部分叶高串列扩压器对离心压气机性能的影响

为了保证离心压气机压比同时拓宽其稳定工作范围,将部分叶高概念引入串列扩压器设计中,获得部分叶高串列扩压器,并基于数值方法研究串列叶栅前后排叶片相对周向位置以及前排叶片相对高度对离心压气机与串列扩压器性能的影响.在相对周向位置为30%的串列扩压器基础上,利用不同部分叶高叶片设计串列扩压器前排叶片,获得不同的部分叶高串列扩压器.结果表明:串列叶栅前后排叶片相对周向位置对扩压器的扩压能力以及稳定工作范围有很大影响,当相对周向位置处于20%~30%内时离心压气机的整体性能达到最佳;与原离心压气机相比,当前排叶片相对高度h/B分别为40%和50%时,离心压气机的喘振裕度可分别增加21%和25%,总压比和等熵效率仅下降1%左右.     

部分叶高串列扩压器对离心压气机性能的影响

为了保证离心压气机压比同时拓宽其稳定工作范围,将部分叶高概念引入串列扩压器设计中,获得部分叶高串列扩压器,并基于数值方法研究串列叶栅前后排叶片相对周向位置以及前排叶片相对高度对离心压气机与串列扩压器性能的影响.在相对周向位置为30%的串列扩压器基础上,利用不同部分叶高叶片设计串列扩压器前排叶片,获得不同的部分叶高串列扩压器.结果表明:串列叶栅前后排叶片相对周向位置对扩压器的扩压能力以及稳定工作范围有很大影响,当相对周向位置处于20%~30%内时离心压气机的整体性能达到最佳;与原离心压气机相比,当前排叶片相对高度h/B分别为40%和50%时,离心压气机的喘振裕度可分别增加21%和25%,总压比和等熵效率仅下降1%左右.     

多级压气机动叶不同CLOCKING位置下尾迹/附面层干扰分析

采用harmonic非定常计算方法模拟了某型燃气轮机中间三级轴流压气机流场,研究第二级动叶处于不同CLOCKING位置下尾迹输运机理,指出在非定常条件下,叶片排之间干扰主要来自于尾迹和势流对叶片排的交替作用。在CLK0位置,上游尾迹的输运主要表现为单个尾迹向下游的传播过程。在CLK2位置,上游动、静叶片尾迹掺混发生显著不同,上游尾迹的输运呈现多个尾迹的传播过程,进而导致下游叶片非定常气动负荷的波动幅值出现显著差异。     

压气机叶片尾缘增厚方法的分析与研究

受限于制造能力,压气机叶片的尾缘需要增厚。为了尽可能保持原有设计的气动性能,对两种不同的尾缘增厚方法进行了数值模拟研究。第一种方法尽可能保持了原有叶型的吸/压力面型线,以移动尾缘圆心的方式获得增厚叶型,叶型的弦长缩短;第二种方法保持了原有叶型的弦长,以改变二维叶型局部厚度分布的方式获得增厚叶型。数值模拟结果显示,在一致的尾缘厚度下,两种尾缘增厚方法对压气机叶片的稠度、展弦比、扩压能力和气流折转能力均产生了不同的影响。相较而言,方法一导致了压气机叶片的负荷降低,扩压和气流折转能力下降;方法二能够更大程度的保持气动性能。建议采用方法二对过薄的叶片尾缘进行加厚处理。     

水平轴风力机尾迹流场PIV实验研究

在水平轴风力机模型不同尖速比条件下,利用PIV粒子图像测速技术对风轮尾迹流场进行了测量。采用锁相平均测量技术,获得了风轮尾迹流场的瞬时速度场、时均速度场、涡量场等有关定量信息,为准确计算风力机的流场、载荷和气动特性等提供了依据。实验结果表明:风轮叶片尾缘后侧的尾迹中存在轴向速度亏损区。尾迹在叶片尾缘生成后,随即发生膨胀。直到风轮下游2倍弦长以后,尾迹低速区逐渐衰减,轴向速度不断增加,尾迹区同时发生收缩现象。风轮尾迹涡从叶片尾缘脱落后,在向下游发展传播过程中,尾迹涡的涡心所形成的运动轨迹是与风轮叶片旋转方向相反的螺旋线,涡量数值随着螺旋线向风轮下游的延伸而减小。由于风力机叶片数少,相邻叶片之间的尾迹基本上不存在互相干扰的现象。     

