PIV MEASUREMENT FOR SWIRLER FLOW FIELD IN GAS TURBINE COMBUSTOR

The characteristics of swirler flow field, including cold flow field and combustion flow field, in gas tur- bine combustor with two-stage swirler are studied by using particle image velocimetry （PIV）. Velocity compo- nents, fluctuation velocity, Reynolds stress and recirculation zone length are obtained, respectively. Influences of geometric parameter of primary hole, arrangement of primary hole, inlet air temperature, first-stage swirler an- gle and fuel/air ratio on flow field are investigated, respectively. The experimental results reveal that the primary recirculation zone lengths of combustion flow field are shorter than those of cold flow field, and the primary reeir- culation zone lengths decrease with the increase of inlet air temperature and fuel/air ratio. The change of the geo- metric parameter of primary hole casts an important influence on the swirler flow field in two-stage swirler com- bustor.

Sensitivity analysis of the vane length and passage width for a radial type swirler employed in a triple swirler configuration

The design of axial or radial swirlers typically governs a number of geometrical parameters that are determined by the desired flow field.In the meantime,the number of unknown parameters increases with the number of concentrically mounted swirlers.The available literature is nonetheless limited,and designers are obligated to increase the number of initial assumptions.In this article,three kinds of triple swirlers are employed and simulations are performed to determine the effect of each parameter on the swirler performance.Based on the correlation provided,overlengthening the radial vane length could result in significant changes in the flow field from the jetlike pattern to a wide swirl-jet angle due to the Coanda effect.Passage width should also have the potential to alter the swirl-jet angle and velocity field at the exit of the swirler.

Investigation and Analysis of High Temperature Corrosion and Degradation of Marine Boiler Combustion Swirler

The present paper investigated and analyzed swirler material consisting of mild steel which was subjected to service for the period of one year in a 30 MW marine boiler. Due to the presence of high temperatures in the furnace coupled with the corrosive marine environment swirler material showed accelerated degradation and material wastage. An investigation into the feasibility of manufacturing the existing swirler with an alternate material or coating the swirler material with a thermal barrier coating was undertaken. Based on their properties and performance, SS 304 and SS 316 were proposed as the replacement materials for the swirler. The other alternative of coating the existing swirlers with a form thermal barrier coating to observe for any improvement in their performance at elevated temperatures was also tested. Stellite, which is a Ni-Co based coating, was carried out on the MS samples and the same were exposed to same temperatures mentioned above. The performance of the available options was evaluated with respect to the grain structure of the material, the hardness value of the materials and deterioration at elevated temperatures. Investigation showed the proposed materials/ coatings like SS 304, SS 316 and Stellite coating revealed that SS 316 is the material best suited for high temperature application.

Tomographic particle image velocimetry measurement on three-dimensional swirling flow in dual-stage counter-rotating swirler

Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.

Influence and optimization of swirler parameters on elbow wear of deep coal fluidization pipeline transportation system

Elbow wear is a major threat to the multiphase pipeline transportation industry,which has a negative impact on the stable operation of the transportation system.In order to find the wear reduction methods of elbows in the fluidization pipeline transportation system for 2000-meter-deep coal resources,the swirler was installed upstream of the elbows,and wear simulations and tests of three kinds of elbows were carried out.The results showed that the maximum wear rate(MWR)of elbows increased and then decreased along the elbow angle.Due to the different directions of gravity,the heavy wear position(HWP)of the horizontal-vertical(H-V)elbow was in front of the vertical-horizontal(V-H)elbow.Because the downstream portion of the horizontal-horizontal(H-H)elbow was still a horizontal pipe,the HWP of the H-H elbow almost covered the whole elbow.The swirler placed upstream of the elbows could make the particles at the elbow move to the intrados of the elbows,resulting in less collision between the particles and the extrados of the elbows,thus reducing the wear of the elbows.The wear reduction effects of swirlers on three different elbows were favorably connected with the guide vane angle(GVA)and negatively correlated with the guide vane length(GVL),decreased first and then increased as the guide vane height(GVH)increased,and were little affected by the guide vane number(GVN)and the guide vane thickness(GVT).The mathematical models between the MWR of the elbows and guide vane parameters were established.By bench tests,the wear reduction effect of three kinds of elbows under the optimal guide vane parameters was 58.4%,76.9%,and 78.6%,respectively.The errors between the bench test results and the simulation results were around 10%.

