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CuAl2/Al复合材料的固相反应合成技术及与Al液的接触反应研究 总被引:2,自引:0,他引:2
朱正吼 《南京航空航天大学学报》1997,29(5):564-569
研究了Al,Cu在真空状态下的纯固相接触反应情况,试验表明,Al粉、Cu粉在600℃,保温6h时,两者以完全发生反生成CuAl2(θ相),生成的θ相沿铝基体组织晶界分布并在结晶过程中具有择优取向特性,形成仅含沿晶界方向的主干与垂直于晶界的二次晶轴的树枝晶形貌。 相似文献
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喷流噪声特性与控制研究 总被引:4,自引:0,他引:4
本文着重研究喷流噪声机理及工程计算方法。通过实验研究了声功率与喷流速度的关系,表明在Mα>0.4时Lighthill方程和Lilley方程均与实验数据吻合,可分别使用。而Mα<0.4时,均偏差较大,通过本文实验表明,若改为6次方关系较为恰当。文章同时对喷流噪声指向性、谱特性进行了分析。最后对一种引射消声器进行了发展性研究,获得在135dB噪声条件下,降噪17dB的效果。 相似文献
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流体推力矢量喷管型面固定、活动部件少、结构重量轻,能够为高机动飞行器提供有效的飞行控制手段,但无源流体推力矢量喷管热喷流的偏转控制规律尚未完全掌握。为了推进无源流体推力矢量技术的实用化,本文设计研制了适用于微型涡喷发动机的耐高温喷管模型,对该喷管在微型涡喷发动机热喷流状态下的控制规律进行研究。利用非接触光学显示和测量手段——红外热成像拍摄和粒子图像测速(PIV)技术对主射流流动特性进行研究,获得流动矢量角随二次流控制阀门闭合度变化的控制规律;利用六分量盒式天平测力实验研究无源流体推力矢量喷管的力学特性,获得推力矢量角随二次流控制阀门闭合度变化的控制规律。研究结果表明:该构型喷管在微型涡喷发动机热喷流下主射流连续可控偏转,最大流动矢量角为-12.3°/12.3°,最大推力矢量角为-12.9°/12.8°,控制规律接近线性,不存在主射流偏转突跳问题。 相似文献
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《中国航空学报》2020,33(10):2535-2554
Introducing active flow control into the design of flapping wing is an effective way to enhance its aerodynamic performance. In this paper, a novel active flow control technology called Co-Flow Jet (CFJ) is applied to flapping airfoils. The effect of CFJ on aerodynamic performance of flapping airfoils at low Reynolds number is numerically investigated using Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation with Spalart-Allmaras (SA) turbulence model. Numerical methods are validated by a NACA6415-based CFJ airfoil case and a S809 pitching airfoil case. Then NACA6415 baseline airfoil and NACA6415-based CFJ airfoil with jet-off and jet-on are simulated in flapping motion, with Reynolds number 70,000 and reduced frequency 0.2. As a result, CFJ airfoils with jet-on generally have better lift and thrust characteristics than baseline airfoils and jet-off airfoil when Cμ is greater than 0.04, which results from the CFJ effect of reducing flow separation by injecting high-energy fluid into boundary layer. Besides, typical kinematic and geometric parameters, including the reduced frequency and the positions of the suction and injection slot, are systematically studied to figure out their influence on aerodynamic performance of the CFJ airfoil. And a variable Cμ jet control strategy is proposed to further improve effective propulsive efficiency. Compared with using constant Cμ, an increase of effective propulsive efficiency by 22.6% has been achieved by using prescribed variable Cμ for NACA6415-based CFJ airfoil at frequency 0.2. This study may provide some guidance to performance enhancement for Flapping wing Micro Air Vehicles (FMAV). 相似文献
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《中国航空学报》2016,(3):789-798
This paper presents an integrated fuzzy controller design approach to synchronize a dis-similar redundant actuation system of a hydraulic actuator (HA) and an electro-hydrostatic actu-ator (EHA) with system uncertainties and disturbances. The motion synchronous control system consists of a trajectory generator, an individual position controller for each actuator, and a fuzzy force tracking controller (FFTC) for both actuators. The trajectory generator provides the desired motion dynamics and designing parameters of the trajectory which are taken according to the dynamic characteristics of the EHA. The position controller consists of a feed-forward controller and a fuzzy position tracking controller (FPTC) and acts as a decoupled controller, improving posi-tion tracking performance with the help of the feed-forward controller and the FPTC. The FFTC acts as a coupled controller and takes into account the inherent coupling effect. The simulation results show that the proposed controller not only eliminates initial force fighting by synchronizing the two actuators, but also improves disturbance rejection performance. 相似文献
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Electromechanical actuators (EMAs) are becoming increasingly attractive in the field of more electric aircraft because of their outstanding benefits, which include reduced fuel burn and maintenance cost, enhanced system flexibility, and improved management of fault detection and isolation. However, electromechanical actuation raises specific issues when being used for safety-critical aerospace applications like flight controls: huge reflected inertia to load, jamming-type failure, and increase of backlash with service due to wear and local dissipation of heat losses for thermal balance. This study proposes an incremental approach for virtual prototyping of EMAs. It is driven by a model-based system engineering process in order to enable simulation-aided design. Best practices supported by Bond graph formalism are suggested to develop a model’s structure efficiently and to make the model ready for use (or extension) by addressing the above mentioned issues. Physical effects are progressively introduced, and the realism of lumped-parameter models is increased step-by-step. In particular, multi-level component models are architected to ensure continuity between engineering activities. The models are implemented in the AMESim simulation environment, and simulation responses are given to illustrate how they can be used for preliminary sizing, control design, thermal balance verification, and faults to failure analysis. The proposed best practices intend to provide engineers with fast, reusable, and efficient means to assess performance virtually and enhance maturity, performance, and robustness. 相似文献
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在设计控制系统模型时,首先引入了有限差分法(FDM)离散化后的波动方程,然后基于H∞最优控制原理,检查闭环控制系统的稳定性和可探测性,对控制系统传感器和作动器的位置进行优化配置.通过计算闭环反馈系统的范数,最终得到了控制系统的最优控制算法.仿真结果表明,利用波动方程来优化控制系统传感器和作动器位置的算法是可行的,可广泛应用于飞控系统的设计中. 相似文献