改进的预测气体燃料贫油熄火边界的半经验公式

为了进一步考察采用气体燃料时,火焰体积(FV)模型对贫油熄火边界预测的适用性,推导了气体燃料的FV模型。经过对7种典型的航空发动机燃烧室(即采用双径向旋流器和双轴向旋流器,分别改变一级旋流器、二级旋流器的进气面积和主燃孔的个数)进行验证实验,并与液体燃料FV模型和Lefebvre模型的预测结果进行比较。结果表明,上述三种模型虽然基本都可以用于气体燃料贫油熄火边界的预测,但各自的预测精度不同。在实验范围内,气体燃料FV模型、液体燃料FV模型、Lefebvre模型的预测精度依次为±5.6%,±6.9%,±7.1%。气体燃料FV模型在预测气体燃料的贫油熄火边界时有最好的预测精度。     

拉力试验机数据采集与处理系统

本文提出了如何解决机械式拉力试验机存在的问题的方法，介绍了单片机数据采集，处理系统的软硬件，对一些关键问题给出了比较详细的介绍。     

Cyclic variations in the solar lower atmosphere

The Ca K line has been measured regularly nearly every month since 1974 at Kitt Peak. It is well known that the K₁ component of the Ca K line is formed in the temperature minimum region (TMR) of the solar atmosphere. Our study of the data of CaII K profiles over two solar cycles indicates that both in full disc integrated spectra and in center disc spectra, the distance between the red K₁ and the blue K₁ of the profiles and its average intensity show periodic variations. But the variation for the full disc integrated spectra fluctuates in the same way as the sunspot number does, while that for the center disc spectra has a time delay with respect to sunspot number. Non-LTE computations yield a cyclic temperature variation of about 17 K of the TMR in the quiet-Sun atmosphere and a cyclic variation of about 15–20 km in the height position of the TMR.     

大攻角非对称涡特性及消除侧向力和力矩方法

本文提出了一个消除非对称力的头部外形方案。通过风洞实验,论证了方案是有效和稳定的。实验发现由对称涡向非对称涡的转变有一个不稳定区,建议用动态测力,得到与激光蒸汽屏流场相一致的结果,并研究其相互关系。     

成组技术中计算机辅助零件分类方法的探讨

成组技术是有效实现CAD/CAM的基础之一,是提高多品种、中小批量生产水平的重要手段。本文提出了在成组技术中应用模糊数学理论进行计算机辅助零件分类的新方法,并对回转零件进行了分类试验,取得了满意的结果。采用这种方法,不需要对零件进行编码,可以对零件相似性进行定量分析,使得零件分类更具有柔性,为成组技术中零件分类提供了新的方法。     

Ground experiments of Chang’e-5 lunar regolith penetrating radar

The Lunar Regolith Penetrating Radar (LRPR) is an Ultra-Wideband (UWB) array-based Ground penetrating radar (GPR) onboard the lander of Chang’e-5 (CE-5) mission. The primary scientific objectives of the LRPR are to probe the thickness and structure of lunar regolith of the landing site, and support the drilling and sampling process. In order to evaluate the performance of the LRPR, a series of ground experiments are performed using the LRPR prototype mounted on a CE-5 lander model. The performance of the LRPR is evaluated by comparing the experimental data with the simulated data. Data processing and imaging method are verified, and the interferences from the lander and other aspects are analyzed. The results of the ground experiments and simulation demonstrate that the LRPR is able to meet the design requirement of 2-m detection depth. They also indicate that the upper and lower interfaces of the stratified structure in the lunar regolith can be well distinguished by the LRPR when the dielectric constant difference is greater than 0.3, and the imaging effect of the location under the dense antennas is better than that of other positions. However, the identification capability of the LRPR to the independent blocky objects is relatively poor mainly due to the clutters caused by the lander, the sparsity of the antenna elements compared to the size of the basalt block, the limited aperture of the antenna array, and the tail of the transmitted waveform.     

液液同轴离心式喷嘴喷雾过程研究进展

内部流动主要研究了流量系数、液膜厚度和气核半径,分析了内部流场,少量研究涉及内外喷嘴液膜互击、液膜表面波振幅和频率等方面。液液喷嘴外部液膜流动及喷雾特性的研究开展较多,观测了不同工况、结构参数下内外液膜流动形态,少数学者使用理论方法分析了液膜破碎机理。对喷雾特性的研究主要是获得了喷雾锥角、破碎长度、液膜振荡频率等的变化规律,并进一步研究了SMD、液滴速度、混合特性等的变化规律。     

Numerical Analysis of Dry Friction-Induced Vibration of Moving Slider-Elastic Annular Beam System

A disc-pad friction system is modelled as that two moving pads act symmetrically on an annular beam with flexible boundary condition.Simulation procedure is proposed to deal with the moving interactions and calculation is carried out by using the finite difference method,which shows that only the first-order mode vibration of the beam can be induced.Then the partial differential equation of motion of the disk is reduced to a first-order mode vibration system with time-varying stiffness.As the disk speed is decreased below the critical speeds,the relative equilibrium of the pad on the disk loses its stability and stick-slip type limit cycle vibrations are resulted in all directions′movements.Acceleration of the disk motion on the frictional instability is also investigated.The period of stick-slip vibration with large amplitude will be shortened with higher moving deceleration.     

利用视加速度补偿和推力逐级释放的垂直着陆制导方法

针对运载火箭子级垂直返回着陆段的制导问题，本文在应用凸优化的滚动时域在线规划基础上研究了制导鲁棒性的改善策略。为应对着陆后期控制能力不足的情况，在滚动规划过程中引入了推力上界逐级释放的策略。同时，考虑缓解干扰和误差累积的影响，在制导周期内引入视加速度信息对在线规划的推力指令进行补偿，以进一步改善滚动规划的递归可行性。最后，通过数值算例仿真及对比分析验证所提出的补偿策略的有效性。     

一种适用于封闭场景下的遥测信号接收方法

常规的遥测信号接收多是在开阔场景进行,被测对象除了在起飞或降落时短暂低仰角,大部分时间其信号是视距传输,其遥测信道近似于高斯白噪声信道。随着遥测应用场景的逐步扩展,封闭场景下的遥测需求逐步被提出,应用模式和信道条件发生了巨大变化。针对某封闭场景,分析常规遥测接收方法存在的一些问题,提出一种双天线加盲均衡的分集合成和接力接收方案,有效解决了封闭场景下的遥测信号中断问题。方案成功应用于某测试系统,实测结果表明,方案能够极大提升遥测系统的健壮性。