高超声速进气道再入流场特性研究

为揭示超额定工作状态下高超声速进气道的流场特性,针对设计点为飞行高度H=25 km,飞行马赫数Ma=5的二元三波系混压式进气道进行再入流场的数值模拟研究。研究发现:随着再入马赫数增大,两道斜激波不能在唇口处交汇,唇罩内表面分离增大,隔离段上表面的附面层变厚,进气道的总压恢复系数降低。为拓宽进气道在超额定状态下的工作范围,在进气道唇口位置开槽,开槽位置与唇口的距离越远,隔离段下表面的分离包越小;随着槽宽的增大,隔离段上表面附面层厚度先减小后增大,槽宽为2 mm时,附面层厚度减小约71.6%,效果最佳。     

喉道肩点圆弧半径对高超声速进气道性能的影响

对某型二维高超声速进气道进行了数值仿真计算,研究了设计工况和非设计工况喉道肩点圆弧半径对进气道性能的影响。结果表明,在设计工况下,对喉道肩点圆弧处理可以有效提升进气道性能,圆弧半径R=120 mm时性能最佳,总压恢复系数最高可提升4.2%,阻力系数最高降低8.1%。在非设计工况下,喉道肩点圆弧处理对进气道性能有一定提高作用,但随着马赫数的减小,圆弧处理对进气道的性能提升作用降低。     

基于激波形状控制的高超声速轴对称进气道设计

文中主要针对基于二次流控制的高超声速轴对称可调进气道,给出了其具体的流道实现方案,完成了进气道设计工作。而后通过全流道仿真分析,检验了该可调进气道在非设计点的工作情况,获得了其工作特性,仿真说明文中设计的进气道具有良好的工作性能。     

跨音轴流压气机动叶的三维弯掠设计研究

对一单级跨音轴流压气机中的动叶分别进行了前掠和正弯设计的参数研究,并根据研究得到的弯、掠动叶气动性能变化规律对动叶进行了前掠和正弯联合的三维设计,同时对动叶中部截面的叶型进行了二维设计以弥补弯掠动叶中部性能的降低.最终设计的跨音级性能显著提高,级最大效率提高3%,失速裕度提高40%,同时压比有所增加.数值计算结果表明,前掠和正弯叶片都可以使叶顶激波位置移向下游,降低激波强度,减轻叶顶激波与边界层和泄漏涡的作用.弯掠动叶控制激波强度和端壁流动的能力更加突出.     

不同抽吸孔布局的进气道抗反压能力机理分析

基于雷诺平均数值计算方法,针对进出口面积相等的两种布局抽吸孔设计,分析了超声速进气道在不同反压比的进气道流场特性,尤其是不同压比条件下抽吸孔内的流场变化情况,获得了进气道从起动到不起动的抽吸孔内的流场变化及壁面压力分布.结果表明:随着反压比的增大,在进气道喉部区域形成较强的密度梯度;模型-1的正激波传播到进气道唇口区域...     

跨声速压气机转子前缘积叠线的数值优化设计

采用数值优化方法对跨声速压气机转子NASA rotor37前缘积叠线进行了数值优化设计.本优化设计以绝热效率为目标函数,总压比与质量流量为约束条件,进行单目标有约束的优化设计.详细地分析对比了几何形状、总体性能及流场的变化.结果表明,叶片后掠并且加入弯曲,其激波的波形变得倾斜.在中部,强度有所削弱;在底部区域,激波有所后掠.同时指出,单一工况点的设计对变工况性能的控制能力不足.     

