油田注水开发中水嘴节流与地层渗流耦合研究

配水器的选取会对油田注水效果产生明显影响。为精确地描述注水井注入过程中井底压力和流量的动态响应,本文在传统的内边界井处理模型的基础上建立了考虑水嘴压力损失影响的井处理模型。耦合求解井底压力、流量及地层流动,得到了注入过程中考虑水嘴压力损失影响的井底压力和流量响应情况。以此来分析不同水嘴、渗透率对井底压力、注入量随时间变...     

大型天然黄土洞穴系统现场冲刷试验

摘  要：通过现场冲刷试验,结合勘探、调查及室内含泥率测定等手段对大型天然黄土洞穴系统的三维空间展布特征、水文特性及侵蚀特征进行了研究。结果表明：黄土洞穴系统侵蚀过程具有明显的期次性;洞穴过水流量过程曲线可分为增加阶段、相对稳定阶段和减小阶段三个特征流量段,其中在第一阶段普遍存在“滞流效应”,第二阶段具有小幅波动的特性,并发现洞穴内的总渗流损失量随设计注水流量的增大而有所增加;根据含泥率随时间变化曲线,分析了不同流量过程段含泥率的变化特点,通过不同工况的累积侵蚀量对比发现洞穴的侵蚀速率与流量显著正相关。从机理上对产生上述过程、现象及结果的原因进行了合理解释,为黄土潜蚀机理及潜蚀速率的研究提供了可靠的现场试验数据。     

驱替特征曲线在油田开发分析中的应用

含水上升规律的研究,是注水油田动态分析的一个很重要的方面。一般都做成含水与时间,或含水与累积采油量(采出程度)的关系曲线以供分析。但因影响因素繁多,加之井口计量上的误差,实际资料点往往波动较大,规律性不强。文献[1]根据实验室和苏联     

双重孔隙介质中二相驱替理论

裂缝-孔隙地层中的注水驱油问题是近十多年来油田开发和渗流力学中最受关注的问题之一.本文改进了已有的数学模型,即正确地写出了双重孔隙介质中二相渗流的基本方程,并用特征线方法进行了全面的研究,揭示了裂缝-孔隙地层中水驱油过程的基本特征.可把本工作看作是著名的Buckley-Leverett理论在双重孔隙介质中的推广.     

各向异性双重介质垂直裂缝井两相流体渗流

建立了各向异性双重介质中垂直裂缝井两相渗流数学模型,用有限差分法求得了其解,进行了算例分析。得到了含水饱和度沿径向、最大及最小渗透率方向的分布和水驱油前缘等饱和度面随时间的变化,分别讨论了各向异性、吸渗作用对这种介质中两相流体渗流的影响。结果表明：渗透率较在的方向,前缘推进速度较快,油井见水较早;吸渗使前缘推进速度减慢,使油井见水晚。注水开发这种油藏时,见水前注入率不能太大以充分发挥吸渗作用,存在最佳注入率。这对于水力压裂垂直裂缝井注水开发碳酸盐岩裂缝性油藏有指导意义。     

曲线半径对钢轨磨损影响的数值计算与试验分析

用数值计算方法详细分析了静态接触情况下,轮轨接触质点间蠕滑力、黏滑区的分布和摩擦功随曲线半径的变化,利用模拟试验研究了曲线半径对钢轨试样磨损特性的影响.结果表明:钢轨磨损量随曲线半径的增大呈非线性减小,在小于1 200 m的小曲线半径范围内,钢轨磨损量值随曲线半径的减小而急剧增大;随着曲线半径的增大,轮轨接触斑中最大滑动量逐渐减小,滑移区的面积减小,而黏着区的面积增大;轮轨接触斑上摩擦功随曲线半径的增大呈非线性的减小.     

裂纹试件的冲击试验

本文介绍了楔型冲击加载双悬臂梁(D.C.B)试件的动态测试技术。实测了冲击力随时间变化曲线;裂纹尖端及试件中部应变随时间变化曲线,并由测试结果分析计算试件的动态断裂韧K_(1d)性随时间变化曲线。     

