气液两相流体流量或质量含气率的液体取样测量方法

从被测气液两相流体中取样分流出一部分单相液体,通过测量这部分单相液体的流量确定被测气液两相流体的流量或干度.通过将两相流体的测量转化为单相液体的测量,避免了两相流体的波动对测量精度的影响.分析表明:取样液相流量与主管路总流量的比值与主管质量含气率成线性关系.如果已知质量含气率或质量流量其中一个参数可以确定另一个参数.设计了液体取样装置,在气液两相流实验环道上进行实验.结果表明:本实验范围内,流量和质量含气率测量最大误差小于10%.     

汽水两相流体的单圆缺孔板双参数测量方法

提出了电站锅炉汽水两相流体质量流量和干度的测量方法 ,介绍了汽水两相流体质量流量和干度测量数学模型的建立和数据分析处理过程。在某电厂 6 70t/h锅炉上的测试结果表明 ,采用该方法测量汽水两相流体质量流量和干度是可行的。该方法能够有效地克服汽水两相流体流动不稳定性对测量精度的影响 ,显著地提高了测量精度。在试验范围内 ,汽水两相流体的质量流量测量误差小于± 5% ,最好的结果在±3%范围内     

换热器各流路对壳侧气液两相流动特性的影响

针对工业中广泛应用的管壳式换热器，应用空气-水两相混合物实验研究了壳侧旁路，泄漏流对气液两相流体流动特性的影响，以Ishihara两相流动模型为基础，建立了以横掠管束的主流路为基础的错流区通用两相压降计算关联式，通过错流区，泄漏流的分相流动模型，分析计算了主流路，旁路，泄漏流中气液分布，也分析了泄漏流对壳侧单相，两相总流量在各个分流路的流量分配影响，研究表明，主流路和旁路中气液各自占相应总流量的比例在不同的流型下明显不同，且比例值的波动范围较大，气液流量的分布在壳侧是不均匀的，折流板/换热管之间的泄漏流对壳侧的两相流动特性影响较小，而折流板/壳体之间的泄漏流影响较大。     

管壳式换热器壳侧气液两相流路分析法的研究

以Tinker壳侧流动模型为基础，提出了适宜于单相和气液两相流路分析法的壳侧单元流动模型。以主流、旁路流和泄漏流等各分流路的气液流量分布在稳态下应使壳侧流动的能量损耗达到最小的原则为基础，建立了壳侧气液两相流路分析法，给出了各流路的气液流量比例及错流区、窗口区压降的预测步骤，也给出了壳侧总压降计算式。建立的两相流路分析法预测结果与试验结果符合较好。     

气液两相流体润滑冷却在金属切削加工中应用的研究

气液两相流体润滑冷却,是近些年发展起来的一种有效的润滑与冷却的方法。实验研究表明,此种方法与技术对金属切削加工也有良好的适用性。文本在分析气液两相流体射流的一般特性的基础上,探讨了其润滑和冷却降温的机理,从而可以解释它优于单相切削液的原因。最后,我们还专门讨论了气液两相流体润滑与冷却技术在汽轮机零部件加工中的应用问题。     

文丘里管内气固两相流动的数值模拟和实验

文丘里流量计以价格低廉、结构简单、运行稳定和安装方便在单相流体测量中得到了广泛的应用.通过多年的实验研究和理论分析,文丘里管被认为是传统的差压流量计中最适合用于气固两相流流量测量的仪表.利用双流体模型对文丘里管内的气固两相流动进行了数值模拟,分析了气相和固相物质间的相互作用和流动形式,仿真结果验证了模型的准确性.     

非牛顿流体液滴铺展过程的格子Boltzmann模拟北大核心CSCD

格子Boltzmann可有效模拟气液两相流动,成功应用于牛顿流体动态湿润领域和非牛顿流体单相流动领域的研究。将牛顿流体的两相流动格子Boltzmann模型与非牛顿流体单相流动格子Boltzmann模型相结合,建立了幂指流体两相流动格子Boltzmann模型,模拟了牛顿流体和幂指流体液滴铺展过程,并将液滴半径随时间的变化规律模拟结果与液滴铺展理论模型进行了比较,对两类流体的铺展指数与流变指数变化关系进行了分析讨论。     

气液双相流体干度测量的研究与发展

本文介绍了气液双相流体干度测量的研究状况及存在的问题,讨论了这一领域研究工作的发展趋势.并提出了两种基于反问题想法的间接测量方法.     

短管道中平均气体流速测量系统的原理与应用

短管道气体流量的高精度低阻力可靠在线测量是实现四角切圆煤粉燃烧锅炉燃烧优化的基础条件。提出了基于伯努利流体动压测量原理,采用格栅整流、感压孔管道全截面分布、大腔体均压的测量实现方法。从数学上证明了可以利用平均压力的概念进行流量计算,分析了引压的阻力条件及其对格栅数量的要求,进而利用一次元件增大动静压差,开发了气体、气一固两相流体管道平均气体流速测量装置。工程应用得到了良好的效果,表明该测量方法具有广泛的应用前景。     

两相流垂直下降横掠"T"形柱体的斯特罗哈数

试验研究了两种规格梯形柱体，在垂直下降气液两相流中，发生气液两相涡衡时，气液两相特斯罗哈数的变化规律。在测得大量数据的基础上，得出了发生气液两相涡街时，气液两相斯特罗哈数的通用关系式。研究表明，气液两相斯特罗哈数在两相工况下为一变数，与来流截面含气率、涡街发生体形状与特征尺寸和来流方向等因素有关。应用此关系式，根据测得的两相涡街频率可将涡街发生体作为测量两相流流量与组分的测量元件。     

Flow through a porous medium in the presence of a magnetic field

Unsteady free convective flow of an electrically conducting fluid through a porous medium bounded by an infinite vertical and porous plate is considered. The free stream velocity of the fluid vibrates about a mean constant value and the temperature of the plate is constant. The influences of the permeability parameter and the magnetic parameter on the velocity field are discussed.     

