Aerodynamic performance of high-turning curved compressor cascade with boundary layer suction

The impact of boundary layer suction on the aerodynamic performance of a high-turning compressor cascade was numerically simulated and discussed.The aerodynamic performance of a curved and a straight cascade with and without boundary layer suction were comparatively studied at several suction flow rates.The results showed that boundary layer suction dramatically improved the flow behavior within the flow passage.Moreover,higher loading over the whole blade height,lower total pressure loss,and higher passage throughflow were achieved with a relatively small amount of boundary layer removal.The integration of curved blade and boundary layer suction contributed to better aerodynamic performance than the cascades with only curved blade or boundary layer suction used,and the more favorable effect resulted from the weakening of the three dimensional effects of the boundary layer close to the endwalls.

In uence of Endwall Boundary Layer Suction on the Flow Fields of a Critically Loaded Di usion Cascade

Boundary layer suction is an e ective method used to delay separations in axial compressors. Most studies on bound?ary layer suction have focused on improving the performance of compressors,whereas few studies investigated the influence on details of the flow fields,especially vortexes in compressors. CFD method is validated with experi?mental data firstly. Three single?slot and one double?slot endwall boundary layer suction schemes are designed and investigated. In addition to the investigation of aerodynamic performance of the cascades with and without suction,variations in corner open separation,passage vortex,and concentration shedding vortex,which are rarely seen for the flow controlled blades in published literatures,are analyzed. Then,flow models,which are the ultimate aim,of both baseline and aspirated cascades are established. Results show that single?slot endwall suction scheme adjacent to the suction surface can e ectively remove the corner open separation. With suction mass flow rate of 0.85%,the overall loss coe cient and endwall loss coe cient of the cascade are reduced by 25.2% and 48.6%,respectively. Besides,this scheme increases the static pressure rise coe cient of the cascade by 3.2% and the flow turning angle of up to 3.3° at 90% span. The concentration shedding vortex decreases,whereas the passage vortex increases. For single?slot suction schemes near the middle pitchwise of the passage,the concentration shedding vortex increases and the passage vortex is divided into two smaller passage vortexes,which converge into a single?passage vortex near the trailing edge section of the cascade. For the double?slot suction scheme,triple?passage vortexes are presented in the blade passage. Some new vortex structures are discovered,and the novel flow models of aspirated compressor cascade are proposed,which are important to improve the design of multi?stage aspirated compressors.

表面微沟槽对压气机叶栅气动性能的影响

为减小叶型损失,在压气机叶栅叶片表面布置沿流向的对称V形微沟槽,采用数值模拟方法研究了沟槽宽度和顶角、沟槽间隔、沟槽覆盖范围、进口湍流度以及来流马赫数对叶栅气动性能的影响。结果表明,总压损失降低主要由吸力面沟槽产生,合理匹配沟槽几何参数、覆盖范围以及来流条件,可实现较优的减损效果。对吸力面局部带沟槽结构,相同冲角下无间隔沟槽的减损效果优于有间隔沟槽的减损效果,当无间隔沟槽顶角度为60°时减损效果最优;相同沟槽结构的减损效果与冲角相关。来流湍流度增加使得相同冲角下光滑叶片和带沟槽叶片的总压损失增大,相同沟槽结构在同一冲角下的减损效果及最优减损效果对应的冲角受来流湍流度影响。冲角不变时相同沟槽结构的减损效果随来流马赫数增大整体呈下降趋势,最佳减损效果对应的无量纲沟槽宽度和具有减损效果的无量纲沟槽宽度范围不同。当保持沟槽无量纲宽度不变和沟槽其它参数不变时,不同来流马赫数条件下的最佳减损效果及其对应的冲角不同,较低来流马赫数条件下最佳减损效果更突出。微沟槽能够减小壁面平均剪切应力和湍动能,降低湍流边界层损失,同时能够推迟边界层流动分离,使得叶型损失降低。

