浸没循环撞击流反应器的压力脉动特性

The characteristics of pressure fluctuation in a submerged circulative impinging stream reactor (SCISR) were experimentally studied. The instantaneous signals of pressure fluctuation resulting from the turbulence in the SCISR were measured by sensors and recorded by a computer. The pressure signals at some special positions were sampled at different rotary speeds of propeller. After analyzing the signals with the Power Spectrum method, it was found that there was an inherent frequency in the dynamic pressure signals. The inherent frequencies of the point on the impinging plane were greater than 1000 Hz, so the pressure fluctuation was called high-frequency fluctuation. The fluctuation velocities with high inherent frequency resulted in a strong shear force field, which enabled the fluid to mix quickly on the micro-scale and the agglomerates of solid particles to disperse effectively.     

The Model of Thermal Response of Liquefied Petroleum Gas Tanks Partially Exposed to Jet Fire

This paper describes a mathematical model developed to study the behavior of liqupfied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone submodels which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.     

液化石油气储罐在喷射火焰作用下的热响应模型

Abstract This paper describes a mathematical model developed to study the behavior of liquefied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.     

升温升压过程对聚丙烯在超临界水中降解的影响

The effect of increasing course of temperature and pressure on polypropylene （PP） degradation in supercritical water was investigated for developing a process of recycling waste plastic. A group of experiments was carded out in a reaction system at a pressure of 26MPa, temperature of 380℃ or 400℃ for 30min, 70min, and 120min by Course One （the increasing course of temperature and pressure is via gaseous regions to supercritical regions）, and the other group was carried out at corresponding holding conditions by Course Two （the increasing course of temperature and pressure is via liquid regions to supercritical regions）. The time of the increasing courses was about 30min. Products were analyzed by Ostward-type viscometer, gaseous chromatography, and mass spectrometers （GC/MS）. Characterization results suggested that different increasing courses of temperature and pressure would give rise to different results, although they were treated under the similar holding conditions. It was also found that Course Two was more effective on PP degradation in supercritical water.     

超声场对氢键缔合体系解吸平衡的影响研究

Effects of ultrasound on intensification of separation process were investigated through the experiment of desorption equilibrium behavior. Tri-butyl phosphate (TBP) on NKA-X resin and phenol on a solvent impregnated resin, CL-TBP resin, were used for desorption processes. The desorption rate was measured with and without ultrasound. Desorption equilibrium was studied under various ultrasonic power densities or thermal infusion. Results showed that the desorption rate with ultrasound was much higher than that with normal thermal infusion. Both ultrasound and thermal infusion broke the desorption equilibrium existed at room temperature. However, after the systems were cooled down, the amount of solute desorbed in the liquid phase in the presence of ultrasound was much higher than that at the temperature corresponding to the same ultrasound power. It is proved that the initial desorption equilibrium was broken as a result of the spot energy effect of ultrasound.     

Adsorption Refrigeration Performance of Shaped MIL-101-Water Working Pair

A new metal-organic framework of MIL-101 was synthesized by hydrothermal method and the powder prepared was pressed into a desired shape. The effects of molding on specific surface area and pore structure were investigated using a nitrogen adsorption method. The water adsorption isotherms were obtained by high vacuum gravimetric method, the desorption temperature of water on shaped MIL-101 was measured by thermo gravimetric analyzer, and the adsorption refrigeration performance of shaped MIL-101-water working pair was studied on the simulation device of adsorption refrigeration cycle system. The results indicate that an apparent hysteresis loop ap-pears in the nitrogen adsorption/desorption isotherms when the forming pressure is 10 MPa. The equilibrium ad-sorption capacity of water is up to 0.95 kg·kg^-1 at the forming pressure of 3 MPa （MIL-101-3）. The desorption peak temperature of water on MIL-101-3 is 82℃, which is 7 ℃ lower than that of silica gel, and the desorption temperature is no more than 100 ℃. At the evaporation temperature of 10 ℃, the refrigeration capacity of MIL-101-3-water is 1059 kJ·kg^-1, which is 2.24 times higher than that of silica gel-water working pair. Thus MIL-101-water working pair presents an excellent adsorption refrigeration performance.     

