩装置、燃烧器组成,测试了5 cm燃烧尺度下二硫化碳、苯乙烯、乙腈、乙酸乙酯燃料在1～14μm红外波段上燃烧火焰光谱,以及二硫化碳分别与苯乙烯、乙腈、乙酸乙酯三种不同燃料按照1∶1混合的火焰光谱,获取了二硫化碳火焰光谱特征波段,构建了二硫化碳火焰光谱特征库。在燃料单独燃烧火焰光谱研究中,二硫化碳燃料燃烧时火焰呈蓝色不发烟,其火焰光谱辐射主要来自于高温下SO_2, CO_2和H_2O三种分子辐射,其中SO_2特征峰为4.05, 7.4和8.51μm, CO_2特征峰为2.7和4.3μm, H_2O特征峰为2.5, 2.7和5.5～7μm,乙腈、乙酸乙酯燃料燃烧火焰光谱特征基本一致,火焰光谱辐射主要来自于高温下CO_2, H_2O分子辐射,苯乙烯火焰光谱辐射除了高温气体辐射外还有较强的炭黑辐射,炭黑辐射中心波长在7μm,温度大约在414 K。除此之外,苯乙烯燃料与其他三种化学品相比,在3.6μm波段处存在独有的C—H健伸缩振动峰。二硫化碳火焰燃烧产物与苯乙烯、乙腈、乙酸乙酯三种燃料相比具有独有的SO_2分子,其在4.05, 7.4和8.51μm处存在特有的特征峰,这些特征峰可作为航天探测识别其火灾依据之一;在燃料混合燃烧火焰光谱研究中,二硫化碳与苯乙烯、乙腈、乙酸乙酯三种燃料混合燃烧时,燃烧火焰光谱特征基本相似,火焰光谱辐射主要来自高温下CO_2, H_2O和SO_2分子辐射,实验表明,在混合燃烧时,二硫化碳的火焰光谱特征峰未被其他燃料的组分干扰,特征峰仍然明显。这一研究结果可为后续利用航天遥感探测技术探测识别二硫化碳火灾研究奠定基础。     

水辅助下的OH自由基与CH_3OOH气相反应机理的理论研究

利用量子化学计算方法对单个水分子不存在与存在的情况下OH自由基与CH3OOH的气相氢抽取反应进行了理论研究.在BHand HLYP/6-311++G(2df,2pd)理论水平下优化了所有驻点的几何构型,在此基础上利用CCSD(T)/cc-p VTZ方法对所有驻点的单点能重新进行了计算.计算结果表明,OH自由基与CH3OOH反应的主要通道是OH自由基抽取CH3OOH中的-OH基团上的H原子.在单个水分子存在的情况下,反应的主要通道没有改变,但是水化过渡态的能量显著地降低,显然单个水分子对OH+CH3OOH反应具有催化效应.     

瞬态光谱法确定环氧丙烷DDT过程中起主导作用的基团

解决了燃料爆燃转爆轰(DDT)过程初始阶段弱辐射瞬态光谱测试问题、反应中间产物辐射相对强度定标问题和瞬态光谱测试系统同步控制问题后,从爆炸激波管的6个不同侧窗,拍摄了环氧丙烷DDT过程不同距离处的曝光时间为2～8 μs、分辨率达到0.2 nm的瞬态发射光谱。对所测光谱进行相对强度定标后,得到了主要反应中间产物光辐射强度随燃烧波阵面传播距离的变化曲线, 此曲线反映出DDT过程中反应中间产物的发展过程和其相应的浓度变化。结果显示,在爆燃阶段,燃烧气体的化学反应速率平缓增加,反应中间产物浓度逐渐增大;但在爆燃转爆轰的瞬间,反应急剧增快,反应中间产物的浓度突跃式地成倍增大。其中CO分子和CHO,OH自由基的浓度增幅显著大于其他反应产物,表明这几个基团是环氧丙烷爆燃转爆轰过程中起主导作用的重要基团。     

环氧丙烷爆燃转爆轰过程反应产物的光谱法确定

采用由增强型ICCD光谱探测器、SpectraPro-275光谱仪和DG535同步控制器组成的瞬态光谱测量系统,在解决了测试系统时间同步问题、弱光探测问题、提高光谱分辨率问题和波长定标及防止误触发问题后,在长4.0 m,内径为0.10 m的爆炸激波管侧窗,拍摄到了持续时间仅为数ms的环氧丙烷爆燃转爆轰过程的曝光时间为1～16 μs的瞬态发射光谱。测量系统的光谱分辨本领达到了0.2 nm 。根据由碳、氢和氧组成的小分子和自由基的特征辐射谱带带头波长值,经过对所测光谱进行分析和辨认,确定了在环氧丙烷的爆燃转爆轰过程中有OH,CH,C₂,C₃,CO,CO₂,CHO和CH₂O这些反应产物出现。这些反应产物的确定,是进一步分析环氧丙烷爆燃转爆轰过程的微观机理必不可少的实验依据。     

