A New Method for Measurement of Helium Mass Flow Rate in the Cryogenic System of TORE SUPRA

The TORE SUPRA Tokamak was built by EURATOM-CEA association. The NbTi conductor of superconducting coils is inserted in a tight enclosure filled with pressurized superfluid helium of 0.125 MPa at 1.8 K. The thick casing is cooled to 4.5 K by 1.8 MPa in 4.5 K supercritical helium circulation. Around this thick casing, a 80 K thermal shield protects the parts at very low temperatures from the thermal radiation, which is cooled by pressurized helium at 80 K and 1.8 MPa. A new measurement method for helium mass flow rate of 80 K shield and 4.5 K casing is described in this paper. The commissioning was done on the two helium loops of the cryoplant: the supercritical 4.5 K thick casing and 80 K shields. The purpose is to improve control of the 4.5 K and 80 K refrigeration loops.

Lumped Parameter Mass Flow Rate and Pressure Control Characteristics Model for High-Speed Pneumatic PWM on/off Valve

Aiming at solving the problem of strong coupling characteristic of the key parameters of high-speed pneumatic pulse width modulation( PWM) on / off valve, a general lumped parameter mathematical model based on the valves time periods was well developed. With this model,the mass flow rate and dynamic pressure characteristics of constant volumes controlled by high-speed pneumatic PWM on /off valves was well described. A variable flow rate coefficient model was proposed to substitute for the constant one used in most of the prior works to investigate PWM on /off valves' dynamical pressure response, and a formula for disclosing the inherent relationship among the PWM command signal,static mass flow rate,and sonic conductance of the valve was newly derived.Finally,an extensive set of analytical experimental comparisons were implemented to verify the validity of the proposed mathematica model. With the proposed model, PWM on /off valves' characteristics,such as mass flow rate,step pressure response of the valve control system,mean pressure and ripple amplitude,not only in the linear range,but also in the nonlinear range can be wel predicted; Good agreement between measured and calculated results was obtained,which proved that the model is helpful for designing a control strategy in a closed loop control system.

Design of fan beam optical sensor and its application in mass flow rate measurement of pneumatically conveyed solids

The fan-beam optical sensor is made up of many semiconductor lasers and detectors fixed around the wall alternately at a cross section of pneumatically conveying pipe. When the sensor works, a scanning light source emits a 50° lamellar fan-beam through the gas-solid two phase flow, and the projection data resulting extinction effect of solid particles are detected at the same time. With the projection data, the flow rate mass can be calculated, and then the flow image can be reconstructed. In this paper, the design of the sensor including spatial arrangement of the structural parts, basic principle and measurement sensitivity distribution are introduced. The mathematical measurement model of solid mass flow rate is presented together with the testing results.

Effects of fluid recirculation on mass transfer from the arterial surface to flowing blood

The effect of disturbed flow on the mass trans- fer from arterial surface to flowing blood was studied nu- merically, and the results were compared with that of our previous work. The arterial wall was assumed to be vis- coelastic and the blood was assumed to be incompressible and non-Newtonian fluid, which is more close to human arte- rial system. Numerical results indicated that the mass trans- fer from the arterial surface to flowing blood in regions of disturbed flow is positively related with the wall shear rates and it is significantly enhanced in regions of disturbed flow with a local minimum around the reattachment point which is higher than the average value of the downstream. There- fore, it may be implied that the accumulation of cholesterol or lipids within atheromatous plaques is not caused by the reduced efflux of cholesterol or lipids, but by the infiltration of the LDL （low-density lipoprotein） from the flowing blood to the arterial wall.

Experimental Analysis of the Flow Characteristics of an Adjustable Critical-Flow Venturi Nozzle

The response of an adjustable critical-flow Venturi nozzle is investigated through a set indoor experiments aimed to determine the related critical flow rate,critical pressure ratio,and discharge coefficient.The effect of a variation in the cone displacement and liquid content on the critical flow characteristics is examined in detail and it is shown that the former can be used to effectively adjust the critical flow rate.The critical pressure ratio of the considered nozzle is above 0.85,and the critical flow control deviation of the gas flow is within±3%.Liquid flow can reduce the gas critical mass flow rate accordingly,especially for the cases with larger liquid volume and lower inlet pressure.The set of results and conclusions provided are intended to support the optimization of steam injection techniques in the context of heavy oil recovery processes.