亚声速可压缩流场叶片边界层热线测速方法研究

为了能够开发一种简单有效的亚声速可压缩流场叶片边界层速度测量方法,从而为叶型设计和相关数值研究工作提供支撑,本文围绕热线风速测量技术,针对可压缩流场密度变化对热线标定结果的影响,以及实际测量中速度、密度耦合而无法直接获取的问题,通过理论分析,提出了适用于边界层测量的恒定压力热线标定方法和引入叶表稳态静压进行速度解耦的方法,并对所提出方法的主要误差进行了分析评估。在此基础上进行了热线标定和边界层速度测量试验验证,明确了恒定压力热线标定数学模型系数随压力的线性变化规律,同时针对温度非线性影响提出了一种基于过热比调整的修正方法,该方法能够将约13℃的温度偏差对热线电压的影响降低到1%以内,进一步简化了恒定压力热线标定流程,结合基于叶表稳态静压的速度解耦方法,为亚声速可压缩流场叶片边界层瞬态速度测量提供了一种简单可行的高频响测速方法。

A combined application of micro-vortex generator and boundary layer suction in a high-load compressor cascade

In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex generator with a special configuration and the longitudinal suction slot are adopted. The calculated results show that a reverse flow region, which is considered the main reason for occurring stall at 7.9° incidence, grows and collapses rapidly near the leading edge and leads to two critical points occurring on the end-wall with the increasing incidence in the baseline. As the micro-vortex generator is introduced in the baseline cascade, the corner separation is switched to a trailing edge separation by the thrust from the induced vortex. Meanwhile, the occurrence of failure is delayed due to the mixed low energy fluid and main flow. The synergistic effects between the micro-vortex generator and the boundary layer suction on the performance of the cascade are superior to the baseline at all the incidence conditions before the occurrence of failure, and the sudden deterioration of the cascade occurs at 10.3° incidence. The optimal results show that the farther upstream suction position, the lower total pressure loss of the cascade with vortex generator at the near stall condition. Moreover, the induced vortex with a leg can migrate the accumulated low energy fluid backward to delay the occurrence of stall.

Boundary layer separation control on a highly-loaded,low-solidity compressor cascade

Separated flow can be effectively controlled through the management of blade boundary layer development.Numerical simulations on a highly-loaded,low-solidity compressor cascade indicate that combined blowing and suction flow control technique can significantly improve cascade performance,especially in increasing the cascade loading and static pressure ratio as well as decreasing the loss coefficient.Meanwhile,it is more effective to improve cascade performance by blowing near leading edge on suction surface than suction near trailing edge.Both the locations and flow rates of blowing and suction are major impact factors of this method to cascade performance.Comparing to the baseline,the static pressure ratio increases by 15% and loss coefficient decreases by 80%,with a blowing fraction of 1.7% and a suction fraction of 1.38% of the inlet mass flow.

Computational Study on the Boundary Layer Suction Effects in the Supersonic Compressor Flow with a Bowed Blade

Flow control methodologies have been widely used to eliminating flow separation and increasing the blade load in axial compressor.Aiming at revealing the flow mechanism of coupled bowed blading and boundary layer suction in a supersonic compressor cascade,a cascade with a diffusion coefficient of 0.62 is numerically presented.First of all,according to the available experimental data,the numerical method was validated;then,different bowed blading effects on flow field in detail were investigated;at last,based on the flow physics of purely bowed blading,the positively bowed blade was coupled with boundary layer suction on blade suction surface,whereas the negatively bowed blade was coupled with endwall suction.For coupled control method,influence mechanism on flow field,especially on the shock structure was revealed,and different aspect ratios of coupled control method were investigated as well.Results showed that the coupled positively bowed blading and suction surface suction can eliminate the flow separation effectively.Compared with that of baseline supersonic cascade,the total pressure loss coefficient of the coupled scheme was reduced by 37.4%at most.At mid-span,the shock moved downstream and the single shock was separated to a dual-shock structure since the positively bowed blading reduced the static pressure of mid-span.The coupled negatively bowed blading and endwall suction also effectively enhanced the performance of cascade by removing the corner separation,with the loss coefficient reduced by as much as 41.9%.However,the suction coefficient of optimal coupled negatively bowed blading scheme reached 10.5%,which is too high for practical use.After coupled control,the 3 D shock structure became“C”shaped distribution along spanwise because of the difference in influence mechanism of negatively bowed blading on different spanwise location.Due to the opposite influence effect of positively and negatively bowed blading,the shock structure in the two different schemes of cascades were different and showed opposite variation trends as aspect ratio increased.

