三维空间拦截的前置追踪变结构制导律(英文)

This article aims to develop a head pursuit （HP） guidance law for three-dimensional hypervelocity interception, so that the effect of the perturbation induced by seeker detection can be reduced. On the basis of a novel HP three-dimensional guidance model, a nonlinear variable structure guidance law is presented by using Lyapunov stability theory. The guidance law positions the interceptor ahead of the target on its tlight trajectory, and the speed of the interceptor is required to be lower than that of the target, A numerical example of maneuvering ballistic target interception verifies the rightness of the guidance model and the effectiveness of the proposed method.     

Design and development of a five-axis machine tool with high accuracy,stiffness and efficiency for aero-engine casing manufacturing

In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with high accuracy, stiffness and efficiency, including whole structure design,key components design, and supporting stiffness design. First, an appropriate structure of five-axis machine tool is determined considering the processing characteristics of aero-engine casing. Then, a dual driv...     

Numerical study of a trapezoidal bypass dual throat nozzle

Bypass Dual Throat Nozzle (BDTN) is a novel type of fluidic thrust vectoring nozzle. To improve the infrared stealth performance of BDTN, a nozzle based on BDTN is proposed and numerically simulated. Each cross-section along the x-axis of the novel nozzle becomes a trapezoid, which is named “BDTN-TRA.” The main numerical simulation results show that BDTN-TRA can produce a thrust vectoring angle when the upper or lower bypass valve is open. The angle difference between the two conditions mentioned above is usually approximately 1°–2°. Even if the two bypasses are closed, BDTN-TRA can produce a small thrust vectoring angle at around 3°–5°. When the sidewall angle increases from 60° to 90°, the thrust coefficient and thrust vectoring angle under each work condition usually decrease. A larger aspect ratio indicates better performance. As the aspect ratio increases over 7.2, the performance of BDTN-TRA is quite close to that of BDTN with rectangular cross-sections at the same aspect ratio. These features will benefit the control and trimming for future aircraft design, especially for the flying wing layout aircraft. Last but not least, BDTN-TRA has a more extraordinary mixing performance compared with BDTN. The distributions of static temperature and axial velocity along the x-axis of BDTN-TRA with sidewall angle of 60° decrease faster than those of BDTN. When the total temperature of the inlet equals 1600 K, the static temperature difference between BDTN-TRA with sidewall angles of 60° and 90° is over 360 K at twice the length of the nozzle downstream of the nozzle exit, which is the reflection for excellent infrared stealth for the fighter.     

A novel method of utilizing static mixer to obtain mixing homogeneity of multi-species powders in laser metal deposition

Real-time mixing of multi-species powder challenges Laser Metal Deposition (LMD) of Functionally Graded Materials (FGMs). The current work proposes a novel method of using a static mixer to realize rapid, uniform multi-species powder mixing. Firstly, copper powder and 316L stainless steel powder are selected to complete the powder mixing observation experiment with Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). Secondly, computational fluid dynamics and particle mixing simulation models are used to analyze the flow field and particle motion characteristics in the static mixer. Finally, LMD experiment and metallographic observation are carried out with 316L stainless steel powder and WC powder to verify the feasibility of the static mixer. This study provides a theoretical and practical basis for powder mixing in laser processing with a static mixer. The conclusions can also be applied to other processing fields requiring real-time and uniform mixing of multi-species powders.     

进气道出口截面形式对补燃室掺混性能的影响研究

为研究进气道出口截面形式对补燃室掺混气动特性和燃烧性能的影响，本文对双下侧布局形式的固冲发动机内流场进行数值模拟，对比分析了补燃室相同压比下两种不同进气道出口截面形式在不考虑燃气的混合和反应时掺混段的气动特性和考虑燃气反应时补燃室的燃烧性能。结果表明：两股空气掺混过程中，研究的两种进气道出口截面方案的整体总压损失大致相同，但进气道圆形出口截面的掺混段内流线表现为不稳定的螺旋点形态，相比于方形出口截面的掺混段，其使气流掺混更剧烈，短距离内掺混已经很均匀，且旋流强度小；在考虑燃烧时，进气道圆形出口截面对应的补燃室出口总压恢复系数比方形截面的高约2%，方形进气道出口截面的补燃室出口截面总燃烧效率为95.58%，而圆形截面的达到99.86%。