Thermal simulation of basic volcanic fluid influence on different source rocks

Based on thermal simulation experiment, interactions between volcanic fluids and source rocks were studied. Gas generations in the dry system and fluid system under different temperatures were analyzed. The results showed that the various types of source rocks are similar in composition, containing gaseous C1-C5 hydrocarbons, H2 and CO2 whose gas yields increase with increasing temperature. The gas yield of source rocks of type is Ⅰ the highest, followed by type Ⅱ, and that of source rocks of type is Ⅲ the lowest, indicating that the yield of hydrocarbon gases is related to their hydrocarbon generating potential. Although the generating potential of type is Ⅲ the lowest, it can still be regarded as a useful gas source when it is buried deeply enough. The basic volcanic fluid restrains the generation of gaseous hydrocarbons in different types of source rocks, but promotes the generation of inorganic gases.

Direct numerical simulation of viscoelastic-fluid-based nanofluid turbulent channel flow with heat transfer

Our previous experimental studies have confirmed that viscoelastic-fluid-based nanofluid(VFBN) prepared by suspending nanoparticles in a viscoelastic base fluid(VBF, behaves drag reduction at turbulent flow state) can reduce turbulent flow resistance as compared with water and enhance heat transfer as compared with VBF. Direct numerical simulation(DNS) is performed in this study to explore the mechanisms of heat transfer enhancement(HTE) and flow drag reduction(DR) for the VFBN turbulent flow. The Giesekus model is used as the constitutive equation for VFBN. Our previously proposed thermal dispersion model is adopted to take into account the thermal dispersion effects of nanoparticles in the VFBN turbulent flow. The DNS results show similar behaviors for flow resistance and heat transfer to those obtained in our previous experiments. Detailed analyses are conducted for the turbulent velocity, temperature, and conformation fields obtained by DNSs for different fluid cases, and for the friction factor with viscous, turbulent, and elastic contributions and heat transfer rate with conductive, turbulent and thermal dispersion contributions of nanoparticles, respectively. The mechanisms of HTE and DR of VFBN turbulent flows are then discussed. Based on analogy theory, the ratios of Chilton–Colburn factor to friction factor for different fluid flow cases are investigated, which from another aspect show the significant enhancement in heat transfer performance for some cases of water-based nanofluid and VFBN turbulent flows.

A New Mathematical Simulation Approach for Thermal Cracking Furnace Studies

Thermal cracking of hydrocarbons for olefin production is normally carried out in long reactor tubes suspended in a large gas fired furnace. In this paper, a coupled furnace-reactor mathematical model based on a computational fluid dynamics (CFD) technique is developed to simulate the complex fluid dynamics phenomena in the thermal cracking furnace. The model includes mass transfer, momentum transfer, and heat transfer, as well as thermal cracking reactions, fuel combustion and radiative heat transfer. The rationality and reliability of the mathematical model is confirmed by the approximate agreement of predicted data and industrial data. The coupled furnace-reactor simulation revealed the details of both the transfer and reaction processes taking place in the thermal cracking furnace. The results indicate highly nonuniform distribution of the flue-gas velocity, concentration and temperature in the furnace, which cause nonuniform distribution of tube skin temperature and heat flux of the reactor tubes. Profiles of oil-gas velocity, pressure, temperature and product yields in the lengthwise direction of the reactor tube are obtained. Furthermore, in the radial direction steep velocity and temperature gradients and relatively slight gradients of species concentration are found. In conclusion, the model can provide more information on the fluid dynamics and reaction behavior in the thermal cracking furnace, and guidance for the design and improvement of thermal cracking furnaces.

Effect of Thermal Buoyancy on Fluid Flow and Inclusion Motion in Tundish without Flow Control Devices——Part II :Inclusion Motion

Following up the fluid flow simulation in a 60 t tundish, the trajectories of inclusions in the 60 t tundish without flow control are simulated by considering the force balance between the drag force and the inertial buoyancy force. The Stochastic model yields more accurate inclusion motion than the non-Stochastic model due to including the effect of the turbulent fluctuation. The average residence time of inclusions decreases with increasing size. The thermal buoyancy favors inclusions removal especially the small inclusions. Using solute transport like the dye injection in water model and copper addition in the real steel tundish cannot accurately study the motion of the inclusions. In the simulation, more than 68% inclusions bigger than 10μm are removed to the top, and less than 32% enters the mold. The thermal buoyancy has little effect on the fraction of inclusions moved to the top of the inlet zone, and it mainly favors the removal of inclusions smaller than 100μm to the top surface of the outlet zone. For inclusions bigger than 100μm, the effect of thermal buoyancy on their motion can be ignored compared to the inertial buoyancy effect.