Effect of dilution holes on the performance of a triple swirler combustor

A triple swirler combustor is considered to be a promising solution for future high temperature rise combustors. The present paper aims to study dilution holes including primary dilution holes and secondary dilution holes on the performance of a triple swirler combustor. Experimental investigations are conducted at different inlet airflow velocities（40–70 m/s） and combustor overall fuel–air ratio with fixed inlet airflow temperature（473 K） and atmospheric pressure. The experimental results show that the ignition is very difficult with specific performance of high ignition fuel–air ratio when the primary dilution holes are located 0.6H（where H is the liner dome height）downstream the dome, while the other four cases have almost the same ignition performance. The position of primary dilution holes has an effect on lean blowout stability and has a large influence on combustion efficiency. The combustion efficiency is the highest when the primary dilution holes are placed 0.9H downstream the dome among the five different locations.For the secondary dilution holes, the pattern factor of Design A is better than that of Design B.

Effects of swirler position on flame response and combustion instabilities

This study is concerned with the experimental and theoretical investigation of the combustion instabilities in a premixed swirl combustor.It is focused on the effects of the swirl mixing distance on the intrinsic thermoacoustic mode.The swirler as an origin of the swirling flow is also the source of the flow disturbance,which has effects on the flame response.The location of the swirler is varied in the experiment to study the effect on combustion instabilities and flame transfer functions.A low order model is built to analyze the thermoacoustic instabilities of the combustion system.The experimental results show that the ITA switches from an unstable state to a stable state as the swirl mixing distance changes with an increment of 15 mm;while the instability of the quarter-wave mode is not varied.The measured Flame Transfer Functions(FTFs)show that the gain curves of the frequency-dependent FTFs seem to be stretched or compressed with the modulation of the swirler position,which has effects on frequencies and instabilities of thermoacoustic modes.With the low order model,the effects of flame response on combustion instabilities are analyzed and the flame dominant nature of the ITA mode is confirmed.

Effect of the Structure Parameters of a Low Swirler on Premixed Characteristics

Combustion with lean premixed and low swirl is an effective way of flame organization.It can improve the flame stability and reduce NOX emission.In this kind of combustion,one of the most important issues is fuel/air premixed characteristics.How the structure parameters influence that issue is figured out through numerical simulation.The structure parameters concerned in the study are as follows.They are shape of blades,number of blades,location and shape of gas jet.The influences of them are analysed with comprehensive consideration of many aspects.With the same light shading rate and stagger angle,the axial swirler with curved blades has worse premixed uniformity and lower pressure loss than the one with straight blades.With the same structure of each blade,the decrease of the quantity of blades does influence the pressure loss,while the quantity of gas jets changes correspondingly.But it has little effect on premixed uniformity in a certain range.However,more blades make contribution to better premixed performance.When the total flow area is the same,the axial and circumferential positions of the fuel jets also greatly influence the premixing process.When the fuel jets are upstream the blades and locate at middle of the vanes,the premixing performance is the best.Meanwhile,the jet direction of the fuel jets is a very important influencing factor of the premixing process.When the fuel jet direction is oblique downward at an angle of 30°to the horizontal,the premixing effect is better than the horizontal outflow,which is better than the oblique upward structure.

Swirl diffusion flame control by the plasma swirler

In this paper, the design of plasma swirler is presented in detail. The experiments were carded out to verify the feasibility of using plasma swirler to control diffusion flame. The plasma swider consists of multiple electrodes with staggered arrangement on both sides of combustor＇s expansion section. The plasma swirler can enhance combustion stability through ionizing the air to produce active free radical and promoting the swirling air. In the experiments, the flame response to the plasma swider was examined with OH distribution by planar laser induced fluorescence （PLIF）. The experimental results showed that the flame reaction zone was broadened with the increase of the plasma exciting, and this demonstrated that the plasma swirler could be used to control diffusion flame. The design of plasma swirler is feasible.

粉末注射成形制备复杂薄壁TiAl合金旋流器

旋流器作为航空发动机的重要部件,实现其轻量化制造对提升发动机服役性能具有重要意义。轻质高强耐热TiAl合金是一种极具应用潜力的高温结构材料,但其本征脆性大、制备加工困难,严重限制其在高性能旋流器制造方面的应用。为此,本研究采用粉末注射成形(powder injection molding,PIM)制备方法,结合水溶性芯模的模具设计及高保形聚甲醛(POM)基黏结剂开发,通过催化脱脂、热脱脂及两步烧结工艺,直接近净成形制备出复杂薄壁TiAl合金旋流器,无需机加工过程。结果表明:成分为82%(质量分数,下同)POM-5%高密度聚乙烯(HDPE)-5%乙烯-醋酸乙烯共聚物(EVA)-8%硬脂酸(SA)的黏结剂具有较高的粉末装载量和较佳的充模性能,其喂料粉末装载量为62%(体积分数),流动行为指数n为0.56,黏流活化能E为22.95 kJ/mol,综合流变学因子为9.59;常压两步烧结方法可实现高致密度和细晶的协同控制,当烧结工艺为1430℃/1 h+1250℃/5 h时,PIM所制备TiAl合金的致密度达到96.3%,且片层团尺寸约为100μm,后续结合热等静压处理实现了TiAl合金的近全致密化,所制备复杂薄壁TiAl合金旋流器的尺寸偏差为±0.1 mm,表面粗糙度Ra为1.046μm,室温抗拉强度为577 MPa,屈服强度为466 MPa,伸长率为0.96%。