串列叶栅扩压器弦长比对离心压气机的性能影响研究

为研究串列叶栅前后排叶片的弦长比对离心压气机性能的影响规律,采用数值模拟的方法对某离心压气机扩压器进行串列改造,并在弦长比为0.7、1.0和2.0时对离心压气机级性能进行分析。研究结果表明:串列叶栅扩压器效率优于楔形扩压器,且可以明显扩宽压气机的工作裕度;串列叶栅弦长比在一定范围内数值越大,即前排叶片越短,压气机性能越佳。在串列叶栅扩压器后排叶片前缘附近添加合适弦长的小叶片可以在不降低离心压气机效率与工作裕度的同时提高总压比,同时拓宽其最大通流能力。     

串列叶栅前后排叶片周向相对位置对离心压气机性能的影响

串列叶栅前后排叶片相对位置对串列扩压器的性能有重要影响.根据离心叶轮出口气流参数设计了一离心式串列叶栅扩压器,并利用数值模拟方法在前、后排叶栅周向相对位置分别为10%、20%、30%、40%、50%、60%、70%、80%和90%时对离心压气机级进行了计算和分析,研究周向相对位置变化对离心压气机性能的影响以及作用机理.数值模拟结果表明:随着前后排叶栅周向相对位置变化,后排叶栅前缘滞止高压区相对前排叶栅的位置发生了变化,影响了前排叶栅压力面的压力分布,从而改变了前排叶栅压力分布及大小;当前后排叶栅周向相对位置为30%时,扩压器性能达到最佳,使压气机总压比和等熵效率最大,稳定工作范围增大;前后排叶栅所形成的渐缩通道可抑制后排叶栅吸力面边界层的分离.     

平面叶栅中两类叶型探针影响特性的对比研究

采用平面叶栅吹风试验方法,针对压气机叶栅中两类叶型探针（A类、B类）的影响特性进行对比研究,在整理分析原型叶栅变工况流动特性的基础上,从叶片表面等熵马赫数、总体性能参数与栅后尾迹等三个层面详细考察了两类叶型探针的影响程度及变化规律。研究结果表明：对于叶栅通道内没有激波的亚音流场环境,A类探针的综合影响程度略小于B类探针,而对于叶栅通道内会形成强激波的跨音流场环境,A类探针的综合影响程度要大于B类探针;A类探针对叶栅出口尾迹分布的扰动作用大于B类探针,预示在压气机多叶排环境下B类探针的工程适用性更好。     

单级轴流压气机周向槽与梯状间隙结构的对比

在验证了计算模型的可靠性后,对单级轴流亚音压气机进行了71%设计转速下,实壁机匣,周向槽机匣与梯状间隙结构工作特性的数值模拟。结果表明,周向槽机匣与梯状间隙结构都能在一定范围内起到扩稳作用。周向槽的作用更多地体现在对叶片前缘叶顶泄漏涡的控制上,因此更适于设计在叶片通道的前半段。梯状间隙结构在叶片通道前半段与后半段都能起到扩稳作用,只是施于叶片前缘时,压气机效率损失较大,而施于叶片尾缘时,可以减小叶片尾迹分离区的面积,对提高压气机效率有益。     

基于预定涡尾迹法的风力机性能研究

以三叶片水平轴风力机为研究对象,建立了尾迹扩张模型,研究了叶片尾迹流动结构。涡面模型叶片无量纲环量的计算结果与经典环量数据对比,结果吻合较好。计算了根尖涡模型风轮面诱导速度随尾迹扩张系数的变化关系,得出了尖速比对气动性能的影响:推力系数与环量及尖速比成正比;对于不同环量,功率系数存在最佳尖速比。分析了尾迹扩张模型对气动性能的影响:推力系数和功率系数与尾迹扩张系数成正比,尾迹收敛参数对其影响甚微。     