氦氙混合工质轴流涡轮设计与激波控制研究

基于氦氙混合工质特性,利用Axial软件对比了不同载荷系数和流量系数情况下涡轮的效率,在载荷系数和流量系数分别为1.8和0.6的情况下涡轮效率较高。在此条件下利用AxCent软件对轴流涡轮进行了三维叶片造型。在ANSYS CFX软件中选用SST湍流模型,在给定的工况下对设计好的叶片采用数值模拟方法分析尾缘折转角、尾缘楔角及安装角对激波损失的影响。研究表明：尾缘折转角在5.5°~6.5°之间,尾缘楔角在11°~13°范围内激波损失最低;安装角在43°~48°之间,随着安装角的增大会使激波损失降低;同时,对原始叶型的优化表明,吸力面改进为直线型并且增大压力面曲率会降低激波损失。     

高速轴流压气机二维特性计算

采用二维流线曲率法数值模型,建立了适应于高速轴流压气机的落后角和损失模型,对某跨声速轴流压气机转子的非设计工况点进行计算,并与实验结果进行了对比。结果表明,该方法具有较好的计算精度,可为轴流压气机设计和优化提供参考。     

高压燃油喷雾诱导激波产生机理及频率特性

基于纹影法对不同工况下的燃油喷雾诱导激波产生机理及频率特性进行了试验,结果表明:喷雾周围的激波主要分为前导激波和伴生膨胀波,其产生原因以及对喷雾的影响均不同.喷射初期喷孔出口处喷雾前锋面马赫数大于1直接导致了前导激波的产生,根据喷雾前锋面马赫数的大小不同,前导激波又分为斜激波和弓形激波两种形态.喷雾体的周围是伴生膨胀波的产生位置之一,且喷雾周围的伴生膨胀波为膨胀马赫波,伴生膨胀波强度与喷雾锥角相互联系,在低背压下不明显;喷孔出口处喷雾剪切层也可能是激波产生位置之一,且为弱激波.另外,对激波的频率特性进行了研究,结果表明:低频激波频率平均值约为111.11,kHz,当背压相同时,激波的平均频率大小与喷射压力呈正相关关系;当喷射压力相同时,激波平均频率大小与背压呈正相关关系.激波频率的增加促进了缸内的混合气扩散,喷雾的雾化效果更好.     

跨音速压气机中展弦比弯掠叶片气动性能影响的分析

将一跨音速静叶栅数值计算结果与实验结果进行了比较,表明计算与实验结果吻合的较好.为了讨论跨音速压气机中弯掠叶片适用的展弦比条件,在0°攻角下,展弦比为1.25、1.50和2.00,对0～30°弯掠叶片流场进行了数值分析,结果表明,当10°弯掠角时,小展弦比弯掠叶片对叶片性能影响较为明显;而在20°弯掠角时,大展弦比弯掠叶片对叶片性能影响较为明显.弯掠叶片使前缘激波转化为斜激波,并减弱了通道激波的强度,因而降低了叶栅激波损失.可以证明,在跨音速条件下展弦比的大小是如何使用弯掠叶片的一个重要的参考因素.     

Shock wave boundary layer interactions in hypersonic flows over a double wedge geometry by using conjugate heat transfer

Shock wave boundary layer interaction phenomena play a critical role in the design of supersonic and hypersonic vehicles. Consequently, this paper mainly focuses on hypersonic flow over a double wedge model, flow fields around concave corners are relatively complicated, and produce several classical viscous flow features depending on the combination of the first and second wedge, and the important characteristic phenomena are mainly the shock‐boundary layer and shock‐shock interaction. For these interactions, aerodynamic heating and pressure loads increase greatly when interactions are present. The conjugate heat transfer (CHT) technique is expected to exactly predict the separation bubble length, heat flux, skin friction coefficient, and pressure distributions in double wedge studies in hypersonic applications. In the present CHT studies, the different wall materials used are thermal insulation, Macor, and SiC, it is clearly shown that while using Macor and thermal insulctation wall material in CHT studies, the interface temperature, skin friction coefficient, heat flux distribution along the length change significantly with increase in simulation time. In comparing the CHT results with the fluid flow solver with the wall, considering isothermal and adiabatic boundary results, it is clearly indicated that the fluid flow solver results are either underpredicting or overpredicting the interface properties, but CHT studies give an accurate prediction of the separation length and interface properties.     

