Diffusion coefficients of natural gas in foamy oil systems under high pressures

The diffusion coefficient of natural gas in foamy oil is one of the key parameters to evaluate the feasibility of gas injection for enhanced oil recovery in foamy oil reservoirs. In this paper, a PVT cell was used to measure diffusion coefficients of natural gas in Venezuela foamy oil at high pressures, and a new method for deter- mining the diffusion coefficient in the foamy oil was de- veloped on the basis of experimental data. The effects of pressure and the types of the liquid phase on the diffusion coefficient of the natural gas were discussed. The results indicate that the diffusion coefficients of natural gas in foamy oil, saturated oil, and dead oil increase linearly with increasing pressure. The diffusion coefficient of natural gas in the foamy oil at 20 MPa was 2.93 times larger than that at 8.65 MPa. The diffusion coefficient of the natural gas in dead oil was 3.02 and 4.02 times than that of the natural gas in saturated oil and foamy oil when the pressure was 20 MPa. However, the gas content of foamy oil was 16.9 times higher than that of dead oil when the dissolution time and pressure were 20 MPa and 35.22 h, respectively.

Modeling of fluid dynamics interacting with ductile fraction propagation in high pressure pipeline

This paper presents a computational model for the fluid dynamics in a fractured ductile pipe under high pressure. The pressure profile in front of the crack tip, which is the driving source of crack propagation, is computed using a nonlinear wave equation. The solution is coupled with a one dimensional choked flow analysis behind the crack. The simulation utilizes a high order optimized prefactored compact-finite volume method in space, and low dispersion and dissipation Runge-Kutta in time. As the pipe fractures the rapid depressurization take place inside the pipe and the propagation of the crack-induced waves strongly influences the outflow dynamics. Consistent with the experimental observation, the model predicts the expansion wave inside the pipe, and the reflection and outflow of the wave. The model also helps characterize the propagation of the crack dynamics and fluid flows around the tip of the crack.

高压辊磨机用硬质合金柱钉的磨损和断裂行为

硬质合金柱钉性能的好坏直接影响高压辊磨机的使用寿命和生产效率,但关于柱钉的力学性能和使用性能的相互对应关系缺乏研究,导致在使用过程中缺乏硬质合金设计标准。本文通过研究柱钉硬度、抗弯强度和断裂韧性等性能特性对柱钉的耐磨性和抗断裂性能的影响规律,获得了破碎高硬石英岩的理想柱钉。结果表明:影响柱钉断裂数量的主要因素是断裂韧性,而非抗弯强度;随着断裂韧性从16.21 MPa·m^(1/2)增大至21.57 MPa·m^(1/2),抗疲劳断裂能力提升,断裂数量百分比从3.77%降低至0。柱钉的磨损主要为磨粒磨损,随着硬度从HRA 86.2增大至HRA 88.3,抗磨损性能提升,磨损速率从7.92μm/h降低至2.33μm/h。对于石英含量高达64.23%、单轴压缩抗压强度达159 MPa的矿石破碎,当柱钉的硬度达到HRA 87.8、断裂韧性达到19.55 MPa·m^(1/2)时,能有效抑制柱钉的磨损和断裂。

坚硬顶板高压磨料射流侧向切顶煤柱卸荷技术研究

针对坚硬顶板下临空巷道存在的高应力、大变形、难支护等问题,分析了磨料射流能量分布情况,研究了磨料颗粒及高压水射流的冲击破岩作用。基于“砌体梁”原理,建立不同岩性条件下的岩层周期破断力学模型,研究了巷道侧向切顶条件下上覆岩层断裂情况,采用数值模拟分析切顶前后煤柱应力变化情况,提出了磨料射流侧向切顶煤柱卸荷技术。现场试验结果表明,采用磨料射流切顶后巷道高度变形量减小38.7%,宽度变形量减小45.8%,巷道变形得到有效控制。同时,切顶后每日最大总能量降低85.5%,平均每日总能量降低82.6%。验证了磨料射流侧向切顶对坚硬顶板的弱化效果,为坚硬顶板弱化治理提供了一种新的技术手段。

