三级旋流杯燃烧室流场测量与数值模拟

为满足高温升高热负荷燃烧室头部设计要求,参照旋流器设计准则,设计4种不同三级旋流杯燃烧室,采用数值模拟和PIV试验相结合方法对其冷态流场进行初步研究。研究结果表明:第3级旋流器叶片安装角增加,火焰筒头部旋流特性更显著,回流区直径增大,有利于火焰稳定;同时主燃孔射流深度增加,有利于截断火焰。第3级旋流器叶片数增加,主流速度衰减加快,气动损失增大,使火焰筒头部进气量减少,同时削弱三级旋流杯出口气流旋转强度,火焰筒头部回流区直径减小,不利于燃烧。     

火焰筒扩张角与旋流匹配对燃烧特性的影响

为研究旋流器流量分配对干式低排放(Dry Low Emission,DLE)燃烧室燃烧特性的影响规律,针对单头部中心分级旋流燃烧室,以天然气作为燃料,在保持旋流数不变的前提下开展两级旋流器不同空气分配比例下的试验测试和数值模拟,获得不同结构参数条件下燃烧室的综合燃烧性能以及污染物排放等变化规律。研究表明：随主燃级/预燃级旋流器流量比增大,燃烧室中心回流区变小、回流区长度变短;预燃级局部当量比的增大造成燃烧室出口CO排放增加,主燃区燃烧加剧,热力型NOx排放也增加;同时,燃烧室中心高温区域向燃烧室出口方向扩张,出口温度分布均匀性变差。     

旋流器安装角对低旋流燃烧流场的影响

分别采用粒子速度影像（PIV）技术和数值模拟方法研究低旋流燃烧器出口下游冷态流场,分析旋流器安装角对低旋流流动结构的影响．结果表明：旋流器安装角与流场中产生回流区时的临界旋流数无关,高旋流与低旋流的分界点约为0．47;安装角较大的旋流器下游流场的发散角和低速区较大;随着轴向距离增大,中心轴线上无量纲轴向速度衰减很快,并且两个旋流器的衰减速率基本相当,左右有两个峰值,安装角较大的旋流器两个峰值衰减速率较大并且峰值之间的距离增大幅度较大;径向速度随着中心射流流速的增大而增大,安装角较大旋流器的径向速度较小;旋流器安装角为40°时后方的流场具有较高的湍动能,火焰传播速度更高．     

旋流杯结构对火焰筒头部流场影响的试验研究

为深人研究旋流杯安装角、两级流量比、二级流通面积和套筒扩张角对火焰筒头部冷态流场的影响， 采用2D-3C粒子图像测速仪在常温常压下开展了相关试验研究。结果显示:适当增加叶片安装角可增大气 流的径向与切向速度分量，这一效果有助于提高油气掺混质量；内外两级流量比的增加将导致高速脉动区域 向内部移动，有利于燃油雾化，但回流区较窄、轴向速度较大，不利于稳定火焰和合理温度场的形成；随着二 级旋流面积的增大，回流区直径增大，射流速度降低，有利于稳定火焰;套筒扩张段在一定程度上对旋转射流 起引导作用，增大套筒扩张角将导致气流径向扩散能力加强。     

一体化加力燃烧室燃烧性能数值研究

针对某两级中心分级分区单头部燃烧室结构参数对头部下游流场结构的影响,采用数值模拟结合正交设计的方法研究了头部结构参数（一/二级旋流数、值班级套筒张角、隔离段高度比）的变化对燃烧室流动特性的影响规律和程度。结果表明：中心回流区最大宽度随着二级旋流数、隔离段高度比、一级旋流数、值班级套筒张角4个结构参数的增大而增大,并且影响程度依次降低;中心回流区长度随着一/二级旋流数的增大而增大,套筒张角和隔离段高度比则对中心回流区长度的影响程度较小;值班级和主燃级旋流器的旋流数偏大以及值班级套筒张角偏大都会导致台阶回流区消失     

中心分级燃烧室旋流角变化对燃烧特性的影响

实验研究了一种中心分级燃烧室值班级旋流角变化对燃烧性能的影响。采用了单头部单管式燃烧室,值班级一级旋流器旋流数分别为0. 63、0. 72和0. 93,实验研究了采用不同旋流数时燃烧室的点火、慢车贫油熄火、污染物排放和燃烧效率等燃烧特性。实验结果表明:旋流数变化对燃烧室的点火、慢车贫油熄火、污染物排放及燃烧效率等有很大影响;旋流数及一级旋流器和二级旋流器的旋流数差值增加后燃烧室的点火和慢车贫油熄火特性得到改善。一级旋流器旋流数的增加会导致污染物排放的增加及燃烧效率的下降。     

