一种适用于煤粉工业锅炉燃烧器的冷态流场特性研究

利用试验和数值模拟的方法对一种适用于煤粉工业锅炉燃烧器的冷态流场特性进行了研究.结果表明,回流区的长度随内二次风旋流强度的增大而明显增大,随钝体阻塞率的减小而缩短;燃烧器回流区内的回流速度随一次风风速的增加略有降低,随内二次风旋流强度的增加而增大,随钝体阻塞率的增加呈先增大后减小的趋势.试验结果为该燃烧器的设计和热态试验提供了一定的指导.     

二次风旋流强度对燃烧器回流场影响的数值模拟

旋流燃烧器因为能够形成较大的中心回流区,卷吸高温烟气,促进煤粉的着火和稳燃,在工程上得到了广泛的应用。本文采用Real-izablek-ε模型研究了二次旋流风的旋流强度对煤粉燃烧器回流场的影响,分析了不同旋流强度回流区的分布,形状及其大小的影响,为燃烧器设计提供理论依据。     

1913t／h超临界四角切圆锅炉冷态空气动力场的试验研究

为了解某电厂1913t／h超临界四角切圆锅炉大修后炉内空气动力场的分布特性,进行了锅炉冷态空气动力场试验。对6台磨煤机的一次风挡板特性及两侧二次风道挡板特性进行了测量,并对一、二次风风速进行了调平,对贴壁风速及水平烟道风速进行了测量。试验结果表明,一、二次风挡板特性较好,经调整各粉管及燃烧器喷口风速均匀,贴壁风速及水平烟道风速合理。     

改进型漩流燃烧器技术在在E JI-670-13.8-545 тK锅炉中的应用

改进型旋流燃烧器.根据牡丹江第二发电厂入炉煤质灰分高、挥发分适中的特点,为确保一次风出喷口后形成较大的回流区,实现低负荷稳燃性能,在一次风喷口内侧加装稳燃齿并将=:次风旋流器由原位置向炉膛方向适当推进.经计算设计为:(1)扩流锥占一次风流通面积百分比为:40~50%,一次风扩流锥优化角度α;一次风稳燃齿数6个,一次风扩口优化角度B:(2)二次风叶片数16,::次风扩口角度lO度,叶片遮盖度1.5,二次风叶片倾角64度.(3)为延长二次风旋转射流在炉膛内的长度,二次风旋流器由原位置向炉膛适当推进.由于入炉煤质灰份较大,一次风侧部件磨损问题尤为突出.本次改造方案采用的耐热和防磨措施如下:(1)据相关资料:磨损速率与含粉气流流速成三次方关系,含粉气流流速对磨损影响极大.在保证稳定燃烧的情况下,为减轻磨损,燃烧器一次风速选用较低的21.9 m/s,低于一次风管道流速28.5 m/s:(2)适当减小冲击角,优化设计一次风扩流锥防磨环角度;(3)燃烧器喷口采用特殊性能的耐热合金钢,其耐热温度达1250℃.扩流锥所在位置距炉膛较近,必须具有良好的耐热耐磨特性.材料选用耐热抗磨铸钢,900℃时,HRC≥26.     

改进型漩流燃烧器技术在在ЕЛ-670-13．8-545тК锅炉中的应用

改进型旋流燃烧器。根据牡丹江第二发电厂入炉煤质灰分高、挥发分适中的特点，为确保一次风出喷口后形成较大的回流区，实现低负荷稳燃性能，在一次风喷口内侧加装稳燃齿并将二次风旋流器由原位置向炉膛方向适当推进。经计算设计为：（1）扩流锥占一次风流通面积百分比为：40～50％，一次风扩流锥优化角度α，一次风稳燃齿数6个，一次风扩口优化角度β：（2）二次风叶片数16，二次风扩口角度10度，叶片遮盖度1．5，二次风叶片倾角64度。（3）为延长二次风旋转射流在炉膛内的长度，二次风旋流器由原位置向炉膛适当推进。由于入炉煤质灰份较大，一次风侧部件磨损问题尤为突出。本次改造方案采用的耐热和防磨措施如下：（1）据相关资料：磨损速率与含粉气流流速成三次方关系，含粉气流流速对磨损影响极大。在保证稳定燃烧的情况下，为减轻磨损，燃烧器一次风速选用较低的21．9m／S，低于一次风管道流速28．5m／s：（2）适当减小冲击角，优化设计一次风扩流锥防磨环角度：（3）燃烧器喷口采用特殊性能的耐热合金钢，其耐热温度达1250℃。扩流锥所在位置距炉膛较近，必须具有良好的耐热耐磨特性。材料选用耐热抗磨铸钢，900℃时，HRC≥26。[     

