固体火箭发动机气动喉部的两相流数值模拟

本文对两相流条件下的环缝式气动喉部方案进行了数值模拟。气-粒两相流动模型采用二维轴对称欧拉-拉格朗日模型。研究了二次流不同喷射位置、角度、流率及喷嘴个数对气动喉部调节有效喉部面积大小的影响规律。模拟得到了两相流条件下气动喉部的流场特征,结果表明使二次流的喷入位置越靠近喉部、增大二次流流量或减小喷射角度都能明显增加气动喉部调节性能;由此归纳出增强气动喉部对主流扼流能力的两种主要机制,即增加挤压和流阻。     

固体火箭发动机流体喉部推力矢量特性

针对采用水作为二次流工质的流体喉部进行了冷流实验及数值模拟研究.研究了该种固体火箭发动机流体喉部的一般规律,包括不同二次流射流方式,不同二次流流量下流体喉部的扼流性能,推力偏角及推力效率,数值模拟及实验结果吻合较好.结果表明:扼流性能与二次流的注射位置、注射角度及流量比有关,且随二次流/主流流量比的增大而增大.喉部二次流喷射能有效的调节有效喉部面积进而调节推力大小,当流量比为0.4时,最大有效喉部面积比为0.8;扩张段二次流喷射能有效调节推力方向,当流量比为0.4时,最大推力偏角为20°;喉部二次流与扩张段二次流入射位置存在相位差可有效降低喉部与扩张段二次流干扰.      

固体火箭发动机环缝式气动喉部研究

对固体火箭发动机气体二次流控制的环缝式气动喉部方案进行了数值模拟.研究了二次流不同喷射位置、角度、流率及喷嘴几何参数对气动喉部调节性能的影响规律.计算得到了气动喉部的流场特征,即气动喉部的声速线起点在二次流喷口的下游,并得到了气动喉部特征存在的喷注范围.结果还表明使二次流的喷入位置越靠近喉部、增大二次流流量或减小喷射角度都能明显增加气动喉部调节性能.      

流体喉部推力调节特性实验

采用空气与水作为二次流工质,进行流体喉部的冷流实验,研究了固体火箭发动机流体喉部的推力调节特性.分析了不同二次流工质、注射方式,注射流量下的推力响应时间、扼流性能、推力偏角和推力效率.实验结果表明:注射液态二次流推力响应时间更短;扼流性能、推力偏角与二次流的注射位置及注射角度有关,且随流量比的增大而增大;相同的流量比下,气态二次流的推力性能要比液态二次流的效果更好,但提供相同的流量比,液态二次流需要压比更小,且流量比的调节范围更大.      

圆孔喷嘴形成气动喉部的定常数值研究

对固体火箭发动机上由圆孔喷嘴喷入二次流所形成的气动喉部进行了三维数值模拟.考察了圆孔喷嘴形成气动喉部的典型三维流动特征和喷嘴流量特性.研究了不同喷嘴面积比、喷嘴个数、喷射角度、喷嘴构型及主要喷管参数对气动喉部调节喉部面积能力的影响.结果表明在相同的喷嘴面积比下,增加喷嘴个数、采用逆向喷射或选用收缩喷嘴构型都能显著提高气...     

固体火箭发动机气动喉部非定常过程

利用流体计算软件FLUENT,通过UDF编程对气动喉部调节固体火箭发动机推力的典型工作过程进行了数值模拟。对推力调节过程中的瞬态轴对称燃烧室流场进行了分析,得到了压强-时间曲线。分析了发动机空腔容积、二次流喷射角度对推力响应特性的影响,并得到了典型的推力-二次流总压调节特性曲线。其研究结果可为利用气动喉部技术的变推力发动机设计提供一定依据。     

底部二次流对塞式喷管影响的实验研究

基于单元塞式喷管的实验数据,研究了底部二次流对塞式喷管性能和底部特性的影响,测得了不同环境反压下塞锥表面的压强分布.实验表明,底部在不同压比下具有不同的气动状态.二次流的注入使底部开闭过渡点的压比值升高,底部开始提供推力的压比值下降,有利于避免底部开闭过渡时推力出现较大幅度降低.二次流流量达到主流的2.0%后,再加大底部二次流流量不再影响底部压强,过多地注入反而会降低塞式喷管的总体效率,1.5%～2.0%主流流量的二次流注入是比较好的选择.在低压比范围,塞锥表面有压强峰出现,随着高度的增加,压强峰后移并强度减弱.     

