不同导流条安放角下的管道双车车间断面轴向流速特性研究

鉴于筒装料管道水力输送是一种绿色环保的输送方式,通过理论分析与模型试验相结合的方法研究了该输送方式下同型管道双车在不同导流条安放角条件下运行时车间断面的螺旋流轴向流速特性。结果表明,不同导流条安放角条件下,车间各断面的轴向流速分布趋势基本相同,轴向速度均呈现随半径的增加而增加,速度的变化率则随半径的增加而减小;随着车间断面与管道后车支撑体距离的增加,轴向流速整体增加且分布趋于均匀化;随着导流条安放角的增加,相同测点轴向流速变化呈现先增长再保持平稳的状态。研究结果为筒装料管道水力输送技术应用于工程实践提供理论支持。     

不同导流条安放角下管道双车车间断面周向流速分布特性

为了进一步研究管道双车车间断面螺旋流的水力分布,选取5种导流条安放角(5°、10°、15°、20°、25°),利用粒子图像测速仪(PIV)测量试验管段内管道双车车间流场,分析不同导流条安放角下管道双车车间断面中螺旋流周向流速的分布规律.结果 表明,随着导流条安放角的增加,周向流速分布呈旋转对称的分布趋势;导流条安放角为...     

不同环状缝隙宽度下管道车车后断面轴向流速特性研究

管道车车后流场作为柱系绕流流场的一部分,尾迹绕流可能会对管道车柱系结构产生影响,进而影响管道车柱系结构稳定性。为此分析了4个不同缝隙宽度下管道车车后断面的轴向流速特性。结果表明,车后断面轴向流速受管道车结构影响呈区域性分布;距离管道车一定时,环状缝隙越小,相同断面轴向速度变化幅度越剧烈;管道车车后轴向流速变化幅度沿程减小,管道车对水流的影响沿程衰减,速度大小沿程向断面平均流速靠拢。     

不同荷载管道车弯管启动时环隙流场数值模拟

为研究不同荷载条件下管道车在弯管启动时环隙流场的分布，采用数值模拟结合物理模型试验验证的方法研究不同荷载管道车水平弯管启动时环隙流场。结果表明，荷载的增加不会改变缝隙流场流速的整体分布规律，仅仅改变缝隙流场流速数值的大小；不同荷载条件下，水平弯管内管道车缝隙流场轴向流速从管道内壁到管道车外壁有先增大后减小的规律。周向流速在管道车缝隙流入口断面处和车中断面处分布较为均匀，但在缝隙流出口断面处出现密封盖两侧流速相反分布。径向流速越远离支撑体和密封盖分布越均匀，且在管道车缝隙流出口断面支撑体处出现流速明显增大现象。该研究解释了环状缝隙流场分布规律形成原因，获得了不同荷载管道车在弯管处启动时缝隙流场的流速分布规律。在完善丰富环状缝隙流理论的同时，为筒装料管道水力输送的应用提供了理论依据。     

管道双车在不同车间距下车间螺旋流轴向速度特性研究

为进一步研究筒装料管道水力输送技术,了解管道双车在不同车间距下车间螺旋流速度特性,得出管道双车的最优运行间距。采用模型试验、理论分析相结合的方法,研究了双车间距分别为10、30、50、70、90cm情况下管道双车间螺旋流轴向速度特性。试验采用两个相同型号的管道车模型在水平光滑的有机玻璃圆管内完成,流量恒定控制为30m~3/h。结果表明,间距为10、30cm时,水流紊动混掺强烈,圆管周围间隔120°存在三个速度极大值区域,而圆管中心为速度极小值区域;间距为50、70cm时,圆管周围已无明显的涡形区域,圆管中心区域速度梯度较小,水流相对比较稳定;间距为90cm时,水流稳定,与无管道车时满管水流断面流速分布类似。由此得出,管道双车的合理间距为50~70cm。     

管道车平稳运移时的环隙流速分布特性

管道车平稳运移时环隙内水流流速分布特性关系着管道车与水流相互作用,从而也会影响管道车的运动特性与管道内的水力特性。通过物理试验与理论分析的方法研究了管道车平稳运移时环隙内水流流速整体与局部分布特性,对比了不同直径的管道车环隙内水流流速分布特性与输送效率之间的关系。结果表明,管道车平稳运移时,环隙进口断面处的流速最大,其次为车中断面,车后断面处的流速最小;靠近管道车壁面处的流速沿程变化较大,且流速大小与管道车速度有关,靠近管壁处的流速沿程变化较小;不同直径的管道车环隙水流流速分布情况影响着管道车的输送效率,当环隙水流流速与管道内水流流速之比接近于1时,管道车的输送效率最大。     

弯道二次流对床面地形响应特性的试验研究

弯道水流受床面地形的影响变得更加复杂,不同的地形边界使水流结构发生明显的改变。通过U形弯道水槽清水及冲刷试验,分析了弯道水面横比降、断面v-w流速场分布、断面涡量分布及涡通量沿程变化,发现断面环流分布特性、沿程变化趋势以及断面环流演化过程与床面地形之间存在较强的相关性。为深入探讨弯道二次流的发展演化及其与床面地形的相互影响提供了科学依据。     

