载人航天器独立飞行时密封舱内内流动换热及热湿分析研究

载人航天器密封舱以通风换热方式对舱内人员及其设备进行散热,控制舱内温度,利用冷凝干燥组件调节舱内湿度.针对某一处于独立飞行状态下、由返回舱和轨道舱组成的密封舱,采用数值模拟软件I-DEAS对其速度场、温度场以及湿度场进行了稳态数值分析,研究了密封舱内的温度分配和湿度分布,并对密封舱的温湿控制方案的合理性进行了评价.     

微通道内亲疏水壁面特性对入口段长度的影响

针对水力直径为200μm的微尺度通道,采用数值模拟的方法研究了壁面亲疏水特性产生的速度滑移对微尺度通道入口段长度的影响,建立了包含滑移长度影响的入口段长度修正计算公式.研究表明:相同流量下,速度滑移的存在使得微尺度通道充分发展段的最大速度减小,从而缩短了入口段长度,且在低雷诺数区域,入口段的缩短效应更为显著.针对不同的...     

An improved real-time cycle slip correction algorithm based on Doppler-aided signals for BDS triple-frequency measurements

Doppler, which is an instantaneous GNSS observable signal, has been proven effective in determining velocity and acceleration due to its high availability and accuracy. We propose a real-time triple-frequency cycle slip correction (CSC) method based on Doppler-aided signals because Doppler shift is time-independent and immune to cycle slips. When the sampling interval is less than 1 s, cycle slips on triple-frequency can be detected and repaired using pure Doppler data with high reliability; however, this method cannot be used when the sampling interval exceeds 1 s because the integral cumulative error of Doppler increases significantly. For such cases, a modified triple-frequency CSC approach has been developed based on the raw phase and smoothed code data that was refined using the Doppler signal. To suppress the effect of the integral Doppler error, a balance factor is introduced to adjust the contributions of the raw code and Doppler observables. After the refinement of the GNSS data, three independent combinations need be selected to detect and repair cycle slips with triple-frequency observations. Four constrained criteria have been proposed to select optimal combinations that can reduce the residual ionospheric delay (RID) and measurement noise to a low level. Finally, experiments were carried out to test the performance of the new method using real triple-frequency BDS observations (GPST: 3:15:00–5:55:00, March 23, 2018). The results show that pure Doppler can detect and repair cycle slips effectively with small intervals, and modified Hatch-Melbourne-Wübbena (HMW) method based on Doppler-aided signals can achieve 99.7% success rate in cycle slip correction with large intervals (up to 30 s).     

Velocity pointing error analysis for symmetric spinning thrusting Cubesat

To solve the problem of thrust vector misalignment from the Cubesat center of mass during orbital maneuver, spin-stabilized method is applied to eliminate velocity pointing error. Spinning thrusting Cubesat model involves the effects of mass variation and jet damping is established. Analytical solutions for the angular velocity, nutation angle, Euler angle, and inertial velocity with nonzero initial conditions are derived. Simulations show that the analytical solutions closely match numerical simulations. Based on the analytical solutions, the velocity pointing error influencing factors is analyzed. The results show that the velocity pointing error caused by initial transverse velocity, nutation angle and transverse disturbance torque can be reduced by raising the spin rate, but the initial Euler angle need to be limited. Also, the spinning thrusting maneuver can allow for a lower spin rate by increasing the axial moment of inertia.     