天然气低排放旋流燃烧室头部结构性能研究

本文设计了一种旋流燃烧室的旋流器及预混段结构。通过冷态数值模拟的方法评估了掺混段出口的总压损失及掺混不均匀度。计算结果显示同向双级旋流器能够在相对较低的总压损失下获得较好的掺混效果。之后通过相同的方法确定影响该型旋流器性能的四个几何参数:内层旋流数、外层旋流数、喷嘴直径和内外层流道面积比。研究结果得出了旋流器设计的具体尺寸。配合该旋流器设计,又通过燃烧数值模拟设计了三种掺混区布局。结果表明,较短的中心钝体结构会引起火焰锋面位置向燃烧室下游偏移,造成平面型火焰面,另外还会在掺混区中产生不稳定的回流区。最后通过改变预混段外径、中心体长度和直径得到了综合性能良好的燃烧室结构。     

旋流器结构参数对TAPS燃烧室性能的影响

利用数值模拟手段探究旋流器叶片角度对双环预混旋流(TAPS)燃烧室性能的影响。针对本文研究的特定结构及工况,结论如下:一级、二级叶片角增大时,参考线上切向速度仅在特定位置变化较明显,燃烧效率与压力损失均呈上升趋势。三级叶片角增加,火焰筒中心区域气流切向速度变化较大,回流区体积明显增大,燃烧效率与压力损失也逐渐升高。预测所得压力损失y与燃烧效率z随三级叶片角x的变化关系式分别为:y=0.063 17×x+3.313 96和z=0.026 11×x+97.821 39。结果可为燃气轮机TAPS燃烧室的旋流器设计提供参考。     

贫预混低旋流燃烧器吹脱极限和流场的测量

贫预混低旋旋流燃烧是增强火焰稳定性和控制NOx排放的有效手段,旋流器安装角对于火焰稳定性和流场结构具有重要影响。对两个不同安装角的低旋流燃烧器吹脱极限和冷、热态流场进行了测量分析。结果表明,吹脱旋流数与当量比呈线性关系,旋流器安装角较大时燃烧器稳定火焰的能力受当量比的影响较大。发散角、回流区和湍动能均受旋流器安装角变化的影响。     

几何参数对气膜孔流量系数的影响

在燃气轮机涡轮叶片的冷却设计中,气膜孔的流量系数是最关键的参数之一,它会影响气膜的实际冷气流量和气膜冷却效果。使用数值计算方法研究了孔倾斜角、孔复合角、长径比、孔入口圆角、孔出口圆角等几何参数对气膜孔流量系数的影响。提出了一种基于选定基准工况的气膜孔流量系数的关联式,该关联式将这些几何参数的影响考虑在内。与文献中试验数据的对比表明,该关联式精度较高,可以为涡轮叶片冷却设计提供参考。     

两级动叶可调轴流风机内流特征的数值模拟

采用Fluent软件对某600 MW机组配套的两级动叶可调轴流一次风机进行了全三维定常数值模拟,分析了风机第一、第二级叶轮内流特征和动叶安装角对风机性能的影响.结果表明：第二级叶轮出口总压整体呈现高压区和次高压区交替分布的特征,且比第一级叶轮的对称性差;第一、第二级叶轮叶片压力面、吸力面的总压和静压分布规律相似;第二级叶轮叶片压力面和吸力面相应位置上的静压值均大于第一级叶轮叶片;随着动叶安装角的增大,第一、第二级叶轮的总压升系数和静叶的扩压系数均增大,且第二级叶轮大于第一级叶轮,表明第二级叶轮的做功能力和静叶的扩压能力均比第一级叶轮的大.     

Influence of Swirlers on Flow and Heat-transfer in Direct Air-cooled Condenser Unit

To improve the heat exchange of air-cooled condenser unit (ACCU), the numerical simulations of ACCU with a new swirling device (named swirler) installed at outlet of the fan (improved air-cooled condenser unit, named IACCU) is executed, under various vane angles of different swirlers compared to the same conventional air-cooled condenser unit (CACCU) without swirler. The swirl intensity theory is presented, and the flow fields and temperature distributions of the IACCUs are obtained and compared with that of the CACCU. The simulated results show that the heat transfer characteristic and the flow field characteristic of the IACCU are both better than that of the CACCU. The vane angle of the swirler is optimized for the IACCUs with four different kinds of swirlers, and the most effective one of these devices is found out.     