行驶车辆对城市街谷内空气流动与污染物扩散影响的数值模拟

通过城市街谷内单个车辆在任意时刻对空气的曳力计算,提出更具一般意义的欧拉-拉格朗日方法,实现对行驶车辆引起空气流动及湍流的模拟。模拟结果显示,在不同的背景来流风速下,行驶车辆对街谷内湍流有显著影响,而对平均流场的影响相对较弱;行驶车辆诱导的湍流主要分布的靠近路面的区域,且在靠近背风面的地方湍流强度增大最为显著;街谷内行驶车流诱导湍流强度及分布受背景来流风速的影响显著,而受车辆行驶速度的影响相对较弱。街谷内行驶车流对风场的影响非常复杂,简单地以车辆行驶速度或背景来流风速进行参数化的模型很难模拟不同情形下的流场特征。     

三叶型回转窑温度场及影响因素的数值模拟

采用三维建模软件Pro/E建立三叶型回转窑内部流场三维模型,运用计算流体动力学(CFD)流体仿真分析软件Fluent,设置边界条件,选用非预混燃烧模型、离散相模型求解窑内温度分布情况;通过对一次风速、一次风温、叶片倾斜角、二次风速、油喷射角度各影响参数进行分析对比。结果表明:当处于50~60 m/s的一次风速,200℃的一次风温,150 m/s的二次风速,旋流叶片角度为30°左右,喷油角度15°时窑内能得到理想的温度分布,研究结果为三叶型回转窑设计制造和工程应用提供参考依据。     

建筑物风沙流场与荷载的风洞试验研究

通过风洞试验研究了同一风速下不同落沙量时的风沙流场特性,包括风速、湍流度和沙浓度的分布规律,基于流场分析的结果在该风沙环境下开展了风洞高频动态天平测力试验,探究了风沙流场中建筑物迎风面所受到的风压力和沙粒冲击力规律,并采用沿高度方向等分迎风面的方法对风沙荷载沿建筑物高度方向的变化规律进行了探究。研究结果表明:风沙流场下的沙浓度梯度分布与落沙量及高度有关。沙颗粒对风速有一定的削弱作用,而对湍流度有一定的增强作用,且沙浓度越大该削弱作用和增强作用越明显。风沙流场下建筑物迎风面所受到的风压力和沙粒冲击力之和随着高度和沙浓度的增大而增大;其中风压力随着高度的增大而增大,而随着沙浓度的增大而减小,沙粒冲击力随着高度的增加而减小,而随着沙浓度的增大而增大。     

台风“白鹿”影响下泉州湾近地脉动风速功率谱及其拟合参数分析

国内高速铁路网不断完善,沿海铁路海湾地形的风场特性亟待研究。基于福厦客专—泉州湾跨海大桥桥址处40 m风塔,实测获得了201911台风"白鹿"影响下的泉州湾近地风场实测数据。基于经验模态分解(EMD)技术得到了台风全过程时变平均风及相应脉动风样本,采用四参数风速功率谱模型拟合了台风纵向、横向及竖向功率谱,在此基础上对拟合参数进行了平均风速影响分析及概率密度分析。建立了38 m高度处台风演化功率谱并与同风速范围的相关规范建议风谱进行了对比。研究表明:四参数风谱模型能较好适用于实测台风风谱,各拟合参数随平均风速变化并不显著,拟合参数B随A呈指数型增长;核密度估计方法能较好拟合风谱参数的概率密度分布,拟合谱中的A参数概率密度近似对数正态分布,而B,C及α参数则与正态分布接近;测点接近7级风圈时所测脉动风湍流动能较位于风圈内时强;规范风谱并不能很好地反映"白鹿"台风引起的跨海大桥主梁高度处湍流功率谱密度(PSD)特征。     

