Aiming at the problem of low intelligence of horizontal transport vehicles in container terminal, the research on cooperative vehicle infrastructure system is carried out combined with the characteristics of closure and low-speed for container terminals. The model for the behavior control and optimization of unmanned vehicles is designed based on Q-Learning, and the cooperative vehicle infrastructure system of container terminal is developed. A verification experiment is designed. Through sensor information recognition and behavior control training, the accuracy rate of driving behavior control of the system is more than 90%, which can effectively command vehicles, ensure traffic safety and improve traffic efficiency.

To solve the problem of path optimisation and obstacle avoidance of automated guided vehicles (AGV) in the horizontal transportation of container terminals, this study proposed three operation modes of terminal vehicles and summarised four vehicle behaviour modes. Considering the vehicle behaviour pattern as the top-level object, based on heuristic rules and an object-oriented timed coloured stochastic Petri network (OOTCSPN) algorithm, a scheduling framework model of the AGV was established to optimise vehicle scheduling. A path planning model for three vehicle operation modes was designed for AGV path planning and real-time random obstacle avoidance based on the A-star(A*) algorithm fusion dynamic window approach (DWA). The simulation results indicate that the container handling efficiency increased by 13.2% using the improved algorithm. The scaled-down experiment confirms that the proposed method makes the planned path smoother and can also achieve real-time obstacle avoidance.

为了研究当量比、值班燃料量和压力对燃气轮机燃烧室预混喷嘴排放指标的影响,在环境压力下按照等速模化原理进行了燃烧室预混喷嘴的燃烧试验,基于化学反应网络法构建了污染物预测模型,开展了试验和数值对比研究.结果表明:在带值班燃料的情况下该预混喷嘴当量比φ在0.35～0.5时可满足国标排放要求,但是值班燃料量增大会使NOx排放升高;在φ<0.4时,压力对纯预混燃烧NOx生成无影响,φ>0.4时,NOx会随压力升高而增多;带有值班燃料的预混燃烧时,NOx对压力变化敏感,压力升高导致NOx增多;该预混喷嘴混合性能对空气流速不敏感、燃料兼容性强,排放达标当量比范围宽,经进一步设计开发后有潜力应用于燃气轮机低排放燃烧室中.该化学反应器网络模型依赖经验较少,当值班燃料比例≤0.17时,对污染物预测与试验数据符合较好.

根据湍流发生机理,设计了一种新型的定容燃烧弹内湍流发生系统,用于在定容燃烧弹内部产生可调控的各向均匀对称湍流环境.基于Fluent软件建立了湍流定容燃烧弹内部流动的数值模拟模型,在此基础上,对湍流定容燃烧弹内部流动进行了数值模拟,得到了固定参数情况下容弹内部流场的分布特点.对湍流定容燃烧弹内部流场的特点进行分析,结果表明该湍流发生系统可在容弹内部产生各向均匀对称湍流环境.运用数值模拟计算了不同电机转速情况下,容弹中心点位置湍流强度在一个循环内的变化规律.最后,将数值模拟的湍流强度计算结果与试验测量的结果进行对比,验证了原有仿真设计的准确性.

针对目前的三角网切割效率不高的问题,该文提出了一种网格拓扑关系搜索的三角网模型切割方法.利用三角网模型中三角形的索引和顶点索引,构建边的索引,从而构建点索引、边索引和三角形索引之间的拓扑关系,最终形成三维模型的“边-顶点-邻接三角形的拓扑关系”.根据当前屏幕范围,提取三维视景体内的三角形,利用GPU并行运算,快速获取离视点最近的三角形索引,从而获取到所有三角网中的第一层三角网,并根据拓扑关系提取边界三角形,再利用基于边的约束对边界三角形进行重新剖分.实验结果表明,该方法可以快速准确地完成离视点最近的三角网模型表面的切割.

A computational approach to predict external spray characteristics for flashing and cavitating nozzles was presented and validated. It is developed as a fully Eulerian and compressible two-phase flow solver that simulates vaporization and condensation of the fuel using a Homogeneous Relaxation Model (HRM). The flow solver together with the interface area density model was applied to predict spray spreading angle. A method to identify spray plume boundary from the predicted flow field that offers a meaningful comparison to experimental definition was discussed in detail. Using the experimental data available in literature, a comparison between axi-symmetric and asymmetric nozzles was made to assess the nature of the influence of the nozzle geometry and the operating conditions on the ensuing spray. On the basis of this comparison, it was inferred that the spray plume angle of asymmetric nozzles is largely geometry dependent for a wide range of pressure ratios. (C) 2018 Elsevier Ltd. All rights reserved.