进口附面层对串列叶栅气动性能的影响研究

为探究进口附面层对串列叶栅气动性能的影响,以高亚声速压气机常规叶栅及其改型串列叶栅为研究对象,基于数值方法对比分析了不同进口附面层厚度对两叶栅的总体性能及三维角区分离的影响。结果表明:随着进口附面层厚度增加,原型叶栅三维角区分离范围沿展向逐渐增大,而串列叶栅三维角区分离范围的增加主要体现在周向。由于进口附面层的存在,串列叶栅前后叶片之间的缝隙射流与近端壁低能流体的相互作用所产生的通道涡、诱导涡及角涡是总压损失增大的主要原因。串列叶栅与原型叶栅相比能有效降低总压损失和提高静压升,然而附面层厚度的增加会减小这一优势;进口附面层厚度相对叶高的比值为0%,5%,12.5%时,串列叶栅的出口总压损失系数较原型叶栅分别降低11.1%,5.5%和4.1%,静压升系数分别提高7.4%,6.5%和6.4%。

叶栅吸力面吸气位置与角区分离的关联性分析

高压压气机后面级的叶片吸力面三维角区内易堆积大量的低能流体。为了指导吸气槽设计,达到量化分析叶栅吸力面吸气槽位置与角区分离的关联性的目的,以一高负荷压气机叶栅为研究对象,采用计算流体力学仿真软件讨论了全叶高吸气槽轴向位置变化对叶栅性能的影响,并以角区分离起始位置到叶栅前缘之间的距离(ZCS)作为量化标准。研究表明:在设计工况附近,总压损失随着吸气槽轴向位置从前向后移动表现出了先减小后增大的趋势,且叶片吸力面吸气槽在不同工况下存在最佳轴向位置。在0°迎角时,当吸气槽距离分离点间的轴向距离为0.33倍的ZCS时为最佳,可使总压损失系数降低10.9%。这种量化结果借助角区分离结构实现了吸气槽轴向位置设计的标准化指导。

端壁造型与附面层抽吸耦合流动控制对压气机叶栅的性能影响

为改善轴流压气机性能,抑制角区分离,采用数值模拟方法探究端壁造型(PEW)与附面层抽吸(BLS)两种流动控制措施在不同工况下对高负荷压气机叶栅的气动性能影响。使用神经网络作为代理模型,采用多目标遗传算法进行全局寻优,选取得到的5种最优端壁造型结构,与3种不同弦长位置的抽吸缝进行组合。结果表明:兼顾设计工况及近失速工况叶栅气动性能,采用吸力面70%弦长位置抽吸与通道前中部下凹、近压力面上凸的造型组合最优。设计工况下,附面层抽吸抑制了弦长中部转捩泡的生成,有效降低了尾迹损失,此时最优组合减小了12.7%的总压损失。近失速工况下,端壁造型通过控制端区横向二次流,缓解堵塞,抑制了角区分离进而降低尾迹损失,此时最优组合减小了15.5%的总压损失。

