湍流粉碎机吸入腔流场的数值模拟

应用三维粘性流动计算软件NUMECA对湍流粉碎机的吸入腔进行了定常三维紊流流场的数值模拟,得到了吸入腔内部流场的压力、速度分布,直观显示了吸入腔内部的流动现象,为后续阶段的整机联算奠定了基础。     

零方程湍流模型在列车车厢内气流数值模拟中的应用

采用k-ε湍流模型对列车车厢内气流进行数值模拟需要消耗大量的计算时间，为此，提出了采用零方程湍流模型对列车车厢内的气流组织进行数值模拟；分别采用零方程湍流模型与k-ε湍流模型对列车车厢内的空气流动及传热进行了数值计算，经分析比较可知，该两种湍流模型的数值计算结果吻合程度较好，采用零方程湍流模型可大大缩短计算时间，利用其简单、快捷的特点，可以为列车空调系统的工程设计提供简便的数值模拟方法。     

湍流超细粉碎机粉碎腔内流场的数值模拟

为了认识粉碎腔内的流场结构和流动状态,提高粉碎设备的加工效果,本文中根据湍流超细粉碎机的实验设备,建立了单曲率叶型的曲线方程,并借助先进的CFD技术,在FLUENT软件中,对用Pro/ENGINEER建立的计算模型进行了验证,模拟了两种不同叶型时湍流超细粉碎机粉碎腔内的单相三维紊流定常流场,直观显示了粉碎腔内的速度分布特性及两种叶型时粉碎腔内速度的区别,为认识粉碎腔内的流场结构和叶型的改进提供了直观的模拟结果。     

Numerical Investigation on Turbulence and Bubbles Distribution in Bubbly Flow Under Normal Gravity and Microgravity Conditions

Two-phase flows of gas and liquid are increasingly paid much attention to space application due to excellent properties of heat and mass transfer, so it is very meaningful to develop studies on them in microgravity. In this paper, gas-phase distribution and turbulence characteristics of bubbly flow in normal gravity and microgravity were investigated in detail by using Euler–Lagrange two-way model. The liquid-phase velocity field was solved by using direct numerical simulations (DNS) in Euler frame of reference, and the bubble motion was tracked by using Newtonian motion equations that took into account interphase interaction forces including drag force, shear lift force, wall lift force, virtual mass force and inertia force, etc. in Lagrange frame of reference. The coupling between gas–liquid phases was made with regarding interphase forces as a momentum source term in the momentum equation of the liquid phase. Under the normal gravity condition, a great number of bubbles accumulate near the walls under the influence of the shear lift force, and addition of bubbles reduces turbulence of the liquid phase. Different from the normal gravity condition, in microgravity, an overwhelming majority of bubbles migrate towards the centre of the channel driven by the pressure gradient force, and bubbles have little effect on the turbulence of the liquid phase.     

空调室内三维紊流流动与传热的数值模拟

采用三维紊流模型，应用有限容积法计算了室内空调的气固耦合传热问题，并对室内空调的气流组织形式，主要是对流速场，温度场进行了数值模拟计算，为空调室内的气流组织形式的优化设计及舒适性提供了研究依据。     

液态锂铅合金鼓泡器中液相行为的数值模拟

为了完成聚变堆氚增殖包层模块（Tritium Breeding Module,TBM）液态锂铅合金鼓泡器（Liquid Lithium Lead Bubbler,LLLB）的设计与建造,采用流体力学方法建立了描述表观气速、气泡尺寸和平均气含率等流变学指标对液相通量径向分布影响的代数模型。数值模拟结果表明：随着表现气速和平均气含率的增加,气泡尺寸的减小,液体循环流动强度增加,径向通量呈抛物线分布,在流态特性指数一定的情况下,中心区上流与边壁区回流的分界点只受表观气速的影响。     

Investigation on Effect of Gravity Level on Bubble Distribution and Liquid Turbulence Modification for Horizontal Channel Bubbly Flow