Experimental investigation of hypersonic flow induced separation over double wedges

Flow separation occurs over the compression corners generated by deflected control surfaces on hypersonic re-entry vehicles and in the inlet of scram jet engines. Configurations like a double wedge and double cone model are useful for studying the separated flow features. Flow fields around concave corners are relatively complicated and produce several classical viscous flow features depending on the combination of the first and second wedge or cone half apex angles. Particularly characteristic phenomena are mainly shock/boundary layer, shock/shock interaction, unsteady shear layers and non-linear shock oscillations. Although most of these basic gas dynamics characteristics are well known, it is not clear what happens at high enthalpy conditions. This paper reports a result of flow fields over a double wedge at a stagnation enthalpy of 4.8 MJ/kg. The experiment was carried out in a free piston shock tunnel at a nominal Mach number of 6.99. Schlieren and double exposure holographic interferometry were applied to visualize the flow field over the double wedge.     

Study on the effects of geometry on the initiation characteristics of the oblique detonation wave for hydrogen-air mixture

The Oblique Detonation Wave Engine (ODWE) may act as a hypersonic propulsion system operating at high Mach numbers, which is an important member in the family of Scramjet. Hydrogen is a promising fuel for Scramjet, which provides wider Mach number range and is environmentally friendly. The geometry of the engine greatly affects the performance of the ODWE using hydrogen fuel. This investigation focuses on a novel wedge proposed recently, which may be utilized in scramjet engines. The wedge consists of two sub-wedges and a step. This research focuses on how the geometry of the wedge affects the initiation characteristics of the oblique detonation. Simulations are conducted on basis of Euler equations and a 9-species and 19-reactions mechanism. It is found that a larger leading wedge angle leads to a shorter initiation length. A larger step angle induces a longer initiation length. Few effects are observed on the initiation characteristics for the current range of depth. The streamline surface at the rear of the step weakens the rear shock wave and induces a longer initiation length. The streamline surface at the tip of the step begins to take effect when the initiation position is away from the step. This research provides basis for understanding the performance of the oblique detonation wave under different geometries and provides theoretical basis for scramjet engine design.     

电控喷油器电磁控制阀型式选取及特性的试验研究

应用液压流体力学原理,对电控喷油器中的3种电磁控制阀进行了受力分析,推导出了控制阀所受液压力的公式,并进行了仿真计算,比较得出平面阀在关闭过程中所受液压力最大,锥阀最小.基于国内材料及加工工艺,对研制的3种控制阀进行了测试.测试结果与仿真结果有较好的一致性:球阀高压密封性很差,燃油漏泄量大;平面阀与锥阀控制油耗率为28%左右,密封性较好,两者的开启响应时间基本相同;锥阀喷油器关闭响应特性好,其针阀关闭时间可达0.2 ms,喷油规律波形与控制脉冲波形基本一致;平面阀喷油器的针阀关闭时间为0.5 ms,但锥阀工作可靠性差.综合结果采用平面阀作为电磁控制阀可以满足高压共轨的要求.     

Effect of a revolved wedge strut induced mixing enhancement for a hydrogen fueled scramjet combustor

The mixing concept of fuel and air is the burning issue for hypersonic vehicles (scramjet) due to the less resident time of supersonic air in the combustion chamber. So far, significant research has been done for mixing enhancement and introduced different technologies; still, there is a lack of research for mixing improvement. Shock wave and shear mixing layer are the main parameters for investigating mixing criteria at supersonic speed. In this research, an innovative fuel injection strut has been designed to develop mixing enhancement by elevating multiple interactions between the shock wave and shear mixing layer. This new strut has been designed with the reference of the DLR scramjet combustor. From the reference of a wedge-shaped strut, a revolved (wedge shape – circular 3D) wedge strut has been modeled with the same fuel injection base points. This new strut's performance has been analyzed for mixing enhancement by visualizing the development of shock wave, shear-mixing layer, and their interactions. Three-dimensional numerical analysis has been carried out by solving the Reynolds-Averaged and Navier-Stokes (RANS) equations. A comparison of results has been made for the basic wedge and new strut and identified the increase in multiple interactions of the shock wave and shear layer, which leads to an increase in mixing enhancement. For the new strut, complete mixing has been achieved within a distance of 0.180 m with an average increase in mixing efficiency of 9% and increased pressure losses of 12%.     

