非轴对称端壁下高负荷压气机叶栅二次流动分析

探讨了高负荷压气机叶栅中应用非轴对称端壁的有效性.首先利用NUMECA/Design3D优化软件包来完成了对端壁的优化,然后推导并建立了高负荷压气机叶栅出口含全部掺混损失的二次流损失的计算方法,最后在设计攻角和非设计攻角下对轴对称端壁和非轴对称端壁结构的高负荷压气机叶栅内部及出口流场进行了详细的分析.分析结果表明:在设计攻角和非设计攻角下采用非轴对称端壁均能改变端壁附近载荷分布、降低叶片通道的二次流动损失;在设计攻角下使叶栅周向质量平均总压损失减少约为9.4%,在非设计攻角(±3°)下分别减损7.7%和11.8%;当非轴对称端壁幅值为4%叶高时,二次流动损失最小.      

高负荷压气机叶栅开缝射流分离控制效果研究

为了控制高负荷压气机叶栅分离,设计了一种弧线型缝隙射流方法,通过叶栅实验予以验证。结果显示,缝隙射流显著的减小了叶栅尾缘分离的宽度,提高了分离区内的气流速度,降低了叶栅流动损失;抑制了叶栅内复杂的端壁二次流,使出口流场更加均匀。在0°,3°和6°攻角下,叶栅的平均损失系数降低了7.0%,32.1%和32.3%,平均气流转折角提高了4.02°,3.59°和1.78°。在-3°攻角下,平均气流转折角提高了0.59°,但叶栅损失系数提高了12.3%。可见在分离条件下,缝隙射流极大提高了叶栅气动性能,但在无分离条件下会引起额外的损失。在整个攻角范围内,开缝叶栅保持了不低于原型叶栅设计点的静压升系数,且稳定工作范围扩宽了至少3°攻角。     

微型涡流发生器控制压气机叶栅二次流的数值研究

二次流对压气机叶栅的性能有很大影响,为了探究微型涡流发生器(MVG)对于低马赫数来流叶栅的二次流控制情况,以一进口来流Ma0.1的高负荷轴流压气机叶栅为研究对象,用数值方法分别对设计攻角(-1°)以及失速攻角(8°)下的流场进行损失分析,并借鉴失速因子对不同组合形式的MVG进行对比。得出在-1°攻角下,大部分MVG具有延缓分离的作用,但都会引起损失增加;在8°攻角下,所有MVG都具有延缓分离、减少损失的作用。损失减少最多的一组VGdvg3达到6.3%,失速系数减小了46%,因此认为MVG对于大分离区域的控制较为有效。MVG主要控制0%~30%叶高方向损失,并且MVG的叶片间距以及安装位置也存在一个最佳范围,不易过大或过小。     

冲角变化对涡轮静叶栅流场的影响

为了研究亚临界600MW汽轮机高压第九级静叶原型和改型叶栅的变冲角气动特性,对两套环形叶栅在0°和±10°冲角下在哈尔滨工业大学能源科学与工程学院的低速环形风洞中进行了对比实验研究。实验结果表明,冲角变化仅影响改型和原型叶栅流道前半部分的横向压力梯度,对流道后半部分的流动影响不大;与原型叶栅相比较,改型叶栅不仅降低了流动损失,而且比原型叶栅具有更好的变冲角特性。     

前缘复合改型在压气机平面叶栅中的应用初探

为了探究同时应用不同前缘改型对压气机叶栅的影响,以DMU37动叶5%叶高处叶型的平面叶栅为原型,采用数值计算方法,探究4种椭圆形前缘改型及4种椭圆鼓包复合改型对叶栅流场及性能的影响,考虑的主要影响参数分别为椭圆长短轴比和鼓包波幅。结果表明:-6°～+4°冲角时,椭圆形前缘方案可不同程度地降低前缘吸力峰及总压损失系数,特别在正冲角条件时改善效果更好;长短轴之比为4的椭圆形前缘方案综合性能最好,主流区吸力峰高度降低56.3%,+4°冲角时,总压损失系数和可比原型叶栅降低5.8%;0°冲角下,椭圆鼓包复合改型的损失相比原型叶栅均有所增大;+4°冲角时,各椭圆鼓包复合改型方案均能有效降低损失,总压损失系数最多可比原型叶栅降低7.5%,表明椭圆鼓包复合改型在+4°冲角时可以提高叶栅气动性能。     