苦草对明渠水流运动特征影响的试验

为了解含植被水流运动规律,以柔性植物苦草为对象,在室内水槽中开展了苦草斑块对水流时均运动特征影响的试验,观测分析了不同水流(断面平均流速分别为3、5、10cm/s)和不同植株密度(172、86、43、0株/m2)条件下含苦草水流的流速分布结构。结果表明,植被斑块对水平流速分布有影响,在斑块尾部边缘有涡的产生;由于植被的阻流作用,使得植被斑块内部流速沿程减小,斑块外围流速沿程增大;垂线流速呈S型,可划分为底边界层区、冠层次级最大流速区、冠顶过渡区及冠层上部对数流速分布区。植株密度对冠层次级最大流速区影响最为显著,密度越大,流速削减越迅速,逆转梯度越大;断面平均流速越大,植被对水流的影响越显著。     

有压管道内管道车稳定运行时下游水力特性研究

管道列车水力输送作为一种高效、环保、节能的物料运输方式，具有较广阔的应用前景。当管道车在管内静止时可将其视为绕交汇式圆柱系结构，而水流绕过该结构后会产生漩涡，从而造成部分能量损失。运用数值模拟、模型试验和理论分析法研究管道车绕流流场下游的水力特性与流场稳定后的空间涡结构。结果表明，不同直径的管道车下游流场的近场区域可分为回流区与射流区，随着向管道车下游距离增加，断面平均流速呈先略微下降再升高的趋势，在1倍管道车特征长度的距离时恢复接近管道来流的平均速度；随着下游远场区域距离的增加，断面平均流速的波动幅值逐渐减小，流场逐渐趋于稳定；流场内空间涡环结构高度破碎；且涡结构在靠近环形缝隙一侧较多，靠近管轴线一侧较少。     

基于OpenFOAM的旋转管道螺旋流水力特性数值研究

为进一步深入研究旋转管道产生的螺旋流对流场水力特性的影响,基于开源软件OpenFOAM,构建了水箱-管道出流气液两相流数值计算模型,模拟了竖直管、55°和45°螺旋管三种情况下的水流运动过程,通过分析、比较选定断面处速度分布、断面平均压强、湍动能随时间及空间位置的变化,总结了螺旋流对水平管段水力特性的影响。结果表明,相较于直管道,两组螺旋管道使水平管段螺旋流湍动能明显减小,压强变化趋于平缓不易产生负压,且管道内断面流速分布更加均匀。     

基于叶片变形偏航下风力机叶片绕流流场的研究

针对偏航工况下风力机叶片与流场之间的相互作用而产生的变形影响叶片绕流流场问题,基于叶片变形对不同偏航工况下水平轴风力机叶片绕流流场进行双向流固耦合数值计算,分析偏航工况对风力机叶片变形和表面应力的影响,在此基础上研究不同偏航工况对叶片绕流流场的影响.结果表明,不同叶片上的变形和应力呈现不均匀性,且随偏航角增大,不均匀性...     

Experimental investigation of the root flow in a horizontal axis wind turbine

This research investigates the flow behavior and its features in the blade's root region of a horizontal axis wind turbine by using stereoscopic particle image velocimetry (PIV) technique. Wind tunnel tests are conducted to measure the velocity field, phase‐locked with the blade motion, at different azimuth angles and at different spanwise positions. The pressure distribution is obtained from PIV velocity field by solving the Navier–Stokes momentum equations. In this paper, we aim to answer two questions: (i) How is the flow behavior in the root region? (ii) How is the evolution of the root vortex? The analysis of the velocity fields shows an outboard radial flow motion in the root region and a vorticity driven inboard motion at the blade?s maximum chord position. As a result of this vorticity driven flow, an increase in the axial velocity close to nacelle is measured. Wake sheets are observed and further discussed in the measured velocity and vorticity distributions. The formation and evolution of the root vortices conveyed downstream by the axial velocity are analyzed through vorticity and pressure distributions. Although the azimuthal vorticity in 3D representation is showing the trailing vorticity, the tilting of the root vortex tube is observed in the axial vorticity distribution. Moreover, the radial vorticity and azimuthal velocity from chordwise measurements show separation on the suction surface of the blade. This research concluded that the flow in the blade wake is driven by the root vortex; hence, the local effects of the root vortex cannot be ignored. Copyright © 2013 John Wiley & Sons, Ltd.     

