气膜孔结构对涡轮导叶端壁冷却效率的影响研究

对涡轮叶栅端壁上游4种气膜冷却结构模型进行了数值模拟,得出在不同吹风比情况下涡轮叶栅端壁的流动与换热特性。结果表明,无槽气膜孔冷气射流在孔下游与主流相互作用形成1对转动方向相反的耦合涡,主流被卷入耦合涡并冲击到了端壁,使得孔间壁温接近主流温度,气膜冷却效率很低;带槽气膜孔抑制了耦合涡的形成,冷却了孔间端壁,气膜冷却效率较高,而且,随着槽深度的增加,冷气的展向(Y向)宽度逐渐增加,扩大了冷气覆盖区域,提高了端壁气膜冷却效率。     

出流结构对涡轮导叶端壁气膜冷却数值研究

通过对涡轮叶栅端壁上游不同气膜冷却结构模型进行数值模拟,得到了不同吹风比情况下,涡轮叶栅端壁的流动与换热特性。结果表明：圆柱型孔冷气射流在孔下游与主流相互作用形成一对转动方向相反的耦合涡,对涡轮叶栅端壁的气膜冷却效果不利。前向扩张孔降低了孔下游耦合涡的强度,对涡轮叶栅端壁总体气膜冷却效率要优于圆柱型孔。前向扩张缝结构增大了射流宽度,冷却了孔间端壁,对涡轮叶栅端壁总体气膜冷却效率要优于圆柱型孔和前向扩张孔。     

出流结构对涡轮叶栅端壁气膜冷却效率数值研究

通过对涡轮叶栅端壁上游不同气膜冷却结构模型进行数值模拟,得到了不同吹风比情况下,涡轮叶栅端壁的流动与换热特性.结果表明:圆柱形孔冷气射流在孔下游与主流相互作用形成一对转动方向相反的耦合涡,对涡轮叶栅端壁的气膜冷却效果不利.前向扩张孔降低了孔下游耦合涡的强度,对涡轮叶栅端壁总体气膜冷却效率要优于圆柱形孔.前向扩张缝结构增大了射流宽度,冷却了孔间端壁,对涡轮叶栅端壁总体气膜冷却效率要优于圆柱形孔和前向扩张孔.      

具有气膜出流孔和针肋的双层壁冷却结构内的冲击传热性能

针对具有气膜出流孔和针肋的双层壁冷却结构内冲击传热性能进行了试验和数值计算研究。试验采用瞬态液晶（TLC）热像技术,研究的靶板包括光滑靶板、针肋靶板以及带气膜出流孔的针肋靶板。冲击间距比为1.5,射流雷诺数范围为15 000~30 000。结果表明,针肋+气膜出流孔结构明显改善了下游区域横流的影响,明显提高了传热性能,靶板表面传热分布也更加均匀。相比于平板,当射流雷诺数为15 000时,针肋靶板和带气膜出流孔的针肋靶板端壁表面平均Nusselt数提升幅度最大,分别为6.3%和25.3%。针对双层壁冷却结构内射流冲击传热还开展了数值计算,通过采用SST （Shear Stress Transport）k-ω湍流模型计算分析获得了该双层壁冷却结构内的流动和传热特征。     

跨声速叶栅中气膜冷却对平面叶尖流动和传热特性的影响

采用数值模拟的方法,研究了主流跨声速条件下,高压涡轮中平面叶尖上气膜冷却的流动和传热特性.在不带冷却的平面叶尖上,激波在端壁和叶尖表面来回反射,从叶片中部到尾缘,叶尖表面传热系数呈现条带状分布.采用气膜冷却方法后,冷却气体使得叶尖间隙内的流体减速,激波和叶尖上表面传热系数分布的条带结构不明显.冷却气体覆盖了冷却孔下游的区域,当冷却孔进口和叶栅进口总压比从0.7增大到1.0时,叶尖平均气膜冷却效率从18.7%下降到11.5%.和不采用气膜冷却的平面叶尖相比,当气膜孔进口和叶栅进口总压比为0.9时,叶尖平均表面传热系数增加了16.9%,传热量降低了8.7%.      