切向叶片角度对中心给粉旋流燃烧器气固流动特性影响

利用三维激光多普勒测速仪,在气固两相实验台上,对不同切向叶片角度下中心给粉旋流燃烧器出口区域的气固流动特性进行了研究,获得了三种切向叶片角度下的三维平均速度和颗粒体积浓度的分布。结果显示,随着切向叶片角度的减小,轴向、径向和切向平均速度峰值都增加,回流区尺寸和旋流数也增大。同时,在x/d=0.1～0.7截面,随着切向叶片角度的减小,在燃烧器中心区域的颗粒体积流量峰值增加。     

An Investigation of the Swirling Flow and Heat Transfer in a Duct

This paper presents the results of experiments and numerical simulation of the turbulent swirling flow and heattransfer in a duct.The calculated results are in good agreement with data obtained by measurements.It isfound that the swirling flow promotes heat transfer to the wall of the duct;the swirl numbers are dependentupon the vane exit angles of the swirler,distance from the swirler and the duct Reynolds number.But the decayof swirling flow in streamwise direction is related to local Reynolds numbers and is independent of the swirlerexit angle.The swirl flow characteristics presented in this paper may be used for engineering purposes.     

Hydrodynamics and mass transfer in decaying annular swirl flow

This paper reports an electrochemical study of local mass transfer behaviour in decaying annular swirl flow. Initially, flow visualisation experiments were conducted to observe the general behaviour of the flow. It was found that the swirl angle decays exponentially along the tube. Measurements of pressure drop across the vaned swirl generators were correlated in terms of the inverse of the square of the tangent of the vane angle and approximately the square of the mean fluid velocity for vane angles of 30° and over. Measurements of the axial distribution of local mass transfer coefficient for the inner rod were carried out using the electrochemical limiting diffusion current technique and results were correlated for each swirl generator, in the Reynolds number range 3300–50000. It was found that the relative enhancement of mass transfer in swirl flow increases as the vane angle increases and Reynolds number decreases.     

An Investigation on the Effect of Air Swirler Vane Angle on Liquid Fuel Combustion Characteristics

This is an experimental and numerical study on the effect of air swirl vane angle on combustion characteristics of liquid fuel burners. The swirl vane angle varied in a range from 0° to 75° and the values of the dependent variables were determined. The flame temperature was measured by an S‐type thermocouple and a Testo 350 XL gas analyzer was used to determine the NO and CO pollutant concentrations. Also, sprint CFD code along with suitable models was used in analytical modeling. The results indicate that there is an optimum angle for the swirl vane (approximately 45° for the case study). At the optimum angle, the average temperature of the flame increases as much as 12.5% and 28.5% in comparison with small and large angles, respectively. Therefore, combustion efficiency reaches its maximum level and CO emission is at an extremely low level. The results also demonstrate that large swirl angles decreases NO emission.     

高压共轨大功率柴油机喷油嘴内部两相流动仿真研究

用AVL-FIRE软件建立了TBD234V6高压共轨大功率柴油机喷油器喷嘴内部流动的仿真计算模型;研究了共轨大功率柴油机喷油器主要结构参数,包括喷孔直径、喷孔个数、喷孔长径比、喷射夹角等,对燃油在喷嘴内部流动的影响。分析表明：喷嘴结构参数不同会使各喷孔内气穴产生的时刻、分布区域以及强度不一致,最终影响各喷孔的流量特性,...     

Effects of the layout of film holes near the vane leading edge on the endwall cooling and phantom cooling of the vane suction side surface

In the current research, effects of the layout of film holes near the first-stage vane leading edge on the endwall cooling and phantom cooling of the vane suction side surface were numerically studied. The computational results indicate that the case with a positive film-hole angle achieves a higher cooling effectiveness level on the endwall and vane suction side surface compared to the case with a corresponding negative film-hole angle. Furthermore, the location of the film hole has a significant influence on the cooling performance of the endwall and vane suction side surface. In addition, the case with a smaller distance from film holes to the vane stagnation also attains a slightly higher cooling effectiveness (phantom cooling effectiveness) on the vane suction side surface.     

变几何涡轮可调导叶瞬时转动气动特性研究

为探究单级变几何涡轮(VGT)在导叶转动过程中的过渡态性能,对某动力涡轮进行了非定常数值计算,应用动网格技术实现导叶转角的改变,并对导叶通道开大或关小过渡过程中涡轮性能进行了分析。结果表明：导叶转角从0°变化到-5°时,单级涡轮效率逐渐下降1.6%,从0°变化到6°时,效率逐渐提高0.5%;质量流量和导叶出口绝对气流角随转角改变接近线性变化,而动叶出口相对气流角、熵增、效率和导叶出口总压损失等随转角改变呈抛物线型变化;过渡态下导叶流场内损失变化主要受上、下端壁处间隙泄漏涡影响,动叶出口熵增变化规律主要受动叶吸力侧泄漏涡和下部通道涡影响,其中下部通道涡的改变是引起熵增变化的主要原因。