多级轴流压气机彻体力模型——三维应用

利用基于彻体力模型建立的时间推进三维计算模型,获得了某单级跨声速压气机在周向总压进气畸变下的总体特性及流场分布,并与相关试验数据进行对比,以验证该模型的准确性及可靠性。随后利用该模型详细分析了进口分别存在周向总压进气畸变及对涡旋流畸变下某四级低速轴流压气机内部流场特征。单级跨声速压气机总体特性的计算结果与相关试验数据的相对误差不超过2%,且内部流场参数的分布特征也与试验结果相吻合。四级低速轴流压气机的计算结果反映周向总压进气畸变导致压气机气动性能及稳定性恶化,对涡旋流进气畸变则影响有限。同时揭示了不同形式的进气畸变在多级轴流压气机内部的传递过程,充分说明该模型在进气畸变这类工程问题中的广泛应用前景。      

一种工程实用的多级轴流压气机特性二维数值计算方法

采用二维(轴对称)数学模型, 应用流线曲率法求解多级轴流压气机特性.各种不同因素对落后角和损失的影响以分量的形式表示.该方法通过了大量试验数据的校核, 具有较高的准确度.对一台多级轴流压气机的计算结果与试验数据的对比分析表明, 该方法能较好地预测多级轴流压气机的特性和非设计工况下级间参数的分布.      

周向总压畸变对多级轴流压气机稳定性影响的逐级模拟方法

介绍了1种分析进口总压畸变对多级轴流压气机特性影响的逐级模拟方法。应用该方法对J85-13压气机的进口总压畸变进行了分析,并对压气机在稳态和畸变情况下特性的逐级模拟计算结果进行了详细的数值分析,讨论了压气机的失稳关键级以及有效进气攻角对多级轴流压气机特性的影响。计算结果与试验结果的比较表明,该模拟方法是合理可行的。     

指数外推法和支持向量机相结合的压气机特性扩展方法

针对航空发动机起动建模中压气机低转速特性计算精度较低的问题,提出了指数外推法和支持向量机(SVM)相结合的特性扩展计算方法.首先分析了指数外推法的计算方法及其局限性,然后将压气机已知的高转速特性作为SVM的训练集,以指数外推法获取的低转速特性作为测试集,同时将压气机特性转换为按出口气流参数表示以降低SVM原始数据的非线性,利用交叉验证算法选择SVM参数并进行模型训练,预测并获得压气机低转速特性.通过与单纯使用指数外推法获取的特性对比分析表明:指数外推法和SVM相结合的压气机特性扩展计算方法,最大相对误差减小了约2.8%,有效提高了特性扩展计算精度.      

跨声速轴流压气机不同工况下转子激波与导流叶片尾迹相互干涉研究

应用3维黏性流动计算软件Fine/Numeca,对某型1.5级跨声速轴流压气机进行内部流场和全工况特性数值模拟,得到该压气机特性曲线。在最高效率点和近失速点,在2种质量流量下,对压气机内部流场进行非定常对比计算,分析了在质量流量变小时,压气机内部流场的变化情况。     

轴流压气机叶片排流场非定常频谱特性试验技术

为了揭示轴流压气机叶片排的非定常流动特性，同时与压气机气动性能和气动稳定性相关联，开展了轴流压气机叶片排流场非定常频谱特性试验研究，并对该试验的试验技术和参数测试方法做了相应介绍。试验结果表明，该试验技术对进行轴流压气机叶片排流场非定常频谱特性试验是行之有效的。     

某型发动机压缩系统高空稳定性计算研究

本文通过不同进口条件下的某型发动机低压压气机和高压压气机特性计算，研究分析了该压缩系统在高空条件下的气动稳定性。计算结果与压气机地面特性试验、整机高空台模拟试验结果符合性良好，可作为确定该发动机压缩系统高空稳定工作范围或适应性改进的理论依据。     