A Numerical Simulation of Air Flow in the Human Respiratory System Based on Lung Model

The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airways of human lungs is considered. The basis of a lumped parameter model or a transport equation is modeled during the inspiration process, when oxygen enters into the human lung channel. The quantitative measurements of oxygen are detached and the model equation is solved numerically by explicit finite difference schemes. Numerical simulations were made for natural breathing conditions or normal breathing conditions. The respiratory flow results for the resting conditions are found strongly dependent on the AD effect with some contribution of the unsteadiness effect. The contour of the flow rate region is labeled and AD effects are compared with the variation of small intervals of time for a constant velocity when breathing is interrupted for a negligible moment.

隧道火灾相向射流排烟系统烟气质量流率比例系数

为探究隧道相向射流排烟系统中火灾发生时烟气的流动特性,通过FDS数值模拟研究隧道内不同上、下游风速工况下的上、下游烟气质量流率变化。基于等效风速、理论分析和数值模拟结果得到上、下游风速与烟气质量流率比例系数的关系式。结果表明:当等效风速小于临界风速时,上、下游烟气质量流率比值和烟气质量流率比例系数随等效风速增加而减小,并且等效风速与上、下游烟气质量流率比值存在线性关系;当等效风速大于临界风速时,上、下游烟气质量流率比值和烟气质量流率比例系数为0。

聚乙烯相对分子质量及其分布快速评价方法研究

以国内外采用不同工艺和催化剂生产的17种聚乙烯的测试结果为基础,通过理论推导与模型拟合相结合,建立了以熔体流动速率快速计算相对分子质量及其分布的方法,并由此计算出数均分子量。经验证,该方法准确性较好,可弥补凝胶渗透色谱法的不足,有利于装置生产过程中准确控制产品质量和提高新产品开发效率。

高压含水气井两相流态节流判断与控制方法

井筒气水两相管流节流前后动态特性分析与控制,对保障致密气等高压含水气井高效稳定安全开采和水合物防治具有重要意义。考虑等熵绝热、等压热容、等容热容、不同井深节流能量等因素,推导气水两相流体流经喷嘴的能量、动能和温度动态变化等热力学微分方程组,建立高压含水气井两相节流能量、节流系统热量、节流物质平衡和流体质量流量变化等井下节流场数学模型,提出一种气水两相井筒节流前后动态特性分析与控制方法,为优化井下节流器及其节流喷嘴的结构参数和保障气井流动安全提供理论依据。最后依据数值模拟手段及其判断结果,以鄂尔多斯盆地东缘大宁-吉县区块为例进行验证,以揭示高压含水气井喷嘴尺寸和深度、含水率、节流前压力和温度对节流前后动态特性的影响规律。结果表明:高压含水气井气水两相流体质量流量先是随节流压力比减小而呈指数级增大,并在压力比降至0.55阈值附近时达到最大值,增大喷嘴下入深度和含水率、同时降低节流前压力和温度,可提高节流后温度,有利于抑制水合物生成;且节流过程临界质量流量受喷嘴内径的影响最大,含水率和节流前压力次之,而节流前温度和喷嘴深度的影响最小,且增加含水率会提高临界质量流量,但产气量也随之下降;大宁–吉县区块现场工程实例分析表明,井下节流喷嘴内径由3.0 mm扩至5.0 mm和节流前压力由14 MPa增至18 MPa时,气水两相流体的临界质量流量提升幅度分别为179.3%和27.8%,而利用地层温度等将节流前温度由313 K升至333 K时,节流过程临界质量流量反而小幅下降且下降幅度仅为5.15%,为此,增大喷嘴内径及其下入深度和节流前压力同时降低节流前温度,有利于提高气水两相流体节流过程中临界质量流量,并提升高压含水气井的产气量。

基于NSGA-Ⅱ算法的含汞天然气脱水脱烃单元工艺参数优化

在含汞天然气的脱水脱烃处理过程中,部分汞会进入外输干气。为降低外输干气中汞的质量流量并考虑系统能耗,利用HYSYS软件模拟了高含汞天然气脱水脱烃单元,探究低温分离器进料温度、乙二醇质量分数、乙二醇质量流量对外输干气中汞质量流量以及系统能耗的影响。在此基础上,依据响应面法建立各关键参数与外输干气中汞质量流量以及系统能耗的多目标优化模型,并使用NSGA-Ⅱ(非支配排序遗传算法Ⅱ)进行多目标寻优。结果表明:经过NSGA-Ⅱ算法计算出的Pareto解值与HYSYS模拟值误差小于1%,其结果精确度较高。且经优化后的外输干气中汞的质量流量以及系统能耗均有所下降,故可利用NSGA-Ⅱ算法求解得到的Pareto解集可为天然气脱水脱烃流程的参数优化提供指导。