叶轮式湍流磨单相流动数值模拟

采用计算流体动力学方法对叶轮式湍流磨内部流场进行单相流动数值模拟;通过分析不同转速、不同出口压力下磨腔内部气体温度、压力、速度、速度梯度、湍动能等流场参数,探讨物料粉碎机理及湍流磨工作特性。结果表明:叶轮与轴向齿槽间隙内切向速度梯度大于15 000 s~(-1),且存在峭壁结构,为主要研磨区;湍流磨转速大于6 000 r/min时温升较大,且随转速增大温升越来越剧烈;出口段气流存在强烈旋转,表现为强迫涡流,涡流使气体沿径向形成压力梯度,管道中心出现负压,进而引起回流。     

Effect of liquid and air swirl strength and relative rotational direction on the instability of an annular liquid sheet

Summary Instability of a swirling annular liquid sheet in swirling inner and outer air streams has been investigated by a temporal linear stability analysis. The effects of the swirling and axial motion of the liquid and the air streams, as well as the effects of relative inner and outer air swirl orientation with respect to the liquid swirl direction on the instability have been investigated. Results show that for a non-swirling liquid sheet axial inner air stream is more effective than axial outer air stream in enhancing the sheet instability. This is opposite of a swirling liquid sheet where axial outer air is more effective in promoting sheet instability compared to axially moving inner air stream. The liquid swirl has a destabilizing effect at the outer interface but has a stabilizing effect at the inner interface. At high liquid swirl Weber number, the outer air (with axial and swirl velocity components) is more effective in enhancing sheet instability compared to the inner air (with axial and swirl velocity components). To understand the effect of air swirl orientation with respect to liquid swirl direction, four possible combinations with both swirling air streams with respect to the liquid swirl direction have been considered. Results show that at high liquid swirl Weber number a combination of counter-rotating-inner air stream and co-rotating-outer air stream has the largest most unstable wave number. However, at low liquid swirl, co-inner/counter-outer combination has the largest most unstable wave number. The combination of inner and the outer air stream co-rotating with the liquid has the highest growth rate. In many combustion applications, the liquid sheet is injected in high pressure environment where the effect of high ambient pressure results in increased aerodynamic interaction due to high air density. Hence the effect of high ambient pressure is studied in terms of the dimensionless parameter of air-to-liquid density ratio. Results show significantly higher disturbance growth rates at high air pressure. However, the qualitative sheet stability behavior is similar to that at atmospheric pressure.     

碰撞式微型压电风能采集器实验研究(英文)

为提高基于风致振动机理的微型风能采集器在低风速下的输出功率,设计了一种新型的碰撞式微型压电风能采集器.采集器主要由圆柱形钝体、铰接分隔板、压电悬臂梁和支架组成.通过铰接分隔板和压电悬臂梁的碰撞有效降低了采集器的工作风速.加工制作了采集器的原理样机并在小型风洞内进行了实验测量.通过实验发现分隔板与压电片横向间距对采集器的工作风速和输出功率有很大的影响.压电悬臂梁自由端添加质量块可以提高输出功率.风速15 m/s、外接200 kΩ优化负载时,采集器最大输出功率为64μW.     

CFD simulation and performance optimization of a new horizontal turbo air classifier

A new horizontal turbo air classifier equipped with two inclined air inlets has been introduced. The flow field and classification performance of the classifier have been investigated using CFD method and response surface methodology (RSM). Simulation results show that the flow field is composed of the primary swirling flow and the secondary upward washing air, and the uniformly distributed swirling flow occupies the classifying chamber. The tangential gas velocity reaches the maximum value on the outer surface of the rotor cage, generating strong centrifugal force for the particle classification. The discrete phase model (DPM) can predict the cut sizes, but cannot present the fish-hook phenomenon. The desirable experimental condition by targeting the cut size of 20 μm and minimizing the classifying accuracy index is, rotor speed of 1373.6 rpm, primary air volume flow rate of 261.8 m³/h and secondary air volume flow rate of 42.4 m³/h. The corresponding fine and coarse fraction loss are less than 1.42% and 7.24%, respectively. This study provides a new strategy to design the horizontal turbo air classifier.     