动态高压微射流协同糖基化处理对β-乳球蛋白热稳定性和结构的影响

采用动态高压微射流(dynamic high pressure microfluidization,DHPM)协同葡聚糖糖基化处理对β-乳球蛋白(β-lactoglobulin,β-Lg)进行改性,研究其热稳定性和结构的变化。结果表明,β-Lg的峰顶温度为73. 48℃,经DHPM不同压力(40、80、120 MPa)处理后,其热稳定性先下降后上升,但经DHPM协同糖基化处理后,其热稳定性均呈上升趋势。理化分析结果显示,80 MPa DHPM协同糖基化处理的β-Lg具有最低的游离氨基酸含量(2. 20 mg/m L)和最高的褐变程度(A294=1. 092,A420=0. 062),说明DHPM预处理可以促进β-Lg-葡聚糖的糖基化反应,且80 MPa为最佳处理压力。结构分析表明,DHPM处理可明显提高β-Lg的表面疏水性和自由巯基含量,降低其内源荧光强度,使其发生二级结构变化。经DHPM协同糖基化处理后,β-Lg的表面疏水性有所降低,但仍高于天然β-Lg的表面疏水;自由巯基含量呈现先降低后升高趋势,在80 MPa时明显高于天然β-Lg,内源荧光强度随着压力的增加呈先降低后上升的趋势,但均明显低于天然β-Lg的内源荧光强度。因此,DHPM 80 MPa预处理样品具有最高的热稳定性和糖基化程度,且β-Lg的糖基化程度越高,其热稳定性越好。

面向碳-碳复合材料的激光和水射流组合制孔工艺仿真建模和实验研究

针对碳-碳复合材料在孔加工过程中容易出现撕裂、分层等缺陷的问题,提出了碳-碳复合材料的激光和高压磨料水射流组合制孔工艺。先采用激光对碳-碳复合材料进行预制孔,再利用高压磨料水射流进行切割扩孔,对水射流直接冲击制孔和激光与水射流组合工艺制孔仿真过程中碳-碳复合材料内部应力和层间位移大小进行对比分析。结果表明,利用激光与高压磨料水射流组合制孔工艺,可以有效减少碳-碳复合材料在孔加工过程中受到的应力,从而减少其出现分层的现象,改善和提高了碳-碳复合材料孔的质量。通过开展相应的实验,验证了激光与水射流组合加工工艺去除碳-碳复合材料可获得较好的制孔效果,证实了模型的正确性。

微米γ-Al_2O_3高压相变制备亚微米α-Al_2O_3

采用微米γ-Al_2O_3为原料,利用国产铰链式六面顶压机,在5 GPa压强下,经不同的温度和保温时间,实现了由γ-Al_2O_3向α-Al_2O_3的相转变。X射线衍射分析结果表明,得到的粉体和块体材料中均仅含α-Al_2O_3单相;扫描电镜结果显示合成的α-Al_2O_3最小晶粒尺寸为80 nm。在5 GPa压强、800℃条件下合成的样品平均晶粒尺寸为340 nm,实现了用微米γ-Al_2O_3高压相变制备亚微米α-Al_2O_3。与常压烧结方法相比,采用高温高压烧结,可在600℃实现γ-Al_2O_3向α-Al_2O_3的转变,显著降低α-Al_2O_3材料的合成温度。

Research on Prediction Model for Erosion and Abrasion of Barrel Based on LSSVM

To predict the erosion and abrasion of high bore pressure tank gun barrel, the least square support vector machine (LSSVM) algorithm was used. Based on the gun firing test data, the prediction model for barrel's erosion and abrasion was established. It was adopted to predict the wear increment of gun barrel. The results show that the prediction values given by the model coincide with the measured data better, and the model can predict the barrel's wear accurately and rapidly.

