Study of Flow and Heat Transfer in an Ejector-Driven Swirl Anti-Icing Chamber

The formation of ice on the leading edge of aircraft engines is a serious issue,as it can have catastrophic consequences.The Swirl Anti-Icing(SAI)system,driven by ejection,circulates hot fluid within a 360°annular chamber to heat the engine inlet lip surface and prevent icing.This study employs a validated Computational Fluid Dynamics(CFD)approach to study the impact of key geometric parameters of this system on flow and heat transfer characteristics within the anti-icing chamber.Additionally,the entropy generation rate and exergy efficiency are analyzed to assess the energy utilization in the system.The research findings indicate that,within the considered flow range,reducing the nozzle specific areaφfrom 0.03061 to 0.01083 can enhance the ejection coefficient by over 60.7%.This enhancement increases the air circulating rate,thereby intensifying convective heat transfer within the SAI chamber.However,the reduction inφalso leads to a significant increase in the required bleed air pressure and a higher entropy generation rate,indicating lower exergy efficiency.The nozzle angleθnotably affects the distribution of hot and cold spots on the lip surface of the SAI chamber.Increasingθfrom 0°to 20°reduces the maximum temperature difference on the anti-icing chamber surface by 60 K.

Experimental study on flow control of the turbulent boundary layer with micro-bubbles

The effect of micro-bubbles on the turbulent boundary layer in the channel flow with Reynolds numbers (Re) ranging from 0.87 × 105 to 1.23 × 105 is experimentally studied by using particle image velocimetry (PIV) measurements.The microbubbles are produced by water electrolysis.The velocity profiles,Reynolds stress and instantaneous structures of the boundary layer,with and without micro-bubbles,are measured and analyzed.The presence of micro-bubbles changes the streamwise mean velocity of the fluid and increases the wall shear stress.The results show that micro-bubbles have two effects,buoyancy and extrusion,which dominate the flow behavior of the mixed fluid in the turbulent boundary layer.The buoyancy effect leads to upward motion that drives the fluid motion in the same direction and,therefore,enhances the turbulence intense of the boundary layer.While for the extrusion effect,the presence of accumulated micro-bubbles pushes the flow structures in the turbulent boundary layer away from the near-wall region.The interaction between these two effects causes the vorticity structures and turbulence activity to be in the region far away from the wall.The buoyancy effect is dominant when the Re is relatively small,while the extrusion effect plays a more important role when Re rises.

Prediction of atomization characteristics of pressure swirl nozzle with different structures

The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment,10 nozzles with different structures are designed to comprehensively cover various geometric factors.In terms of simulation,steady-state simulation with less computational complexity is used to study the flow inside the nozzle.The results show that the diameter of the inlet and outlet,the direction of the inlet,the diameter of the swirl chamber,and the height of the swirl chamber all affect the atomization performance,and the diameter of the inlet and outlet has a greater impact.It is found that under the same flow rate and pressure,the geometric differences do have a significant impact on the atomization characteristics,such as spray angle and SMD(Sauter mean diameter).Specific nozzle structures can be customized according to the actual needs.Data analysis shows that the spray angle is related to the swirl number,and the SMD is related to turbulent kinetic energy.Through data fitting,the equations for predicting the spray angle and the SMD are obtained.The error range of the fitting equation for the prediction of spray angle and SMD is within 15% and 10% respectively.The prediction is expected to be used in engineering to estimate the spray performance at the beginning of a real project.

Numerical and experimental study on the particle erosion and gas–particle hydrodynamics in an integral multi-jet swirling spout-fluidized bed

In this paper,using the computational fluid dynamics based on Euler Lagrange and the commercial software Barracuda VR,the gas-particle hydrodynamics and the erosion of particles on the inner wall and internal components of the spouted bed in the integrated multi-jet swirling spout-fluidized bed(IMSSFB)are studied.Erosion experiments have obtained the characterization of particle erosion on internal components and verified the relevant numerical models.The results show that:the particle distribution within the IMSSFB is uneven due to the cyclonic effect of the axial swirl vane(ASV),resulting in particle erosion for the ASV being concentrated on one side;when the gas reaches the top,too high an erosion gas velocity leads to gas backflow.As the filling height increases,there is a tendency for the erosion position of the particles on the ASV to expand upwards.However,the effect of increasing gas velocity on the erosion position is insignificant.

