Investigations of entrainment characteristics and shear-layer vortices evolution in an axisymmetric rear variable area bypass injector

In this study,firstly,for the axisymmetric RVABI,the change-rule of adverse pressure gradient caused by radial velocity during the transition of internal flow mode in variable geometry is summarized,and a Bypass Ratio(BR) iterative algorithm based on the empirical correlation of non-equilibrium pressure is proposed.The algorithm can estimate the nonlinear relationship between area ratio and BR,with an error range falling below 6.5%.Then,we discuss the favorable effect of uniform mixing on the th...     

基于PID的卫星发射主动段遥测接收系统

本文重点针对卫星发射主动段存在遥测盲区问题，开展卫星发射主动段遥测数据接收方法的研究，突破发射场通信建立、地面测控天线指向控制、卫星发射主动段遥测接收系统搭建等关键技术，提出了一种基于PID的卫星发射主动段遥测接收系统，进而高质量实现卫星发射主动段遥测数据全时段接收与监测。提出的方法在大气环境监测卫星发射任务中得到了试验验证，结果表明卫星发射主动段遥测数据接收完整且有效。     

航天器可展开薄膜遮光罩的构型设计与优化

针对当前航天器遮光罩轻量化的需求，在保证薄膜遮光罩有效面积不变的前提下，根据质量和有效面积占比设计了一款柔性平面薄膜遮光罩。以提高薄膜边缘应力的同时尽量避免有效圆面积占比减少为优化目标，对薄膜遮光罩的边缘做弧边优化设计。结果表明，当薄膜遮光罩为正六边形时，既能保证结构对称性，又能获得较低的单位有效面积占比对应质量。通过应力叠加法建立了薄膜遮光罩的应力分布模型，求出薄膜边缘应力的理论计算值。探究了弧边拱高的增加对薄膜边缘应力和有效圆面积占比的影响规律，当二者的函数曲线相交于一点时，可取为薄膜弧边的最优拱高。根据设计的薄膜遮光罩参数，搭建薄膜遮光罩的试验样机并进行展开试验。薄膜遮光罩可完全展开，薄膜边缘张紧度高，证明了薄膜遮光罩系统方案设计的可靠性，弧边设计可有效提高薄膜边缘的应力水平。     

新、老大豆品种冠层产量和光合作用的比较

对10个新、老大豆品种冠层产量和光合作用的研究表明,新品种的产量显著高于老品种(P<0.01),新品种产量主要集中在冠层的中上部,而老品种的产量则以冠层中部最大,冠层上部、下部产量较低且相差不大.新品种植株叶面积和叶面积指数高于老品种,但差异不显著.新品种叶片的光合速率高于老品种,同时,新品种冠层不同部位叶片光合速率差异较小,老品种冠层不同部位叶片光合差异较大,特别是下层叶片净光合速率下降较大;由于新品种的叶面积指数和单位叶面积的净光合速率高于老品种,新品种的光合能力显著高于老品种,特别是冠层下部的光合能力得到了显著改善.     

Experimental research on aero-propulsion coupling characteristics of a distributed electric propulsion aircraft

Distributed Electric Propulsion (DEP) aircraft use multiple electric motors to drive the propulsors, which gives potential benefits to aerodynamic-propulsion interaction. To investigate and quantify the aerodynamic-propulsion interaction effect of the wing section, we built a DEP demonstrator with 24 “high-lift” Electric Ducted Fans (EDFs) distributed along the wing’s trailing edge. This paper explores and compares the aero-propulsion coupling characteristics under various upstream speed, throttle, and EDF mounting surface deflection angles using a series of wind tunnel tests. We compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15–25 m/s freestream flow and angles of attack from ?4° to 16°. The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP configuration. The results show that the EDFs can produce significant lift increment and drag reduction simultaneously, which is accordant with the potential benefit of Boundary Layer Ingestion (BLI) at low airspeed.     

Analysis of grinding mechanics and improved grinding force model based on randomized grain geometric characteristics

Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the surface quality and accuracy. At present, the theoretical models of grinding force are mostly based on the assumption of uniform or simplified morphological characteristics of grains, which is inconsistent with the actual grains. Especially for non-engineering grinding wheel,most g...     

A multi-fidelity simulation method research on front variable area bypass injector of an adaptive cycle engine

Front Variable Area Bypass Injector(Front-VABI) is a component of the Adaptive Cycle Engine(ACE) with important variable-cycle features. The performance of Front-VABI has a direct impact on the performance and stability of ACE, but the current ACE performance model uses approximate models for Front-VABI performance calculation. In this work, a multi-fidelity simulation based on a de-coupled method is developed which delivers a more accurate calculation of the Front-VABI performance based on Comp...     

轴压载荷下薄壁整体壁板强度设计

在最佳设计面积比的情况下,整体壁板的设计可以得到较高的结构承载能力,但是对于整体壁板,蒙皮与筋条分离面的确定给实际设计工作造成很大障碍。本文针对这一问题开展了相关的研究工作,对蒙皮厚度在2.5mm～3.5mm范围内的“T”形整体壁板,在截面面积相同的条件下给定分离面位置,以最大失稳载荷为设计目标,得到蒙皮与筋条的最佳设计面积比。以此面积比设计的厚蒙皮“T”形整体壁板其承受轴压载荷的能力最强。