Deflagration-to-detonation transition in mixtures of finely divided ammonium perchlorate with submicron aluminum powder

Deflagration-to-detonation transition in binary mixtures of fine ammonium perchlorate (20-μm grains) with submicron ALEX-L aluminum powder (0.2-μm particles) is studied using high-speed photography and pressure recording with quartz crystal sensors. The test mixtures were loaded in thin-walled quartz tubes of inner diameter 10 mm. The charges had a porosity of ~50%. It has been shown that, even under very mild conditions (low-strength shell and a weak source of initiation), the deflagration mode of mixture combustion easily transforms into the detonation mode. The shortest length of the region of transition from deflagration to normal detonation (not more than 30 mm) was observed for a lean mixture, with an aluminum content of ~5%. The mechanism of transition to detonation involves the stage of convective combustion, resulting in the formation of a brightly luminescent crescent-shaped area behind the primary flame front, which, in turn, generates a forward (in the direction of propagation) and a backward wave. The forward wave gives rise to low-speed detonation, which later transforms into normal detonation. The pressure profile within the region of low speed detonation is measured. A comparison with similar experiments in which ALEX-L alu- minum powder was replaced by ASD-4 aluminum (4 μm particles) shows that ALEX-L sensitizes the mixture, resulting in a dramatic reduction of the length of the transition region, making it possible to produce normal detonation in low-strength shells.     

环氧丙烷爆燃转爆轰过程中产物C2的发射光谱

采用具有增强功能的光谱探测器增强型电荷耦合器件(Itensified charge coupled device,ICCD)和自行设计的光电转换器,应用激波管技术对环氧丙烷爆燃转爆轰过程的发射光谱进行了拍摄,探测器快门开启时间为2μs,在500-570nm之间进行了多次测量,由压力传感器监测的压力信号来判断爆燃转爆轰过程的重复性。实验结果表明：探测到了产物C2分子的发光光谱,它们可归属为斯旺(Swan)带的d^3∏g-a^3∏u跃迁中△v=-1.0的两个振动序列。各序列的带头分别为516．52nm,512．94nm,563．55nm,558．55nm,554．07nm,550．19nm和544．77nm。通过对所拍摄光谱的分析,推断中间产物C2是环氧丙烷爆燃转爆轰过程中的主要产物之一,并给出了C2自由基形成的几种可能的反应通道。     

The effects of flame generated turbulence for turbulent-induced deflagration to detonation transition

The turbulent deflagration to detonation transition (DDT) process occurs when a subsonic flame interacts with intense turbulence resulting in spontaneous acceleration and the onset of DDT. The mechanisms that govern the spontaneous ignition are deduced intricately in numerical simulations. This work experimentally explores the conditions that are known precursors to detonation initiation. More specifically, the experiment presented investigates the role of flame-generated compression as a cycle that continuously amplifies until a hotspot forms on the flame front and ignites. The study quantifies the compression comparatively against other flame regimes through ultra-high speed pressure measurements while qualitatively detailing flame generated compression through density gradients via schlieren imaging. Additionally, flow field measurements are quantified throughout the flow using simultaneous particle image velocimetry (PIV) and OH* chemiluminescence. The turbulence fluctuations and flame speeds are extracted from these measurements to identify the reactant conditions where flame-generated compression begins. Collectively, these simultaneous high-speed measurements provide detailed insight into the flame and flow field characteristics where the runaway process occurs. This work ultimately documents direct flow field measurements to extract the contribution of flame-generated turbulence on the turbulent deflagration to detonation transition process.     

