状态方程对煤油液滴高压蒸发计算的影响

分别基于RK、SRK和PR等不同真实流体状态方程(EoS)建立了包含亚临界和超临界两种不同机制的瞬态液滴高压蒸发模型。针对我国新一代高压补燃液氧/煤油发动机,对煤油液滴在高压N 2 环境下的蒸发过程进行数值研究,重点分析了不同状态方程对N 2 -C 12 H 26 二元系统高压气液相平衡,及进一步对煤油液滴高压蒸发计算的影响。结果表明：对液滴蒸发速率影响最大的参数是液滴表面蒸气质量分数,而对该参数影响最大的则是所选取的状态方程。基于SRK和PR EoSs的高压气液相平衡及液滴高压蒸发计算结果均与试验数据符合较好,可正确描述液滴高压蒸发特性;而基于RK EoS的相平衡计算结果显著高估液滴表面蒸气质量分数和环境气体溶解度,并低估临界混合温度和偏摩尔相变热,进而在亚临界蒸发状态下高估蒸发速率,在超临界蒸发状态下低估蒸发速率。另外,基于RK EoS的计算中液滴发生跨临界转变所需的环境温度显著低于基于SRK和PR EoSs的。     

超临界自然层流机翼设计及基于TSP技术的边界层转捩风洞试验

为了实现绿色航空节能减排的目标,层流设计技术成为飞行器设计者的研究热点。对于跨声速客机而言,超临界自然层流机翼设计技术将显著减小飞行阻力,提升气动性能,减少燃油消耗和污染物排放。首先,基于高精度边界层转捩预测技术耦合翼型优化设计系统,实现超临界自然层流翼型设计;经过合理的翼型配置,形成超临界自然层流机翼。转捩数值模拟分析结果表明,超临界自然层流机翼的层流流动特性良好。然后,以比例为1：10.4的试验模型在荷兰高速低湍流度风洞进行边界层转捩风洞试验,使用温度敏感材料涂层（TSP）技术拍照获得机翼表面在不同马赫数、雷诺数和迎角工况下的层流-湍流分布。最后,通过超临界自然层流机翼边界层转捩试验结果,探讨了该类型机翼的转捩特性随来流参数的变化规律,总结了超临界自然层流机翼设计的关键因素。此外,该模型也可用来验证边界层转捩预测技术在超临界、高雷诺数工况下的预测精度。     

贫预混燃烧室化学反应器网络模型建模及不确定性分析

基于CFD三维数值模拟结果的化学反应器(CRN)网络模型方法具有快速预估燃烧室NOx排放的特点。研究通过CFD数值模拟手段获得了贫预混燃烧室流场、温度场等特征分布,基于燃料空气掺混特性、速度场、温度场、OH分布以及达姆科勒数,燃烧室被离散划分为预热区、火焰锋面区、火焰过渡区、后火焰区、中心回流区以及角回流区,建立了复杂的CRN模型表征燃烧室内部的流动特征和火焰结构。以贫预混燃烧器为对象,与实验结果进行了对比验证。通过敏感性和不确定性分析获得了反应区域停留时间和烟气回流比例等关键参数对NOx排放的影响规律。结果表明:CFD-CRN混合方法更适用于在高当量比条件下贫预混燃烧室NOx排放的快速有效预测。在相同扰动强度的条件下,反应预热区域和火焰锋面区域的停留时间扰动对CRN模型预测NOx的生成量和稳定性影响更显著。CFD-CRN混合方法应明确在较高的绝热火焰温度条件下烟气回流比的准确性计算及其对NOx生成的显著影响。      

State of art on energy management strategy for hybrid-powered unmanned aerial vehicle