基于云计算的翻转课堂在编程类课程中的应用

面向非理工专业学生开设编程选修课程可使其适应大数据时代的职场及学术要求,但面临缺乏可及性、稳定性强的编程操练环境,理论课程难度较大而课时不足,以及个体化指导和过程性评价不足等困难。在“R语言与数据可视化入门”课程中,通过搭建云计算平台,借助swirl自主学习包实现理论课程翻转教学,借助MOOC/自媒体/自制视频资源实现数据分析与可视化实践课程翻转教学,结合侧重于过程性评价的多元考核方式,达到较好的教学效果。本教学设计对其他非理工专业学生的编程选修课程具有一定示范推广价值。

基于CFD-DEM算法的气力输送气固两相流特性分析

超轻粉体颗粒由于质量较小,在运输过程中易受气流扰动而飘散,物料的管道气力输送过程不稳定,易发生堵塞。为了研究超轻粉体颗粒在旋流气力输送中气固两相流流动特性,采用计算流体力学与离散单元法(CFD-DEM),对Komax型静态混合器内气固两相流动特性进行数值模拟研究。研究发现,带有Komax型元件的水平管道可以改变颗粒的流动情况,改善了水平管道内颗粒堆积和分布不均匀的现象;分别从颗粒相和流体相的流动状态分析得到元件长径比Ar=3时为最优几何结构;通过正交实验极差分析得到影响气固两相流动特性的因素顺序:输送气速>颗粒质量流量>颗粒粒径。当元件Ar=3时,颗粒-颗粒和颗粒-管壁的碰撞次数与碰撞强度呈现负相关,结合出口颗粒流分散状态,优选输送气速为3~4m/s;主要考虑输送气速对管内压降的影响,提出了带有Komax型元件的水平管道气力运输过程中压降与输送气速和轴向位置的经验拟合式。

空间发动机离心喷嘴真空下脉冲工作雾化特性实验研究

为得到空间双组元发动机中的液液同轴离心喷嘴在真实工作时的雾化特性,利用全透明真空舱搭建了真空喷雾实验与测量系统,对同轴离心喷嘴的脉冲雾化过程进行了实验研究。在入口压力1.6 MPa,开启时间分别为8 ms,20 ms和50 ms等典型工况下,对比研究了真空与大气环境下离心喷嘴脉冲工作的雾化特性,测试了同轴离心喷嘴单路脉冲工作以及两路同时脉冲工作的喷雾情况,测量了索太尔平均直径SMD的动态变化,并使用高速相机拍摄了相应的喷雾场图像。真空与大气下的对比实验表明,在真空下同轴离心喷嘴单路脉冲工作稳定段的SMD明显大于在大气中的SMD,且在真空下锥形液膜比较平滑。同轴离心喷嘴两路同时工作的实验结果表明,真空下两锥形液膜不会合并,而在大气下两股液膜会完全混合。

Effect of Pre-Swirling Flow on Performance and Flow Fields in Semi-Opened Axial Fan

In this study, we tried to improve the performance by giving a pre-swirling flow to the radial inflow that occurred in the semi-opened axial fan. In addition, the flow fields of rotor outlet were clarified experimentally, and the effect of pre-swirling flow was considered. The experiment was carried out using a performance test wind tunnel with a square cross section of 880 mm. Three types of casings were prepared, in which the blade tip protruded 0%, 20%, and 40% of the meridional chord length. They were called R25, R15, and R05, respectively, in the casing bellmouth model code. Guide blades for generating a pre-swirling flow were installed on the vertical wall surface of the casing. In addition, a vertical wall was installed 60% upstream of the meridional chord length as an obstacle to prevent axial inflow. The velocity fields of the rotor outlet were measured using a hot-wire anemometer. From the results, the pre-swirling flow did not significantly affect the fan performance. When there was no obstacles wall upstream, there was a partial increase in efficiency, but the difference was not so large. When there was an obstacle wall upstream, the efficiency increased overall in the case of R15, but in the case of R05, the efficiency increased only in the low flow rate region, and conversely decreased in the high flow rate region. By observing the blade outlet flow fields when the performance was improved, it was confirmed that the influence of the tip leakage vortex was weakened.

磁场诱导矩形通道内铁磁流体流动及强化传热

为深入研究外加磁场作用下矩形通道中铁磁流体的流动及换热性能,基于有限体积法对其进行数值仿真计算。分析铁磁流体在不同雷诺数Re、磁场强度B下对努塞尔数Nu及流体阻力系数f的影响,重点对比3种热边界条件下磁场诱导铁磁流体旋流流动的特点、强化传热效果及综合强化性能。结果表明:当外加磁场作用于铁磁流体时,由于磁场-流场-温度场的协同作用,3种热边界条件下,矩形通道内的铁磁流体均产生不同结构的旋流流动,明显强化其传热效果,且施加的磁场强度越大,强化传热效果越好,综合性能更优。在研究范围内,通过对3种热边界条件的比较,四面受热、上下两面受热和底面受热的综合强化因子最大值分别达到了1.372、2.277、2.299。