An experimental investigation of the propagation mechanism of critical deflagration waves that lead to the onset of detonation

The reflection of a CJ detonation from a perforated plate is used to generate high speed deflagrations downstream in order to investigate the critical conditions that lead to the onset of detonation. Different perforated plates were used to control the turbulence in the downstream deflagration waves. Streak Schlieren photography, ionization probes and pressure transducers are used to monitor the flow field and the transition to detonation. Stoichiometric mixtures of acetylene–oxygen and propane–oxygen were tested at low initial pressures. In some cases, acetylene–oxygen was diluted with 80% argon in order to render the mixture more “stable” (i.e., more regular detonation cell structure). The results show that prior to successful detonation initiation, a deflagration is formed that propagates at about half the CJ detonation velocity of the mixture. This “critical” deflagration (which propagates at a relatively constant velocity for a certain duration prior to the onset of detonation) is comprised of a leading shock wave followed by an extended turbulent reaction zone. The critical deflagration speed is not dependent on the turbulence characteristics of the perforated plate but rather on the energetics of the mixture like a CJ detonation (i.e., the deflagration front is driven by the expansion of the combustion products). Hence, the critical deflagration is identified as a CJ deflagration. The high intensity turbulence that is required to sustain its propagation is maintained via chemical instabilities in the reaction zone due to the coupling of pressure fluctuations with the energy release. Therefore, in “unstable” mixtures, critical deflagrations can be supported for long durations, whereas in “stable” mixtures, deflagrations decay as the initial plate generated turbulence decays. The eventual onset of detonation is postulated to be a result of the amplification of pressure waves (i.e., turbulence) that leads to the formation of local explosion centers via the SWACER mechanism during the pre-detonation period.     

Experimental characterization of detonation initiation modes in a confined chamber flush-mounted with small-diameter ignition tubes

This work reports the experimental characterization of detonation initiation modes in a confined chamber in respect to the different types of reacting waves generated in various small-diameter ignition tubes. Depending on the length of the tube and mixtures composition, four types of reacting waves can be generated and utilized to initiate detonation in the main chamber, namely the over-driven detonation ignition wave, CJ detonation ignition wave, high-speed deflagration ignition wave and deflagration ignition wave. Based on the mechanisms of detonation initiation in the main chamber, four initiation modes can be observed: the direct initiation, the local explosion initiation, and the fast and slow deflagration-to-detonation transition (DDT) initiation. By comparing the detonation initiation positions and flame-tip velocities, the first two modes show appreciably shorter initiation distances compared to the DDT modes. The over-driven detonation ignition wave is shown to yield a high probability of direct initiation, while contrary to expectation, the high-speed deflagration ignition wave exhibits superior initiation performance compared to the CJ detonation ignition wave. It is illustrated that the energy decay through diffraction and the effect of precursor shock wave reflection on the wall of the rectangular chamber are viable factors responsible for this observation. The deflagration ignition wave is also shown to be able to rapidly initiate the detonation near the inlet of the chamber, albeit with a lower success rate.     

Deflagrations and detonations as a mechanism of hadron bubble growth in supercooled quark-gluon plasmas

We discuss the possibility that hadron bubbles formed in quark-gluon plasmas below or slightly above the critical temperature start growing by explosive deflagration or detonation processes. In these the phase transition takes place in a thin layer of discontinuity propagating outward from the point of bubble formation. Combustion theory is written in relativistic form, and possible physical deflagration and detonation bubble solutions conserving energy and momentum, producing entropy, and satisfying correct boundary conditions are classified and numerically discussed using the bag equation of state for quark matter. The implications of these solutions to ultrarelativistic nucleus-nucleus collisions and early cosmology are discussed.     

大气压射流等离子体中O及OH自由基的发射光谱在线诊断

OH自由基及氧原子在大气化学、表面处理及化学污染物分解等方面有着重要的作用。利用发射光谱技术在线测量了大气压射流等离子体中OH自由基紫外波段与O自由基777,844 nm波段的发射光谱。研究了OH自由基与氧原子光谱强度随放电功率及放电体系中所加入的氧浓度的变化。将实验测得的OH自由基光谱图与用Lifbase数据库模拟光谱图进行比较,估算了OH自由基的转动温度。结果表明:OH自由基的转动温度随放电功率的增加而增加,随工作气体流速的增加而减小。     

铝粉-空气混合物爆燃转爆轰过程及爆轰波结构

 在长为32.4 m、内径为0.199 m的大型长直水平管道中,对铝粉-空气两相流的燃烧转爆轰（DDT）过程及爆轰波结构进行了实验研究。对铝粉-空气混合物弱点火条件下DDT过程不同阶段的特征进行了分析,实验结果显示混合物经历了缓慢反应压缩阶段、压缩波加速冲击波形成阶段、冲击反应过渡阶段、冲击反应向过压爆轰过渡阶段和爆轰阶段,得到了混合物各阶段的DDT参数,由此进一步分析了DDT浓度的上、下限。在1.4 m爆轰测试段的4个截面的环向上各均匀安装8个传感器,对爆轰波结果进行测试,并对铝粉-空气混合物爆轰波的单头结构进行了分析。