0℃以下含SDS的甲烷水合物生成方式及过程对其分解速率的影响

The dissociation rates of methane hydrates formed with and without the presence of sodium dodecyl sulfate(methane-SDS hydrates),were measured under atmospheric pressure and temperatures below ice point to investigate the influence of the hydrate production conditions and manners upon its dissociation kinetic behavior.The experimental results demonstrated that the dissociation rate of methane hydrate below ice point is strongly dependent on the manners of hydrate formation and processing.The dissociation rate of hydrate formed quiescently was lower than that of hydrate formed with stirring;the dissociation rate of hydrate formed at lower pressure was higher than that of hydrate formed at higher pressure;the compaction of hydrate after its formation lowered its stability,i.e.,increased its dissociation rate.The stability of hydrate could be increased by prolonging the time period for which hydrate was held at formation temperature and pressure before it was cooled down,or by prolonging the time period for which hydrate was held at dissociation temperature and formation pressure before it was depressurized to atmospheric pressure.It was found that the dissociation rate of methane hydrate varied with the temperature(ranging from 245.2 to 272.2 K) anomalously as reported on the dissociation of methane hydrate without the presence of surfactant as kinetic promoter.The dissociation rate at 268 K was found to be the lowest when the manners and conditions at which hydrates were formed and processed were fixed.     

难降解芳烃化合物在超临界水中氧化的COD去除率的研究

Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achieve a high level more than 90% in a short residence time at temperatures high enough. As temperature, pressure and residence time increase, the COD removal efficiencies of the organic compounds would all increase. It is also found that temperature and residence time offer greater influences on the oxidation process than pressure. The difficulty in oxidizing these three compounds is in the order of nitrobenzene > aniline > phenol. In addition, it is extremely difficult to oxidize aniline and nitrobenzene to CO2 and H2O at the temperature lower than 873.15 K and 923.15 K, respectively. Only at the temperature higher than 873.15 K and 923.15 K, respectively, the COD removal efficiencies of 90% of aniline and nitrobenzene can be achieved.     

孔隙尺寸、盐度和气体组分对水合物相平衡的影响(英文)

An experimental device was set up to study the hydrate formation conditions. Effects of pore size, salinity, and gas composition on the formation and dissociation of hydrates were investigated. The result indicates that the induction time for the formation of hydrates in porous media is shorter than that in pure water. The decrease in pore size, by decreasing the size of glass beads, increases the equilibrium pressure when the salinity and temperature are kept constant. In addition, higher salinity causes higher equilibrium pressure when the pore size and temperature are kept constant. It is found that the effects of pore size and salinity on the hydrate equilibrium are quite different. At lower methane concentration, the hydrate equilibrium is achieved at lower pressure and higher temperature.     

Influence of bio-inspired flow channel designs on the performance of a PEM fuel cell

Performance of the proton exchange membrane fuel cell(PEMFC) is appreciably affected by the channel geometry. The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems. The same nutrient transport system can be mimicked in the flow channel design of a PEMFC, to aid even reactant distribution and better water management. In this work, the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates, on the performance of a PEMFC was examined experimentally at various operating conditions. A PEMFC of 49 cm~2 area, with a Nafion 212 membrane with a 40% catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm~(-2) on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate, and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants' relative humidity(RH), back pressure and fuel cell temperature on the performance of the fuel cell was examined; the operating pressure remains constant at 0.1 MPa. It was observed that the best performance was attained at a back pressure of 0.3 MPa, 75 °C operating temperature and 100% RH. The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa, and the other parameters such as operating temperature, RH and back pressure were set as 75 °C,100% and 0.3 MPa. The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field. It was observed that among the different flow channel designs considered, the leaf channel design gives the best output in terms of power density. Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design. The PEMFC with the interdigitated leaf channel design was found to generate 6.72% more power density than the non-interdigitated leaf channel design. The fuel cell with interdigitated leaf channel design generated5.58% more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.     