Nondimensional groups were identified and correlations were established to initialize flash-boiling spray for use in Lagrangian/Eulerian spray simulations. The objective was realized through CFD simulations with nonequilibrium interphase heat transfer and an Eulerian-Eulerian spray model. Parametric studies were carried out on 2D axisymmetric straight and stepped nozzles to study the effects of geometric and operating conditions on the near-nozzle spray. The effects of the inlet corner radius, nozzle diameter, counter-bore diameter and the inner nozzle length were assessed along with the effects of varying injection and ambient pressures and the fuel temperature as part of this study. The influence of these parameters on the coefficient of discharge, the spray-cone angle, and the Sauter mean diameter (SMD) were analyzed both qualitatively and quantitatively. Results indicate that the inlet corner radius dominates the coefficient of discharge; the time available for the fuel to vaporize determines the magnitude of the spray-cone angle. The SMD is dominated by the extent of the fuel superheat, defined as a ratio of the ambient to the saturation pressure of the fuel. The established correlations were incorporated using a user-defined function as a means to initiate flash-boiling Lagrangian spray. The simulated downstream spray angle and SMD were validated against experimental results.

海底油气混输管线因水合物生成引起堵塞问题备受关注.基于CFD-PBM模拟海底管道实际工况下水合物的生成过程,分析水合物生成对气泡的聚并和破碎行为及各相流速的影响,结果表明:当管道的运行环境达到水合物形成条件时,在气液界面逐渐有水合物生成,并在管壁上方堆积.水合物生成消耗一定量气体,导致压降降幅增大,同时产生的水合热导致局部温度升高,但传热受阻使得流体温度提升较小.没有水合物生成时,气泡以聚并为主,气泡直径分布较窄且相对均匀.水合物生成后,气泡大小分布范围变宽,但主要集中在较小直径范围.水合物在气液界面生成并在管壁上方堆积,导致流速局部分布不均,相间滑脱加剧.研究管道流动体系下水合物生成及其影响为管输水合物浆液的稳定安全流动提供理论参考.

A dvanced research in Spark-ignition (SI) engines has been focused on dilute-combustion concepts.For example, exhaust-gas recirculation is used to lower both fuel consumption and pollutant emissions while maintaining or enhancing engine performance, durability and reliability.These advancements achieve higher engine efficiency but may deteriorate combustion stability.One symptom of instability is a large cycle-to-cycle variation (CCV) in the in-cylinder flow and combustion metrics.Large-eddy simulation (LES) is a computational fluid dynamics (CFD) method that may be used to quantify CCV through numerical prediction of the turbulent flow and combustion processes in the engine over many engine cycles.In this study, we focus on evaluating the capability of LES to predict the in-cylinder flows and gas exchange processes in a motored SI engine installed with a transparent combustion chamber (TCC), comparing with recently published data.Numerical simulations are performed using the commercial CFD software, ANSYS Forte, employing a classical Smagorinsky sub-grid-scale (SGS) model for the LES approach.Two important aspects of the model, namely the coefficient of sub-grid viscosity used in the Smagorinsky model, and the numerical scheme for discretizing the convection term in the momentum transport equation, are evaluated.Simulations are performed for 20 consecutive engine cycles after the simulation setup is validated by the predicted in-cylinder pressure, trapped mass, and temperature data.LES-predicted phase-averaged-mean and root-meansquare (RMS) velocity fields are compared with high-speed particle image velocimetry (PIV) data.The comparison and analysis are performed at two crank angles, representing intake and compression strokes, and on two different planes for measurement in the engine combustion chamber.A proper orthogonal decomposition (POD) technique is applied to quantify CCV in both the LES results and the PIV data, to provide a quantitative assessment of the predictions from LES.The flow field statistics predicted by the LES-Smagorinsky model match well with experimental results.Based on these simulation results, optimal practices for the use of Smagorinsky model with respect to the numerical schemes are summarized.

An applied phase-related equilibrium (APPLE) solver using only the Peng-Robinson equation of state is developed based on rigorous classical thermodynamics. The solver is theoretically and thermodynamically consistent with the stringent equilibrium criterion. It is mainly composed of phase stability and phase splitting calculations, which will be called routinely in the course of searching for the globally stable equilibrium state. It also makes use of various robust and efficient numerical methods. To demonstrate its performance, the solver is tested against various mixtures, such as oil and gas mixtures, hydrocarbon mixtures and hydrocarbon-nitrogen mixtures. Phase diagrams of these mixtures are constructed and verified with available experimental data or other researchers' calculations. Results show that the APPLE solver is reliable and fast to solve phase equilibrium problems, including three-phase equilibrium. Finally, its potential applications to droplet evaporation and computational fluid dynamics (CFD) calculations are discussed. (c) 2013 Elsevier Ltd. All rights reserved.

In internal combustion engines the injection of high-pressure liquid fuel into a low-pressure gas through a nozzle passage is an important process to atomize the liquid and achieve optimal fuel-air mixing. A Computational Fluid Dynamics (CFD) model is eveloped in the present work to simulate the internal- and external-nozzle flow fields in an integrated way. The model assumes that the flow within and near the nozzle is continuous, and an Eulerian flow solver is developed using the general conservation laws of fluid dynamics. Differences in the thermodynamic states of the liquid and gas phases are modeled with a Stiffened Gas Equation of State (EOS). A practical phase equilibrium solver is developed, and is implemented into the Eulerian flow solver to predict phase changes in the flows - in particular, cavitation of the liquid within the injector nozzle passage. The combined equilibrium solver is applied to single-component and two component flows with one component being non-condensable air. A number of test problems are simulated to verify the numerical methods and validate the proposed models. These include two-phase shock tube problems, a converging-diverging nozzle flow problem, a submerged liquid jet problem, and a cavitating liquid jet problem. (C) 2014 Elsevier Ltd. All rights reserved.

