表面粗糙度对压气机叶栅流动特性的影响

在低速平面叶栅风洞中,实验研究了表面粗糙度对高负荷压气机流动特性的影响,并对叶片吸力面不同位置布置的表面粗糙度进行了对比分析。通过墨迹流场显示法对叶栅壁面流场进行了测量,利用五孔气动探针对叶栅出口截面进行了扫掠,给出了不同方案出口截面马赫数、二次流速度矢量的分布以及叶栅的流场特征,以分析和探讨表面粗糙度对叶栅流动特性的影响。结果表明,吸力面局部表面粗糙度的增加使得角区分离范围减小;且随着粗糙带向尾缘移动,角区分离范围的减小程度也逐渐增加。     

基于LES的压气机叶栅通道非定常流动结构研究

为了进一步理解压气机叶栅通道内的非定常流动结构,采用大涡模拟(LES)方法研究了来流附面层厚度和稠度变化对叶栅通道内涡系结构及总压损失系数的影响。研究表明：来流附面层增厚将导致端壁处流体的轴向动能降低,使得马蹄涡压力面分支更早地流向相邻叶片吸力面;来流附面层越厚,通道涡在叶栅尾缘沿展向抬升的高度越高,角区分离的范围也越大;叶栅的总压损失随附面层增厚而增加,附面层损失增加显著,二次流损失有所增大;稠度较低时叶栅吸力面表面存在分离,会对通道涡及角区分离产生影响;稠度增大,横向压力梯度减小,叶栅流道的速度分布更均匀,通道涡的强度和尺度减小,角区分离的范围减小;稠度增大使叶表不再分离时,总压损失显著降低,但稠度继续增大会使气流与叶片表面的摩擦损失增加。     

跨声速涡轮叶片半劈缝长度及冷气量对叶栅流场的影响

通过在不同尾部劈缝结构以及冷气量情况下对某型跨声速叶栅数值模拟,得出了劈缝长度及冷气量对叶栅流道内及尾缘附近流场结构影响的规律。主要表现为:尾缘劈缝结构使叶片尾缘内伸波变为两道;长尾缘劈缝以及大尾缘冷气量不仅能够减小尾迹宽度、降低尾缘损失,也能够使叶片吸力面分离泡减小,黏性损失降低。     

康达喷气叶栅喷气内腔体拓扑优化设计及试验研究

为了减小从康达喷气叶栅内部流出的喷气方向与叶栅主流方向的偏差,进一步提升康达喷气对流动分离的抑制效果,本文基于流体拓扑优化技术及布置导流肋的方法对康达喷气叶片原始喷气内腔结构进行优化设计。采用数值计算和高速风洞试验评估优化的喷气内腔结构对康达喷气叶栅气动性能的改善效果。结果表明：优化设计的带肋喷气内腔结构可以减小康达喷气与主流掺混的偏差角,叶片吸力面尾缘的流动分离区域进一步减小;在来流Ma为0.5、攻角为0°、1.25%喷气量下,采用带肋喷气内腔的康达喷气叶栅总压损失系数较采用原始喷气内腔结构降低了7.15%;采用带肋喷气内腔结构能够使叶栅在不同工况条件下的总压损失小于原始内腔结构,且在最佳喷气量下获得最小的总压损失系数。     

跨音速透平叶片尾缘流动状态的试验研究

本文叙述了在跨音速风洞中模拟跨音速透平叶片尾缘流动的试验结果.分析了跨音速透平叶片尾缘流动的机理.说明了诸如附面层、叶片尾缘厚度、来流马赫数等因素对尾缘死水区基压的影响.提出通过改变尾缘形状来改善跨音速叶栅气动特性的途径.图8表1参15     

尾缘造型及冷气喷射对跨声速涡轮叶栅损失的影响

通过对不同尾缘造型、不同尾缘冷气喷射量下某跨声速涡轮叶栅的数值模拟,初步得出了尾缘劈缝冷却对尾缘损失以及叶栅能量损失影响的规律。其主要表现为:从减小叶栅能量损失角度来讲,尾缘冷气喷射流量存在最佳值,且随劈缝长度增加,此最佳冷气喷射流量越小;从减小尾缘激波强度角度来讲,较大的冷气流量以及较长的尾缘劈缝有利于减小激波损失,但会消耗过多冷气并增加掺混损失,导致总损失增加。     

大小叶片扩压叶栅气动性能与流动结构实验研究

针对45°叶型转折角扩压叶栅及增加小叶片后组成的大小叶片叶栅,分别测量了其在设计工况及不同气流攻角下的叶栅气动性能,通过PIV实验获得了对应工况下的叶栅内部流动状态.结果表明：增加小叶片后,叶片压力面至吸力面的压力梯度明显降低,大叶片载荷降低;在设计工况下,叶栅气流落后角仍可参考霍威尔半经验公式进行计算,但偏离设计工况后,该公式存在较大误差;大小叶片叶栅的气流落后角仅在小气流攻角下明显减小,在其余工况下变化不大;不同气流攻角下小叶片对大叶片表面气流流动分离起到约束作用;在设计工况至大气流攻角工况变化过程中,叶栅扩压损失有所降低.     

