船舶直流电推系统选择特性的短路故障模拟

为了研究船舶直流电推系统发生短路后的选择性保护特性,对短路发生后的主要短路源、线路状况及关键器件进行分析,采用基于设备参数的选择性保护分析与建模方法,对船舶直流电推系统选择性进行短路故障模拟.针对工程船舶应用,搭建与实际系统对应的仿真模型,对比仿真结果及短路试验结果可以看出,熔断器熔断时间、电压变化趋势及电压跌落情况都...     

基于高空气流特性的转子发动机进气系统建模与仿真

针对转子发动机进气量难以直接测量的问题,基于某型转子发动机进气系统特点分析,考虑高空气流特性对进气量的影响,建立了转子发动机进气系统均值模型,通过Matlab/Simulink仿真软件仿真得到不同海拔高度下的进气量脉谱图。仿真结果与试验数据对比分析表明:发动机进气流量及进气管压强的仿真结果与试验数据基本吻合;在节气门开度较大时,节气门开度的变化对进气流量的影响逐渐减弱;所建转子发动机进气模型精度高,可用于转子发动机进气量的仿真计算。     

直升机动力舱冷却系统冷却孔进气优化设计

对某型民用直升机动力舱冷却系统冷却孔的进气性能开展优化研究,参考飞机辅助动力单元(Applicant power unit,APU)进气系统形式设计了两类收风装置。采用数值仿真手段,对比分析在多个速度的前飞状态和不同爬升率的爬升状态下3处冷却孔的进气性能。结果显示基于Scoop型设计的收风装置在直升机大速度前飞状态收风效果最好,但在小速度前飞状态进气性能没有得到改善。基于Flush型设计的收风装置同样具有改善进气性能的作用,其最显著优点是在所有飞行状态均保证较高的冷却进气量。为后续的优化设计研究工作指明了方向。     

Maneuver control at high angle of attack based on real-time optimization of integrated aero-propulsion

To reduce the propulsion system installation thrust loss under high angle of attack maneuvering, a control method based on real-time optimization of the integrated aeropropulsion is proposed. Firstly, based on data fitting and physical principle, an integrated onboard model of propulsion system is established, which can calculate various performance parameters of the propulsion system in real time, and has high accuracy and real-time performance. Secondly, to improve the compatibility of optimiz...     

Study of geometric parameters for the design of short intakes with fan modelling

The flow over a short intake is characterised by a strong interaction with the fan, that can only be captured when the rotor blades are modelled in the numerical simulations. In this paper, we use a coupled methodology to derive indications about relevant geometric variables affecting the high-incidence operation of an ultra-high bypass ratio turbofan intake with a length-to-diameter ratio of 0.35. By reproducing the effect of the fan through a body force model, we carry out a parametric study o...     

短碳纤维增强PPEK复合材料的性能研究

采用熔融共混的方式制备了不同短碳纤维含量增强含二氮杂萘酮聚芳醚酮(PPEK)基复合材料，对复合材料的加工性能、力学性能、摩擦性能、耐热性进行了研究。结果表明：短碳纤维增强复合材料均可以注塑成型；短碳纤维对PPEK的增强作用明显，拉伸强度和弯曲强度均有大幅提高；复合材料中短碳纤维起到了明显的自润滑作用，复合材料的摩擦系数和磨损率均随碳纤维含量的增加而明显降低；短碳纤维的加入进一步提高了复合材料的耐热性。     

基于Lyapunov直接法的航天器近程导引控制律

基于C-W方程的相对动力学模型,用Lyapunov直接法设计了一种运行于近圆轨道航天器的近程导引控制律,给出了控制模型。该控制律简单有效,无需求解系统方程即可分析和判断近程导引的稳定性进而施加控制。仿真结果表明,该法的导引精度可满足要求,其收敛时间和燃料消耗也在可接受的范围内。     

Ionospheric differential error determination using ray tracing for a short baseline

Since the United States government discontinued Selective Availability (SA) on 1 May 2000, ionospheric effects have been responsible for the largest errors in GPS systems. The standard Differential GPS (DGPS) method is incapable of completely eliminating the ionospheric error. This paper describes a new approach to determine the differential ionospheric error between geographically distributed receiver stations. The ray paths of GPS signals were simulated using a modified Jones 3D ray tracing programme that includes the effect of the geomagnetic field. A Nelder–Mead optimisation algorithm was embedded in the program to precisely determine the satellite-to-station path. A realistic ionospheric model is essential for accurate ray tracing results and for estimates of differential error that are accurate on sub-centimetre scales. Here, the ionospheric model used in the ray tracing programme was developed by fitting realistic ionosphere profiles with a number of exponential functions. Results were compared to the theoretical approach. Results show that the differential delay is about 1–5 cm at low elevation angles for a short baseline of 10 km, as reported in other literature. This delay is often neglected in DGPS application. The differential delay also shows a pattern similar to that predicted by the Klobuchar model. The method proposed here can be used to improve future GPS applications.     

液体亚燃冲压发动机性能分析研究

随着巡航导弹的作战空域和飞行速度的不断增大,对液体亚燃冲压发动机的性能要求越来越高,亟待对冲压发动机性能的影响因素进行分析研究.通过对液体亚燃冲压发动机的工作过程进行详细的分析研究,编制了冲压发动机性能计算软件,利用该软件分析冲压发动机的各个关键组合件,如进气道、燃烧室、尾喷管以及燃油供应系统等各个组合件的性能对冲压发...     

水空两用无人机进排气系统分析

水空两用无人机的进排气系统对其能够进行水空转换运行有着至关重要的作用。本文针对水空两用无人机进排气系统进行分析．通过CATIA进行设计造型．再将模型导人流体分析软件FLUENT中．分析其对发动机进气量的影响．通过分析确定现有设计方案的可行性．以及对现有方案进行改进完善．为后续研究提供依据。