旋流强化换热器传热与流阻分析

为了研究管程旋流强化中换热器的性能,设计了一种适合气体流动的旋流元件安装于换热器的管程换热管入口处。通过RNG k-ε模型进行了数值研究,对不同参数旋流结构和换热器入口流量为30~50 m3/h的条件进行研究,并模拟结果进行换热器的设计和实验系统的搭建。结果表明:加入旋流元件可以使流动趋于均匀进入各换热管,旋流元件对换热管近壁面处速度提升明显,总体传热系数提高了76.1%~135.9%,压降增加约5.7%~19.5%,旋流元件的加入使得换热器以较小的压力损失的情况下获得较高的换热系数。对其螺旋角度(14°、18°、26°)、长度(32 mm、48 mm、64 mm)以及叶片宽度(8 mm、10 mm、12 mm)进行分析,得到α=18°,L=48 mm,W=10 mm时,换热器效果为最佳。

卧式紧凑型旋流气浮装置旋流筒结构优化数值模拟研究

由于油田开发采出液含水率上升和海上平台空间的限制,亟需紧凑型污水处理设备用于对海上油田含油污水处理。对此设计了卧式紧凑型旋流气浮装置,通过Fluent数值模拟方法对该装置旋流筒区域的流场分布及油水分离性能开展了系统研究,探究了旋流筒结构、入口管径、含油污水入口速度和入口含油率等因素对油水分离效果的影响。结果表明,在入口管径为20 mm,含油污水入口速度为2 m/s时,采用导流叶片的旋流筒结构能获得较好的流场分布;含油污水入口速度越大切向速度衰减越严重;旋流筒在高度为100~300 mm时切向速度衰减较大,在高度为300~650 mm内衰减较小;相同含油污水入口速度下,增大入口管径能使旋流筒内油相体积分数增大;增大含油污水入口速度反而会导致旋流筒内油相体积分数减小;旋流筒内油相体积分数呈“U”型分布,且随入口含油率增大而增大,与入口含油率成正比。

翼型叶片安装方式对粉煤灰气力输送的影响

针对当前螺旋流气力输送中有关叶片安装方式的研究,分析了典型NACA系列翼型截面叶片应用于起旋装置时的流场。通过对观测面轴向流速与切向流速的仿真,计算叶片不同安装方式与安装角度时螺旋流场的旋流强度,确定了前缘迎风的安装方式比尾缘迎风起旋效果更强;安装方式固定时,旋流强度随安装角度的增大而减小。

旋转水力提升多金属结核运动特性数值模拟

采用CFD-DEM耦合方法对多金属结核提升进行模拟,研究了垂直管道中不同旋转流场旋流比对水力提升多金属结核输运特性的影响。结果表明,随着旋转流场旋流比增大,旋转强度显著增强,流体流速最大值增大,颗粒群轴向平均速度增大。旋转流场的旋转强度明显影响管道内颗粒的速度分布:速度大的颗粒逐步分布在管壁周围,速度较小的颗粒分布在管道中心处。旋转流场可降低颗粒群局部浓度,有利于降低因颗粒滞留效应引起局部浓度升高造成的输送管堵塞风险。

体型参数对梯形旋流排沙渠道水力特性的影响

为明确起旋室和排沙洞体型参数对梯形旋流排沙渠道水力特性的影响,采用试验研究与数值模拟相结合的方法,研究了各参数下旋流排沙渠道的分流比、空腔形态、压强、流速,对比分析了不同断面型式的水力特性。结果表明,增大起旋室进口宽度,或减小起旋室出口宽度、起旋室高度、排沙洞直径,均能减小梯形旋流排沙渠道的分流比;起旋室出口宽度是影响分流比的主要因素,排沙洞直径偏小会限制排沙洞内空腔的发展;增加渠道水面与排沙洞出口间的落差后可在排沙洞内形成更有利于泥沙运动的旋转水流;梯形旋流排沙渠道的水资源利用效率更高,当渠道来流量为89.6 m^(3)/h时,梯形旋流排沙渠道的分流比较矩形渠道的降低了6.6个百分点,且同一位置处的旋转水流流速更大。研究成果可为旋流排沙渠道在引水工程中的设计与应用提供参考。

常减压装置电脱盐污水治理的工艺改造与优化

针对常减压装置电脱盐污水中H2S和可燃气体含量高、水质因含油含渣的影响不能稳定达标的突出问题。采用常压闪蒸和高效旋流溶气气浮(CDFU)相结合技术路线配套原有重力沉降除油技术工艺,有效解决电脱盐污水中高含油含渣、可燃气和硫化氢含量较高的问题,改造后石油类降低73.6%,COD(化学需氧量)降低32.7%,H2S、可燃气体和VOCS体积浓度分别下降56.85%、57.93%和38.25%。电脱盐污水水质明显改善,减少对下游污水系统的影响,消除安全隐患。