不同材质风力机叶片绕流流场特征变化PIV实验研究

考虑风力机叶片变形对绕流流场的影响,通过粒子图像测速（PIV）方法,采集两副翼型相同、材质分别玻璃聚酯（叶片Ⅰ）和玻璃聚醋内部填充泡沫（叶片Ⅱ）的水平轴风力机叶片绕流流场信息,对不同测试截面处流场数据进行分析。研究结果表明：相比于叶片Ⅰ,相同工况下,叶片Ⅱ的总体涡量、回流区的面积和时均速度更大,轴向雷诺应力更小;随着相对轴向距离的增加,时均速度在相对高度方向波动减小,材质对轴向雷诺应力影响逐渐减弱。实验工况下,叶片材质对绕流流场特征的影响大于叶尖速比对其的影响,并沿径向方向有增大的趋势。     

Experimental and numerical investigation of tip vortex generation and evolution on horizontal axis wind turbines

The tip vortex of a wind turbine rotor blade is the result of a distribution of aerodynamic loads and circulation over the blade tip. The current knowledge on the generation of the tip vorticity in a 3D rotating environment still lacks detailed experimental evidence, particularly for yawed flow. The aim of this paper is to investigate how circulation at the blade tip behaves and how vorticity is eventually released in the wake, for both axial and 30° yawed flow conditions through the combination of experimental and numerical simulations. Stereo particle image velocimetry is used to measure the flow field at the tip of a 2m diameter, two‐bladed rotor at the TU Delft Open Jet Facility, for both axial and yawed flow; numerical simulations of the experiments are performed using a 3D, unsteady potential flow free‐wake vortex model. The generation mechanisms of the tip vorticity are established. The spanwise circulation along the blade exhibits a similar variation in both axial and yaw cases. A comparison of the chordwise directed circulation variation along the chord between axial and yawed flow is also presented and shown to be different. The analysis is based on contour integration of the velocity field. The tip vortex trajectory for axial flow confirms previous observations on the MEXICO rotor. The experimental results for yawed conditions have clearly shown how vorticity is swept radially away from the blade under the influence of the in‐plane radial component of flow. Such phenomena were only partially captured by the numerical model. The results of this work have important implications on the modelling of blade tip corrections. Copyright © 2015 John Wiley & Sons, Ltd.     

第四代DLE燃烧室流场特性研究

参照西门子的第四代干式低污染(Dry Low Emissions,DLE)燃烧室,设计了模型燃烧室,通过激光粒子图像速度仪(Particle Image Velocimetry,PIV)测量技术,对燃烧室头部出口流场进行了实验研究,分析了头部结构变化和入口空气流量变化对流场特性的影响。研究结果表明:两个主旋流器的旋流方向组合对燃烧室头部出口的流场特性有着很大影响;预混室RPL (Rich-Pilot-Lean)段的流量变化主要影响旋流器中轴线附近的轴向回流速度;入口空气流量变化对流场的影响主要表现在速度值上,但对速度变化趋势没有太大的影响。     

Experimental investigation of coupled conduction and laminar convection in a circular tube

Wall heat conduction effects on laminar flow heat transfer are experimentally investigated. The steady flow of water through a uniformly heated copper pipe is considered in the experiment, which covers a range of Reynolds numbers from 500 to 1900. The thermal behaviour of the test section is simulated numerically and the influence of conduction along the pipe wall is therefore accounted for in the reduction of the data. Fully developed flow results satisfactorily compare with predictions by a theoretical method previously developed by the authors [Heat Technol. 2,72 (1984)]. Results are also reported for the case where the velocity profile is partially developed at the inlet of the heat transfer section. The combined effects on heat transfer of flow development and of wall axial heat conduction are discussed.     

Forced convective mixing in a zero boil-off cryogenic storage tank

This paper presents the results of a study of fluid flow and heat transfer of liquid hydrogen in a cryogenic storage tank with a heat pipe and an array of pump-nozzle units. A forced flow is directed onto the evaporator section of the heat pipe to prevent the liquid from boiling off when heat leaks through the tank wall insulation from the surroundings. An axisymmetric computational model was developed for the simulation of convective heat transfer in the system. Steady-state velocity and temperature fields were solved from this model by using the finite element method. Forty five configurations of geometry and velocity were considered. As the nozzle fluid speed increases, the values of the maximum, average, and spatial standard deviation of the temperature field decrease nonlinearly. Parametric analysis indicates that overall thermal performance of the system can be significantly improved by reducing the gap between the nozzle and the heat pipe, while maintaining the same fluid speed exiting the nozzle. It is also indicated that increased inlet tube length of the pump-nozzle unit results in slightly better thermal performance. Increased heat pipe length also improves thermal performance but only for low fluid speed.     

新型拐角式整体针翅回转热管设计与试验

提出了一种新型拐角式整体针翅回转热管,对该热管进行了详细的理论分析与设计,并对其传热性能进行了试验测试。结果表明:拐角式整体针翅回转热管的轴向温度从蒸发段到冷凝段逐渐降低,最大轴向温差随着转速的增大而减小;回转热管蒸发段的管壁温度沿圆周方向上的温差随转速的增大而变大,冷凝段的管壁温度沿圆周方向上的温差随转速增大而变小;回转热管的整体传热功率随转速的提高而增大;当充液率约为15%时回转热管的热阻最小,传热性能最好;吸液芯对热管传热性能的影响不占主导地位,在低转速工况下吸液芯提高热管传热能力,在高转速下则起阻碍作用;与平行轴回转热管相比,拐角式回转热管传热性能提高了5倍。