PIV技术在暂冲式风洞高亚音速平面叶栅流场测量中的应用

针对PIV技术在暂冲式风洞高亚音速平面叶栅流场测量中遇到的示踪粒子投放问题,本研究通过采用高压雾化式粒子发生器以及安装在稳压段前的撒播器,有效地使示踪粒子均匀地与主流混合,并成功对某扩压叶栅在设计攻角下的叶栅流道及尾迹速度场进行测量,获得了进口马赫数从0.3至0.73的二维速度矢量场。为了验证PIV试验结果的可靠性,对叶栅流场进行了数值模拟。结果对比表明:采用PIV技术测得的叶栅中截面二维速度矢量场合理地反映了叶片槽道及尾迹的流动结构,与数值模拟结果较为接近;对于跨、超音速或大攻角下叶栅流场,需考虑是示踪粒子壁面污染对测量的影响。本研究提出的PIV测量技术可应用于基于吸附式、合成射流等流动控制技术的高亚音速叶栅流场的测量。     

有叶扩压器内部流场的PIV实验测量

采用可以获得瞬时速度场的PIV技术对有叶扩压器内的流动进行了实验研究,测量了不同流量工况下的有叶扩压器内部流场,对实验数据采用整体平均法进行了处理,得到了显示各流量工况下的速度场分布图,并对其进行了分析和讨论。     

采用PIV对大尺寸模型冷态流场测量方法的探索

建立大尺寸低NOx 锅炉冷态模型,采用PIV对流场进行测量。通过示踪粒子的合理选择,长焦镜头的运用,以及激光器加收缩镜的方法,克服了用PIV对大尺寸模型测量的困难。燃烧器冷态流场流线图和速度矢量图的测量结果表明,提出的PIV应用于大尺寸模型的测量方法是可行的。     

扩散燃烧流场测量的PIV应用研究

为了研究燃烧火焰结构及其内部流动状况,考察其在燃烧喷嘴前回流区冷态试验模拟中和实际燃烧状况下的差别,利用二维粒子成像速度仪(PIV)对带钝体燃烧器中的丙烷／空气扩散燃烧的流场进行了测量,实现了火焰内部流动的可视化．通过对热态流场与相应冷态流场的对比分析表明,在复杂燃烧中冷态流场模拟与实际燃烧过程中的流动存在较大差别,实际燃烧中的流动状况变得紊乱,回流区在长度和宽度上都明显增大．     

逆流喷雾式饱和器内两相速度场的实验研究

应用三维粒子动态分析仪(PDA)和二维粒子速度分析仪(PIV)对逆流喷雾式饱和器内湿化过程的气液两相流流场进行了实验测量。通过稳态和瞬态速度场的测量结果,获得了饱和器内各点上水滴的三维平均速度、平均粒径和平均体积流量,以及饱和器中心线上的测量区域内水滴的瞬态速度分布和流线,给出了逆流喷雾式饱和器内液相水滴的三维平均速度、平均粒径和平均体积流量的分布规律,揭示了其内部流动的高紊流特性。图4表1参7     

湍流预混对冲火焰结构及熄火特性试验研究

利用激光层析技术和数字图像处理技术对对冲方式下湍流预混火焰的结构及熄火特性进行了试验研究。采用PIV方法测量了冷态对冲面附近的速度场，获得了速度作为衡量流场对锋面燃烧影响的参数。在不同射流工况配置下（Reynolds数，全局应变率，燃料的化学混合当量，不对称动量），观察到随着湍流对冲强度的提高，在高度皱褶的火焰锋面上存在非连续突触和空洞，这是局部熄火的表现，这些局部熄火点影响的扩展会导致火焰的整体熄火。此观点通过局部火焰锋面曲率的概率统计分析得到支持。另外，获得的在火焰熄火的极限条件下，对实际燃烧器的设计有指导意义。     

N_2稀释对合成气扩散火焰流场的影响

对带有N2稀释的中热值合成气旋流燃烧火焰的热态流场进行了PIV(粒子图像速度仪)测量,分析了不同稀释量对燃烧流场的影响规律.实验结果表明,N2的存在主要改变了射流区的尺寸,火焰的宽度基本不受影响,最高回流速度随稀释量的增加而增大,回流区内的脉动则随之减小,同时稀释量的增加会降低回流区内的湍动能,从而引起火焰温度的降低.     

