主/被动流动联合控制技术对高负荷扩压叶栅流场结构及损失的影响*

为精简附面层抽吸结构、提升吸附式压气机的工程应用性,提出将串列叶栅技术与端壁附面层抽吸技术相结合的主/被动流动联合控制技术。以某多级高负荷吸附式压气机末级静子作为研究对象,借助数值模拟的方法,探讨串列叶栅技术、端壁附面层抽吸技术以及主/被动流动联合控制技术对原型扩压叶栅内部流场结构及气动损失的影响。研究结果表明,主/被动流动联合控制技术结合了两种流动控制技术的优势,对原型高负荷扩压叶栅内部复杂流动的控制效果明显优于单一流动控制技术,通过应用更少的附面层抽吸量,有效地抑制了角区失速的促发,缓解了二维叶型分离流动,叶栅出口参数沿展向分布更为均匀,当端壁附面层抽吸总量为进口流量的0.90%时,总压损失降低了59%。     

端壁附面层抽吸对扩压叶栅变冲角性能影响研究

本文以跨声速扩压叶栅为研究对象,采用数值模拟方法,研究了附面层抽吸对扩压静叶叶栅角区分离流动控制效果和机理。为探究不同抽吸方案对叶栅角区分离的影响以及对叶栅变冲角性能影响,在上端壁处开设流向槽进行抽吸。结果表明附面层抽吸能有效降低叶栅流动损失,提高附面层动能,避免低能流体过早分离,减小角区损失。随冲角增大,叶栅通道内二次流流动加剧,角区分离严重且分离提前。附面层抽吸能控制端壁低能流体向吸力面迁移的能力,明显改善静叶叶栅气动性能。     

高负荷压气机叶栅附面层吹吸对气动性能影响研究

为研究压气机叶栅吹吸气体对附面层分离控制和气动性能的影响,利用数值计算的方法对叶栅流场进行模拟。首先研究吸气量对叶栅气动性能的影响规律,研究结果表明,当吸气孔的位置在距离叶片前缘60%的轴向弦长处时,存在一个最佳吸气量,当吸气量等于进气量的0.8%时,叶栅吸气对附面层分离的抑制效果最佳,对压比的提升最明显。提出四种叶栅开孔吹吸气方案,即吸附式叶栅、吸吹式叶栅、吹吸式叶栅和双吸式叶栅,通过流场和气动性能的对比,发现双吸式叶栅对附面层分离的抑制效果和对气动性的改善效果均最为显著。     

附面层抽吸孔对扇形扩压叶栅分离流动控制效果研究

为探究附面层抽吸对跨声速扇形扩压叶栅分离流动控制、气动性能和流场结构的影响,本文基于CFX数值模拟方法对扇形扩压叶栅进行端壁孔抽吸方案研究,并分析叶栅抽吸效果随抽吸流量的变化规律.抽吸位置分布在上下端壁近吸力面端壁处,将弦长四等分为四个不同方案.对比原型及各抽吸孔方案可以得到,当抽吸流量为原型叶栅进口质量流量的0.7％...     

前缘小叶片对高负荷扩压叶栅性能的影响

针对压气机叶栅角区流动易分离的特点,提出一种在叶栅前缘安装小叶片来抑制角区分离的新型流动控制方法。在利用叶栅试验数据确认数值模拟的可靠性后,对不同攻角下安装小叶片前后叶栅的流场特性进行了数值研究。结果表明:在-6°到9°攻角范围内小叶片改善了扩压叶栅的气动性能,使得总压损失减小,静压升增大。小叶片能使叶栅角区前缘分离点后移,角区分离线后的反流区面积减小,改善了角区流动;更多的流体汇聚到中间叶高,增强叶中部载荷,提高了叶栅的扩压能力。     

附面层抽吸气在通流设计中的应用

吸附式压气机的出现大幅度提高了压气机的负荷能力,但抽吸气的反问题即设计问题的研究是国内乃至于世界上的难题之一.为此,通过在通流设计阶段应用损失模型考虑吸气效果,对跨声速吸附式压气机的设计方法进行了探索.工作结果,(1)三维数值模拟表明,抽吸气设计可以达到更高的压比和效率,转子叶尖和静子流场分离得到了有效抑制.(2)在通流设计中考虑抽吸气效果可以事先预估抽气前后损失的大小,基本确定抽吸气的位置及抽气量,也可以帮助我们在通流设计时调整环量分布等重要设计参数.     