A isochoric‐isoenergetic flash solver using a direct entropy maximization principle for phase splitting and Gibbs free energy minimization for phase stability is developed. The solver searches for the global stable state in a rigorous and thermodynamically consistent way. The solver is demonstrated to be robust and efficient to handle multiphase flash, even in the vicinity of phase boundaries. Dynamic flash computations and gas dynamics simulations of shock waves are considered for pure ethylene and for binary ethylene‐nitrogen mixtures. The simulations show significantly different shock wave characteristics when phase separation is considered due to intensive energy exchange, compared to the frozen flow limiting single‐phase solution. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3013–3024, 2014

Two distinctive condensation mechanisms of pure species, regular and retrograde condensation, are investigated using a one-fluid model and a homogeneous phase equilibrium model based on entropy maximization. Fluid dynamics simulations are performed to model the regular condensation process of ethylene in a converging nozzle, and the retrograde condensation process of a fluorinated compound in a shock tube. To our knowledge, the present simulations are the first CFD simulations of retrograde condensation processes. The simulations show reasonably good agreement with available experimental data both quantitatively and qualitatively, which confirms the consistency between the theory-guided simulations and experiments. For the supercritical injection problem, condensation is found to occur after continuous expansion when ethylene is brought into the two-phase region from a supercritical state. For the shock tube problem, both simulations and experiments show that condensation occurs after the high pressure reflected shock is formed from the end wall. Increase in the initial pressure ratio increases the incident shock strength and reinforces condensation by elevating the liquid volume fraction. A complete liquefaction shock is found at high incident shock Mach numbers when the compression is strong enough to send the fluid from the pure vapor to the pure liquid state by crossing the two-phase mixture region. After condensation, the condensed liquid phase is fully depleted as the pressure wave expands and the fluid is brought back to the vapor state though a continuous evaporation process. (C) 2014 Elsevier Ltd. All rights reserved.

Computational fluid dynamics (CFD) is one of the branches of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Annual hourly fast flow simulations are needed for some applications in building industry, such as the conceptual design of indoor environment, or coupled with energy simulation to provide deep analysis on the performance of the buildings. Year round simulation, which consists of 8760 (365 24) independent hourly simulations, is needed to help the designer investigate the problem clearly. However, CFD computation is time consuming, and usually only two or three extreme cases can be simulated in practice. Annual hourly simulation using the traditional method can be considered as a computational intractable problem. Based on previous researches (Yue Wang and Feng, 2012a)(Yue Wang and Feng, 2012b), even though the fast fluid dynamics (FFD) algorithm combined with the General Purposed Graphics Processing Unit (GPGPU) hardware acceleration can make CFD simulation much faster(400x), annual hourly simulation still requires CFD performance to be further improved by 10-20x to make it practical. In this study, a minimal spanning tree based scheduling algorithm is developed, which always gives the best CFD simulation strategy that reuses previous calculated results to generate new results, thus making iteration convergence much faster. It is shown in the paper that the annual hourly simulation by GPGPU accelerated FFD by using this new algorithm requires a similar simulation time to the one used to perform two or three extreme cases of simulation using the traditional method.

Resolution of droplet-scale processes occurring within engine sprays in multi-dimensional Computational Fluid Dynamics (CFD) simulations is not possible because impractically refined numerical meshes or time steps would be required. As a result, simulations that use coarse meshes and large time steps suffer from inaccurate predictions of mass, momentum and energy transfer between the spray drops and the combustion chamber gas, or poor prediction of droplet breakup and collision and coalescence processes. Several new spray models have been proposed to address these deficiencies, including use of an unsteady gas jet model to improve momentum transfer predictions in under-resolved regions of the spray, a vapor particle model to minimize numerical diffusion effects, and a Radius of Influence drop collision model to ensure consistent collision computations on different meshes. The present work combines these models with improved KH-RT models to improve the consistency of drop breakup predictions. A modified mean collision time model is also proposed to reduce timestep dependency of droplet collision prediction. The models have been implemented into the KIVA CFD code and are demonstrated to achieve independency with respect to both mesh sizes and time steps. The code was validated for non-evaporating and evaporating sprays, and also for diesel engine simulations with variations of larger than one order of magnitude in mesh cell volume and around two orders of magnitude in time steps. The numerical results were found to match available experimental measurements very well, including spray tip penetration, local drop velocity and Sauter mean diameter (SMD) and averaged mean diameter (AMD) of non-evaporating diesel sprays. The new spray models were also applied to simulate evaporating sprays and good agreement was found with measured liquid and vapor penetration lengths. Finally, the engine simulations were also found to agree well with experimental engine data.