Some velocity measurements in a swirling jet and a swirling flame with strong recirculation

The complete flow fields of a swirling jet and a swirling H₂ flame with strong recirculation including all Reynolds-stress tensor components are measured with a three component LDV system. The swirl jet with and without combustion have the same co-flow volume flow rate, momentum ratio, and similar swirl number. The exist profiles of both jets, which are important boundary conditions, are also provided. The main objective of the presented results is to supply a complete flow field data-base for development and assessment of numerical combustion models with focus on turbulence sub-models for flows with recirculation. M. Sc.T. C. Cheng; Dr.-Ing.E.P. Hassel and Prof. Dr.-Ing.J. Janicka, Fuchgebiet Energie- und Kraftwerkstechnik, TH Darmstadt     

Primary particle movement and change of property of cast iron by centrifugal effect in semi-solid processing

The particle distribution in semi-solid slurry under centrifugal field was simulated and the main factors such as fraction of solid, rotation speed, and holding time effecting the particle distributions are discussed. The simulation results showed that primary particles rich zone is produced in radially outer area and these results are in good agreement with the experiment. The centrifugal effect produces the primary particles distribution along the radial direction. Denser particles are concentrated in outside than inner side. For high fraction of solid samples, ‘wall’ appear in the middle of samples because of high viscosity region making particle difficult to move. Longer holding time gives denser primary particles concentrated more in outside than inner side. Higher rotation speed gives increased gradient of hardness in the radial direction. It is due to that number of primary austenite at inner side at higher rotation speed is less than that at lower rotation one. At higher rotation speed, ledeburite forms more at inner side of specimen than at the other one. It is also shown that semi-solid processing at lower fraction of solid gives higher hardness because smaller number of primary austenite, namely more ledeburite forms in microstructure. The present study gives useful information on producing material with locally changing property by semi-solid processing.     

标准低矮建筑TTU三维定常风场数值模拟研究

基于专业计算流体动力学软件平台FLUENT6提供的标准k?ε等多种湍流模型对大气边界层中的TTU(Texas Tech University Building Model)标准低矮建筑的定常风场进行了数值模拟,并将计算结果与场地实测数据及同济大学TJ-2风洞试验结果进行了比较。结果表明,多种湍流模型均能为工程应用提供有效参考,且对于此种体形简单的建筑复杂的雷诺应力模型的预测结果并不优于简单的涡粘模型,这为钝体绕流现象的数值模拟研究提供了有利依据。     

基于润扬大桥南塔顶长期监测数据风场特性分析

通过对润扬大桥健康监测系统获取的长期实测风场数据进行分析,获得了南塔塔顶300d 的平均风速、风向、湍流度、阵风因子、湍流积分尺度、脉动风功率谱等风场特性参数的分布规律以及参数之间相关性的推荐公式。并与跨中风速仪测试数据进行对比分析,得到了平均风速随高度的变化规律以及两点间风场的空间相关性。长期实测结果统计分析表明,润扬大桥悬索桥南塔塔顶的平均风速较小、风向稳定;风场的湍流度比跨中更强,并高出规范建议值近7倍;湍流积分尺度接近正态分布,并与湍流度、平均风速存在一定的相关性;纵向、横向功率谱均与Kaimal 谱相差较大,功率谱密度函数参数与平均风速存在直接相关性;塔顶风场与跨中风场相关性较弱。     

高海拔深切峡谷桥址风场特性实测研究

结合某深切峡谷大跨度桥梁桥址区测风塔长期的风观测数据,统计分析桥址区风场的平均风特性,以风速超过8 m/s为强风标准,分析强风样本的脉动风特性。研究结果表明：深切峡谷地形对风场特征存在显著影响,风特性参数呈各向异性分布,最大风速与极大风速对应风向集中分布在峡谷轴线附近,各观测高度主风向均为SSE方向,强风攻角以负为主,风速、风攻角与风向具有显著相关性;风速垂直分布规律不再准确符合指数律模型,风剖面指数随风速增大而减小,与风向具有显著相关性,拟合风剖面指数的均值为0.09;顺风向、横风向与竖向紊流强度分别为0.17、0.12、0.27,竖向紊流强度偏高,采用线性与非线性模型均能较好地拟合紊流强度与阵风因子的关系;紊流积分尺度高于规范推荐值,随风速的增大而增大;实测功率谱与理论谱吻合程度欠佳,竖向功率谱偏高,脉动风速功率谱在惯性子区不满足各向同性假设。