大型水平管道中环氧丙烷-铝粉-空气混和物爆燃转爆轰的实验研究

 在长为32.4 m、内径为0.199 m的大型长直水平管道中,对环氧丙烷-空气两相流云雾及环氧丙烷-铝粉-空气三相流云雾的爆燃转爆轰（DDT）过程进行了实验研究。对弱点火条件下多相混和物DDT过程的不同阶段特征进行了分析,对比研究了不同浓度时混和物的燃爆情况。结果表明：浓度为513 g/m³的环氧丙烷-空气混和物及浓度为237和643 g/m³的环氧丙烷-铝粉-空气混和物均能在管道中完成爆燃向爆轰的转变,进入自持爆轰阶段,其胞格尺寸分别为0.28和0.50 m。     

瞬态光谱法测量环氧丙烷爆轰温度

采用具有像增强功能的光谱探测器——增强型电荷耦合器件ICCD和DG535同步控制器,应用激波管技术和光纤光谱方法,由压力传感器监测爆燃转爆轰的过程,在解决了同步控制,防止误触发等问题后,从爆炸激波管的侧窗拍摄到了环氧丙烷由爆燃转变为爆轰时刻的曝光时间为2μs,分辨率达到0·2nm的瞬态发射光谱。对所测光谱进行强度定标后,可直接得到环氧丙烷爆轰时刻的热辐射背景,用黑体辐射公式按照最小二乘法原则对其进行拟合,得到了环氧丙烷的爆轰温度为2416K。此爆轰温度的获得,为进一步分析环氧丙烷爆燃转爆轰过程的微观机理提供了实验数据。     

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。     

Combining SAD/SIR iteration and MR iteration in partial-model extension of proteins

There are two kinds of dual-space partial-model extensions which involve the direct-method program OASIS. The first kind, named SAD/SIR iteration, uses SAD/SIR information, while the second kind, named molecular replacement (MR) iteration, does not use that information. In general, the SAD/SIR iteration is more powerful since more experimental information is used. However, in most cases when protein structures are solved with the molecular replacement method, SAD/SIR information is not available. Thus the MR iteration is particularly useful for the completion of models from molecular replacement. The SAD/SIR iteration will be automatically used in OASIS for data sets containing SAD/SIR signals, while the MR iteration will be dedicated to data sets without SAD/SIR signals. The present paper shows that for data containing SAD/SIR signals, a combination of SAD/SIR iteration and MR iteration could lead to significantly better results than that obtained from the SAD/SIR iteration alone.     

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。     

Multipoint Ignition of a Gas Mixture by a Microwave Subcritical Discharge with an Extended Streamer Structure

The results of experimental studies on using an electrical discharge with an extended streamer structure in a quasioptical microwave beam in the multipoint ignition of a propane–air mixture have been reported. The pulsed microwave discharge was initiated at the interior surface of a quartz tube that was filled with the mentioned flammable mixture and introduced into a microwave beam with a subbreakdown initial field. Gas breakdown was initiated by an electromagnetic vibrator. The dependence of the type of discharge on the microwave field strength was examined, the lower concentration threshold of ignition of the propane–air mixture by the studied discharge was determined, and the dynamics of combustion of the flammable mixture with local and multipoint ignition were compared.     

用多种谱仪技术研究环氧丙烷点火的微观特性

利用OMA(光多通道分析系统)谱仪和单色谱仪技术研究了环氧丙烷冲击点火的微观特性.OMA谱仪观察到O,CH2O,C2,CH,CH3O,CO2,H2O等许多中间产物和最终产物.利用三台单色谱仪和压力传感器确定环氧丙烷冲击点火后这些产物出现的顺序并确定了它们的点火延迟时间和临界条件.     