Unsteady Study on the Effects of Matching Characteristic of Tandem Cascade on the Performance and Flow at Large Angle of Attack

To investigate the effects of matching characteristics of tandem cascade on the performance and flow at large angle of attack, the unsteady numerical simulation has been implemented. The influences of different turning angle ratio(TR) and chord length ratio(CR) of two blades and the relative angle of attack of rear blade(Delta) are analyzed. The numerical results indicated that the tandem cascade can obtain overall performance improvement including higher static pressure ratio and lower total pressure loss with the matching parameters in the range of TR=3～5, CR=0.5～1.2, and Delta=-15°～-5°. The separation on the front blade has more prominent impact than that on the rear blade, so the performance improvement of tandem cascade is significantly dependent on the reduction of front-blade separation and loss. Regarding the rear blade, the gap injection effect can periodically control the separation. Temporal and spatial analysis of the flow field shows that the optimal-performance cases generally have much smaller wake loss for both two blades, but the unsteady characteristics of the wake loss is more apparent than that of the poor performance cases.     

The effect of variable stator on performance of a highly loaded tandem axial flow compressor stage

Increasing the aerodynamic load on compressor blades helps to obtain a higher pressure ratio in lower rotational speeds.Considering the high aerodynamic load effects and structural concerns in the design process,it is possible to obtain higher pressure ratios compared to conventional compressors.However,it must be noted that imposing higher aerodynamic loads results in higher loss coefficients and deteriorates the overall performance.To avoid the loss increase,the boundary layer quality must be studied carefully over the blade suction surface.Employment of advanced shaped airfoils (like CDAs),slotted blades or other boundary layer control methods has helped the designers to use higher aerodynamic loads on compressor blades.Tandem cascade is a passive boundary layer control method,which is based on using the flow momentum to control the boundary layer on the suction surface and also to avoid the probable separation caused by higher aerodynamic loads.In fact,the front pressure side flow momentum helps to compensate the positive pressure gradient over the aft blade's suction side.Also,in comparison to the single blade stators,tandem variable stators have more degrees of freedom,and this issue increases the possibility of finding enhanced conditions in the compressor off-design performance.In the current study,a 3D design procedure for an axial flow tandem compressor stage has been applied to design a highly loaded stage.Following,this design is numerically investigated using a CFD code and the stage characteristic map is reported.Also,the effect of various stator stagger angles on the compressor performance and especially on the compressor surge margin has been discussed.To validate the CFD method,another known compressor stage is presented and its performance is numerically investigated and the results are compared with available experimental results.     

基于弯曲叶片的氦气轴流压气机优化设计

针对高负荷氦气压气机中角区分离、叶顶泄漏严重带来的效率损失问题,以单级氦气压缩机为研究对象,利用CFD方法,分析了不同弯曲角度下氦气压气机内部的角区损失和叶顶泄漏损失,并优化了现有五级轴流氦气压气机。结果表明：叶片正弯会增加端区处的静压,减少角区分离,进而降低角区损失;对动叶而言,在设计攻角下正弯也会增加前缘损失;动叶叶顶反弯使泄漏流远离下一个叶片的压力面,而合适的反弯角度可以降低叶顶泄漏量;选取合适的弯曲角度使五级轴流压气机设计点效率提高1.85%。     

最大厚度位置对高亚音轴流压气机叶型设计的影响

为了在具有不同负荷的压气机叶栅的初始设计过程中选取最大厚度位置,采用数值方法对在不同折转角的高亚音来流条件下对扩压叶栅进行了大量的系统性研究,分析了最大厚度位置、折转角以及稠度3个叶栅几何参数对叶栅变冲角特性以及对最小损失冲角下的叶栅气动性能的影响规律.基于大量叶栅样本建立数学模型,用来定量描述最小损失冲角,以及最小损...     