Bubbly flows in the horizontal channel or pipe are often seen in industrial engineering fields, so it is very necessary to fully understand hydrodynamics of horizontal bubbly flows so as to improve industrial efficiency and to design an efficient bubbly system. In this paper, in order to fully understand mechanisms of phase distribution and liquid–phase turbulence modulation in the horizontal channel bubbly flow, the influence of gravity level on both of them were investigated in detail with the developed Euler–Lagrange two–way coupling method. For the present investigation, the buoyance on bubbles in both sides of the channel always points to the corresponding wall in order to study the liquid–phase turbulence modulation by bubbles under the symmetric physical condition. The present investigation shows that the gravity level has the important influence on the wall–normal distribution of bubbles and the liquid–phase turbulence modulation; the higher the gravity level is, the more bubbles can overcome the wall–normal resistance to accumulate near the wall, and the more obvious the liquid–phase turbulence modulation is. It is also discovered that interphase forces on the bubbles are various along the wall–normal direction, which leads to the fact that the bubble located in different wall–normal places has a different wall–normal velocity.     

全光纤电流互感器的调制相位扰动补偿

为了提高全光纤电流互感器中的电流测量精度,针对正弦调制方案提出了一种改进的信号解调方法.首先给出了有效调制深度的表达式,分析了有效调制深度在实际工程应用中存在的3种外界干扰来源.为了克服这些干扰,采用高次谐波分量实时解出调制深度数值,以实现调制相位的扰动补偿.实验结果表明,被测电流在200~1 500 A范围时,改进的算法使系统的抗干扰性能提高了30倍,系统测量相对偏差维持在0.2%以下,满足高精度电流测量要求.     

Self-Organization of Vortex Line Length Distribution in Dilute Quantum Turbulence

There has been an exponential growth of interest in scale-free structure of quantum turbulence in recent years. Recent studies revealed that the vortex length distribution (VLD), meaning the size distribution of the vortices, in decaying quantum turbulence at zero temperature obeys a power law. This power law is very important because it means that there is a kind of self-similarity in quantum turbulence during the decay. Unfortunately, however, there has been no practical study that answers the important question; why can the quantum turbulence acquire power law VLD? In this paper, we first propose that the nature of quantized vortices allows us to describe the decay of quantum turbulence with a simple model without loosing physical validity. This simple model well reproduces the observed power law and suggests that the emergence of power law VLD is a consequence of two mechanisms; Richardson cascade and dynamical scaling law of vortex dynamics.     

对撞超声速射流场的数值模拟研究

为了探讨对撞式气流粉碎机内部的对撞超声速射流流场结构对粉碎过程的影响,本文中通过数值模拟的方法,对该流场结构进行了研究。通过建立不同的模型,对射流出口与对称平面的距离对粉碎过程的影响,以及射流外围的流动情况进行了分析,为高效气流粉碎机的设计提供了参考依据。     

超音速/高超音速飞行器湍流流场气动光学效应分析

针对高超音速飞行器在大气中流动时所产生的气动光学效应进行定性和定量的分析与计算.通过对高速湍流流场N-S方程的CFD求解,得到在不同飞行参数下,飞行器外围流场的各种参数分布;再运用变折射率流场的光线追迹法,得到红外光在该非均匀变折射率流场中的传输路径;最后应用傅里叶光学理论,结合数值分析方法,计算得到高速湍流流场的气动光学效应传输函数.计算结果表明,气动光学传输函数的幅度响应函数具有低通特征,使得图像发生像模糊;其相位响应函数具有非线性的特点,导致红外成像非线性偏移.本文所得实验结果与理论分析相吻合.     

光纤压电陶瓷相位调制系统及其在线标定

设计了一种低成本,低噪声,高精度的光纤压电陶瓷相位调制系统.包括±100 V线性稳压电源,±12 V线性稳压电源以及三极管压电陶瓷驱动电路.±100V电源纹波电压小于10mV,整个电路系统噪声系数小于2dB,3 dB带宽大于500 Hz,输出峰峰值超过160 V,输出电流大于100 mA.通过光纤3dB耦合器形成的迈克...     