Use of iterative OASIS with low resolution SAD laboratory X-ray source (Cr Kα) data sets

Anomalous scattering methods are widely used for phasing macromolecular structures. OASIS program works on a direct methods procedure and is used to break the phase ambiguity intrinsic in a single wavelength anomalous diffraction (SAD) experiment. An iterative phasing/model-building procedure for processing SAD data includes the initial direct method phasing of SAD data, density modification, automatic model building and direct methods phasing of SAD data with feed back from partial structure information. This dual-space procedure has been tested on two experimental Cr Kα SAD data sets, 2.3 ? for S-SAD and 2.4 ? for I-SAD, of an enzyme glucose isomerase with an approximate molecular weight of 44 kDa (388 residues). HYSS in PHENIX was used to locate the anomalous scatterers for both the data sets (11 sulfurs for 2.3 ? data and 9 iodines for 2.4 ? data). Phasing and density modification were carried out using OASIS, DM and model building was then carried out using ARP/wARP. Two iterative cycles were necessary for the successful structure solution and refinement of the 2.3 ? data set which built 384 residues out of 388. Regular ARP/wARP failed for the 2.4 ? resolution data and hence the modified version of REFMAC5 was used in ARP/wARP. A successful model could be built after three iterative cycles of OASIS using this modified version which built 382 residues out of 388 residues. Minimal manual model building was required at this stage and the structure determination was completed using regular REFMAC5. All the computations mentioned here were carried out using Pentium IV PC.     

铜铝复合管在空调蒸发器中应用的试验研究

主要针对铜铝复合管(CCA管)在空调蒸发器集气(液)管替代铜管应用进行了试验研究。从焊接工艺、弯曲性能和弯曲后抗压性能方面对9.52×0.7型号的铜铝复合管进行替代研究。结果表明:铜铝复合管焊接处的抗拉强度为114.1MP,延伸率为30%,可以满足产品要求。它具有良好的弯曲性能和弯曲抗压性能,经过不多于四次的弯曲试验,复合管集气管的极限压力为19MP,高于饱和制冷剂3倍工作压力。将铜铝复合管集气管的空调与原机在焓差实验室进行整机性能试验,结果表明:它们的制冷量相差10W,能效比基本不变,可以满足国家标准,对空调器的性能基本没有影响。同时在噪声实验室对整机进行噪声测试,测试结果显示,与原机型相比,在高中低三种风量状态下,噪声分别增加0.5/0.6/1 dB(A),满足原机型噪声标准。与铜管相比,在相同条件下,复合管集气(液)管可以降低成本29.2%。     

环氧丙烷点火的光谱研究

 利用多种光谱技术，提出了一种确定燃料冲击点火延迟时间的新方法。用这种方法所获得的实验值比国内外常用光电二极管（峰值波长约在800 nm）方法的所测值更接近实际值。环氧丙烷受冲击后，反应中间产物出现的时间是不同的，辐射强度也不同。在冲击波作用下，基团出现的顺序便可确定，它们依次为O、CH₂O、C₂、CH、CH₃O、CO₂、H₂O等，而O原子总是首先出现。     

The vaporization of a metallic target by a microsecond pulsed TE-CO2 laser radiation

The analysis of some new experimental data has proved that the evaporation of a stainless steel target in vacuum under the action of powerful TE-CO₂ microsecond pulsed laser radiation is initiated on the initial spike or not at all. The minimum “tail” duration to get evaporation was deduced as a function of the temporal pulse shape characteristics and the metal thermophysical properties. The vaporisation process was accompanied by nonequilibrium heating of vapour clouds leading to the target surface shielding. Two self-regulated evolutions were recognised which were attributed to the intense vaporisation and the target evaporation by the UV plasma emitted radiation, respectively.     