两种气动推力矢量技术的数值模拟研究

对两种收扩喷管推力矢量控制技术:激波矢量控制技术和喉部偏移控制技术,进行了流场计算和性能比较。本研究中,喷管进口至喉部几何型面固定,扩张段长度为定值,二次流喷射位置、角度保持不变,采用CFD数值模拟方法计算喷管膨胀比不同时的流场。从计算结果可以看出,喉部偏移控制技术适用于膨胀比小于1.5的收扩喷管,而激波矢量控制技术适用于膨胀比大于1.5的收扩喷管。喉部偏移控制技术的特点在于其可以限制喷管主流流量,影响主、次流流量比的主要因素为二次流与主流的总压比。     

二元收扩喷管设计参数对气动性能影响的数值研究

采用正交试验设计方法进行喷管气动性能数值模拟算例的设计,综合研究了二元收扩喷管8个设计参数对气动性能的影响,研究的设计参数包括圆到矩超椭圆型面过渡段几何参数（长径比、横截面积变化率、长半轴变化率、短半轴变化率）和主喷管段几何参数（喉部宽高比、喉部型面半径比、收敛半角、扩张半角）,并且对喉部宽高比、喉部型面半径比、收敛半角、扩张半角等4个参数对喷管气动性能影响的灵敏度进行了分析.结果表明:喉部型面半径比R_W/R₈是二元收扩喷管气动性能影响的最主要参数,因此在喷管设计中应尽量增大R_W/R₈,尤其是在收敛半角α较大时,增大R_W/R₈可使喷管气动性能明显增大;喉部宽高比不是二元收扩喷管气动性能影响的主要参数;二元收扩喷管的气动性能几乎与过渡段型面无关.      

双喉道喷管与飞翼布局无人机气动数值研究

利用超椭圆方法,设计了双喉道射流矢量喷管的气动外形,并采用S-A湍流模型数值研究了次主流压比、次流方向及喷管外形参数对其气动特性的影响。研究表明,当确定次主流压比SPR=3时,可依次确定该型喷管外形参数分别为空腔长度l=3h,空腔扩张角θ1=10°,空腔收敛角θ2=30°,二次流注入角α=120°时,矢量喷管的气动特性最优。将设计的气动最优喷管与飞翼布局无人机后体进行一体化设计,数值模拟了喷管对飞翼布局无人机升阻特性的影响,结果表明,双喉道射流矢量喷管能够很好地运用于飞翼布局无人机。     

航天发射任务测量船应急测控海域设计方法

针对某些航天发射任务中测量船任务海域纬度高、气象复杂多变的特点,提出了测量船应急测控海域的设计方法,为预定任务海域出现危害性以上海况时实施快速正确船舶机动和应急测量工况设计提供依据,给出了设计实例。     

2-D奇异系统鲁棒稳定性的状态空间测度

考虑具有非结构摄动的2-D奇异系统Roesser模型(简称2-DSRM)鲁棒稳定性的状态空间测度问题.利用其容许、稳定的充要条件及矩阵的奇值分解,分析其鲁棒稳定性,给出了不破坏2-D奇异系统稳定的摄动的最大上界.     

Design for testability for future digital avionics systems

The authors describe an integrated testing approach called the Maintenance and Diagnostic System (MADS), which was developed for digital avionics systems using VHSIC and semicustom devices. Mission/operational requirements dictate high availability with capability to detect 98% of all faults and isolate 90% of these faults to a line replacement module (LRM) or 95% of the faults to two LRMs. MADS achieves these goals by defining a module maintenance node (MMN) chip set for each LRM in the system and the design for testability concepts for hardware. The MMN aids parallel, high-speed testing of LRMs, isolating the fault(s) to a module/chip level while incurring less than 10% overhead. It uses the concepts of scan set design, pseudorandom test vector generation, output response compression, and separate scan set loops to test the SSI-MSI logic on the LRM. It also stores interim test results and run-time fault information to isolate the hard-to-reproduce failures and performs verification of interchip and intermodule wiring     

Simulation Environment for Machine Vision Based Aerial Refueling for UAVs

The design of a simulation environment is described for a machine vision (MV)-based approach for the problem of aerial refueling (AR) for unmanned aerial vehicles (UAVs) using the USAF refueling method. MV-based algorithms are implemented within the proposed scheme to detect the relative position and orientation between the UAV and the tanker. Within this effort, techniques and algorithms for the visualization the tanker aircraft in a virtual reality (VR) setting, for the acquisition of the tanker image, for the feature extraction (FE) from the acquired image, for the feature matching (FM) of the features, for the tanker-UAV pose estimation (PE) have been developed and extensively tested in closed-loop simulations. Detailed mathematical models of the tanker and UAV dynamics, refueling boom, turbulence, wind gusts, and tanker's wake effects, along with the UAV docking control laws have been implemented within the simulation environment. This paper also presents the results of a study relative to the use of passive markers versus feature extraction for the problem of estimating in real time the UAV-tanker relative position and orientation vectors.     