基于神经网络的双轴向旋流器结构参数影响分析

针对目前航空发动机燃烧室旋流器研究工作中存在的研究变量单一、对比范围窄等问题,采用神经网络模型结合数值模拟结果,以有效流通面积、旋流扩张角、中心回流区宽度为目标,预测了不同叶片安装角、套筒扩张角、旋向组合等11项关键结构参数下目标函数的变化规律,并对各关键结构参数进行了敏感性分析。结果表明:有效流通面积主要受面积比及叶片安装角的影响,旋流扩张角及回流区宽度随各结构参数的变化趋势与相应研究文献一致,即旋流扩张角随套筒扩张角的增加而增大,随文氏管出口至套筒扩张段距离、一二级面积比的增加而减小;中心回流区宽度随套筒扩张角、各级叶片安装角的增加而增大,随文氏管出口至套筒扩张段距离的增加而减小;旋向组合对旋流扩张角与中心回流区宽度的影响相对较小。基于训练模型可选取多组符合优选条件的结构组合,优选组合中套筒扩张角均大于90°,一二级叶片安装角大多在40°上下,一二级面积比增加、旋向相反时,可选方案增加。

不同旋流器作用下气液螺旋环状流动特性研究

管内气液螺旋环状流动可以通过设置固定叶片的旋流器形成,旋流器的结构极大地影响了形成的螺旋环状流动的稳定性。对此,选取了四种典型旋流器结构开展三个典型来流工况下螺旋环状流形成的实验研究。通过图像处理结合概率密度函数(probability density function,PDF)拟合的方法分析了形成螺旋环状流的稳定性,同时结合液膜波动特性与旋流器内部作用过程分析发现:平板式及平板有中心柱式旋流器在不同来流工况下产生的液膜相较于螺旋叶片式A/B旋流器都更加稳定,相同工况下的失稳距离也更长,而螺旋叶片式A/B旋流器产生的螺旋环状流的稳定性较差,在更短的距离内即发生了螺旋环状流失稳现象;不同工况下液相折算速度的上升有助于提高液膜稳定性与螺旋环状流失稳距离,从而形成更稳定的螺旋环状流;叶片作用下流体内部压力梯度和气液相分布规律高度相关,压力梯度和周向速度是形成螺旋环状流动的主要因素,并且压力梯度和周向速度的大小一定程度决定了螺旋环状流动气液交界面的稳定性。

反向和同向旋流滑动弧等离子体点火助燃头部的燃烧特性

非平衡态等离子体点火助燃技术是新型的燃烧调控技术.面对航空发动机燃烧室稳定燃烧的迫切需求,为发挥滑动弧等离子体技术在改善雾化、提高燃烧效率等方面的优势,搭建了航空发动机燃烧室实验平台,并开展了不同旋流方向下滑动弧放电等离子体的燃烧特性实验.实验通过采集燃烧过程OH^(*)化学发光强度图像,着重分析了不同旋流方向滑动弧等离子体对燃烧室燃烧强度、温度分布以及燃烧效率的影响.研究表明,施加等离子体助燃后,燃烧室内的平均已燃区相对强度明显提升,且反向旋流等离子体助燃的提升效果更加明显;反向旋流滑动弧助燃的径向温度分布相较于同向旋流滑动弧助燃均匀性提升,当余气系数为2.0时,反向旋流等离子体助燃的径向温度分布系数为0.3022,同向旋流等离子体助燃的径向温度分布系数为0.3223;反向旋流滑动弧助燃的燃烧效率高于同向旋流滑动弧放电的燃烧效率,当余气系数为2.0时,反向旋流等离子体助燃的燃烧效率为89.56%,同向旋流等离子体助燃的燃烧效率为83.41%.