Study of magnetic properties of La2/3Sr1/3MnO3 nanotubes by Monte Carlo simulation

Magnetic properties of a single nanotube whose walls are constituted by nanograins of La_2/3Sr_1/3MnO₃ are studied by means of Monte Carlo (MC) simulation. The system is considered as composed by ferromagnetic grains which couple via dipolar interaction. The grain size distribution is obtained from experimental measurements and the inter-grain distance distribution is obtained from a study of distance distribution among magnetic particles distributed in the tube walls. We show the magnetization behavior for a tube of 700 nm of diameter and 3.5 μm length. We discuss the simulation for different temperatures and external fields. As a main result, we show that the distribution of inter-granular distances has a unique behavior for tubular structures of similar diameter/length aspect ratio, independent of their sizes. This scaling relation allows us to perform the simulations using a tube of smaller dimensions. We succeed in explaining the magnetization curves, finding that dipolar interaction is necessary to explain the experimental behavior and that the grains behave as having magnetic dead layers.     

High-efficiency hybrid brillouin/ytterbium fiber laser

A high-efficiency hybrid Brillouin/ytterbium fiber laser (BYFL) is demonstrated using a 41.5-cm-longhighly ytterbium-doped fiber and a 10-m-long single-mode optical fiber. The BYFL operates at 1 052.92nm, and the difference between it and the Brillouin pump (BP) wavelength matches the expected stimulated Brillouin scattering (SBS) Stokes shift. Its output power reaches 70.1 mW, which is more than seven times higher than the seeded BP power. The BYFL has an optical signal-to-noise ratio that is greater than 65 dB and has many potential applications, such as in controllable optical delay lines, sensing, and RF photonics.     

Influence of Burner Geometry on Heat Transfer Characteristics of Methane/Air Flame Impinging on Flat Surface

An experimental study has been conducted to find the heat transfer characteristics of methane/air flames impinging normally to a flat surface using different burner geometries. The burners used were of nozzle, tube, and orifice type each with a diameter of 10 mm. Due to different exit velocity profiles, the flame structures were different in each case. Because of nearly flat velocity profile, the flame spread was more in case of orifice and nozzle burners as compared to tube burner. Effects of varying the value of Reynolds number (600–2500), equivalence ratio (0.8–1.5) and dimensionless separation distance (0.7–8) on heat transfer characteristics on the flat plate have been investigated for the tube burner. Different flame shapes were observed for different impingement conditions. It has been observed that the heat transfer characteristics were intimately related to flame shapes. Heat transfer characteristics were discussed for the cases when the flame inner reaction cone was far away, just touched, and was intercepted by the plate. Negative heat fluxes at the stagnation point were observed when the inner reaction cone was intercepted by the plate due to impingement of cool un-burnt mixture directly on the surface. Different heat transfer characteristics were observed for different burner geometries with similar operating conditions. In case of tube burner, the maximum heat flux is around the stagnation point and decay is faster in the radial direction. In case of nozzle and orifice burner, the heat transfer distribution is more uniform over the surface.     

Tube vibration in a half-scale sector model of a helical tube steam generator

This paper presents the experimental technique and results of tests on a half-scale sector model of a steam generator helical coil tube bank. A series of tests was performed: (1) bench tests of a single helical tube in air; (2) tests of the sector model in air; (3) tests of the sector model in stationary water to determine natural frequencies and damping; (4) tests in flow. The experimental results reveal the general characteristics of the sector model and provide the information for the design evaluation of a helical tube array to avoid detrimental fluidelastic instability.     

曙光一号自由电子激光器(FEL)电子束发射度的分析

对曙光一号自由电子激光装置电子束发射度的测量值进行了深入的分析。严格地计算了不同发射度的束流在摇摆器内的传输,计算了发射度对激光功率的影响。由此得出,曙光一号自由电子激光器可以省去9米长的束流选择段。     

Turbulent flame propagation limits of polymethylmethacrylate particle cloud–ammonia–air co-combustion