Multi-EAP:Extended EAP for multi-estimate extraction for SMC-PHD filter

The ability to extract state-estimates for each target of a multi-target posterior, referred to as multi-estimate extraction (MEE), is an essential requirement for a multi-target filter, whose key performance assessments are based on accuracy, computational efficiency and reliability. The probability hypothesis density (PHD) filter, implemented by the sequential Monte Carlo approach, affords a computationally efficient solution to general multi-target filtering for a time-varying num-ber of targets, but leaves no clue for optimal MEE. In this paper, new data association techniques are proposed to distinguish real measurements of targets from clutter, as well as to associate par-ticles with measurements. The MEE problem is then formulated as a family of parallel single-estimate extraction problems, facilitating the use of the classic expected a posteriori (EAP) estima-tor, namely the multi-EAP (MEAP) estimator. The resulting MEAP estimator is free of iterative clustering computation, computes quickly and yields accurate and reliable estimates. Typical sim-ulation scenarios are employed to demonstrate the superiority of the MEAP estimator over existing methods in terms of faster processing speed and better estimation accuracy.     

航空发动机润滑供油系统仿真研究

以某型航空发动机为研究对象,建立其润滑供油系统数学模型。利用Matlab编程计算得出系统在不同转速、不同温度下各润滑点滑油流量、滑油压力等性能参数数据。重点分析了不同温度下,系统增压级流量、压力的变化趋势。研究结果为发动机润滑系统的设计和故障诊断提供参考。     

Numerical approach for assessment of dynamic strength for riveted joints

Numerous rivets have to be modelled for aeronautical framework crashes. A numerical procedure based on FE modelling and characterisation of material failure constitutive models is proposed in order to limit the experimental procedure. Quasi-static and dynamic experiments are carried out on elementary tension (punched) and shear (riveted) specimens. No strain rate sensitivity has been measured on the riveted joint assemblies failure. The experiments are used to identify, by an inverse method, the Gurson damage parameters of each material (2024-T351 and 7050 aluminium alloys for the sheet metal plate and the rivet). The characterisation gives rise to a satisfactory correlation between FE models and experiments. Optimised parameters are validated for each material by means of a uniaxial tension test for the sheet metal plate and an ARCAN type specimen in pure tension for the rivet. Results can then be used to identify macroscopic failure criterion to model the rivet behaviour in aeronautical framework crashes. FE tools can also resolve problems linked to limit-design or the design of new riveted joint assemblies more rapidly and cost effectively than experiments.     

空管灾害诱因分析及监测指标体系的构建

从操作人、空管设备、空管环境和管理的角度对空管的致灾诱因进行了详细分析。按照科学性、实用性、关联性和可操作性的原则,筛选出一组监测指标,在考虑空管行业数据来源的情况下,提出了现阶段和理想情况下的监测指标体系,目的在于通过对空管安全状态进行监测和诊断,及时采取预警和预控对策,促进空管系统处于安全状态,降低事故率。     

全信息代表飞行起落疲劳载荷谱编制方法研究

针对某重型歼击机的实际使用特点,在只有少量飞行载荷实测数据的基础上,利用外场飞机实际使用情况,提出全信息代表飞行起落法编制该型飞机疲劳载荷谱的方法,为先进飞机的载荷谱的编制提供一种切实可行的科学理论。     

纵列式双旋翼直升机气动力和流场的数值模拟

纵列式双旋翼直升机的旋翼尾迹受前飞自由流、机身和旋翼之间的干扰影响,旋翼尾迹不仅影响机身的空气动力,也影响旋翼自身的空气动力特性.应用欧拉方程与计算流体力学(CFD)方法,采用自适应非结构直角网格技术生成计算域网格,数值模拟纵列式双旋翼直升机全机流场,给出了考虑旋翼影响的机身表面压力分布以及全机流场特性.