水坝瞬态热传导分析中的拟初始条件边界元法

使用一种时域边界元方法对混凝土水坝进行瞬态热传导分析。在对时间积分进行离散计算时,采用一种拟初始条件法,即在时间步迭代计算的过程中,将之前计算结果对当前时间步的影响都视作当前时间步的初始条件。在所取时间步长较小的情况下,这种处理方法容易导致数值结果不稳定,即每一步的计算误差会累计放大,最终导致计算崩溃。本文提出一种虚拟时刻方法以缓解这类数值不稳定现象,在该方法中,时间步长首先放大至合适尺度,计算某个虚拟时刻(往往在真实计算时刻之后)的温度和流量分布,再通过插值方法换算出真实时刻的温度和流量分布。在虚拟时刻点上的温度和流量计算过程中,边界已知温度或流量由真实时刻的温度或流量进行外插得到。本文简单证明了该方法在温度和流量随时间呈线性变化情况下的正确性,最后给出了两个分析实例,验证了该方法的准确性和稳定性。     

非爆炸且不可还原农用硝酸铵热分解反应动力学的研究

利用加速度量热仪分别对普通硝酸铵和非爆炸且不可还原农用硝酸铵的绝热分解过程进行分析,分析结果通过动力学模型编程在微机控制系统上进行数据分析处理,得到了绝热分解温度与压力随时间的变化曲线、自加热速率随温度的变化曲线、准速率常数随温度的变化曲线、最大温升速率所需时间随温度的变化曲线,计算了分解动力学参数表观活化能、指前因子、不可逆温度和自加速分解反应温度。所有实验结果都表明,非爆炸且不可还原农用硝酸铵具有良好的热稳定性、安全性。     

基于声发射能量分析的周期注水应力改造下煤系页岩裂缝扩展规律试验研究

周期注水作为一种有效开采页岩气的应力改造技术,其对页岩裂缝起裂扩展影响机制尚不明确。基于页岩储层真实三维应力环境,研制了真三轴水力压裂试验系统,以黑龙江双鸭山矿区煤系页岩为研究对象,制作了煤系页岩相似材料模型,进行了先周期注水应力改造、后水力压裂的页岩裂缝扩展模拟试验。利用声发射技术监测了应力改造阶段和压裂阶段裂缝起裂扩展过程,根据声发射能量变化和频谱特征,分析了应力改造和水力压裂阶段的裂缝特征、起裂扩展规律,提出了基于声发射能量分析的水力压裂裂缝由起裂阶段进入扩展阶段的判别指标和判定方法。试验结果表明:应力改造阶段裂缝尺寸以微裂缝为主,随周期注水压力增加,张拉型裂缝占比减少,剪切型裂缝占比增加;压裂阶段裂缝尺寸以宏观裂缝为主,随周期注水压力增加,张拉型裂缝占比增加,剪切型裂缝占比减少,当周期注水压力为1.6MPa时为最优,易形成缝网。提出以平均声发射能量能率k作为裂缝起裂判据,发现当k降幅超过26.87%时,裂缝由起裂阶段进入扩展阶段。周期注水应力改造可以产生微裂缝,沟通水力裂缝降低压裂时裂缝起裂难度,从而提高页岩气开采率。所得结论可为水力压裂应力改造效果评价与裂缝控制提供参考。     

纳米阵列中气体驱替液体的流动特征

纳米尺度下气体驱动液体流动特征在纳流控芯片及页岩气开发中具有广泛的应用前景. 利用管径规格为292.8 nm,206.2 nm,89.2 nm,67.0 nm,26.1 nm的氧化铝膜为纳米阵列,进行气驱水实验和单相气体流动实验,分析纳米尺度下气驱水流动特征. 实验表明,纳米阵列中气驱水时气体流量随驱动压力变化经历三个阶段:第一阶段流量缓慢增大,且比单相气体流量降低约一个数量级;第二阶段纳米阵列中的水被大量驱替出,流量迅速增大;第三阶段纳米阵列中的水全部被驱替出,流动特征与单相气体流动保持一致. 分析表明,气驱水第一阶段存在气液界面毛细管力的“钉扎”作用及固液界面相互作用力的影响,是产生非线性流动的主要原因;而一旦“钉扎”作用破坏,气体进入管道推动界面运动,气柱与液柱之间的毛细曲面曲率变化,毛细管力减小,气体流量急剧增大,其中毛细管力随驱替压力增大急剧变化,是造成第二阶段气体流量突变的主要原因.      

初始压力对多孔介质中气体水合物生成的影响

利用自制的一维天然气水合物生成与开采模拟实验系统,实验研究多孔介质中天然气水合物生成时不同初始压力对生成量、生成时间的影响.分别用相同气水比注入、相同注气量不同注水量、相同注水量不同注气量三种方式来控制初始压力.结果表明:在砂粒粒径300μm～500μm,盐水质量浓度2%,系统温度为2℃、初始压力为5MPa～9MPa的条件下进行水合物的等容生成实验时,初始压力越大,生成的水合物量越多,水合物开始生成的时间越早;但初始压力越大,实验系统中水合物生成最终稳定所需的时间越长.本实验系统采用的三种不同的控制初始压力的方式都可以得到上述结果.由此,可以为今后室内进行天然气水合物的生成实验提供科学指导.     