基于支持向量机和粒子群算法的压气机特性计算

改进和实现了支持向量机用于函数回归估计的算法,并将支持向量机和粒子群优化算法运用于压气机特性计算,以寻找压气机进口换算空气流量和效率随增压比、转子转速、压气机进气角度变化的非线性函数关系,将进气角度作为一个影响因子列入考虑范围,改进了以往只考虑压气机特性随转子转速和增压比变化的计算方法。用支持向量机回归估计压气机特性随各因子变化的非线性函数,用粒子群优化算法对非线性函数逼近度进行全局优化,计算结果表明,设计的算法能准确地回归估计出描述压气机特性的非线性函数,算法是有效的。      

多级轴流压气机特性的一种计算方法

本描述了多级轴流压气机特性计算的一种方法，流场计算采用流线曲率法解完全径向平衡方程。本在特性计算中引进了环壁附面损失模型，考虑了叶片去亏损力，二次流和径向间隙漏流等影响。采用了新的流场计算模型，流场计算稳定，收敛较快。并对计算结果与试验数据进行了对比，认为这种计算方法可以用于轴流压气机特性计算。     

基于时间推进的轴流压气机气动性能计算模型

基于时间推进方法,通过求解周向平均带体积力源项的流动控制方程,融合发展较为完善的落后角及损失模型,考虑径向掺混影响,同时引入Koch稳定边界模型,建立了一个轴流压气机性能预测计算模型。利用该模型对两台四级低速轴流压气机及两台单级跨声速压气机展开计算,得到了相应的特性曲线,并将计算值与相关实验数据进行对比分析。结果表明,该模型能可靠预测轴流压气机总体特性,可为多级压气机特性分析提供有效的技术支撑。     

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.      

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 ℃).     

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.     

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.     

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。     

GA-Based Model Predictive Control of Semi-Active Landing Gear

Semi-active landing gear can provide good performance of both landing impact and taxi situation, and has the ability for adapting to various ground conditions and operational conditions. A kind of Nonlinear Model Predictive Control algorithm （NMPC） for semi-active landing gears is developed in this paper. The NMPC algorithm uses Genetic Algorithm （GA） as the optimization technique and chooses damping performance of landing gear at touch down to be the optimization object. The valve＇s rate and magnitude limitations are also considered in the controller＇s design. A simulation model is built for the semi-active landing gear＇s damping process at touchdown. Drop tests are carried out on an experimental passive landing gear systerm to validate the parameters of the simulation model. The result of numerical simulation shows that the isolation of impact load at touchdown can be significantly improved compared to other control algorithms. The strongly nonlinear dynamics of semi-active landing gear coupled with control valve＇s rate and magnitude limitations are handled well with the proposed controller.     

Simulation and Analysis of Crashworthiness of Fuel Tank for Helicopters

Crashworthiness requirement of fuel tanks is one of the important requirements in helicopter designs. The relations among the protection frame, textile layer and rubber layer of the fuel tank are introduced. Two appropriate FE models are established, one is for an uncovered helicopter fuel tank without protection frame, and the other is for fuel tank with protection frame. The dynamic responses of the two types of fuel tanks impinging on the ground with velocities of 17.3 m/s are numerically simulated for the purpose of analyzing energy-absorbing capabilities of the textile layer and protection frame. The feasibility of the current crashworthiness design of the fuel tank is examined though comparing the dynamic response behaviors of the two fuel tanks.     

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.     

(高)超声速流动试验技术及研究进展

近年来,与高速飞行器相关的(高)超声速流动受到了极大的关注。这类流动所具有的非定常性、强梯度和可压缩性对试验方法和风洞设计技术提出了挑战。超声速纳米示踪平面激光散射(NPLS)技术是由作者所在团队研发的非接触光学测试技术。它能够以较高的空间分辨率来揭示超声速三维流场的一个瞬态剖面的时间解析的流动结构。介绍了NPLS技术以及基于NPLS开发的密度场测量、雷诺应力测量和气动光学波前测量等方法,并回顾了这些技术在超声速边界层、超声速混合层、超声速压缩拐角、激波/边界层相互作用和光学头罩绕流等流动中的应用,清晰地再现了边界层、混合层、激波等典型流场结构及其时空演化特性。另外,为了模拟和研究高空大气条件下边界层自然转捩和超声速混合层的转捩特性,介绍了高超声速静风洞、超-超混合层风洞的设计技术以及层流化喷管的设计方法。