Dynamic fracture toughness of high strength metals under impact loading:increase or decrease

An elusive phenomenon is observed in previous investigations on dynamic fracture that the dynamic fracture toughness （DFT） of high strength metals always increases with the loading rate on the order of TPa.m1/2.s-1. For the purpose of verification, variation of DFT with the loading rate for two high strength steels commonly used in the aviation industry, 30CrMnSiA and 40Cr, is studied in this work. Results of the experiments are compared, which were conducted on the modified split Hopkinson pressure bar （SHPB） apparatus, with striker velocities ranging from 9.2 to 24.1 m/s and a constant value of 16.3 m/s for 30CrMnSiA and 40Cr, respectively. It is observed that for 30CrMnSiA, the crack tip loading rate increases with the increase of the striker velocity, while the fracture initiation time and the DFT simultaneously decrease. However, in the tests of 40Cr, there is also an increasing tendency of DFT, similar to other reports. Through an in-depth investigation on the relationship between the dynamic stress intensity factor （DSIF） and the loading rate, it is concluded that the generally increasing tendency in previous studies could be false, which is induced from a limited striker velocity domain and the errors existing in the experimental and numerical processes. To disclose the real dependency of DFT on the loading rate, experimentsneed to be performed in a comparatively large striker velocity range.

Heat Treatment of Centrifugally Cast High-Vanadium Alloy Steel for High-Pressure Grinding Roller

The roller is one of the main parts of a high-pressure grinding roller, which is a type of highly efficient ore crushing equipment. Its working life is strongly affected by the materials used. In this paper, a new kind of roller material, the high-vanadium alloy steel （HVAS）, was investigated. The results showed that the as-cast microstructures of the HVAS roller contained martensite, residual austenite, and alloy carbides. The HVAS sample quenched at 1,080 ℃ had a high hardness, and it had much higher compressive strength and abrasive wear resistance after tempering at 560 ℃ for 30 rain. The mechanical properties of the HVAS are more sufficient than the existing roller materials, which are feasible for larger machine design.

Accident at Fukushima Dai-lchi Nuclear Power Plant--Lessons Learned for the Czech Republic

Accident at Fukushima Dai-ichi nuclear power plant significantly affected the nuclear industry at time when everybody was expecting the so called nuclear renaissance. There is no question that the accident has at least slowed it down. Research on this accident is taking place all over the world, in this paper, we present the findings of research on Fukushima nuclear power plant accident in relation to the Czech Republic. The paper focuses on the analysis of human performance during the accident. Lessons learned from the accident and main human errors are presented. First, the brief factors affecting the human performance are discussed. They are followed by the short description of activities on units 1-3. The key human errors in the accident mitigation are then identified. On unit 1, the fuel damage was probably impossible to prevent, however, on units 2 and 3, it could be probably prevented.

基于三维扫描的水射流冲击下再生混凝土断面形貌特征分析

国内每年因旧建筑物拆除产生的建筑垃圾超过17亿t,造成建筑垃圾快速增长的主要原因是现有拆除方式侧重于高效拆除和定向倒塌,而忽略了对于混凝土原材料和构件再利用性能的保留。将混凝土旧建筑物中仍具备再利用价值的主要承重构件无损拆除,作为再生混凝土构件再利用成为目前研究的重点问题。再生混凝土断面粗糙度直接影响新旧混凝土构件的界面连接性能,基于此考虑,开展了高压磨料水射流拆除混凝土旧建筑物的试验研究,提出了一种基于三维扫描数据在宏观层面定量分析混凝土断面粗糙度的简单计算方法,对比分析了水射流冲击下普通混凝土和加速老化混凝土的断面形貌特征,使用扫描电子显微镜观察了混凝土骨料与水泥浆体结合状态的微观特征。结果表明:在水射流冲击下,普通混凝土断面纹理深度为0~4.0 mm,加速老化影响了混凝土的破碎效率,面对水射流冲击时纹理深度提升了0.5~1.0 mm。基于点云重构封闭曲面数据计算的普通混凝土断面粗糙度在1.11~1.19,加速老化混凝土的断面粗糙度普遍提升了4.0%~14.9%。水射流冲击下的混凝土破坏模式主要以压缩剪切和拉伸剪切破坏为主,断面区域大致可分为光滑区、过渡区和撕裂区。研究结果可为水射流拆除混凝土旧建筑物的工艺优化和工程应用提供指导。