Variable slip window technology in transition detection on pitching airfoil

In the pitching motion, the unsteady transition and relaminarization position plays an important role in the dynamic characteristics of the airfoil. In order to facilitate the computer to automatically and accurately calculate the position of the transition and relaminarization, a Variable Slip Window Technology (VSWT) suitable for airfoil dynamic data processing was developed using the S809 airfoil experimental data in this paper and two calculation strategies, i.e., global strategy and single point strategy, were proposed: global strategy and single point strategy. The core of the VSWT is the selection of the window function h and the parameters setting in the h function. The effect of the VSWT was evaluated using the dimensionless pulse strength value (INB), which can be used to evaluate the signal characteristics, of the root mean square (RMS) value of the fluctuating pressure. It is found that: the h function characteristics have a significant influence on the VSWT. The suitable functions are H_n function constructed in this paper and step function. For the left boundary of the magnified area, the step function can obtain the largest INB value, but the robustness is not good. The H₁ function (Gaussian-like function, n = 1) can show higher robustness while ensuring a large INB value. The two computing strategies, which are single point strategy and global strategy, have their own advantages and disadvantages. The former strategy, that is the single point strategy, can achieve a higher INB value, but the RMS magnification at the feature position needs to be known in advance. Although the INB value obtained by the latter strategy, that is the global strategy, is slightly smaller than the calculation results of the former strategy, it is not necessary to know the RMS magnification at the feature position in advance. So the global strategy has better robustness. The experimental data of NACA0012 airfoil was used to further validate the developed VSWT in this paper, and the results show that the VSWT developed in this paper can still double the INB value of the transition/relaminarization position. The VSWT developed in this paper has certain practicability, which is convenient for the computer to automatically determine the transition/relaminarization characteristics.     

单轴拉伸和压缩镁合金各滑移系的Schmid因子计算

针对单轴拉伸和压缩条件下的镁合金,计算了不同滑移系（基面滑移、柱面滑移、锥面滑移、锥面滑移）在整个取向空间中的Schmid因子分布.计算结果表明,基面滑移、柱面滑移和锥面滑移系的Schmid因子在取向空间中都有0.5的极大值;而锥面滑移系的Schmid因子普遍较低,当θ在80°左右,ψ在70°左右时的最大值仅为0.383.计算结果为镁合金变形机制的分析提供基础.     

核心机驱动风扇级在非设计模式下的匹配方法研究

核心机驱动风扇级(CDFS)是双涵道变循环发动机的关键部件之一。为了开展CDFS在非设计模式下(双涵道模式)的匹配分析,利用速度三角形建立了CDFS在双涵道模式下的匹配特性图,该图能够正确反映双涵道模式下CDFS的工作特点和主要气动参数的变化趋势。结果表明:给定CDFS在双涵道模式下流量时,随着压比下降,需要降低CDFS在双涵道模式下的转速才能保证转子进口相对气流角不变;给定双涵道模式的流量和压比时,若要使转子进口相对气流角下降,需要增加CDFS在双涵道模式下的转速。     

考虑时间约束的无人飞行器航迹规划

在分析时间误差分配的基础上,本文提出了一种考虑时间约束的航迹规划方法.该方法对传统的航迹结构进行了改进,通过速度调整策略和在代价函数中加入时间约束驱使算法找到使到达目标点时间误差尽可能小的航迹.同时,分别研究了起飞时间误差,速度调节能力及飞行速度误差三个因素对到达目标点时间误差的不同影响.     

通用核心机涡轮气动设计准则

针对通用核心机对涡轮部件性能的要求,尝试给出了描述涡轮气动通用性的定义,研究了速度三角形系列参数对涡轮气动通用性的影响规律,在此基础上,得到了通用核心机涡轮部件气动设计参数选取准则,并通过S2和三维数值模拟手段,利用一组真实涡轮的数据对涡轮气动通用性的定义和设计参数选取准则进行了验证。结果表明:在涡轮设计参数选择中,存在使涡轮部件气动通用性最优的速度三角形参数范围;一般情况下气动设计参数在Ω=0.35～0.45,μ=1.65～1.9,K1=0.55～0.6区域内时,所设计的涡轮气动通用性较好;一系列涡轮气动设计参数的分析表明本文给出的涡轮部件气动通用性的定义和得到的涡轮部件气动设计参数选取准则基本合理。     

耀斑后环珥系速度场的定量研究

本文研究了在太阳重力、偶极磁压强梯度和气体压力梯度联合作用下环珥系内物质的下落运动,并在等温、定常假设下用数值方法计算了该环系的二维视向速度场。通过将速度场的理论计算跟文[1]中给出的观测速度场拟合,导出了该环系的有关参数及分布。计算表明环系内物质密度和磁场强度对物质下落运动影响较显著。