叶顶凹槽间隙气膜冷却的传热数值研究

采用三维气热耦合数值模拟方法,分析了凹槽间隙底面受到泄漏流冲击的流动特性,对气膜冷却参数对凹槽间隙气膜冷却换热效果的影响进行了研究,探讨了吹风比、冷却孔位置、冷却孔角度对壁面换热的影响,并结合三维流固耦合计算,研究了叶顶气膜冷却方式对叶顶表面传热的影响。结果表明,冷却孔位于间隙流动冲击凹槽底面上游位置能有效降低壁面Nu数,获得较低的叶片表面平均温度,此时大吹风比效果更好;所选取的冷却方式使得E3高压涡轮第一级动叶的最大无量纲温度降低了0.156。     

带冲击-气膜双层壁结构的涡轮导叶冷却特性源项法数值研究

为了降低由于大量冷却孔导致的计算资源消耗,采用源项法对带冲击-气膜双层壁冷却结构的Mark II涡轮导叶传热进行了简化数值模拟,并与不采用源项法的结果进行了对比。分析了冷却孔网格密度以及流量系数经验关系式对源项法模拟精度的影响。结果表明,采用源项法能够基本准确地模拟叶片表面温度分布并且缩短75%的计算时间。当冷却孔进出口面网格最小尺度小于孔径的1/10时,数值模拟结果将不随面网格密度改变。影响模拟精度的主要因素是经验关系式能否准确模拟总冷气流量以及横流对流量系数的影响。     

端壁转动对凹槽叶尖流动换热性能的影响

为了研究端壁转动对跨声速凹槽叶尖流动换热性能的影响,采用数值方法,详细研究了三种冷却孔结构凹槽叶尖在端壁转动条件下的叶尖间隙流场、冷却流流态、气膜冷却效率、叶尖表面换热系数和叶尖泄漏流量,同时考虑凹槽深度和端壁转动速度的影响。结果表明:端壁转动在叶尖凹槽内形成与泄漏流分离涡方向相反的旋涡,使泄漏流在凹槽底面的再附增强,在凹槽突肩的再附减弱。端壁转动能减少叶尖泄漏流量,研究范围内,叶尖相对泄漏流量最多减小20%。随着凹槽深度增大,叶尖平均气膜冷却效率随之增大,叶尖平均换热系数和叶尖泄漏流量随之减小。随着端壁转速减小,叶尖泄漏流量随之增大,压力侧和吸力侧冷却孔模型的叶尖平均气膜冷却效率随之减小,而中弧线冷却孔模型的叶尖平均气膜冷却效率随之增大。压力侧喷入冷却气流,叶尖的气膜冷却效果最好。     

间隙射流对端壁冷却和传热特性影响的研究

采用数值求解三维Reynolds-averaged Navier-Stokes(RANS)方程和k-ω湍流模型,研究了间隙射流对燃气轮机叶片端壁冷却和传热特性的影响。通过数值结果与实验数据的比较,验证了数值方法的正确性。在此基础上,研究了间隙射流质量流量比、间隙射流角度对端壁流动结构、气膜冷却性能以及传热特性的影响规律。结果表明,受到端壁二次流结构的限制,冷却气体主要集中在叶片前部吸力面侧。当间隙射流质量流量比小于1%时,会发生主流入侵现象,从而削弱前缘马蹄涡,并且会增加通道喉部区域的热负荷;随着质量流量比的增加,端壁气膜覆盖面积增大,而当射流质量流量比大于1%时,主流入侵现象消失,间隙射流将增强前缘马蹄涡,提高端壁前部的传热,并且减少端壁前部热负荷。随着间隙射流角度的增加,射流引起的分离涡增强,导致端壁前部的传热增强,而端壁气膜有效度降低,端壁热负荷增加。特别是在质量流量比为1.5%时,射流角度从30°增大到90°时,端壁平均气膜有效度减小53.4%。     

涡轮叶栅前缘上游端壁气膜冷却的传热实验研究

对前缘上游有单排和双排孔冷却的涡轮导向叶栅端壁进行了详细的传热实验,在吹风比1,2,3下获得了当地气膜冷却效率和换热系数,结合流场测量结果分析了端壁冷却和换热规律。结果表明端壁气膜冷却在很大程度上受二次流的影响,冷却效果主要由吹风比决定,低吹风比喷射时,压力面附近的一个三角形区域没有冷气的覆盖,中、高吹风比喷射可以大幅度提高平均冷却效率并使冷气很均匀的覆盖在端壁上,双排孔喷射比单排孔喷射平均效率提高1倍左右。结果还表明尽管冷气喷射使端壁换热系数随吹风比的增大而显著增大,气膜冷却还是能有效的降低端壁的热负荷,其中以中吹风比双排孔喷射的效果最为显著。      

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.