压气机叶片仿鲨鱼鳃开槽对叶栅气动性能的影响

基于鲨鱼鳃射流减阻的思想,采用数值方法,将仿鲨鱼鳃结构应用在压气机平面叶栅中。在叶片根部从压力面向吸力面开槽,采用单个进口、两个出口的开槽结构,以期在获得较大的出口射流的情况下实现对压气机叶片的减阻,达到提高叶栅气动性能的效果。在保证开槽结构的进出口宽度、出口起始位置、开槽内的隔板宽度、深度等几何参数不变的基础上,研究开槽进口起始位置、开槽高度对叶栅性能的影响。结果表明:合理的仿鲨鱼鳃开槽结构可以有效改变叶片吸力面根部角区的流动结构,抑制气流沿叶高方向的流动,从而降低流动损失;最佳方案为开槽结构位置位于48%~53%压力面弧长处,开槽高度为15%叶高,可以使压气机叶栅总压损失减小7.16%。

Method for utilizing PIV to investigate high curvature and acceleration boundary layer flows around the compressor blade leading edge

Particle Image Velocimetry(PIV)is a well-developed and contactless technique in experimental fluid mechanics,but the strong velocity gradient and streamline curvature near the wall substantially limits its accuracy improvement.This paper presents a data processing procedure combining conventional PIV and newly developed Mirror Interchange(MI)based Interface-PIV for the measurement of the boundary layer parameter development in the blade leading edge region.The synthetic particle images are used to analyze the measurement errors in the entire procedure.Overall,three types of errors,namely the errors caused by the Window Deformation Iterative Multigrid(WIDIM)algorithm,the discrete data interpolation and integration,and the wall offset uncertainty,comprise the main measurement error.Specifically,the errors due to the discrete data interpolation and integration and the WIDIM algorithm comprise the mean bias,which can be corrected through the error analysis method proposed in the present work.Meanwhile,the errors due to the WIDIM algorithm and the wall offset uncertainty contribute to the measurement uncertainty.Computational fluid dynamics-based synthetic particle flows were generated to verify the newly developed PIV data processing procedure and the corresponding error analysis method.Results showed that the data processing method could improve the accuracy of PIV measurements for boundary layer flows with high curvature and acceleration and even with significant flow separation bubbles.Finally,the data processing method is also applied in a PIV experiment to investigate the boundary layer flows around a compressor blade leading edge,and several credible boundary flow parameters were obtained.

附面层吸除对压气机叶栅稠度特性影响

数值模拟了不同稠度下吸气量及位置对某大转角吸气式压气机叶栅气动性能影响。结果表明,附面层吸除(BLS)使得吸力面角区低能流体积聚减弱,气流折转能力加强;随稠度增加,叶栅总压损失最高降低分别为32.9％、27.7％和25.1％,出口气流角最大增加值为5.0°、4.2°和3.1°,即小稠度叶栅具有较佳气动性能;BLS导致的栅内扩压能力恢复和通道涡三维分离效应的改善应是确定最佳设计参数的判定原则。吸气式叶栅附面层承受逆压梯度能力强的特点为高负荷、小稠度压气机设计提供了极具潜力的技术途径。

边界层吹吸气对高负荷扩压叶栅性能的影响

采用边界层流动控制能够有效抑制扩压叶栅的流动分离。以某大弯折角低稠度扩压叶栅为研究对象,利用数值模拟手段研究了原型、叶片表面边界层单独吹气以及吹吸气相结合等边界层控制手段下的流场和叶栅性能变化情况。结果表明,无论是单独吹气还是吹吸气相结合的边界层控制方法,都能有效控制扩压叶栅中的边界层分离,从而较大幅度地增大叶栅负荷,并降低气动损失;计算表明,吹气和吸气的效果不尽相同,且吹吸气口位置及吹吸气流量对边界层的流动亦有较为明显的影响。其中采用1.7%的吹气流量,结合1.38%的吸气量,可以使静压增压比提高15%以上,而损失系数降低至原型的20%以内。

