【作者】 罗钜；

【导师】 胡骏；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2013， 博士

【摘要】 压气机作为航空发动机三大核心部件之一，其叶片通道内部的损失直接影响着整台发动机的性能、稳定性和经济性。当现代先进航空发动机的设计趋势朝着高推重比的方向不断发展时，压气机通道内的逆压梯度和叶片负荷随之不断增加，此时角区分离或者轮毂-角区失速极易在通道内出现并造成严重的总压损失。三维叶片设计技术通过改变积叠线的空间位置，引入了径向上的作用力，改变了叶片表面和端壁面的压力分布，减弱了叶片端部和轮毂表面低能流体的积聚，从而降低角区分离强度，减小叶片通道内的流动损失，压气机的效率和稳定裕度得以提高。本质上而言，通道内的流动过程就是不同涡系的发展运动及其相互掺混作用的过程，只有从涡运动的角度出发，通过详细的参数化计算和流场测量实验，才能更深入地了解和揭示三维叶片在通道内部的减损机理和影响规律。本文以一台双级低速轴流压气机试验器为研究对象，通过数值方法，改变第1级静子的积叠线形式以及弯高、弯角等积叠线参数，研究了带有根部间隙时的简单贝塞尔曲线（SBC）和直线-贝塞尔曲线-直线(BLB)两种积叠线形式的弯曲静子和不带有根部间隙下的BLB形式弯曲叶片对压气机性能和通道内涡系结构的影响，从而揭示弯曲叶片在两种安装形式下的降损机制。根据数值计算的结果，选取了带有根部间隙下效果最好的一组BLB形式弯曲叶片进行加工，并加装在压气机上进行实验研究。实验获得了直叶片和弯曲叶片压气机的特性曲线，并通过4根不同长度的五孔探针和1根四孔探针，测量了最大流量工况和近失速工况下直叶片和弯曲叶片通道内不同轴向位置截面上的气流参数。除此之外，本文还在不同畸变进气条件下对直、弯叶片压气机进行了总特性测量和第1级静子出口截面流场测量。对弯曲叶片在畸变进气条件下的作用机理进行了简要的探讨。从不带有根部间隙的计算结果可知，在小流量范围内，轮毂-角区失速是压气机第1级静子S1通道内损失的主要来源。由于弯曲叶片减小了叶片两端的叶片负荷和轮毂表面低压区的面积，减弱了叶片端部低能流体的聚积和端壁附面层低能流体从压力面到吸力面的横向流动，轮毂表面分离涡和集中脱落涡的强度由此降低。同时分离涡在向下游发展过程中，不再向上跃起与吸力面集中脱落涡进行掺混，因此叶片通道内的损失大幅度地降低。弯曲叶片积叠线分别为SBC和BLB两种形式时，效率最大增幅都达到1个百分点左右。带有根部间隙的计算结果表明，在带有根部间隙的叶片通道中，叶尖分离涡、叶根泄漏涡以及叶根泄漏涡与下通道涡之间的掺混是造成总压损失的主要原因。弯曲主要是通过改变端部的叶片负荷，从而控制叶尖和叶根的附面层聚积以及轮毂低能流体横向移动，主要涡系的强度因此减小，同时下通道涡的位置更远离泄漏涡，它们之间的相互掺混程度也由此降低，总压损失减小。当叶片带有根部间隙时，BLB形式的弯曲叶片主要改善了小流量范围内的压气机性能。在近失速点附近，弯高为10%叶高，弯角为15°的叶片获得了最大的效率增益，为0.3个百分点。无论是否带有间隙，计算的结果均表明，弯曲的效果主要体现在通道内损失较大的小流量范围，而在损失较小的大流量范围内，弯曲对压气机性能的改善并不明显；同时，弯角和弯高过大使得叶片表面摩擦损失增加，甚至导致弯曲叶片压气机的效率低于直叶片压气机的。这是由于弯曲叶片最终降损效果是其减小的分离损失和弯曲带来的摩擦损失之间的折衷。带有根部间隙的弯曲叶片压气机实验证实了弯曲叶片对压气机性能的改善作用，其对压气机的性能提升也主要体现在损失较高的小流量范围。由于数值计算对叶尖区域的分离预估相比实验值要小，实验得到的效率增益大于数值计算的结果。在流量系数为0.637时，效率增益达到最大的1个百分点。静子通道内的损失主要来源于叶尖角区分离、叶根泄漏涡以及其与下通道涡的掺混。在小流量范围内，弯曲叶片降低并减小了叶尖分离涡、叶根泄漏涡和下通道涡的强度和尺度，同时使得后面两个涡系的形成位置更加靠后，从而减小了通道内的总压损失。弯曲叶片同样能在畸变进气条件下改善压气机的性能。在叶尖径向进气畸变和180°周向进气畸变下，弯曲叶片的最大效率增益均为1个百分点左右。但在叶尖径向畸变下，弯曲叶片主要是在大流量范围内提升压气机的性能，随着流量减小，弯曲叶片压气机的性能最后基本与直叶片压气机的相差无几。而在周向畸变下，弯曲叶片的效果随着流量的减小逐渐得以体现。造成这样的原因是因为叶尖径向畸变使得叶尖的损失加大，而叶根损失减小。在小流量范围，由于弯曲叶片在叶尖区域的降损能力非常微弱，而叶根处的损失相对较小，损失减小幅度也并不大。在周向畸变下，压气机可以简单近似地被看作是“均匀进气”下两台工作在不同流量的子压气机组合。当弯曲叶片在进口流量较小的子压气机内降损能力较弱时，而在另一台子压气机内还有一定的降损能力，因此整台压气机的性能得以继续提升。更多还原