气液固三相并流系统流型的混沌识别

运用确定性混沌分析技术，研究了气液固三相并流系统散式鼓泡流、聚式鼓泡流、柱塞流、泡沫流及环状流压力波动信号的混沌动力学行为。结果表明，吸引子可以用来表征气液固三相并流系统的动力学行为，混沌特征参数相关维D2和K熵可以用来定量识别以上五种流型。以混沌定量识别为基础，给出了三相并流系统的流型图。     

中低负荷下脉动热管壁温信号的分形特性分析

运用功率谱、小波分解、相空间重构、关联维数计算等非线性分析方法对脉动热管壁面温度波动信号分析。表明:功率谱呈现连续谱线,时间序列存在自相似性,展现温度波动信号的混沌行为;小波分解表现出温度波动的分形特性;重构吸引子展现出4种不同的空间分形结构,说明温度信号波动属于分形下的混沌行为。计算分形维数与传热性能的关系,发现系统存在3~6个分形维;随嵌入维数的增加,分形速度关系为R134a大于丙酮大于去离子水,基本表现为分形维数越大,传热性能越好。并发现关联维和热阻成负相关关系。     

Flow Regime Transitions in an Internal‐Loop Airlift Reactor

The flow regime transitions of the riser and downcomer in an internal‐loop airlift reactor are investigated. Analysis of the effects of mean value, standard deviation and chaotic time series on pressure fluctuation signals is recorded to determine the transition of the hydrodynamics in the riser and downcomer of the internal‐loop airlift reactor. Two major chaotic invariants, the correlation dimension and the largest Lyapunov exponent, are employed to indicate the regime transitions. The regime transitions are determined by the sudden increase and decrease of the chaotic invariants, which are computed by the pressure fluctuation signals obtained by varying the gas flow velocity. The determination of chaotic invariants predicts that there is no heterogeneous phase existing in the downcomer of the internal‐loop airlift reactor. The experimental observations agree well with the predicted results.     

浸没循环撞击流反应器撞击区压力波动的混沌分析

浸没循环撞击流反应器撞击区的压力瞬态信号包含了该区域内流体的许多动态信息,为了分析这些动态信号,采用了一种新的非线性分析方法,即混沌分析.利用小波理论对信号进行过滤,采用重构相空间理论恢复已过滤信号的吸引子.利用数学方法计算刻画混沌吸引子的3个特征参数：关联维、K熵和最大Lyapunov指数.对不同螺旋桨转速及同一y平面上不同测量点位置上算得的特征参数值进行研究,研究结果显示浸没循环撞击流反应器撞击区流体具有混沌特性,而且3个特征参数在不同的螺旋桨转速下及不同的测量点位置具有相同的变化趋势.     

振动流化床中流动结构的混沌分析

在内径90mm、静床高800mm的高床层流化床中,用动态压力传感器检测了不同气速条件下普通流化床和振动流化床中沿轴向的压力脉动信号,通过小波变换对信号除噪后,用混沌理论对信号进行了分析.通过关联维数和Kolmogorov熵定量表征振动流化床中的流动结构特征.结果表明:压力脉动信号的关联维数和Kolmogorov熵能够描述振动流化床中的流化状态;振动流化床中床层的流动结构存在两个区,在近分布板区域为射流区,床层主体部分为均匀流化区.     

Studies on the Hydrodynamics of Chaotic Bubbling in a Gas‐Liquid Bubble Column with a Single Nozzle