端壁抽吸位置对压气机叶栅角区分离控制的影响

以某高负荷压气机叶栅为研究对象,应用数值模拟方法探索了叶栅端壁不同抽吸位置对角区流动结构、通道漩涡发展过程以及叶栅性能的影响规律,寻求控制角区分离的可行方法。研究结果表明:在叶栅前缘上游5%C(弦长)位置实施抽吸,延缓了通道涡的形成,但导致叶栅来流攻角发生改变,在角区形成角区分离涡,并且该漩涡与通道涡相互促进,进一步恶化叶栅流场,导致叶栅落后角增大,损失增加;在叶栅通道激波后25%C端壁抽吸,吸除了上游端壁积累的高熵低能气流,制约了通道涡的迅速发展,改善了叶栅通道的流场结构,降低了流动损失,但并未对上游流场产生较大影响,是一种可行的方案。然而25%C处抽吸后,未能完全消除分离,在端部与叶栅通道主流之间存在较高损失区域。

吸附式亚声速压气机叶栅气动性能实验及分析

以亚声速平面叶栅风洞为实验平台,在不同来流马赫数、攻角和吸气量状态下,测试吸附式压气机叶栅吸力面、压力面表面压力分布和叶栅尾缘等参数.结果表明,附面层吸除能促进附面层减薄,减少分离损失,有助于降低叶栅总压损失,提高气流折转能力,改善叶栅气动性能.合适吸气槽位置和吸气量的选择,有利于叶栅内部流动更趋合理.

端壁采用孔式抽吸对扩压叶栅气动性能的影响

为明晰孔式附面层抽吸技术对压气机叶栅气动性能的作用效果,实验研究了在端壁不同位置设置抽吸孔时对大折转角扩压叶栅壁面流谱、出口二次流及损失的影响。研究结果表明,端壁抽吸改变了原型叶栅内部流场结构,角区分离起始点前进行附面层吸除可有效延缓通道涡的形成,降低叶栅损失;分离起始点之后角区分离已经充分发展的位置不宜布置抽吸孔;相比较抽吸槽,采用抽吸孔可以通过更少的抽吸量达到相同程度地对叶栅流动性能的改善。

缝隙扩压叶栅近壁流场与流动损失实验

为了探索缝隙射流对高负荷扩压叶栅气动性能与近壁流场结构的影响机制,实验研究了设计冲角下有/无缝隙结构的高负荷弯曲扩压叶栅近壁流场结构与出口气动损失分布规律,获得了叶片近壁压力场数据、流动图谱以及叶栅出口流动损失参数。结果表明,缝隙两端压差导致的从叶片压力面到吸力面的射流能够增加附面层高熵流体的能量,缝隙射流将局部积聚的低能流体及时引向主流,减小高熵流体在叶展中部或端区掺混撞击,抑制了栅后尾迹高熵流体的过度聚集,从而有效提高高负荷压气机叶栅气动性能。

端壁附面层抽吸对大转角扩压叶栅旋涡影响的实验研究

为探明附面层抽吸技术对压气机叶栅气动性能的影响及其与栅内旋涡结构的关联,通过十个横截面的实验测量结果研究了高负荷压气机叶栅抽吸端壁附面层前后的主要旋涡结构以其对应损失的演变过程。研究对象为矩形低速扩压叶栅,来流马赫数约为0.23。研究结果表明,端壁附面层的变化对叶栅端区的主要旋涡发展过程影响显著。在原型方案中,壁面涡、尾缘脱落涡的演变过程对应着较高的流动损失,通道涡自身产生的损失较小,主要起到向远离端壁的方向输运低能流体的作用;在流向槽吸气方案中,壁面涡和尾缘脱落涡因端壁附面层径向迁移及角区分离受到抑制而被明显削弱;而来流附面层抽吸方案则最为有效地控制了通道涡的演变过程。

压气机弦向缝隙叶栅的气体动力学研究

就高负荷轴流式压气机弦向缝隙叶栅提出了确定弦向缝隙位置的数学模型 ,并给出了弦向缝隙叶栅流场计算的方法 ,作为分析这种叶栅气动性能的基础。