压气机动叶抽吸气的数值模拟探索

为了研究吸附式压气机,改善压气机性能,开展了在压气机动叶上采取主动流动控制措施对压气机性能影响的研究.采用计算流体力学(CFD)数值模拟方法,通过大量计算选择合适的吸气位置和吸气量,在动叶吸力面上开吸气孔进行附面层吸除,可以在一定程度上改善流动状况,从而对转子的效率、压比以及喘振裕度产生有利的影响.通过对NASA Rotor37实例计算表明,吸气后附面层分离状况得到明显改善,采用较小的吸气孔面积和吸气量就能对转子的效率、压比和喘振裕度产生正效应.不同的吸气位置,存在对应的最佳的吸气量.计算表明,转子最佳吸气位置在附面层的过渡区(包括附面层厚度的极大值位置).     

串列叶栅和叶片弯曲对角区失速和叶尖泄漏流的耦合作用

为了提高压气机叶栅的气动性能,本文针对高负荷串列叶栅进行数值模拟,研究了叶片正弯和串列叶栅对角区失速和叶尖泄漏流的耦合作用.结果表明,在串列叶栅前叶排存在比较严重的角区失速,叶片正弯能有效控制高负荷串列叶栅中的角区失速,在最优工况叶栅总损失降低了37.6％.串列叶栅中只有"前排叶片弯曲"的方案能取得与"两排叶片都弯曲"...     

跨音速轴流压气机叶栅附面层抽吸三维数值模拟

针对轴流压气机在低工况工作条件下附面层分离的问题,运用NUMECA软件对rotor37动叶的三维流场进行模拟。选取不同的吸气位置、吸气量研究条件改变时叶栅气动性能的变化规律。数值模拟的结果表明:吸气孔的位置应根据激波发生的位置选取,吸气孔在距离叶片前缘50%轴向弦长位置时,叶栅吸气对附面层分离抑制效果最佳;吸气孔位于此位置时,当吸气量等于进气量的0.4%时,对压比和效率提升较高,但随着抽吸量的增大,压比和效率的提升幅度最终会减小,因而不能为了提升压比和效率而只是简单地增大吸气量。     

叶片开槽对大涵道比风扇的流动控制研究

提出利用空心结构在涡扇发动机大涵道比风扇内部从前缘到吸力面开槽,利用来流速度冲量在吸力面形成微喷气控制吸力面附面层的流动控制方法。研究不同槽道进、出口宽度和出口位置对二维叶栅的影响,选取最优方案进行三维叶片开槽。结果表明：叶片开槽可有效抑制吸力面附面层发展,减少附面层和尾迹损失,使效率增加了0.46%,失速裕度增加了1.8%,总压比增加了1.3%;微喷气流量适中并作用在吸力面附面层发展的起始位置时对附面层的抑制效果最好。     

Investigation on the aerodynamic performance and boundary layer characteristics of high deflection industrial turbine cascade at off-design conditions

This research leads to reach the effects of the off-design operation on the aerodynamic performance, boundary layer behavior, and associated loss occurring in a high deflection industrial turbine blade. Numerical simulations, proved opposed to experimental results, are used to achieve the detailed flow field of the cascade, incidence angels ranging from −15° to +10° at inlet chord Reynolds number varied from 9.63E+04 to 2.24E+05. Boundary layer specifications covering thickness, displacement thickness, and momentum thickness are achieved in the 15 points on the suction side and talk about detail on the authority of numerical simulations in various flow conditions. Results indicate that profile loss is forcefully increased by the rising up the incidence angle mostly in the positive range. Studying the effect of incidence angle on the boundary layer behavior indicates that as incidence angle varies from negative to positive, all three characteristics of the boundary layer increase gradually.

     

正冲角下高负荷吸附式压气机叶栅数值研究

数值研究低速条件下边界层吸除对某高负荷压气机叶栅气动性能的影响.对该高负荷压气机叶栅原型进行数值研究,通过与前期试验数据的对比,校核商业计算流体力学(Computational fluid dynamics,CFD)计算代码的可靠性.结果表明,计算得到的性能曲线与试验数据有较好的一致性,所应用的数值模拟手段是可行的;分...     

小型通用飞机翼根气动性能及流动机理研究

小型通用飞机通常需要采用相对简单的增升系统及自身良好的气动性能以满足起飞和着陆阶段的安全和效益的匹配要求,这些与大迎角空气动力学特性有关。而控制翼身结合部的流动分离, 对改善小型飞机的大迎角性能具有重要的工程应用价值。通过数值模拟的方法,对某一典型通用飞机外形的着陆构型的气动性能及翼根处的流动机理研究得出,翼根处产生的马蹄涡及边角涡以及根部前缘吸力峰增高是导致翼根气流分离的主要原因,由此可通过前缘整流、展向整流和中后段三方面进行相关的整流方案设计。     

Performance analysis of the two-stage axial compressor with 90-degree bend inlet conditions