外来扰动频率对涡轮叶栅流动稳定性的影响

应用非线性PSE方法预测和评价某型超临界蒸汽轮机调节级导叶栅边界层流动的稳定性,研究了扰动频率对叶栅流动稳定性的影响。结果表明,当来流扰动频率变化时,扰动会对叶栅边界层稳定性产生很大的影响,此时存在一个最大扰动频率,在这一频率下流动最容易发生转捩。最大扰动频率受边界层厚度雷诺数的直接影响,其数值沿着流向逐渐减小,即叶片入口流动对高频扰动敏感,叶片出口流动对低频扰动敏感。     

跨音速透平叶栅尾缘劈缝射流气动性能分析

基于定常RANS方程,采用Spalart-Allmaras(S-A)湍流模型,数值模拟某跨音速导叶尾缘劈缝射流的定常流动结构,分析尾缘劈缝射流对尾缘激波结构、尾迹流动特性及叶栅气动性能的影响。研究表明:开缝射流显著降低尾缘压力面侧燕尾波强度,并使激波在相邻叶片吸力面入射点向上游移动;当叶栅出口马赫数小于1.35时射流使吸力面燕尾波强度减弱,而达到1.35后射流使该侧激波强度增大;在不同出口马赫数下射流均能降低叶栅动能损失。     

汽轮机空心静叶吹扫性能的试验研究和数值计算

在气-液两相流试验装置上研究了汽轮机空心静叶缝隙热气吹扫对二次水滴尺寸的影响,并结合数值方法分析了热气吹扫对叶栅气动性能的影响.试验结果表明:热气流吹扫使二次水滴的尺寸显著减小,尾缘处的缝隙吹扫对减小二次水滴的尺寸最明显,而压力面时二次水滴尺寸的影响最小,并且提高吹扫压比有助于提高吹扫效果.数值分析表明:压力面和吸力面吹扫缝隙后出现严重的流动分离;扩压区增大,使压力损失增大;尾缘吹扫需对叶片尾缘加厚,但这却导致了严重的尾迹损失;热气吹扫造成叶栅效率降低高达4%.     

Numerical study of improving aerodynamic performance of low solidity LPT cascade through increasing trailing edge thickness

This paper presents a new idea to reduce the solidity of low-pressure turbine (LPT) blade cascades, while remain the structural integrity of LPT blade. Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness (TET). The solidity of the LPT cascade blade can be reduced by about 12.5% through increasing the TET of the blade without a significant drop in energy efficiency. For the low solidity LPT cascade, increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by 1.86% for Reynolds number (Re) of 25,000 and freestream turbulence intensities (FSTI) of 2.35%. The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented. The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.     

Research on the Influence of Guide Blade Trailing Edge Structure on Turbine Performance

The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turbine) is calculated out in three dimensions. In the HP turbine guide vane, the trailing edge cutback configuration is adopted. Through three-dimensional simulation, the complex flow around the trailing edge with cutback cooling configuration is presented in this study, and the manufacturing precision reduction due to the complex structure at trailing edge is considered. Furthermore, the effect of trailing edge lip thickness and deflection of the stator on the turbine performance is discussed. Overall, as the press-side lip thickness increasing, the turbine efficiency and turbine inlet flow are reduced. However, the changes in the turbine work output are relatively complex. On the other hand, as the spacing between suction-side lip and press-side lip increases, turbine performance becomes worse. Both of the turbine efficiency and the turbine work output become smaller, while the turbine inlet flow becomes bigger. The effect of the spacing between suction-side lip and press-side lip is obviously greater than that of the press-side lip thickness. The change of the press-side lip thickness has little effect on the relation between the turbine performance and the spacing between suction-side lip and press-side lip. However, when the spacing between suction-side lip and press-side lip deviates from the baseline value, the effect law of the press-side lip thickness on the turbine performance will be affected. As the press-side lip thickness increases, it leads to an increase in the low-velocity zone at both of the pressure-side and suction-side trailing edge. And more main stream is affected or mixed into the wake flow. When the spacing between suction-side lip and press-side lip becomes smaller, the low-velocity zone at the trailing edge is smaller, and the change of vortex with the press-side lip thickness is affected. With a bigger spacing between suction-side lip and press-side lip, the variation is contrary.     