【Abstract】 As a principal part of the aero-turbo engine, the flow loss in the blade channel is affecting totalaerodynamic performance, stability, and economy. The adverse pressure gradient and blade loadingin compressor blade channel keep increasing when the modern aero-tubo engine design demandshigher and higher thrust-weight ratio. The corner separation or hub-corner stall will arise and causegreat total pressure loss. The three-dimensional blading design technique changes the location ofblade stacking line to introduce the radial force, which will change the static pressure distribution onthe suction and hub surface, to control the vortex development and strength of shockwave, so it hasthe ability to improve total performance and stability of the compressor. The flow development in thecompressor blade passage is the development and mixing of all kinds of vortex, so it is necessary tostudy the loss decrease mechanism and effect law of the three-dimensional blade through detailednumerical simulation and flow field measurement in the view of vortex development.Numerical investigation is carried out on a two-stage low speed axial compressor. The SBC andBLB type stacking lines of the first stage stator S1are chosen to study the effect of bowed parameter,bowed height and bowed angles, on the total performance and vortex with and without hub clearance,after that the loss decrease mechanism is discussed. Based on the numerical simulation results, a set ofBLB blades with best effectiveness is produced and installed on the compressor. Then experiments arecarried out in the straight blade compressor and bowed blade one. The flow field at five differenttransverse sections is measured by four different lengths of five-hole hole probes and a four-holeprobe. Finally, experiments of the both compressor with inlet distortion are carried out. Through theexperiment total performance of compressor and flow field of outlet transverse sections of S1aremeasured, the mechanism of loss decrease with inlet distortion is discussed.It is found that hub-corner stall is the main cause for the rapid increase of total pressure loss inthe compressor stator passage with hub clearance at near stall condition. Bowed stator has suppressesthe accumulation of low energy fluid at both ends of blade and the cross-flow on the hub surface bydecreasing the blade loading at both blade ends and the area of low static pressure on the hub surface,so it decreases the strength of hub separation vortex and concentrated shedding vortex. Moreover, thehub separation vortex does not go up and mix with concentrated shedding vortex so the loss isdecreased greatly and the hub-corner stall disappears. Efficiency has been increased by one percentaround both in the SBC b and BLB type blade. The result with hub clearance shows that tip separation vortex, hub leakage vortex and lowerpassage vortex are the main cause for the increase of loss in the blade passage. The bowed bladereduces the blade loading at both ends to suppresses the accumulation of low energy fluid, and thecross-flow at the hub surface, so the distance between lower passage vortex and hub leakage vortexgets bigger, which makes the mixing loss between the two vortexes decrease. At the near the stallpoint, the BLB blades with10%blade height and15°degrees has increased the efficiency by0.3percent. It is proved that bowed blade improves the performance of compressor mainly at low flowrate, whether with hub clearance or without. While at great flow rate the effect of bowed stator is notclear. Moreover, the efficiency of bowed blade compressor may be smaller than the straight one. It isbecause that bowed blade can decrease the flow loss, it also bring the surface friction loss on the otherhand. It is a comprehensive result for bowed blade.The experiment has verified that the bowed stator with hub clearance can improve theperformance indeed. The biggest efficiency profit is about one percent at the flow rate of0.637. Themain flow loss is caused by the tip corner separation, hub leakage vortex, and the mixing between hubleakage vortex and lower passage vortex. At low flow rate, bowed blade has decrease the strength ofthose vortexes, and it also has delays the appearance of hub leakage vortex and lower passage vortex,so the flow loss has decreased.Bowed blade can also improve performance of the compressor with inlet distortion. Theefficiency profit of bowed blade is one percent both under radial distortion and circumferential one.Bowed blade improves performance of the compressor mainly at great flow rates. As the flow rategets smaller, there is nearly no different between bowed blade compressor’s performance and straightone. While the effect of bowed blade becomes more and more clear when the flow rate gets smaller.The reason is that tip radial distortion makes the loss near the blade tip more serious, while the lossnear the hub less serious. As the flow rate gets smaller, the bowed blade’s capability of reducing lossis reaching its limitation. On the other hand, the loss near the hub is not serious, so there is noobvious efficiency profit near the hub. Under the circumstantial distortion the compressor is dividedinto two segment compressors. One segment is under a bigger flow rate, the other is under a smallerflow rate. So when the bowed blade in the former reaches its limitation, while the latter still has someresidual capacity to reduce the loss. So the entire compressor’s performance keeps improved.更多还原