A Maintenance Model Based on Phase Type Distribution for Equipment under Two Types of Failures

A maintenance model is put forward for equipment, which is subjected to internal and external failures. In the model, two maintenance policies-perfect minimal repair and replacement are considered. The operational time has a phase type distribution (PH distribution). Failures' arrival follows a Markovian Arrival Process (MAP). Some failures require the replacement of the system, and others minimal repairs. The performance measures-the mean number of minimal repairs and replacements are analyzed and calculated.     

包含光源面积的整体相位衬度调制传递函数

在部分相干光学理论的基础上,建立了一个整体相位衬度调制传递函数理论模型,模型中包含了光源焦点面积大小对X线相衬成像系统相位调制的影响,并通过数值模拟和数据计算,提出了X线相衬成像系统对光源焦点面积的选择原则,和焦点面积确定条件下的成像参数优化方法,结果表明,这种包含X线光源面积因素的相位衬度调制传递函数模型,更能反映整个系统的光学成像性能,更能有利于成像参数的优化设计。     

Reliability Analysis of a Novel Pulse Code Modulation Flow Control Valve with Self‐compensating Ability

In this paper a self‐compensating pulse code modulation compound flow control valve and its self‐compensating algorithm are introduced. After adopting a self‐compensating method, the compound valve can maintain good control quality when one or more turn on/off valves (TOVs) fail by adjusting the activities of unfailed TOVs. A stochastic fault model for the compound valve is established and a Monte Carlo approach is used to calculate its life distribution. The results indicate that there is about 20–50% increase of mean controllable life. This might be of great importance when immediate emergency shutdown is not allowable or too costly, such as in the case of aircraft control and in the control of continuous processes. The extra life can leave a large enough time margin to plan a more graceful shutdown and maintenance. Copyright © 2006 John Wiley & Sons, Ltd.     

湍流模型在大钢锭中间包内流场数值模拟中的适应性研究

以多炉连浇大钢锭中间包为研究对象,采用标准k-ε模型和Realizable k-ε模型对大钢锭中间包内钢液流动状况进行了数值模拟,并将数值模拟结果与物理模拟结果相比较,以验证模拟结果的准确性.研究结果表明,对于深熔池、大通钢量的大钢锭中间包,采用Realizable k-ε模型的模拟结果与物理模拟结果更为接近,且对安装控流装置的中间包内流场模拟效果更好.     

微通道换热器两相流分布研究现状与展望

两相流进入微通道换热器容易出现分布不均匀的现象,显著降低微通道换热器的性能.本文对微通道换热器两相流分布的研究动态进行了归纳与分析,主要介绍了微通道换热器中两相流分布特性的影响因素、提升微通道换热器中两相流分布均匀性的技术方案、微通道换热器两相流分布特性的仿真研究及相分离技术在微通道换热器中的应用;论述了两相流在微通道...     

行波型热声发动机谐振管的调相作用

基于环形圈加谐振管的热声发动机的两自由度模型构思,在调相机理上开展了工作.系统分析和仿真研究表明:谐振管对于热声发动机系统不仅是决定系统工作频率、储能和稳定工况,还对行波型热声发动机的声场产生调相作用.针对不同形式的谐振管(谐振管,谐振腔和容腔),以及不同体积的容腔负载(10 L,20 L,40 L)进行仿真计算.研究不同条件下,对回热器处的压力和体积流率之间的相位调节作用及声功的影响.在此基础上,对回热器起点、中点和终点3个位置的流体微团进行分析,得到不同位置的p-V图.结果表明,谐振管的确起到调节声场相位的作用,容腔形式的谐振管更有利于回热器内声场的优化,而容腔的体积大小对回热器声场的影响不大.     

多因素耦合影响亚音速喷口强化气体流场分布研究

为了研究多因素耦合条件下亚音速喷口内气体流场分布演变的作用机制与影响规律,基于标准k-ε湍流模型,对压力-流速-收缩比耦合条件下的亚音速喷口构造均匀气体流场进行了数值模拟,通过定义top-hat流场分布关键参数的方式,定量评估压力-流速-收缩比对强化后流场分布的耦合影响.结果表明:多因素耦合条件下,亚音速喷口通过影响压...