Thermal and hydraulic performance of a three-phase fluidized bed cooling tower

An experimental study was made of the thermal and hydraulic characteristics of a three-phase fluidized bed cooling tower. The experiments were carried out in a packed tower of 200 mm diameter and 2.5 m height. The packing used was spongy rubber balls 12.7 mm in diameter and with a density of 375 kg/m³. The tower characteristic was evaluated. The air-side pressure drop and the minimum fluidization velocity were measured as a function of water/air mass flux ratio (0.4–2), static bed height (300–500 mm), and hot water inlet temperature (301–334 K).

The experimental results indicate that the tower characteristics KaV/L increases with increases in the bed static height and hot water inlet temperature and with decreases in the water/air mass flux ratio. It is also shown that the air-side pressure drop increases very slowly with increases in air velocity. The minimum, fluidization velocity was found to be independent of the static bed height.

The data obtained were used to develop a correlation between the tower characteristics, hot water inlet temperature, static bed height, and the water/air mass flux ratio. The mass transfer coefficient of the three-phase fluidized bed cooling tower is much higher than that of packed-bed cooling towers with higher packing height.     

Experimental study of inverted annular film boiling in a vertical tube cooled by R-134a

An experimental investigation of inverted annular film boiling heat transfer has been performed for vertical up-flow in a round tube. The experiments used R-134a coolant and covered a pressure range of 640–2390 kPa (water equivalent range: 4000–14,000 kPa) and a mass flux range of 500–4000 kg m⁻² s⁻¹ (water equivalent range: 700–5700 kg m⁻² s⁻¹). The inlet qualities of the tests ranged from −0.75 to −0.03. The hot-patch technique was used to obtain the subcooled film boiling measurements. It was found that the heat transfer vs. quality curve can be divided into four different regions, each characterized by a different mechanisms and trends. These regions are dependent on pressure, mass flux and local quality. A detailed examination of the parametric trends of the heat transfer coefficient with respect to mass flux, inlet quality, heat flux and pressure was performed; reasonably good agreement between observed trends and those reported in the literature were noted.     

Assessment of gas thermodynamic characteristics on fluidic thrust vectoring performance: Analytical,experimental and numerical study

The cross injection in a supersonic flow is an issue encountered in several aerodynamic applications such as fuel injection in scramjet combustor, missile control, drag reduction and thrust vector control. In a recent work, an analytical model has been presented to calculate the fluidic thrust vectoring performance for a supersonic axisymmetric nozzle. The model is able to take into account both the injected gas thermodynamic properties and the geometrical nozzle characteristics. The analytical model has been successfully validated following the cold air flow experimental analysis, in the case of fluidic thrust vectoring applied to conical nozzle. The aim of this work is to show how far the injected gas thermodynamic properties, different from that of the nozzle main flow, could influence the fluidic thrust vectorization parameters.In this work, the experimental performance of the fluidic thrust vectoring concept, using numbers of gases as injectant, has been qualitatively and quantitatively analyzed. Schlieren visualization, force balance and wall pressure measurements were used in the case of a truncated ideal contour nozzle. The experimental results are compared to the numerical and analytical findings.Performance analysis are conducted and basic conclusions are drawn in terms of thermodynamic gas properties effect on the fluidic thrust vector system. The primary effect was related to the gas molecular weight and its specific heat ratio product. It is observed that for fixed injection conditions, the vectoring angle is higher when the injected gas molecular weight and specific heat ratio product is less than that of the primary gas. For a given mission of the launcher, it can be concluded that the mass of the embedded gas, used for the fluidic vectorization system, can be significantly reduced, depending on its molecular weight and specific heat ratio.     