The 90-degree bend is one of the basic connection components applied in industrial flowing systems. This bend influences the aerodynamic performance of the downstream connecting equipment. In this study, the performance of a two-stage axial compressor with a 90-degree bend inlet was numerically and experimentally analyzed under low rotating speed. The testing results show that the outflow of the bend was numerically non-uniform in the circumferential and radial directions. To analyze the performance influence of the bend on the downstream compressor, a full passage compressor model with and without the inlet bend was simulated. The size of the distortion region gradually spread to the entire cascade, and the intensity of the distortion obviously dropped after the first stage as the compressor ran with the bend. The deterioration of the compressor performance, especially in the first stage, was verified numerically and experimentally. The total pressure coefficient and isentropic efficiency decreased by 2.6 % and 1.13 %, respectively. To save simulation cost, a model with a downstream single blade passage and cylindrical inlet was proposed, and the distorted flow was set as the inlet boundary condition. In addition, the unsteady numerical simulation was performed with the rotating inlet distortion region. Compared with the full blade passage model, the unsteady single blade passage model obtained the downstream spread characteristic of the distortion and performance deterioration. The latter can therefore be suggested as a compromised approach for obtaining the propagation characteristics of the inlet distortion with acceptable accuracy and low computational cost.

     

合成射流对钝尾缘翼型气动特性的影响

研究吸力面存在合成射流的情况下,钝尾缘翼型TR-4000-2000流场结构的变化及其升阻力系数等气动特性参数的变化趋势。在相同射流入口速度条件下,采用计算流体力学软件Fluent对相同来流速度不同攻角情况下翼型流场进行非定常数值模拟计算,分析射流前后翼型升阻力系数变化及翼型表面压力的波动状况;在此基础上,对不同射流频率和不同射流速度情况下翼型流场进行模拟计算,寻求最佳射流参数。结果表明,由于射流及尾缘涡的相互作用导致翼型的升阻力特性不断变化,钝尾缘翼型吸力面合成射流有明显的增升减阻效果,在15°攻角时尤为明显,升力系数提高约40%,阻力系数减小约25%。在量纲一射流速度和量纲一射流频率均为1时,射流对翼型的增升减阻效果最佳。     

利用边界层理论确定弹性金属塑料瓦油膜能量方程的进油温度边界条件

针对推力轴承的基本结构,利用边界层理论确定弹性金属塑料瓦（EMP瓦）油膜能量方程的进油温度边界条件,结合“三峡推力轴承方案”中EMP瓦推力轴承数据,分析考虑热边界层对进油温度影响时,EMP瓦推力轴承润滑性能的变化情况。计算结果表明：考虑热边界层对进油温度的影响时,进油平均温度和最高油膜温度均有所升高,最大压力也有所增加,最小油膜厚度、流量及功耗都有所下降,说明热边界层对推力轴承的润滑性能产生了一定的影响。     

气动弹片对翼型气动及噪声特性的影响

在NACA0018翼型吸力面布置固定气动弹片后,比较了原始翼型和弹片翼型的气动性能及噪声特性。采用数值模拟方法,在6°～24°范围内计算攻角气动弹片对翼型气动性能及噪声特性的影响,并分析了其流动控制机理。结果表明：气动弹片在大攻角下的效果较好,升力系数可提高37.11%,且可减缓流动分离向前缘发展,提高气流下洗能力;攻角较大时,气动弹片可以减小翼型在接收点处的噪声总声压级的4.23%,且翼型噪声总声压级在指向性分布上呈现偶极子特性。     

离心压缩机小流量级叶片扩压器的改进研究

采用数值模拟方法对某一离心压缩机小流量级内部全三维有粘流场进行了详细的分析,得到了内部各元件主要气动参数的分布情况.通过减小D4/D2值,减小叶栅稠度,增大当量扩张角等方法有效减小了叶片扩压器内的摩擦损失.数值计算结果表明,改进后计算模型多变效率提高约1.02％,效果显著.     

Computation of turbulent flows and radiated sound from axial compressor cascade

The losses at off-design points from a compressor cascade occur due to the deviation from a design incidence angle at the inlet of the cascade. The self-noise from the blade cascade at off-design points comes from a separated boundary layer and vortex sheddings. If the incidence angle to the cascade increases, stalling in blades may occur and the noise level increases significantly. This study applied Large-Eddy Simulations (LES) using deductive and deductive dynamic SGS models to low Mach-number, turbulent flow with each incidence angle to the cascade ranging from −40° to +20°, and compared numerical predictions with measured data. It was observed that the oscillating separation bubbles attached to the suction surface do not modify wake flows dynamically for cases of negative incidence angles. However, an incidence angle greater than 8° caused a separated vortex near the leading edge to be shed downstream and created stalling. The computed performance parameters such as drag coefficient and total pressure loss coefficient showed good agreement with experimental results. Noise from the cascade of the compressor is summarized as sound generated by a structure interacting with unsteady, turbulent flows. The hybrid method using acoustic analogy was observed to closely predict the measured overall sound powers and directivity patterns at design and off-design points of blade cascade.