几何参数对涡轮低压导向器变工况性能的影响

在低速风洞上,对某型弹用涡扇发动机涡轮低压导向器原型和改型进行了变工况条件下的详细流场测量。与原型低压导向器相比,改型低压导向器多种几何参数发生了改变,主要包括采用优化的子午型线、正弯叶片、后部加载叶型以及前缘负冲角设计等,因此二者的冲角特性有较大差异。实验分别对两种导向器叶栅测量了3种工况条件,分别为正冲角工况、设计工况和负冲角工况,并对结果进行了对比分析。实验结果显示:改型不仅在设计工况下能量损失较小,而且具有较好的攻角适应性,表现为在所测工况范围内叶栅出口总压损失随工况的变化幅度很小,而原型出口损失则对冲角敏感,损失变化幅度相对较大。      

船用推进器低压透平末两级改型设计

为了改进船用汽轮机低压缸末两级涡轮的气动性能,对叶栅和子午流道进行了改型设计,并运用计算流体力学方法对原型方案和改型方案的内部流场进行了数值模拟.计算结果表明,在流量不变的情况下,这种综合优化设计方法能使汽轮机性能大幅提高,最终汽轮机效率提高了2.162％,功率增加了1.7％.最后对次末级动叶进行了环形叶栅试验,测量了叶片表面压力和总压损失沿叶高的分布.试验结果表明,改型设计优化了动叶中的载荷分布,从而有效地降低了叶栅二次流损失和叶型损失.     

变冲角下压力面小翼控制高亚声速扩压叶栅气动特性的研究

为了探究变冲角时压力面小翼对高亚声速扩压叶栅气动特性的影响,采用数值模拟软件ANSYS CFX对不同来流冲角下(0°,±3°,±6°)原型叶栅及加装了不同宽度压力面小翼的改型叶栅进行了数值计算。结果表明:不同冲角下压力面小翼都可以削弱泄漏涡的强度,改善叶顶间隙流动,降低叶栅流动损失。不同冲角时具有不同的最佳小翼方案,PW1.5方案在+6°冲角下性能提高最大,与同冲角下的原型叶栅相比,PW1.5方案的总压损失降低了14.4%。     

高负荷轴流压气机叶栅二次流动与损失关联性探讨

为探讨压气机中二次流与损失生成的关联性,对一高负荷轴流压气机叶栅开展数值模拟研究。首先对叶栅流动进行定性分析,在此基础上推导定量模型估算流场中的损失源,并由此获得二次流动诱发损失的机理与影响。研究结果显示,在大部分攻角范围内,二次流诱发的损失未超过50%。相对于二次流间接作用于低速流而诱发的损失而言,其直接耗散产生的损失仅为小量;在角区失速时的详细观测也显示,通道横流的流向变化,也即二次流对低速流间接影响的变化是导致通道内损失随攻角激增的主要原因。     

端壁抽吸控制下攻角对压气机叶栅叶尖泄漏流动的影响

为减少叶尖泄漏损失并改善由泄漏涡造成的叶尖流道堵塞,对端壁流向开槽抽吸方案对扩压叶栅叶尖泄漏流动的控制效果进行了数值模拟研究,重点分析了来流攻角对流动控制效果的影响。结果表明:端壁抽吸方案通过直接影响叶尖泄漏流的发展,减弱泄漏涡强度,减小了泄漏损失;抽吸对负攻角和小攻角下叶栅流场的影响范围仅局限于叶尖区域。但在大的正攻角下,抽吸使得低叶展区域的附面层分离提前,且叶背分离涡脱落位置升高至约70%叶高处,端壁抽吸对叶栅的整体影响由泄漏损失降低和分离损失增大综合决定。抽吸量为07%时,抽吸后叶栅总体总压损失系数分别在-8°、0°和+4°攻角下降低约90%、108%和68%,而在+8°攻角下增大约57%。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.