小型堆中窄矩形通道自然循环临界热流密度实验研究

针对窄矩形通道在换热过程中有较高功率密度的问题,本文为了解决在小型反应堆中的应用,采用所搭建的小型窄矩形自然循环通道,进行实验研究,并结合BP神经网络方法对实验数据进行预测,分析在不同参数工况下临界热流密度随不同参数的变化情况以及不同参数对临界热流密度的影响程度。研究结果表明:质量流量与系统压力对临界热流密度点的影响呈现正相关;出口干度对临界热流密度呈现负相关;且质量流量对临界热流密度的影响程度最大;压力对临界热流密度的影响程度最小。利用相关实验数据,基于影响因素大小,通过BP神经网络方式,建立了适合于自然循环窄通道小堆的模型。BP神经网络算法的预测值与实验值符合良好,误差为10%;Katto模型与实验数据相比误差较大,Zhang公式和拟合公式的误差较小,所建立的临界热流密度模型可作为窄矩形通道自然循环临界热流密度的计算公式。

某双油路离心式喷嘴雾化性能分析

燃油喷嘴的雾化对于解决航空发动机燃烧室问题是至关重要的,为探究某双油路离心式喷嘴的雾化性能,运用两相界面追踪流体体积(Volume of Fluid,简称VOF)方法对该喷嘴的内外部流场进行数值仿真。以双油路离心喷嘴的雾化锥角、质量流率以及液膜厚度作为雾化性能指标,分别模拟出主油路单独供油、副油路单独供油以及主副油路同时供油三种不同工作模式在不同压差条件下喷嘴燃油流动的稳态情况,获得双油路离心喷嘴的雾化性能指标并对其影响规律进行研究。结果显示:数值仿真能较好地模拟出喷嘴的雾化特性,随着压差增大,扩口式主油路单独工作时的雾化锥角减小,平口式副油路单独工作时的雾化锥角增大。当主、副油路同时工作时,雾化锥角随压差的增大而增大且始终处于单路单独工作时的雾化锥角之间;质量流率随着压差的增大而增大且增幅逐渐减缓;液膜厚度在低压区随压差的增大而迅速减小,随后趋于稳定。

同心和偏心锥形煤斗卸料流动特性研究

为了研究颗粒在同心锥形煤斗和偏心锥形煤斗中的卸料流动特性,采用离散元法在EDEM软件中建立颗粒离散元模型,对半顶角不同的煤斗进行颗粒卸料流动的数值模拟,对颗粒的质量流量、流动稳定性和煤斗中心线处颗粒速度进行了分析。结果表明:参数条件相同时,偏心锥形煤斗的质量流量大于同心锥形煤斗,同心锥形煤斗存在质量流量变化的临界半顶角,而偏心煤斗不存在明显的临界半顶角;随着半顶角的减小,2种煤斗的质量流量随之增大;偏心锥形煤斗的卸料稳定性优于同心锥形煤斗,但2种煤斗在半顶角大于60°后,变异系数都出现大幅增加;2种煤斗在半顶角为0°—40°时表现为整体流,在半顶角大于60°时表现为中心流。说明偏心锥形煤斗卸料整体性能优于同心锥形煤斗。

基于主被动冷却耦合的棱柱电池热管理系统研究

随着电动汽车电池包容量的增加和电池单元能量密度的提高,电池的热管理已经成为当前电动汽车设计制造过程中的重点和难点。本文基于单个电池单元和电池模组逐级热分析的方法,在电池模组的热管理系统中,引入液冷板作为主动式制冷,同时采用风冷和均热板作为被动式制冷。首先,通过对单个电池单元进行细致建模,计算得到不同电池单元放电倍率下的产热量。然后,对组装成的电池模组进行主动和被动热管理系统的建模。接着,分别对两种不同的热管理系统—风冷与液冷耦合系统、液冷与均热板耦合系统进行最高温度和温度均匀性的模拟仿真,并选择冷却性能更优的结构。最后,对选定的热管理系统在不同质量流量下对系统冷却效果的影响进行优化设计。研究结果表明,随着冷却液流量的增加,最高温度呈现下降趋势,且在2.125 L/min之后冷却效果趋于平缓。综合考虑冷却效果和系统能耗,2.125 L/min的进口流量是在液冷与均热板耦合系统下的最佳选择。