可变尾缘进口导叶滞后角的计算

根据一系列平面叶栅风洞试验的结果,确定了轴流式压气机中可变尾缘进口导叶的气动特性,从而总结出可变尾缘进口导叶滞后角按卡特公式计算时必须进行的修正和适用的范围。     

The influence of synthetic jet excitation on secondary flow in compressor cascade

The detailed numerical simulation has been carried out to investigate the effect of synthetic jet excitation on the secondary flow at 5° incidence in a compressor cascade, in which the synthetic jet actuation is equipped on the suction surface. The influence of excitation position, one fixed near the trailing edge and the other fixed a little far from the trailing edge, has also been studied. The results show that unsteady disturbance of desirable synthetic jet effectively enhances the mixing of the fluid inside the separation region, which reduces the vortex intensity and the energy loss, improves the flow status in the cascade, and also suppresses velocity fluctuation near the trailing edge. Additionally, the actuation fixed near the separation region proves to be more effective and exit load distribution is more uniform due to the employment of the synthetic jet.     

增加风力机叶片翼型后缘厚度对气动性能的影响

以FFA-W3翼型族为研究对象,对其系列翼型的后缘作了加厚处理。利用XFOIL软件对修改前后的翼型的气动性能进行了计算,利用Viterna-Corrigan失速后模型将气动性能数据的攻角扩展到了90°。对修改前后的翼型的气动性能数据的改变作了对比分析。利用原翼型和修改后翼型的气动性能数据对同一个风力机进行了气动性能计算,并对计算结果作了对比分析。结论认为,对翼型后缘进行适当加厚处理对气动性能影响不大,为满足工艺要求在叶片的生产中对翼型后缘作加厚处理是可行的。     

Trailing edge noise reduction of wind turbine blades by active flow control

In the current study, we investigate a route to reduction of the turbulent boundary layer–trailing edge interaction noise. The trailing edge noise is generated by surface pressure fluctuations beneath a turbulent boundary and scattered at the trailing edge of wind turbine blades. Trailing edge noise is considered to be the dominant noise source of modern wind turbines. Therefore, efforts are constantly made to attenuate the noise. Today, noise emission can be reduced by proper airfoil design or passive devices, such as trailing edge serrations. A further improved candidate technology for trailing edge noise attenuation is active flow control in the form of wall‐normal suction. With active flow control, the boundary layer features responsible for trailing edge noise generation can be manipulated, and correspondingly the trailing edge noise can be reduced. Detailed experimental investigations were performed at the Universities of Tel‐Aviv and Stuttgart. The tests showed that steady wall‐normal suction has a positive effect on the trailing edge noise by reducing the boundary layer thickness, and with it the integral length scales of the eddies within the boundary layer. Copyright © 2014 John Wiley & Sons, Ltd.     

汽轮机叶型几何特性及机械特性研究

基于Bézier曲线定义的叶型,以曲线间公切线以及公切圆的求解方法为基础,对叶型的原始信息进行逆向工程研究.计算得到了包括叶型前后缘小圆、中弧线、最大厚度、叶栅通道收敛性等在内的详细的几何特性,同时采用积累弦长参数化方法,获得了叶型面积、重心、惯性矩等一系列机械特性参数,为新叶型的开发研究奠定重要的基础.     

不同攻角下压气机叶栅涡流噪声辐射特性的研究

采用大涡模拟模型和边界元方法对压气机叶栅的非定常流场与声场进行了分析,研究了来流攻角对叶栅尾缘非定常涡脱落及其噪声辐射特性的影响.结果表明：压气机叶栅流场中存在着尾缘涡脱落现象,尾缘涡脱落的强度随着攻角的变化而变化.在较大的正攻角下,吸力面存在的分离涡与下游的尾涡相互影响,引起较大的升力脉动,使得噪声辐射增强;而在较大负攻角下,压力面的分离涡同样影响尾缘涡的脱落,噪声辐射水平也有增强趋势.来流攻角对噪声辐射的指向性影响不大.声压级的最小值出现在阻力系数最小的攻角下.     

风力机翼型尾缘厚度对粗糙敏感性影响的研究

综合应用涡面元和RANS方法,研究DU93-W-210、DU91-W2-250及DU97-W-300这3种常用翼型经尾缘修型后尾缘厚度对粗糙敏感性的影响.在涡面元方法中采用设置固定转捩和在RANS方法中采用设置锯齿形边界条件的方式来模拟翼型前缘污染,研究发现前缘污染造成翼型吸力峰降低,引起翼型气动性能下降,然而随着尾缘...