采用NND方法计算三维喷管气流场

本文运用NND显式差分格式，计算了三维喷管气流场。气流场计算的基本方程为一般贴体坐标系下三维守恒型的欧拉方程。采用了时间分裂法和Steger-Warming矢通量分裂技术。在喷管内沿周向的每个由轴线和壁面构成的子午面上根据泊松方程生成贴体网格。本文运用三维程序计算了轴对称JPL喷管，同时与实验结果和前人采用轴对称二维程序所计算的结果做了对比。最后，本文还计算了三维矢量喷管，计算结果与现有的实验结果一致。通过轴对称JPL喷管和三维矢量喷管的计算考核，表明建立的算法和编写的计算程序是正确的。文中提出了采用子午面形式的贴体网格时奇性轴的处理方法。计算结果表明在喷管壁面处，马赫数与压强的计算结果与实验值吻合较好，而在喷管轴线处，只有当网格较密时，才能得出与实验结果接近的计算结果。     

The spray characteristics of a pressure-swirl injector with various exit plane tilts

The gasoline spray characteristics of a pressure-swirl injector were investigated with various exit plane tilts. The analysis focused on the correlation between tilt angle and flow angle. Mie-scattering technique and phase Doppler anemometry were employed to analyze the macroscopic spray development and droplet size distribution of the spray. An analytical method for mass flux estimation was applied to understand the velocity distribution at the nozzle exit. The results showed that the spray shape and velocity distribution of the spray were more asymmetrical at high tilt angles. In particular, an opened hollow cone spray was formed when the tilt angle is greater than the complementary flow angle. The pressure drop inside the spray, one of the crucial factors for the swirl spray collapse at various surrounding conditions, was attenuated in this opened hollow cone spray since the pressure inside the spray was assimilated to the surrounding air pressure. The spray collapse at high fuel temperature and back pressure conditions did not appear when the tilt angle is larger than the complementary flow angle due to the reduced pressure drop inside the spray. However, tilt angle should be optimized to fulfill the requirements of spray robustness and avoid the locally rich area. The droplet size of 70° tilted nozzle spray shows a value similar to that of the original swirl spray in the plane that includes nozzle axis and the major axis of exit surface ellipse (Major axis plane) while it shows an increased value in the plane that includes nozzle axis and the minor axis of exit surface ellipse (Minor axis plane).     

Two-phase flow instabilities in a silicon microchannels heat sink

Two-phase flow instabilities are highly undesirable in microchannels-based heat sinks as they can lead to temperature oscillations with high amplitudes, premature critical heat flux and mechanical vibrations. This work is an experimental study of boiling instabilities in a microchannel silicon heat sink with 40 parallel rectangular microchannels, having a length of 15 mm and a hydraulic diameter of 194 μm. A series of experiments have been carried out to investigate pressure and temperature oscillations during the flow boiling instabilities under uniform heating, using water as a cooling liquid. Thin nickel film thermometers, integrated on the back side of a heat sink with microchannels, were used in order to obtain a better insight related to temperature fluctuations caused by two-phase flow instabilities. Flow regime maps are presented for two inlet water temperatures, showing stable and unstable flow regimes. It was observed that boiling leads to asymmetrical flow distribution within microchannels that result in high temperature non-uniformity and the simultaneously existence of different flow regimes along the transverse direction. Two types of two-phase flow instabilities with appreciable pressure and temperature fluctuations were observed, that depended on the heat to mass flux ratio and inlet water temperature. These were high amplitude/low frequency and low amplitude/high frequency instabilities. High speed camera imaging, performed simultaneously with pressure and temperature measurements, showed that inlet/outlet pressure and the temperature fluctuations existed due to alternation between liquid/two-phase/vapour flows. It was also determined that the inlet water subcooling condition affects the magnitudes of the temperature oscillations in two-phase flow instabilities and flow distribution within the microchannels.     

Experimental study on hydrodynamic behaviors of high-speed gas jets in still water

The present paper describes experimental investigation on the flow pattern and hydrodynamic effect of underwater gas jets from supersonic and sonic nozzles operated in correct- and imperfect expansion conditions. The flow visualizations show that jetting is the flow regime for the submerged gas injection at a high speed in the parameter range under consideration. The obtained results indicate that high-speed gas jets in still water induce large pressure pulsations upstream of the nozzle exit and the presence of shock-cell structure in the over- and under-expanded jets leads to an increase in the intensity of the jet-induced hydrodynamic pressure.     

After fogging process in water injected gas turbine systems

In gas turbine system with after fogging, water droplets are injected after compressor. After fogging could have more significant potential for enhancement of specific power production compared to inlet fogging alone, since a larger water injection rate is possible. Transient analysis of after fogging process is carried out by using a heat and mass transfer modeling on water droplet evaporation. Transient variables such as droplet diameter and air temperature are evaluated as the droplet evaporation proceeds for different values of initial droplet diameter, pressure ratio of compressor, and water injection ratio. The evaporation time for injected droplets are also estimated. Present results show that the evaporation time decreases sensitively with increasing pressure ratio or initial droplet diameter. However, the effect of water injection ratio on evaporation time is relatively insignificant unless water injection ratio is near the critical ratio.