旋流器构型对全环燃烧室性能的影响

为研究旋流器构型对燃烧室性能的影响,针对配装双级轴向旋流器和双级径向旋流器的全环燃烧室开展了实验研究。结果表明,在本文研究范围内,地面点火状态下,轴向方案和径向方案点火油气比分别为0.011~0.022和0.015~0.026,轴向方案比径向方案具有更宽的点火边界。轴向方案贫油熄火油气比为0.009~0.020,径向方案贫油熄火油气比为0.006~0.019,径向方案比轴向方案具有更宽的贫油熄火边界。在地面慢车和空中慢车状态下,轴向方案比径向方案具有更好的出口温度分布品质。轴向旋流器对应的燃烧室压力脉动强度显著强于径向涡流器:油气比为0.011时,轴向方案和径向方案的燃烧室主频分别为525 Hz和555 Hz,相对压力脉动分别为1.9%和0.3%;油气比为0.018时,轴向方案的燃烧室主频为475 Hz,相对压力脉动为1.1%,而径向方案无明显主频。

双旋流燃烧室冷态流场2维湍流特性试验

为研究燃烧室流场湍流结构特性,采用粒子图像测速仪(PIV)对双级旋流器燃烧室流场进行测量,得到了不同进气速度下的速度场分布、雷诺应力分布和湍流度分布。结果表明:随着进气速度的提高,旋流器出口射流速度提高,中心回流区轴向速度变化较小;在2维平面上,燃烧室轴向测量截面出现5个高雷诺应力区域,分别为中心回流区外、中心回流区与高速旋转射流交汇区(剪切层)2处以及高速旋转射流与燃烧室头部模拟壁面接触区2处;回流区与高速旋转射流交汇区较高的雷诺应力分布有利于燃料与空气充分混合;湍流度分布与速度波动幅值和平均流速有关,中心回流区与高速旋转射流交汇区处湍流度较高。

选煤用旋流器分离性能及参数匹配分析

针对旋流器在选煤工作中的分离性能及其参数匹配问题,基于FX350型旋流器,对FX350型旋流器的结构组成和工作原理分析,研究其内部流场的速度和压力分布,揭示旋流器内不同流场形态对分离效率的影响,采用实验和模拟分析方法,探讨旋流器直径、锥体角度、入口尺寸等结构参数对分离效率的显著影响,发现入料浓度、入料流量、安装角度等运行参数的调节对提高分离效率至关重要。通过调整入料浓度至14g/L、入料流量至80m3/h、安装角度至80°,旋流器表现出最佳的分离性能,采用响应面法进行参数匹配分析,构建的数学模型通过方差分析和误差统计验证,表现出高度的预测准确性。现场验证表明,通过精准控制操作参数,可以提升旋流器的分离效率。

内旋流器旋流数对三级旋流流场特性的影响

为探讨内级旋流器旋流数对三级旋流流场结构的影响,采用2D-PIV流场测试技术,对三级旋流燃烧室简化模型开展试验研究。研究结果表明:内级旋流器旋流强弱并不是回流区形成的主要决定因素;随着内级旋流器旋流数的增加,回流区轴向长度逐渐变短,最大回流量逐渐增大,而对涡心位置、回流区径向宽度影响较小;回流区形状同时受内级旋流器旋流数及外级旋流器旋流数的影响,当内级旋流器旋流数相对外级旋流器旋流数足够小时,较易出现尾迹区。

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.

旋流器流量分配对三级旋流流场特性的影响

为探讨三级旋流器流量分配对旋流器出口流场的影响,针对旋向组合为"顺时针-逆时针-逆时针",内级、中间级、外级旋流器旋流数分别为1.4,1.0,0.6的三级旋流器,开展了相同进口条件下不同流量分配方案的数值研究。研究结果表明:当内级旋流器流量分配一定时,随着中间级/外级气流流量比的增大,回流区轴向长度、径向宽度,回流率及旋流数逐渐增大;当中间级旋流器流量分配一定时,随着内级/外级气流流量比的增大,回流区轴向长度、径向宽度、回流率及旋流数逐渐减小;当外级旋流器流量分配一定时,随着内级/中间级气流流量比的增大,回流区轴向长度、径向宽度,回流率及旋流数逐渐减小。

反向与同向双旋流器流场的试验研究

运用已经校准的五孔探针测定双旋流空气雾化喷嘴中同向和反向旋转的双旋流器产生的流场。实验表明，反向旋转的双旋流器产生的流场与同向旋转的双旋流器产生的流场比较起来，有以下一些特点：反向旋转时旋转射流的切向速度及轴向速度沿轴线的衰减比同向旋转时快，反向旋转时产生的回流区比同向旋转时产生的回流区直径要小，长度要短。