基于集肤电伴热的集输管道节能评价研究

为实现集输管道热力消耗方面的节能挖潜,在热油管道温降理论计算基础上,根据集中加热和集肤电伴热两种原油加热输送方式的不同,探讨了不同因素对节能比的影响,研究了停输工况下集肤电伴热的加热效果趋势,掌握运行能耗、维温效果等多项技术参数。结果表明,理论上集肤电伴热恒优于集中加热方式;节能比与总传热系数、管径、管道长度呈线性负相关,与质量流量、原油比热容呈指数正相关,在一定条件下集肤电伴热的节能效果显著;现场管道中的电伴热停止工作后,38 h后温度才突破设定的下限温度,每年可节约热能15543.55 kW,相当于关停13台1160 kW的管式加热炉,可年减少碳排量10.215 t CO_(2)。

DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

Accelerated Gas Carburizing (URX Gas Carburizing)

URX gas Carburizing is an accelerated gas Carburizing method with 50% CO + 50% H2 gas which comes from CFLt gas + CO2 gas. By using this gas composition, the Carburizing reaction rate increases to the maximum and the controllability of carbon potential improves. A carbon mass flow rate is the product of the Carburizing reaction rate multiplied by the difference of carbon percent between carbon potential of the gas and the carbon content of the surface of treated steel parts. We have obtained excellent results from the experimental tests at our laboratory as mentioned bellow. 1) Carburizing time can be shortened by 40% for 0.5 - 0.9 mm effective case depth. 2) Uniform Carburizing case depth 3) Less internal oxidation with the same case depth. We have already developed the new roller hearth type continuous Carburizing furnace and the new URX gas generator .

Numerical Study of Fluid Flow over Bundle Tubes

In this paper, a bank of tubes containing a flowing fluid which is immersed in a cross flow second medium of fluid with different temperature has been studied numerically using computational fluid dynamics. Laminar steady flow with a low Reynolds number has been studied in this work. Inlet mass flow rate and the bulk temperature are known and numerical method has been implemented to study the convective heat transfer to investigate the temperature and flow fields. Effects of different inlet bulk temperatures and mass flow rates have been investigated on temperature and pressure variations.

水稻液体肥变量施用调节系统设计与试验

【目的】设计一种机电式流量调节阀,与已研制的气力引射式施肥器集成构建液体肥变量施用调节系统,实现水稻近根部微小流量液体肥精准施用。【方法】通过试验标定了系统质量流率理论模型,建立控制系统传递函数模型,设计了基于模糊推理的PID控制器结构、规则和初始参数;通过仿真试验,分析了PID和模糊PID控制的调控响应能力。【结果】仿真试验结果表明,模糊PID控制阶跃信号响应超调量、调节时间和稳态误差分别为0.12%、2.51 s和0.007,与PID控制的对应值42.90%、4.44 s和0.010相比均较低,表明模糊PID控制动态调节和稳定性更好;在幅值为0.5、持续时间为0.1 s的脉冲信号干扰下,模糊PID控制的调节时间为0.61 s,比PID控制(1.67 s)更短,具有更强的抗干扰能力。性能试验结果表明,10种目标质量流率条件下,模糊PID控制的质量流率绝对误差均低于PID控制,控制精度为93.93%~96.88%,高于PID控制(90.00%~95.21%);在施肥量变化时,模糊PID控制的超调量为12.2%,上升时间、调节时间和峰值时间分别为1.5、10.7和1.7 s,均低于PID控制的17.4%、2.1 s、13.3 s和2.3 s。【结论】基于模糊PID控制的水稻液体肥变量施用调节系统具有较高的质量流率控制精度和跟踪性能,为研制水稻田液体肥变量施肥装备奠定了基础。

孔板空化器参数数值模拟与实验

为了研究孔板空化器的孔数和孔板厚度对水力空化效果的影响,采用数值模拟的方法,通过压力、速度、气含率云图确定了径向监测面;借助云图观察流场内气核的析出位置及压力与气含率的分布情况,并以气相质量流率作为评判空化强度的标准定量分析孔板厚度、孔数在不同压差下对孔板空化特性的影响。实验以纯水作为介质,从水的电导率和温升的角度研究孔板空化特性,验证数值模拟的规律,在0.2~1 MPa压差下的空化效果与数值模拟相吻合,为同类空化器的设计及应用提供依据。