体型参数对旋流排沙渠道水沙特性的影响

为明确关键体型参数对渠道和排沙洞内水沙特性的影响,在模型试验研究的基础上开展了旋流排沙渠道的水沙两相流数值模拟。结果表明:起旋室高度对截沙率影响较为显著,最大相差5.41%;排沙洞直径、倾角和起旋室出口宽度对分流比影响显著,最大相差8.13%,增大倾角后改善了原排沙洞封闭端因壁面条件影响而产生的泥沙淤积;起旋室出口宽度对渠道内水沙特性基本无影响;不同体型下旋流排沙渠道均可高效、持续排沙,截沙率均大于90%,经过起旋室后,高含沙水流从排沙洞流出,下游渠道含沙量急剧减小。

加勒比文学书写中的生态整体观论析——以《黑漩涡》和《口技艺人的故事》为例

伴随着日益严峻的生态危机,加勒比文学当中的自然书写逐渐被发掘,从而成为近年来文学研究的热点。其中,戴比丁探讨自然和人类关系寓言的《黑漩涡》和梅尔维尔探讨人与自然一体隐喻的《口技艺人的故事》呈现了加勒比文学中的生态整体观意识。本文通过分析《黑漩涡》中人类与自然的博弈和《口技艺人的故事》中圭亚那美洲印第安自然意识和资本主义理性世界的冲突,揭示了加勒比文学中的生态整体观和存在观。

旋流排沙渠道中旋转水流的排沙效果研究

旋流排沙渠道是基于旋转水流强挟带能力的特点提出的一种渠道水沙分离新技术,为了明晰其水沙特性,在试验研究的基础上,采用Realizable k-ε模型、VOF法及离散相模型,对旋流排沙渠道内的水沙两相流特性进行了数值模拟,通过与模型试验成果的对比确定了不同粒径泥沙的球度,研究了持续来沙条件下旋流排沙渠道的排沙效果,分析了渠道和排沙洞内泥沙的分布规律。结果表明:不同粒径泥沙的球度介于0.2~1.0之间时,在渠道顶部局部来沙条件下旋流排沙渠道对粒径为(0.075,3.000]mm泥沙的计算截沙率与试验值吻合良好,二者的相对误差仅为3.5%,误差主要来源于(0.075,0.160]mm的极细颗粒泥沙;当上游渠道水流进口来沙质量流量为60 g/s时,渠底高含沙水流由起旋室的分流,渠道含沙量迅速降低,起旋室前部和后部渠底水流含沙量分别为44.00 kg/m^(3)和0.07 kg/m^(3);排沙洞内的旋转水流对泥沙的挟带作用明显,在强离心作用下泥沙主要分布在排沙洞近壁面,最大泥沙含量约为200.00 kg/m^(3);在持续来沙条件下旋流排沙渠道对粒径为(0.075,3.000]mm泥沙的截沙率为95.98%,仅少量极细泥沙以悬移质形式进入下游渠道,渠道和排沙洞内无大量的泥沙淤积,表明旋流排沙渠道是一种可实现高效且连续排沙的水沙分离技术。本成果可为旋流排沙渠道在工程中的应用和水沙特性的研究提供有益参考。

套筒阀消能与气蚀研究及结构改进

对套筒阀的消能率进行研究,建立三维模型并利用Fluent仿真软件对其进行内部流场的数值模拟,分析了传统套筒阀不同开度下的流场分布及消能效果。通过结构改进,提出一种新型的旋流式套筒阀,研究旋流式套筒阀套筒窗口切向角的变化对阀消能效果的影响,对比分析了传统套筒阀和旋流式套筒阀在各开度下的消能效果及气蚀特性。结果表明:传统套筒阀消能效果低于旋流式套筒阀,且在管壁及套筒处易发生气蚀现象;增大旋流式套筒的切向角能够提高其消能效果,且管壁及套筒处不易发生气蚀现象。综合消能率及气蚀分析,槽口切向角为30°时旋流式套筒阀消能降压效果较好,阀内含气率较低,能够防止气蚀对阀内零件及管道壁面的破坏。

部分旋流对加力燃烧室流动和燃烧性能的影响

为改善先进加力/冲压燃烧室燃烧组织困难等问题,采用设置进口部分旋流,在燃烧室中产生局部离心力来增强油气掺混和加速火焰传播。通过数值模拟和试验的方法,研究了不同旋流进口位置及角度下部分旋流加力/冲压燃烧室的流动特性、燃烧效率及值班点火火焰发展过程。研究发现:多区域旋流进口与不同旋流角度的组合会使流动损失增大,但可以在燃烧室建立一个局部超重力场,增强油气掺混和加速点火过程火焰传播。相比于无旋流,旋流进口可以提高值班火焰传播速度;旋流进口最高可提升2.35%的燃烧效率。