PIV技术在柴油机缸盖水套流场测量中的应用

研究柴油机缸盖水套内流场的结构,进一步认识冷却液的流动机理,急需流场试验数据的验证.针对缸盖内部几何尺寸狭小、空间结构复杂以及光路安排困难等问题,发展了一种用于测量柴油机缸盖水套内流场的粒子图像速度场测量技术(PIV).在不影响试验件内部流场的基础上,对缸盖试验件进行了改造,使其符合PIV系统光路要求;选取了合适的示踪粒子,并研制了粒子投放装置;对测量视场进行了标定;最终,获得了狭窄区域流场不同截面上的速度场、涡量场和湍流度等流动信息.     

汽油机PIV稳态进气试验及滚流比计算

针对某3缸汽油机,搭建了粒子图像测速(PIV)可视化试验测试系统,并进行缸内流场测量。研究了通过不同流场切面进行滚流比计算的试验方法,并进行了试验与仿真结果的对比。研究结果表明:基于2D3CPIV试验测得的缸内横切面速度场与AVL FIRE软件仿真数据具有较好的一致性,试验与仿真计算的流量系数与滚流比随气门升程的变化趋势吻合,误差在合理范围内。通过2D2C PIV可以测得缸内不同切面的速度场来表征缸内三维的流场变化,其中气门轴对称切面很好地表征了滚流的运动状态,此外,通过一系列PIV测量得出的等间距轴向切面与旋转轴向切面可以拟合横切面的速度场,其速度分布与梯度变化趋势与2D3C测得的速度场相同,但测得滚流比计算值偏小。     

丙烷/空气扩散火焰流场的PIV试验研究

为了研究燃烧火焰结构及其内部流动特征,利用粒子成像速度仪(PIV)对丙烷/空气扩散燃烧的流场进行了测量。并进行了冷、热态流场的对比,结果分析表明:热态回流区的速度明显的增大,回流区中心位置稍偏下,速度梯度大,更紊乱,并且沿轴向速度衰减慢。     

加湿湍流燃烧火焰稳定的速度场特性分析

1引言目前,湿空气透平循环(HAT循环)等先进热力循环成为人们研究的重点。此类循环在提高效率和减少NOX排放量的同时,燃烧火焰的温度降低了,火焰将愈加不稳定,所以对加湿湍流燃烧火焰稳定的速度场等特性进行研究是非常有必要的。目前燃烧实验研究大多是基于激光诊断测量技术基础     

PIV measurement and turbulence scale in turbulent combustion

We have investigated turbulent combustion by PIV (Particle Image Velocimetry) technique. Comparing with LDV data, the validity of PIV measurements has been confirmed. Particularly, the conditions of sampling number and spatial resolution have been shown to yield reliable data using PIV. Based on the velocity fields in cold flow and combustion, the interaction between flame and flow has been discussed. It was observed that the flow field is changed by combustion and the turbulence is reduced. In order to determine statistical quantities such as mean velocity and RMS of velocity fluctuation, a sampling number of 1000 is needed. Moreover, the velocity correlation coefficient was evaluated to obtain the integral length scale of the flow. For both cold flow and combustion, the PIV estimated scale is very close to that of LDV based on the assumption of Taylor's hypothesis. As a result, the spatial resolution in this study is about 6 times smaller than the integral length scale. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 501–512, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20129     

Experimental study on velocity characteristics of recirculation zone in humid air non-premixed flame

To examine the effect of the flow field within the recirculation zone on flame structure, the characteristic velocity fields of methane/humid air flame in non-premixed combustion behind a disc bluff-body burner were experimentally studied by particle image velocimeter (PIV).The results show that two stagnation points exist on the centerline in the recirculation zone flame. However, the distance of the two stagnation points in humid air combustion shortens, and the minimal dimensionless velocity increases compared with the conventional nonhumid air combustion. In addition, the positional curves of the minimal velocities can be partitioned into three phases representing three different flame patterns. The analysis of axial minimal velocities on the centerline and their positions under different co-flow air velocity conditions reveals that fuel-to-air velocity ratio is the crucial parameter that governs humid air combustion flame characteristics. __________ Translated from Journal of Shanghai Jiaotong University, 2007, 41(3): 357–360, 365 [译自: 上海交通大学学报]     