New energy sources such as solar energy and hydrogen energy have been applied to the Unmanned Aerial Vehicle(UAV), which could be formed as the hybrid power sources due to the requirement of miniaturization, lightweight, and environmental protection issue for UAV. Hybrid electrical propulsion technology has been used in UAV and it further enforces this trend for the evolution to the Hybrid-Powered System(HPS). In order to realize long endurance flight mission and improve the energy efficiency of UAV, many researching works are focused on the Energy Management Strategy(EMS) of the HPS with digital simulation, ground demonstration platforms and a few flight tests for the UAV in recent years. energy management strategy, in which off-line or on-line control algorithms acted as the core part, could optimize dynamic electrical power distribution further and directly affect the efficiency and fuel economy of hybrid-powered system onboard.In order to give the guideline for this emerging technology for UAV, this paper presents a review of the topic highlighting energy optimal management strategies of UAV. The characteristics of typical new energy sources applied in UAV are summarized firstly, and then the classification and analysis of the architecture for hybrid power systems in UAV are presented. In the context of new energy sources and configuration of energy system, a comprehensive comparison and analysis for the state of art of EMS are presented, and the various levels of complexity and accuracy of EMS are considered in terms of real time, computational burden and optimization performance based on the optimal control and operational modes of UAV. Finally, the tendency and challenges of energy management strategy applied to the UAV have been forecasted.     

针对海南文昌发射场的载人航天器盐雾效应试验及防护方法

空间站工程大吨位载人航天器均在海南文昌发射场发射,面临盐雾效应这个新的环境要素。文章针对海南文昌发射场盐雾环境对载人航天器的影响开展分析和验证工作,研究文昌发射场盐雾水平,分析盐雾效应产生机理和常规盐雾模拟试验方法,针对载人航天器测发流程特点提出主动盐雾防护与盐雾效应摸底试验相结合的工程方法。基于盐雾效应机理总结提出的盐雾效应筛查表格可指导开展沿海地区发射航天器的盐雾防护设计和敏感因素筛查。     

均等通信时滞下多UAV协同编队控制

多无人机(UAV)系统编队控制中,时滞是无法回避的问题,研究时滞对多UAV编队形成和系统稳定性的影响,具有重要理论价值。重点研究均等通信时滞下多UAV协同编队控制问题,并获得系统的稳定性条件。首先,设计具有均等通信时滞的协同编队控制律,得到多UAV编队系统的闭环时滞状态方程;在恒定均等时滞下,考虑到系统模型不确定性,基于线性矩阵不等式(LMI)理论得到系统的时滞依赖稳定性条件;最后,进行仿真实验,结果表明多UAV编队系统是稳定的,期望的编队队形能够形成并保持。     

Improving the process forming limit considering forming defects in the transitional region in local loading forming of Ti-alloy rib-web components

The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local load ing process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element (FE) simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increas ing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology (RSM).The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the pro cess forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great impor tance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.     

C/C复合材料螺栓受拉破坏模式分析

文摘采用试验的方法研究了两种不同结构C/C复合材料螺栓的拉伸破坏形式。结果表明,螺栓头的结构决定了其破坏模式。对于受拉而导致的螺栓头剪切破坏,不是由单方向的层间剪切和面内剪切决定,而是两个方向剪切综合作用的结果,因此细化螺栓头结构设计能最大程度发挥复合材料的力学性能极限。     

一种新的激光捷联惯导系统级温度补偿方法

激光捷联惯导工作时,惯组内的温度会随着时间不断升高,引起惯性器件标度因数和零偏的变化,从而无法满足惯组在全温范围内工作.因此,有必要采取相应措施来减少温度带来的误差.提出一种通过3次样条插值法建立初始模型,不断迭代计算模型偏差修正样条曲线的方法,确立激光陀螺和石英挠性加速度计的温度误差模型存入DSP 中,最终由导航计算机实现惯组输出的实时补偿.通过标定和静态通电验证了模型的正确性和重复性,为进一步提高惯导精度奠定了基础.     

不同类型的翼梢小翼在无人机设计中的应用

针对某型无人机进行融合式、双叉弯刀式2种不同形式翼梢小翼设计,对6组不同参数的小翼构型进行了基于RNAS控制方程的数值模拟计算,结果表明,双叉弯刀式小翼在气动效率的提高、横航向稳定性影响方面明显优于融合式翼梢小翼。结合数值模拟计算结果,从气动机理上对加装翼梢小翼后的纵向、横航向特性影响进行了分析,得出了2种不同形式小翼的气动特点及其各参数对气动性能的影响,其结论对中小型无人机翼梢小翼的设计提供了一定的参考依据。