Shape of isolated bubble in intermittent flows in a horizontal pipe

An experimental study on the shape of a single bubble similar to those observed in a horizontal plug/slug flow was performed using visual observation and conductance probes. The results indicated that the shapes of the bubble nose and the bubble body depend on the Froude number defined by gas/liquid mixture velocity, whereas the shape of the back region of the bubble depends on both the Froude number and bubble length. The photographic images showed that the structural feature of the bubble head is related to the motion characteristics of the bubble. The transition from plug flow to slug flow occurs when the tail of the bubble changes from a staircase to hydraulic jump pattern with the increasing of the Froude number and bubble length. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 276– 285, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20161     

弯曲管内的泰勒-迪安流动的数值模拟

流过横截面为正方形的弯曲管内的泰勒-迪安流,除了外墙以外的其它墙壁随着弯曲管中心轴旋转,沿着管的轴向具有压力梯度.数值计算使用光谱分析法.内圆筒旋转的流动和由于压力的流动的综合作用所产生的流动,在较宽的角速度和压力梯度范围内进行了计算.获得了断面二次流动类型的变化的情况.并对得到的解进行了线性稳定性分析.     

平行流蒸发器内气液两相流分配均匀性实验研究

平行流蒸发器内气液两相(特别是液相)在各扁管间的分配对其传热性能影响较大,如果各扁管间的气液分配不均匀其传热性能将显著地下降.在不同气-液流量下实验研究了6种不同形式的平行流蒸发器的分支管液体流量分配情况,实验中观察到流型以环状流为主.研究发现,对于竖直向下流动和竖直向上流动,用通过增加管径的方法不能改善液体流量在各分支管的分配,而主管中气液入口的位置对于流量分配均匀性影响较大.     

A Study of the Gas Flow through a LNG Safety Valve

A safety valve functions to control an upper limit of pressure inside the LNG line of transportation.If the pressureinside the safety valve nozzle exceeds a pre-determined value on the valve sheet which plugs the nozzle,an ex-cess of LNG discharges through the gap between the nozzle exit and valve sheet.In this situation,the forces act-ing on the valve sheet are gasdynamic forces generated by the discharge of LNG and mechanical forces supportedby the spring behind the valve sheet. The flow through the gap is very complicated,involving vortices,flowseparation,and shock waves.These affect adversely on the system accompanying with noise and vibration.Thepresent study aims at understanding the flow physics of safety valve.A computational work using the two-dimensional,axisymmetric,compressible Navier-Stokes equations is carried out to simulate the gas flow betweenthe nozzle exit and valve sheet,and compared with the theoretical results. It has been found that there exists adistance between nozzle exit and valve sheet in which the thrust coefficient at the valve sheet increases abruptly.     

板式换热器单边流动与对角流动数值模拟

基于传热学控制方程,采用数值计算方法,对板式换热器单边流动和对角流动时的流动与换热特性进行分析。在分析过程中保持换热器的结构参数不变,只改变进出口的流动方式,结果发现:在相同的流速下,单边流动的总对流换热系数要高于对角流动,而总压降单边流动要低于对角流动,在流速u=0.6 m/s工况下,努谢尔数单边流动比对角流动高出10.87%,压降对角流流动比单边流动高出5.13%。随着进口流速的增大,单边流动与对角流动的冷热流体进出口温差均减小,而且减小的趋势对角流动要大于单边流动,摩擦因子f和传热因子j逐渐减小。单边流动的流动和传热特性要优于对角流动。     

Discharge of a shock wave from an open end of a tube

IntroductionWhen a Pressure wave such as the shock waveprOPagates along a constant area straight tube andreaches at the open end, an impulsive wave is emittedOutward from the tube exit toward the surrounding areaand causes an impulsive noise laal a sonic boomproduced by a supersonic aircraft. Therefore, someauthors have investigated the discharge of a weakcompression wave from an open end in order to reducethe impulsive noise in relation to'the high speed railWaytUImel in the previous paped'…     

Influences of a Kind of Groove-blade on the Flow Field in a Compressor Cascade

This paper presents an experimental investigation of effects of a kind of streamwise-grooved blades on the flowfield in a compressor cascade.The flow field downstream the cascade and the boundary layer on the suctionsurface were measured using a mini 5-hole pressure probe at different incidence angles.The flow field in thegroove cascade was compared with that in the smooth cascade.The measurement results indicate that:(1)thegroove surface can restrain the development of the boundary layer on the suction surface;(2)the grooves canrestrain the radial migration of the low-energy fluids in the boundary layer on the suction surface;(3)the grooveblades can reduce total pressure loss and flow blockage in the cascade at the incidence angles of 0°,5°and 8°;(4)the maximum benefit of 8.6% loss reduction was obtained at the incidence angle of 5° while negative benefit of-3.0% loss reduction occurred at the incidence angle of-5°.     

Computer-aided numerical solution for the flow of compressible fluid through a series of identical annular orifices

The paper represents a general semi-empirical model for the calculation of the pressure distribution and the mass flow rate of a compressible fluid flowing through a set of concentric annular orifices in series. The flow through a single orifice is discussed taking into consideration the variation of the discharge coefficient and the effect of kinetic energy being carried from one throttling to the next one. The study is extended to a set of orifices resulting in the general model. A computer program based on this model is described which is applicable for different geometries and overall pressure ratios. Comparison with available experimental results shows that the model gives fairly accurate results.