In this work, the chaotic bubbling mechanism in a gas‐liquid bubble column with a single nozzle was investigated. The signal for the analysis was the time series of pressure fluctuations measured from a pressure transducer probe placed in the bubble column close to the nozzle. In order to study the bubbling process, statistical analysis, qualitative and quantitative nonlinear analyses were carried out for the pressure fluctuations. Power spectra used as standard statistical measures provided preliminary evidence that bubbling in the middle values of gas flow rates may be chaotic in nature. Phase plots provided a qualitative means of analyzing the fine geometry structure of the attractor reconstructed from the bubbling time signal. Positive finite estimates of the Kolmogorov entropy provided a quantitative evidence of behavior consistent with chaos. Besides previous diagnostic tools, the local nonlinear short‐term prediction was also used as a supplement method. It was found that the bubbling process exhibits a deterministic chaotic behavior in a certain range of the gas flow rate. When increasing the gas flow rate, the sequence of periodic bubbling, primary and advanced chaotic bubbling, and jetting or random bubbling were successively observed. However, no clear period doubling sequence leading to chaotic behavior was observed. The sharp loss of the ability to predict the pressure signal successfully with the nonlinear prediction method provides the strongest evidence of the presence of the chaotic bubbling. The variations of the nonlinear invariants, such as the Kolmogorov entropy and the correlation dimension together with the plot of the correlation integral with the operation conditions, might be developed as potential and effective quantitative tools for flow regime identification of the bubbling process.     

Experimental comparison between acoustic and pressure signals from a bubbling flow

Experiments were performed on both the acoustic and pressure signals produced by bubbles formed from an underwater nozzle. The data were analyzed by a comprehensive set of spectral and nonlinear-dynamical techniques. As air flow rates increase, it is well known that such flows became chaotic. However, the present study of both acoustic and pressure signals showed that chaos could appear in different regimes and was manifested in different ways in the acoustic and pressure signals. The use of different time delays for the chaotic analysis of acoustic and pressure signals were found necessary. The acoustic signals offer data primarily on the bubble size while the pressure signals offer data primarily on the bubble production rate. The present results suggest that chaos can appear in the bubble size and bubble production rate independently.     

汽液固三相流动沸腾传热系统的非线性特性

运用功率谱分析、自相关分析、相图、关联维数和K熵等非线性分析技术对汽液固三相流动沸腾传热系统中的温度波动信号进行了定性和定量研究.研究表明：此类系统具有非线性混沌特性;定量计算结果表明,系统存在2～3个分维,K熵的变化也具有同样的趋势,且为有限正值;传热特性和非线性特征量之间有一定的关系,即颗粒体积含量越大,非线性特征量越大,传热系数越大.     

气液两相流中压力波动信号的混沌分析

对气液两相垂直向上并流中压力波动信号的混沌分析表明：外界噪声的干扰不可避免地会进入压力波动信号,从相空间内的吸引子图可明显地观察到噪声的存在,实验中采取多种手段,尽可能地把噪声的干扰降到最低极限,为提取反映系统特征的有效信息作前期准备。将预处理过的数据进行混沌分析得到,气液两相流的压力波动信号特征由两部分组成,低频部分（大气泡的运动或大尺度气液波动）和高频部分（如液体脉动、界面湍动等）。并且对应于不同操作条件下的流动体系,相关分维和Ｋｏｌｍ ｏｇｏｒｏｖ 熵均有较大变化,由此可区分流型。研究表明,对压力波动信号的混沌分析有助于深入理解系统的动力学特征。     

竖直上升螺旋流内瞬态压力波动信号混沌吸引子形态特性

为了探讨湍流状态下(雷诺数Re=1756~3512)旋流静态混合器内混沌拓扑结构演化规律,对采集的360组竖直上升螺旋流瞬态压力波动时间序列进行相空间重构,通过在其混沌吸引子域中放置参考截面,考察旋流静态混合器内瞬态流混沌吸引子形态特征量与雷诺数、轴向位置和径向位置之间的关系. 结果表明,轴截面内径向二次流为不同尺度强制涡和自由涡组合的兰金涡,在rm/R≤0.3和rm/R>0.8(rm为测量点到截面中心距离,R为混合管半径)处混沌吸引子特征量随Re增大而减小,而0.4≤rm/R≤0.8处主体区内压力波动信号混沌吸引子特征量随Re增大呈先增大后减小再变大的趋势. 瞬态压力波动信号混沌吸引子形态特征量对漩涡结构演化敏感,有助于理解竖直上升螺旋流的非线性混沌动力学机制.