Study on laminar combustion characteristic of low calorific value gas blended with hydrogen in a constant volume combustion bomb

In this paper, the laminar combustion velocity of low calorific value gases blended with hydrogen was experimentally studied in the constant volume combustion bomb. An experimental system of constant volume combustion bomb was set up, and the variation trend of laminar flame velocity of low calorific value blended hydrogen was analyzed under different initial conditions. The experimental results show that increasing the initial pressure will reduce the laminar combustion velocity of the flame, while increasing the initial temperature will increase the laminar combustion velocity of the flame. With the increase of hydrogen ratio, the laminar combustion velocity of flame and instability of flame increases. The influence of equivalence ratio on laminar combustion velocity of flame is quite complex, generally, the burning speed of the rich mixture is greater than that of the lean mixture. This research can provide experimental basis for the design and development of low calorific value gas blended with hydrogen engine.     

应用于燃油锅炉的富氧空气助燃技术探讨

介绍富氧助燃技术,并论述该技术应用于燃油锅炉的节能减排效果。通过对燃烧过程进行热工分析得知,采用含氧浓度为28%的富氧空气进行助燃时,烟气排放明显减少,燃烧室理论温度可由1340K左右提高至1720K以上。在富氧空气气氛下,柴油燃烧速度也有一定提高。以常见的系统工艺及实际情况为例,对富氧空气助燃的经济可行性加以论述,并初步提出了技术改进方案。结果显示,采用富氧空气助燃技术可以达到节约能源、降低排放的效果。     

湍流燃烧模型对某燃气轮机燃烧室性能计算的影响

针对某型燃气轮机环形燃烧室,通过数值模拟,对比分析了Standardk—ε、RNGk-ε、Realizable k-ε、Standard k-ω、雷诺应力五种湍流模型以及简单概率密度模型（PDF）、有限速率模型、涡耗散模型（ED）、涡耗散概念模型（EDC）四种燃烧模型对环形燃烧室性能计算的影响。结果表明：Realizable k-ε模型模拟的冷态流场与PIV试验测量结果最符合;EDC模型最能合理的模拟燃烧效果,但在预测NOx排放时不如有限速率模型精确。以上结论为后续该型号燃气轮机环形燃烧室的数值计算和设计提供了参考。     

一种高效率的内燃机燃烧模式

本文探讨了以双燃料发动机为代表的预混合和扩散燃烧共存的复合燃烧模式。认为这种燃烧模式兼有预混合燃烧和扩散燃烧的优点，而且有比传统的燃烧模式更高的热效率。实验证明，采用这种燃烧模式工作的发动机可以有比火花点火式发动机更高的压缩比，有比压燃式发动机更高的燃烧速率。最后对这种发动机的燃烧特性及获得较高热效率的原因进行了分析。     

Numerical and experimental study of the conversion of methane to hydrogen in a porous media reactor

In this paper, conversion of methane to hydrogen within a porous media reactor was investigated over the fuel-rich equivalence ratio range of 1.5 to 5. Experimental data were taken to validate the computational model and good agreement was established between the two. The characteristics of interest were wave velocity, peak combustion temperature, flame structure, volumetric heat release, wave thickness, and hydrogen yield. The parameters investigated that affect these characteristics included inlet velocity, equivalence ratio, and the thermal conductivity and the specific heat of the porous media. The computational model predicted a peak percentage conversion of methane to hydrogen of approximately 59% while experimental results show a peak of approximately 73%. The model also predicted the experimental trend that conversion efficiency increases as the inlet velocity of the initial fuel-air mixture increases. Species profiles obtained from the computational model showed the signature dual-reforming regimes known as partial oxidation and steam reforming inherent with fuel-rich filtration combustion. The main contribution of this paper is an understanding of the transient nature of the combustion wave for fuel-rich conditions and how the nature of the combustion wave influences conversion efficiency. As the combustion wave progresses, the steam-reforming zone thickness increases, resulting from the constant heat addition to the solid. A thick, high-temperature zone, which promotes steam reforming and is heavily dependent upon the specific heat of the porous media, is preferred to maximize conversion efficiency.