碳纤维复合材料加工技术探析

碳纤维增强树脂基复合材料是一种新型的复合材料,具有良好的性能,广泛应用于航天航空等领域。但由于其复杂的组成结构,其属于难加工材料。如果加工方式选择不当,则容易造成工件尺寸偏差和表观质量不合格。因此,本文对碳纤维复合材料的加工技术进行了探析,阐述了复合材料机械加工的机理与特点,介绍了高压磨料水射流、激光束加工两种特种加工方法,其具有常规机械方法无法比拟的优点。

基于纤维缠绕超高压混合磨料罐的设计优化研究

超高压前混合磨料罐需要承担磨料的存储和相应的压力,所以对其强度具有非常高的要求,因此提出了基于纤维缠绕的超高压前混合磨料罐的优化设计,然后基于网格理论开展设计,对磨料罐的筒身与封头段等进行了力学的特性分析,并得出筒身和封头需要缠绕的厚度和角度。经对磨料罐的上罐口进行结构性的优化设计后,利用有限元软件加以验证分析,主要针对纤维铺层的应力和应变进行分析,再和传统的磨料罐加以对比研究。

Synthesis of C_3N_4 crystals under high pressure and high temperature

C\-3N\-4 crystals with the size of several micrometers have been synthesized from C\-3N\-4H\-4 in the presence of nickel\|based alloy or cobalt as catalyst under high pressure of 7 GPa and temperature of about 1400℃ for 10 min. Scanning electron microscopy, energy\|disperse X\|ray analysis, and X\|ray diffraction were used to examine the grown crystals. The general rule on selecting the starting materials for synthesis of carbon nitride crystals at high pressures and high temperatures is suggested.

磨料浆体射流切割技术的研究

针对国外磨料浆体射流切割技术在我国推广和应用的瓶颈问题,研制出一种新型的磨料浆体射流切割工艺设备。介绍了系统的工作原理及优势所在,并通过一系列试验及分析,初步掌握了该种切割技术的切割性能及影响因素。

高压磨料射流割缝技术及其在防突工程中的应用

分析了煤层巷道煤与瓦斯突出机理,提出了整体卸压理念,开发了高压磨料射流割缝防突技术并且在煤层巷道掘进工作面进行了实际应用.应用结果表明:该技术可用于具有突出或冲击危险的煤层,可以使钻孔之间相互沟通,造出缝隙,使煤体得到充分卸压、煤体中的瓦斯得到排放和应力得到解除,为掘进工作提供较为安全的工作环境.

磨料水射流冲击材料壁面的模拟与试验

为了在小尺度范围内揭示磨料水射流的作用机理,对工作压力为250 MPa时磨料射流在靶距为3.0 mm处的断面上的射流中心、射流外缘以及两者平均速度进行计算.利用有限元软件对不同厚度的钢板在上述3个速度下进行冲击计算.结果表明:边缘处由于磨料速度较小,对钢板的冲击产生较小的形变,钢板表面出现微小的破坏,磨料被反弹;磨料速度在平均速度附近时对钢板的冲击使钢板出现较大的形变,且表面的破坏较明显,此时磨料颗粒嵌入到钢板内;在射流中心处由于磨料的速度较高,直接将钢板穿透,钢板的形变量比边缘处磨料作用时的更小.在相同条件下进行试验,利用光学轮廓仪对实际切割断面的粗糙度进行显示以验证模拟结果,模拟结果与试验结果基本吻合.

高压水射流切割技术发展及应用现状

作为一种高能束流加工技术,高压水射流切割因其独特的切割模式,被广泛应用于机械加工、食品医疗、海洋工程等领域。介绍了高压水射流切割技术的切割机制及磨料混合机制,并就其研究进展和应用现状做了相关总结和概括,为今后水射流技术的研究和发展提供了参考。

高压磨料水射流水下切割不锈钢的实验研究

采用高压磨料水射流切割装置,用3档切割压力(320、350、380 MPa),分别在2、5、8 mm切割靶距和6种切割速度下,对不锈钢进行水下切割实验。分析切割压力、靶距、切割速度等参数对切割厚度的影响,建立基于实测数据的半经验数学模型。对获得的实验数据进行分析表明,切割压力、靶距和速度与被切割厚度呈现指数关系。