Shock wave diffraction about a wedge in a gas-microdroplet mixture

Shock wave interacts with the droplets as a high-speed flight vehicle penetrates cloud or rain storm in the earth’s atmosphere. Interaction of the shock with the gas-droplet two-phase medium significantly affects the aerodynamic performance of the flight vehicle. In the present paper, we investigate the aerodynamic field and wall variables as the moving shock wave diffracts over a wedge in the droplet-gas mixture. We used the compressible two-fluid model equations that have been solved by the HLL-based weighted average flux (WAF) method. The viscous drag force and the heat transfer terms have been included in the model to let the gas and the droplet phases interact. We investigate the effects of the three parameters associated with the microdroplets: the void fraction, the size and the material. We elaborate how the relaxation zone created by the shock wave diffraction is structured and changed in the droplet-gas mixture.     

氢能发电技术的研究（Ⅲ）—离子交换膜对离子膜颜料电池放电性能的影响

测试分析了3种不同离子交换膜材料的水存留量,溶涨率和离子导电率,结果表明水存留量的膜材料溶涨率和离子导电离也相应较大,对不同离子交换膜的耐热和耐压稳定性测试结果发现3种离子交换膜在200℃以下范围内都没有发生相变或其它结构性变化,失重率都低于5％,因此3种膜材料在200℃以下温度范围内使用是安全可靠的,不同膜材料的耐压机械强度均随着热压处理温度升高而逐渐下降,在相同热压温度条件下的耐压强度的,SH117B膜大于或等于Nafion117膜,Nafion117膜大于或等于SH117A膜,离子交换膜也是影响燃料电池放电性能的一个重要因素,Nafion117组装的燃料电池最大放电功率密度分别是SH117A膜和SH117B膜组装的燃料电池最大放电功率密度的1．28倍和2．4倍。     

Numerical simulation of integrative flow field for hypersonic vehicle

Introduction'The development of hypersonic vehicles isemphasised by many countries because of 'theirpotential capabilities in aerospace area. AccuratePredichon for the aerodynalnic characteristics in a widerrange of each number is critical in the shape designprocess for hypersonic Vehicles. The integhaon designof fuselage and engine must be considered:for theairbreathing engine; because it is difficult to taclde theichow and the outflow separately in some situations,and without the integhaon…     

Flow Visualization around a Double Wedge Airfoil Model with Focusing Schlieren System

In the present study, aerodynamic characteristics of the double wedge airfoil model were investigated in a transonic flow by using the shock tube as an intermittent wind tunnel. The driver and driven gases of the shock tube are dry air. The airfoil model of double wedge has the span of 58 mm, chord length c = 75 mm and its maximum thickness is 7.5 mm. The apex of the double wedge airfoil model is located on the 35% chord length from the leading edge. The range of hot gas Mach numbers are from 0.80 to 0.88, and the Reynolds numbers based on chord length are 3.11×105-3.49×105, respectively. The flow visualizations were performed by the sharp focusing schlieren method which can visualize the three dimensional flow fields. The results show that the present system can visualize the transonic flowfield clearer than the previous system, and the shock wave profiles of the center of span in the test section are visualized     

Dissipation of shock wave in a gas-droplet mixture by droplet fragmentation

In this paper, we investigate the shock wave dissipation in a gas-droplet mixture over a wedge. A similar gas-droplet mixture had been considered earlier but this time we take account of breakup of the large droplets and see how the shock wave is affected. We consider a droplet breakup model dependent on the critical Weber number and add the equation of droplet number density evolution to the compressible two-fluid model. The viscous drag force, the heat transfer, and the phase change of the droplets are all included in the present model for interaction between phases. The fractional step method is used to solve the two-fluid governing equations in two parts: the hyperbolic operator is solved by the second-order WAF-HLL scheme and the source operator by the fourth-order Runge–Kutta method. We elaborate how the shock dissipation and pressure distribution is affected by the droplet size and droplet volume fraction.