数字角跟踪系统设计

本文介绍了一种根据现代角跟踪理论设计的空-空导弹数字角跟踪系统及其设计过程,叙述了该系统的特点、结构及工作原理。该系统中的比较、转换、计算均已数字化,精度大为提高。文中给出了各功能模块的设计框图和工作原理图。     

超超临界锅炉受热面管角变形对应力的影响

角变形是电站锅炉受热面管子安装过程中常见的缺陷，严重的角变形不仅影响传热，而且会降低管子的使用寿命。本文针对超超临界锅炉水冷壁管，分别模拟了管子不发生角变形及角变形为1％、3％、5％的4种情况下的应力分布情况，结果表明角变形会引起焊缝区域的应力集中，且角变形越严重，应力集中情况越明显。     

长清模拟科威特油井灭火试验中的流体力学计算问题

根据当时灭火试验提供的数据和模拟灭火现场的具体条件,从流体力学理论的角度,计算出完成水压试验和最后灭火试验所需的基本参数,为试验圆满成功提供了理论依据。     

Analysis and prediction of traffic fatalities resulting from angle collisions including the effect of vehicles' configuration and compatibility

Although the rapid growth in light truck vehicle (LTV) sales, including minivans, sports utility vehicles (SUVs), and light-duty trucks, has not been associated with an overall increase in collisions or traffic deaths in the US, there is a need for a research program to determine whether particular types of collisions have become more frequent or injurious because of the increase in the percent of LTVs in traffic. This paper presents an analysis of the effect of the increasing number of LTV registrations on fatal angle collision trends in the US. The analysis investigates the number of annual fatalities that result from angle collisions as well as collision configuration (car-car, car-LTV, LTV-car, and LTV-LTV). The analysis uses the Fatality Analysis Reporting System (FARS) crash databases covering the period 1975-2000. Results showed that death rates differ based on the collision configuration. Time series modeling results showed that fatalities in angle collisions will increase in the next 10 years, and that they are affected by the expected increase in the percentage of LTVs in traffic. Forecast showed that the total number of annual deaths is expected to reach 6300 deaths by the year 2010 (an increase of 12% over 2000). Analysis into the configuration of the collision indicated the seriousness of angle collisions involving an LTV striking a common passenger car (LTV-car). A time series model illustrated the significance of time lag and percent of LTVs in traffic on the increase of this type of fatal collisions. Forecasts from the time series model indicated a 32% increase in deaths due to this type of collisions in the next 10 years.     

Effect of Magnetic Field on Stability of Jet Motion in Electrospinning

Electrospinning uses an electrical charge to draw fine polymer fibers from a liquid. Stable jet stage and whipping instability stage exist in the electrospinning process. It is difficult to control stability of jet motion. Electrospinning with NbFeB permanent magnets is proposed to enhance the stability of jet motion in this paper. This method is very simple and effective. The electrospinning process assisted by magnets was observed by a high-speed camera, and the magnetic field was numerically analyzed by finite element method. The experimental results showed that the stability of jet motion increased obviously. We have explained that the magnets restricted and focused the motion of charges as a magnetic lens and created a uniform electric field distribution as an auxiliary electrode at the end of spinneret. The stable jet length, whipping instability cone angle, and fiber diameter were measured by experiments. The stable jet length increased significantly, the whipping instability cone angle decreased, and the average diameter of fibers increased slightly and distributed more evenly as the magnets were fixed at the end of spinneret.     

Numerical Study on the Effect of Cavitation on Flow and Diesel Fuel Atomization Characteristics

Computational fluid dynamics (CFD) models based on the turbulent mixture multiphase model were applied to consider the effect of cavitation on the spray of diesel fuel. The effects of injection pressure and length‐to‐width (L/W) ratio on the velocity distribution, cavitation number, discharged coefficient, and nozzle exit velocity were investigated and the performance of the model was compared with the experimental data. The results indicate that the cavitation generated in the nozzle has a strong impact on the fuel injection and spray quality, whereas the L/W ratio is a highly effective parameter for cavitation behavior. In addition, by increasing the L/W ratio, the range of cavitation number, wall friction, and flow resistance increase but in the cavitation region the velocity profile in radial and axial directions, spray cone angle, nozzle exit velocity, and the discharged coefficient decrease.     

角钢孔型设计中几个问题的探讨

根据角钢孔型设计的特点,对其中涉及的几个主要问题进行了分析,并结合生产实际推导了计算模型,提出了合适的计算方法。将这些模型和算法应用于角钢孔型优化设计,可获得较好的效果。     

可调式气体喷射器调节性能计算分析

提出在喷射器喷嘴内插入喷针来调节喷射器工作参数的方案,建立了可调式喷射器性能计算模型,计算分析了喷嘴截面积变化对喷射系数、气体压力、气体流量等参数的影响。结果表明,通过对喷射器喉口面积的调节,可拓宽喷射器的有效工作范围,减小喷射器入口参数对出口参数的影响。     

等圆心角法球面数控加工插补方法的研究

针对目前常用球面数控加工方法效率较低、加工精度不一的缺点，提出了一种改进方法即等角度分割插补法确定加工层切削深度。本文阐述了该方法的思路，详细推导了所需公式，经过仿真软件的验证，证明该方法具有较高的加工效率，且加工精度较高，能用于球面的数控粗、精加工，具有较好的实用价值。     

风偏角与杆塔结构对500 kV同杆双回线路绕击耐雷性能的影响

分析500kV双回输电线路的绕击耐雷性能,对EGM进行了改进。在计算过程中为考虑风的影响,引入风偏角;同时引入了雷击避雷线与雷击地面击穿强度比值随杆塔高度h变化的系数β。用暴露弧法计算每根导线绕击跳闸率,以暴露弧为0时对应的雷电流作为雷电的最大绕击电流,并分析了风偏角、杆塔结构等因素对500kV双回输电线路各导线绕击跳闸率的影响。结果表明,风偏角增大,绕击跳闸率增大;总绕击跳闸率随避雷线横担增长而减小;各导线绕击跳闸率与杆塔结构间的关系复杂,需具体计算分析。理论分析和计算验证了该方法的实用性和有效性,具有一定的工程指导意义。