Numerical Calculation of Thermal Effect on Cavitation in Cryogenic Fluids

A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cryogenic fluids generates substantial thermal effects and strong variations in fluid properties, which in turn alter the cavity characteristics. To date, fewer investigate the thermal effect on cavitation in cryogenic fluids clearly by the numerical methods due to the difficulty of the heat transfer in the phase change process. In order to study the thermal effect on cavitation in cryogenic fluid, computations are conducted around a 2D quarter caliber hydrofoil in liquid nitrogen and hydrogen respectively by implementing modified Merkle cavitation model, which accounts for the energy balance and variable thermodynamic properties of the fluid. The numerical results show that with the thermal effect, the vapour content in constant location decreases, the cavity becomes more porous and the interface becomes less distinct which shows increased spreading while getting shorter in length. In the cavity region, the temperature around the cavity depresses due to absorb the evaporation latent heat and the saturation pressure drops. When the vapour volume fraction is higher, the temperature depression and pressure depression becomes larger. It is also observed that a slight temperature rise is found above the reference fluid temperature at the cavity rear end attributed to the release of latent heat during the condensation process. When the fluid is operating close to its critical temperature, thermal effects on cavitation are more obviously in both the liquid nitrogen and hydrogen. The thermal effect on cavitation in liquid hydrogen is more distinctly compared with that in liquid nitrogen due to the density ratio, vapour pressure and other variable properties of the fluid. The investigation provides aid for the design of the cryogenic pump of the liquid rocket.

CFD Simulation on Ethylene Furnace Reactor Tubes

Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.

考虑热障涂层及冷却结构影响的某F级燃气轮机火焰筒数值研究

以某F级燃气轮机燃烧室火焰筒为研究对象,考虑热障涂层及冷却结构对火焰筒气动传热影响,基于流热固耦合方法对额定工况下的火焰筒进行了内部流场、温度场和应力场分析,并将数值分析结果与火焰筒实际损伤情况进行对比。结果表明:数值分析结果的火焰筒高应力区域与火焰筒实际损伤区域基本吻合,采用流热固耦合方法可以预测火焰筒实际损伤情况;不同位置的热障涂层陶瓷层隔热效果相近;基体和热障涂层陶瓷层在冷却结构附近的区域均为高应力区域。

径向磁液轴承定子温升及热变形研究

提出一种新型的磁液轴承,以电磁悬浮支承为主、静压支承为辅,实现双重支承,并可以实时调控。通过建立磁液轴承的有限元分析模型,对其进行流-固-热耦合求解,得到轴承的流场、温度、应力及应变分布云图。通过调整轴承系统的结构参数(进油孔直径和线圈匝数)及运行参数(输入电流、进油流量、转子转速)分别进行有限元建模,利用ANSYS软件进行仿真分析,求解不同参数对轴承温升及定子热变形的影响规律。结果表明:流体造成的压力在进油孔内最高为1 MPa,流体在油膜处流速最高为0.8 m/s;轴承定子温度分布对称,有利于散热。研究结果为磁液轴承系统的优化设计提供理论依据。

“牛角管”式组合桨釜内中药膏剂的流动传热特性

为解决高黏度中药膏剂在搅拌釜内受热不均、混合效率低下等问题,设计了新型“牛角管”式组合桨。基于计算流体动力学(computational fluid dynamics,CFD)中的瞬态滑移网格法,对内盘管加热下搅拌釜流场进行数值模拟研究,并对其中一种工况进行了普适性的实验验证,探究搅拌釜内中药膏剂的流场情况及温度分布规律,分析了同一组合桨不同转速下以及同一转速下不同组合桨对流场情况的影响。结果表明:新型组合桨在转速300 r/min时釜内温度以及流场混合效率最高,在该转速下,将新型组合桨与传统组合桨进行对比,“涡轮叶片”式组合桨对釜内温度分布影响能力弱,不适用于工业生产,“大叶片”式组合桨机械搅拌功耗和釜内温差均大于新型组合桨,使得新型组合桨在多方面优于传统组合桨。研究结果为工业生产提供参考。

氢燃料电池无人机舱型和呼吸孔设计与分析

氢燃料电池无人机舱内空间狭小,适宜的热环境是氢燃料电池系统健康高效工作的前提保障。针对无人机舱内环境保障问题,开展舱型对比分析和呼吸孔位优化设计,以保障舱内具有充足空气燃料和适宜温度条件。通过热流耦合仿真分析,对比长方体与圆柱体两种舱型对舱内温度条件的影响,作为氢燃料电池无人机舱型设计的参考。优化布置机舱开孔位置,保障空气流量的同时,寻找最佳舱内温度条件的布孔方案。研究结果表明相比于圆柱体舱型,长方体舱型的舱内温度更低,温度均匀性更好;机舱两侧均为居中开孔时,流体围绕换气孔附近流动,可以与舱内氢燃料电池进行最充分的热交换,舱内整体温度水平最低。