Ammonia is a highly promising energy carrier for achieving a carbon-neutral society. The co-combustion of solid particle clouds–ammonia, in particular, is considered an efficient and feasible method of reducing carbon dioxide emissions. Understanding turbulent flame stabilization and extinguishment processes during the two-phase hybrid-mixture co-combustion of solid particle clouds–ammonia is essential for the co-combustion technology to be used in combustors. To the best of our knowledge, this is the first study to describe the turbulent flame propagation limits and associated mechanism on the co-combustion of solid particle clouds–ammonia–air. Turbulent flame propagation experiments on silica particle clouds–ammonia–air mixing combustion and polymethylmethacrylate (PMMA) particle cloud–ammonia–air co-combustion were conducted in this work using a novel fan-stirred constant-volume vessel to clarify the turbulent flame propagation limits and associate mechanism of solid particle cloud–ammonia–air co-combustion. Results showed that adding inert silica particles contracted the turbulent flame propagation limits of premixed ammonia–air mixtures. However, adding PMMA particles expanded and then contracted the turbulent flame propagation limits of a premixed ammonia–air mixture as the ammonia equivalence ratio increased from lean to rich. In the solid particle cloud–ammonia–air co-combustion, reactive particles induce two types of effects on the turbulent flame propagation limits of premixed ammonia–air mixtures: The local equivalence ratio increment effect is caused by adding volatile matter from preheated particles in the preheat zone of the flame front, and the heat sink negative effect is induced by the unburned particles.     

环氧丙烷爆燃转爆轰过程的瞬态发射光谱

采用爆光时间最短可达 5ns ,且具有像增强功能的光谱探测仪器ICCD ,用自行研制的光电转换器将光触发信号转变为电脉冲去外触发DG5 35数字延迟发生器 ,由DG5 35在设定的延迟时间后开启探测器快门并控制其曝光时间 ,从而使被测光信号与快门的打开达到同步 ,用芯径 1mm的塑料光纤从爆炸激波管端窗引出被测光信号至光谱仪色散后到达ICCD ,直接对环氧丙烷爆燃转爆轰 (DDT)的动态变化过程进行了实时光谱测量 ,拍摄到了环氧丙烷DDT过程不同时刻的、曝光时间为微秒量级的瞬态发射光谱。结果显示 ,在DDT初始阶段光辐射很弱 ,主要是原子线状光谱 ;在DDT中间阶段辐射已比较强 ,既有原子线状光谱 ,也有分子带状光谱以及热辐射背景 ;达到爆轰时光辐射强度呈数量级增加 ,原子线状谱、分子带状谱叠加在热辐射背景之上。     

Simulation of the two-phase flow in a thermosyphon using an inclined transparent tube with the lower-end closed and the upper-end open

The initial liquid charge of a vertically orientated two-phase closed thermosyphon for adequate thermal performance as determined theoretically by assuming that the condensate is in the form of a relatively thin film underestimates the amount determined by using experimental correlations. Knowing the physical details of the two-phase flow within the thermosyphon could explain this discrepancy. Because, however, of the difficulty of directly observing two-phase flow in an actual metal thermosyphon it was decided to investigate the two-phase flow by using air and water in a transparent tube. The tube that was used is closed at the lower end and open at the top end, was partially charged with water, and air was introduced into the closed end at increasing air flow rates until water droplets were just about to be expelled from the open end. The flow patterns occurring as a function of air flow rate were identified. The average liquid fraction in four sections of the tube was determined for different initial charge fractions and inclinations. It was observed that even at low air flow rates significant quantities of liquid were propelled up into the tube and that the flow is oscillatory. It was concluded that care would have to be taken in assuming a relatively thin and uniform liquid film in theoretically modelling a thermosyphon.     

放气系统流场的光学干涉测量

对于复杂的非定常流动,流场的测量往往要求无干扰、非接触,并且能够瞬时记录流场的信息。采用光干涉方法对放气系统流场的气压变化进行了测量。在加压法测量空气折射率的迈克尔逊双光束干涉实验装置中,引入特制激光功率计和孔状光阑,记录在自由放气过程中等倾条纹中心强度变化与时间的关系曲线,通过折射率与压强和质量流之间的对应关系,进行流场流速的无干扰、非接触的瞬时测量。实验证明这种测量方法响应度好,准确度高。