基于数值优化的跨音速压气机动叶三维设计

实验验证了三维粘性流场求解程序,然后采用基于梯度法的数值优化程序对跨音压气机动叶积叠线进行优化设计,得到了弯掠结合的三维叶片,并对其进行了数值模拟及详细的流场分析.结果表明采用弯掠的三维动叶可以有效的改变叶片排内三维激波结构,降低尾迹损失,显著提高动叶的整体绝热效率,并使动叶具有更加良好的变工况性能.     

Control of LP Turbine Rotor Blade Underloading Using Stator Blade Compound Lean at Root

IntroductionLP turbines operate over some range of flow regimeson both sides of the nominal operating conditions. Acharacteristic feature of LP tUrbines are strong radial gradients of pressure, Mach number and flow angle, especially downstream of the stator, Where these gradientsdetechne inlet now conditions for the moving bladerow. The changing swirl velocity and swirl angle spanwise require considerable twist of the rotor blades. Forlow loads, low pressures at the inlet to the rotor at th…     

Effects of a kind of non-smooth blade on the unsteady flow field at the exit of an axial fan

An experimental investigation of effects of a kind of streamwise-grooved blade on the unsteady flow field at an exit of an axial-flow fan was performed. The flow field at 25% chord downstream from the trailing edge at hub was measured using a fast-response five-hole pressure probe at different mass-flow conditions. The unsteady flow of the grooved blades was compared with that of the smooth blades. The measurement results indicate that： （1） the grooved blades restrain the velocity fluctuation and the pressure fluctuation by modulating the blade boundary layers, which contributes to the flow loss reduction in the hub region and in the rotor wake region at the design condition; （2） the stream-wise grooves play an important role in restraining the radial migration in the blade boundary layer and abating the tip flow mixing, which contributes to the flow loss reduction in the tip region at the design condition; （3） at the near stall condition, the grooved surface can not reduce the flow loss, even increase the loss nearby when the separation happens in the blade boundary layer.     

Aerodynamic Performance Improvement of a Highly Loaded Compressor Airfoil with Coanda Jet Flap

Coanda jet flap is an effective flow control technique,which offers pressurized high streamwise velocity to eliminate the boundary layer flow separation and increase the aerodynamic loading of compressor blades.Traditionally,there is only single-jet flap on the blade suction side.A novel Coanda double-jet flap configuration combining the front-jet slot near the blade leading edge and the rear-jet slot near the blade trailing edge is proposed and investigated in this paper.The reference highly loaded compressor profile is the Zierke&Deutsch double-circular-arc airfoil with the diffusion factor of 0.66.Firstly,three types of Coanda jet flap configurations including front-jet,rear-jet and the novel double-jet flaps are designed based on the 2D flow fields in the highly loaded compressor blade passage.The Back Propagation Neural Network(BPNN)combined with the genetic algorithm(GA)is adopted to obtain the optimal geometry for each type of Coanda jet flap configuration.Numerical simulations are then performed to understand the effects of the three optimal Coanda jet flaps on the compressor airfoil performance.Results indicate all the three types of Coanda jet flaps effectively improve the aerodynamic performance of the highly loaded airfoil,and the Coanda double-jet flap behaves best in controlling the boundary layer flow separation.At the inlet flow condition with incidence angle of 5°,the total pressure loss coefficient is reduced by 52.5%and the static pressure rise coefficient is increased by 25.7%with Coanda double-jet flap when the normalized jet mass flow ratio of the front jet and the rear jet is equal to 1.5%and 0.5%,respectively.The impacts of geometric parameters and jet mass flow ratios on the airfoil aerodynamic performance are further analyzed.It is observed that the geometric design parameters of Coanda double-jet flap determine airfoil thickness and jet slot position,which plays the key role in supressing flow separation on the airfoil suction side.Furthermore,there exists an optimal combination of front-jet and rear-jet mass flow ratios to achieve the minimum flow loss at each incidence angle of incoming flow.These results indicate that Coanda double-jet flap combining the adjust of jet mass flow rate varying with the incidence angle of incoming flow would be a promising adaptive flow control technique.