超临界碳氢燃料流动不稳定的频域分析与数值模拟

再生冷却通道中的流动失稳是高超声速飞行器发动机热防护技术中的核心问题之一。为研究超临界碳氢燃料在冷却通道中的流动不稳定特性,基于有限体积法及流体物性近似,发展了高效的一维瞬态模拟方法;同时,基于小扰动假设,进一步提出了用于预测稳定行为的频域分析方法。通过相关实验,验证了模型的可靠性。基于时域和频域方法的综合分析,沿内特征曲线讨论了主要失稳类型,重点分析了受密度波及Ledinegg不稳定共同影响的复合不稳定性。随后,进一步分析了工作压力和入口温度对稳定特性的耦合影响,并基于N_(tpc)-N_(spc)空间划分了稳定区域。研究发现,复合不稳定、Ledinegg不稳定以及密度波不稳定,随入口温度升高而相继消失。Ledinegg不稳定及密度波不稳定的稳定边界在N_(tpc)-N_(spc)空间具有高度相似性,而复合不稳定性的区域在较高的压力下略有缩小。

空间泵驱单相流体回路半物理仿真技术研究

鉴于空间泵驱单相流体回路控制系统研制过程中全物理试验验证涉及的高成本、高风险,以及大气环境下等效模拟空间辐射散热行为存在的挑战,提出一种基于CAN总线的半物理仿真试验平台架构。通过空间热模型代替部分物理实物,结合单相流体回路辐射器地面常压等效验证方法,实现空间泵驱单相流体回路控制系统动态特性的在线快速、可信验证。试验结果表明:在3种工况下,系统控温精度普遍可以达到±0.5℃;常规PID控制策略与神经元PID控制策略的控温性能差别不大;短期瞬态高热流冲击对主回路控温点温度的影响不超过1℃。研究可为空间泵驱单相流体回路控制系统开发与验证提供一种新的技术途径。

充气圆环外径尺寸对充气式减速器结构受力特性的影响

充气式减速器在高超声速减速过程中承受巨大的气动力和气动热载荷。为优化充气式减速器在复杂载荷下的受力特性,以NASA的IRVE-3项目为原型,建立4种充气圆环外径尺寸的充气式减速器模型,开展Ma=5飞行条件下的单向流−固−热耦合分析,对比气动力载荷、气动热载荷和两载荷叠加等情况下,充气圆环外径尺寸对充气式减速器受力特性和温度分布的影响。结果表明:充气圆环的外径越小,充气式减速器的整体变形越小,温度越高,防热层应力越高;外径越大,充气圆环的应力集中越明显。可见,过大或过小的充气圆环外径尺寸对充气式减速器的受力特性均有负面影响,减速器设计中须针对具体对象综合考量确定。以上研究结果可为未来的充气式减速器设计提供参考。

多元热流体开发效果模拟及影响因素关联分析

多元热流体在稠油开发中得到了广泛的应用,但是由于其增油机理较为复杂,因此对其注入参数进行合理设计较为困难。利用数值模拟技术分析了多元热流体开发与蒸汽吞吐的作用效果差异,印证多元热流体增油机理的同时,研究了不同注入温度、注入速率以及焖井时间条件下多元热流体对开发效果的影响。结果表明,这些注入参数存在一个最佳的数值范围。进一步结合现场多元热流体应用井的实际生产数据对其开发效果的主控因素进行分析,得到注入强度、注入速度和注入温度是影响多元热流体开发效果的主要因素。研究结果为多元热流体开发工艺参数设计提供了指导。

