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101.
周涛李亚林党铁红 《民用飞机设计与研究》2013,(4):17-24,28
传统的增升装置设计受到各种约束条件的限制,难以充分发挥增升效果,甚至无法达到飞机对增升效果的需求,而流动控制技术可以弥补这些缺陷。通过搜集大量文献,阐述了襟翼涡流发生器、主翼后缘偏折技术、ZHU’s襟翼、自激励运动襟翼、零质量射流、等离子体技术、MEMS技术以及动力增升等各类主动控制技术的工作原理,增升效果分析以及具体应用情况等。结果表明,这些流动控制新技术对于进一步提高民用飞机的增升效果具有巨大的潜力。 相似文献
102.
为探明附面层抽吸技术对压气机叶栅气动性能的影响及其与栅内旋涡结构的关联,通过十个横截面的实验测量结果研究了高负荷压气机叶栅抽吸端壁附面层前后的主要旋涡结构以其对应损失的演变过程。研究对象为矩形低速扩压叶栅,来流马赫数约为0.23。研究结果表明,端壁附面层的变化对叶栅端区的主要旋涡发展过程影响显著。在原型方案中,壁面涡、尾缘脱落涡的演变过程对应着较高的流动损失,通道涡自身产生的损失较小,主要起到向远离端壁的方向输运低能流体的作用;在流向槽吸气方案中,壁面涡和尾缘脱落涡因端壁附面层径向迁移及角区分离受到抑制而被明显削弱;而来流附面层抽吸方案则最为有效地控制了通道涡的演变过程。 相似文献
103.
104.
非定常压力测量中信号失真的管传递函数修正方法 总被引:1,自引:1,他引:0
使用外置压力传感器测量非定常压力会造成非定常测量信号失真. 这是由连接外置传感器和测点之间的管道传压系统引成的. 阐述了一种修正这种非定常信号失真的方法.从而使得运用外置传感器测量非定常压力成为可能.这种技术使用已知的管传递函数在频域中修正非定常测量信号的失真. 同时修正失真信号振幅的变化和相位角的偏移.给出了这种修正技术的运用实例:在叶轮机颤振试验中测量叶片表面非定常压力和在非定常旋涡脱落试验中测量尾迹. 相似文献
105.
Vortex-acoustic coupling is one of the most important potential sources of combustion instability in solid rocket motors (SRMs). Based on the Von Karman Institute for Fluid Dynamics (VKI) experimental motor, the influence of the thermal inhibitor position and temperature on vortex-shedding-driven pressure oscillations is numerically studied via the large eddy simulation (LES) method. The simulation results demonstrate that vortex shedding is a periodic process and its accurate frequency can be numerically obtained. Acoustic modes could be easily excited by vortex shedding. The vortex shedding frequency and second acoustic frequency dominate the pressure oscillation characteristics in the chamber. Thermal inhibitor position and gas temperature have little effect on vortex shedding frequency, but have great impact on pressure oscillation amplitude. Pressure amplitude is much higher when the thermal inhibitor locates at the acoustic velocity anti-nodes. The farther the thermal inhibitor is to the nozzle head, the more vortex energy would be dissipated by the turbulence. Therefore, the vortex shedding amplitude at the second acoustic velocity antinode near 3/4L (L is chamber length) is larger than those of others. Besides, the natural acoustic frequencies increase with the gas temperature. As the vortex shedding frequency departs from the natural acoustic frequency, the vortex-acoustic feedback loop is decoupled. Consequently, both the vortex shedding and acoustic amplitudes decrease rapidly. 相似文献
106.
107.
An improved delayed detached eddy simulation (IDDES) method based on the k-x-SST (shear stress transport) turbulence model was applied to predict the unsteady vortex breakdown past an 80o/65o double-delta wing (DDW), where the angles of attack (AOAs) range from 30° to 40°. Firstly, the IDDES model and the relative numerical methods were validated by simulating the massively separated flow around an NACA0021 straight wing at the AOA of 60°. The fluctuation properties of the lift and pressure coefficients were analyzed and compared with the available measurements. For the DDW case, the computations were compared with such mea-surements as the mean lift, drag, pitching moment, pressure coefficients and breakdown locations. Furthermore, the unsteady properties were investigated in detail, such as the frequencies of force and moments, pressure fluctuation on the upper surface, typical vortex breakdown patterns at three moments, and the distributions of kinetic turbulence energy at a stream wise section. Two dominated modes are observed, in which their Strouhal numbers are 1.0 at the AOAs of 30°, 32° and 34° and 0.7 at the AOAs of 36o, 38° and 40°. The breakdown vortex always moves upstream and downstream and its types change alternatively. Furthermore, the vortex can be identified as breakdown or not through the mean pressure, root mean square of pressure, or even through correlation analysis. 相似文献
108.
109.
气氧/甲烷涡流冷壁燃烧室流场与壁面耦合传热分析 总被引:3,自引:2,他引:1
针对涡流燃烧室的试验模型,耦合计算了其中的燃烧、流动和传热过程。湍流模型采用RNG k-ε两方程模型,辐射传热采用P1辐射模型,化学反应采用有限速率模型。数值模拟了涡流燃烧室在20s内的传热过程,得到了燃烧室和喷管的壁面温度分布随时间的变化。燃烧室侧壁面和头部温度在4秒内就达到较稳定状态,在涡流保护下侧壁面最高温度在650K左右,头部最高温度在785K左右。对于热沉喷管,壁面温度随时间基本呈缓慢线性上升,在一定的时间内可以满足实验要求。 相似文献
110.
《中国航空学报》2020,33(3):840-851
The individual influence of pitching and plunging motions on flow structures is studied experimentally by changing the phase lag between the geometrical angle of attack and the plunging angle of attack. Five phase lags are chosen as the experimental parameters, while the Strouhal number, the reduced frequency and the Reynolds number are fixed. During the motion of the airfoil, the leading edge vortex, the reattached vortex and the secondary vortex are observed in the flow field. The leading edge vortex is found to be the main flow structure through the proper orthogonal decomposition. The increase of phase lag results in the increase of the leading edge velocity, which strongly influences the leading edge shear layer and the leading edge vortex. The plunging motion contributes to the development of the leading edge shear layer, while the pitching motion is the key reason for instability of the leading edge shear layer. It is also found that a certain increase of phase lag, around 34.15° in this research, can increase the airfoil lift. 相似文献