深层—超深层海相碳酸盐岩成储成藏机理与油气藏开发方法研究进展

基于钻井、地震、测井、测试以及实验分析等新资料,针对中西部叠合盆地深层—超深层海相碳酸盐岩层系成储、成藏和油气藏高效开发面临的关键科学问题开展持续攻关。研究表明:(1)断裂主导形成的储集体和古老层系白云岩储层是深层—超深层海相碳酸盐岩两类重要的储层;以断裂为主导形成的规模储集体,根据成因可进一步分为3种类型:断裂活动过程中构造破裂形成的缝洞储集体、致密碳酸盐岩受断裂和流体双重改造形成的储集体与早期丘滩等高能相带受断裂和流体改造形成的储层;优势丘滩相、早期白云石化和溶蚀、酸性流体环境、膏盐岩封盖和超压是优质白云岩储层形成和保持的关键。(2)中国中西部叠合盆地海相碳酸盐岩层系富有机质页岩主要发育于被动陆缘深水陆棚、碳酸盐缓坡等环境中,构造-热体制是控制深层—超深层油气藏赋存相态的重要因素,改造型动力场控制中西部叠合盆地深层—超深层海相碳酸盐岩油气成藏与分布。(3)普光等高含硫酸性气田开发过程中硫析出堵塞井筒,采用井筒溶硫剂配合连续油管解硫堵效果明显;基于沉积模拟的双重介质建模数模一体化技术可以精细刻画水侵前缘空间展布及变化,并据此提出气井全生命周期调、排、堵控水对策。(4)超深断控缝洞油气藏开发过程中,储层应力敏感,渗透率随压力下降而显著降低,产量递减较快;凝析气藏相态变化快,压降显著影响凝析油采出程度;据此提出“注水+注天然气”重力驱油藏开发方法和“高注低采”天然气驱凝析气藏开发方法;采用分层次约束、逐级地质建模和流-固-热耦合的复合介质数值模拟有效提高了油气藏开发生产动态模拟的预测精度。

液流电池堆分析与计算程序

液流电池图形用户界面(graphic user interface,GUI)整合了电池堆内部电流分布、流体阻力、稳态自然对流散热、结构封装压力和螺柱选型。基本满足研发人员独立进行多学科计算的要求,能初步评估一款电池堆的性能。多分堆构型液流电池堆的等效电路图采用网格法进行简化,并结合基尔霍夫电压定律求解恒流运行时的循环电流,并进一步计算出堆内逐节电池的实际通过电流、板框流道内的旁路电流,以及堆内主通道内汇总的旁路电流。电池堆流体阻力受板框流道设计、外接管路、电极参数和液位落差影响。矩形流道的达西摩擦系数采用经验方程计算,可将湍流阻力计算误差控制到10%,层流阻力计算误差极低,局部阻力系数采用达西3K参数式估算。电极流阻受电解液流经长度、电极渗透率和电解液黏度的影响。由于渗透率公式的计算结果偏离实验测量值较大,所以界面设定为实测值输入。电池堆按照有保温和无保温考虑在集装箱内的自然对流稳态散热,需要的输入参数包括电池堆的几何尺寸、保温层厚度、环境温度和堆内温度。封装力计算所用的单电池结构是板框配合内嵌盖板的形式。力主要用于找平板材翘曲、将密封垫压入密封槽、抵消内部液体压力和材料热膨胀,再以此进行螺柱选型。

基于有限元的干式变压器散热结构优化设计

采用有限元法对容量800 kVA的10 kV干式变压器建立三维对称仿真模型,仿真计算了变压器的温度场和空气流体场的分布,并分析了不同结构参数下散热板对变压器温升的影响,为干式变压器的散热优化提供支持。

基于流-热-固耦合分析的数值模拟及结构优化

为解决等径T型管路应力过大问题,提出一种基于流-热-固耦合分析方法的优化方法对等径T型管结构进行优化。首先,基于流、固力学理论建立T型管多场耦合的数学模型和物理模型,对T型管内流体的速度温度变化情况和管路的等效应力的分布情况进行仿真模拟,在仿真结果的基础上对管路进行结构优化。仿真结果表明:冷热流体的压力差会导致流体产生逆流现象,从而导致管路的上游区等效应力值增大。等径T型管的最大等效应力值出现在主支管交汇的下游内壁面处。优化后管路内壁面最大等效应力值下降约14%,可以有效地延长管路的使用寿命。该方法对提高气体管路设计的可靠性具有一定的实践意义。

CFETR ECRH系统发射天线的初步结构设计与分析

电子回旋共振加热(ECRH)是中国聚变工程实验堆(CFETR)实现科学目标必不可少的辅助加热和电流驱动方式。发射天线是电子回旋共振加热系统的核心部件之一。为获得等离子体最佳的电流驱动效率,从发射天线的总体方案、波束的传输、波束的汇聚与发射、中子屏蔽、维护方案等方面对ECRH系统顶部发射天线的初步结构进行了设计。ECCD发射天线通过多波束汇聚方式,在CFETR装置紧凑的顶部颈管内,实现了2组9波束微波功率注入至等离子体共振层。发射天线采用颈管插塞式结构设计,有利于中子屏蔽设计和遥操作维护。通过流-热-固耦合仿真分析,为天线发射镜设计了有效的主动冷却方案。本文的分析和设计,为ECRH发射天线进一步的详细工程设计奠定了基础。