船用6135型脱碳塔的性能优化

为了减少船舶CO2排放,本文以《MARPOL73/78公约》附则VI关于船舶CO2的排放为基础,采用NaOH溶液对船舶尾气中的CO2进行捕集。在研究了NaOH溶液与CO2气液两相传质的基础上,通过数值模拟与实验相结合的方法对船用脱碳塔性能进行优化。本文分别研究了脱碳塔的烟气进气入口形式、入口倾斜角度、喷嘴喷雾锥角与喷嘴的布置方式改变对脱碳塔脱碳效率的影响。研究结果表明,烟气进气入口形式为切入式进气、入口倾斜角度为15°、喷嘴喷雾锥角为90°、最上部的喷嘴向上喷射且高度与中部喷嘴位于同一水平面时,脱碳塔的脱碳效率能够提高4.42%。数值模拟结果与实验结果较吻合,为日后船用脱碳塔的设计及性能优化提供了参考。     

Performance limitations in trajectory tracking control for air-breathing hypersonic vehicles

An integrated approach that considers the performance limitations of tracking control systems for air-breathing hypersonic vehicles is proposed. First, a set of ascent trajectories is obtained as candidates for tracking control through a trajectory design method that considers the available acceleration. Second, the basic theory of performance limitations, which is adopted to calculate the limits on control performance through the trajectory, is integrated. The open-loop dynamics of air-breathing hypersonic vehicles is responsible for these limits on the control system. Comprehensive specifications on stability, tracking accuracy, and robustness are derived, and the flight envelope with constraints and control specifications is identified. Simulation results suggest that trajectory design should consider restrictions on control performance to obtain reliable solutions.     

交流频率及装配质量对单面自动焊接头性能的影响分析

开展了6 mm 2A14-T6铝合金对接接头的单面焊双面成形焊接工艺研究,详细分析了交流频率和装配精度对焊缝成形及接头力学性能的影响规律。结果表明:随着交流频率从60 Hz逐渐增加至80 Hz,2A14铝合金对接接头的平均抗拉强度从356 MPa降低至310 MPa,但接头延伸率没有显著变化。装配精度对焊缝质量的影响分析结果显示:随着装配间隙增大,焊缝背部成形效果变差。当间隙超过20%板厚时,焊缝易直接熔穿或单面切割,无法形成焊漏。随着装配错边增大,焊缝背部成形逐渐变差,出现咬边现象;接头力学性能测试显示,随着装配错边的增加,接头抗拉强度和延伸率均呈逐渐下降的趋势。在实际工程应用中,局部错边应控制在25%板厚范围内。     

转级模式对三维内转组合进气道模态转换性能的影响分析

为满足Xiamen Turbine Ejector Ramjet（XTER）组合循环发动机的工作需求,设计了一种具备涡轮、引射火箭、冲压三种模态,工作速域范围Ma∞=0~6的三维内转四通道组合进气道。重点对比分析了引射火箭至冲压的模态转换过程在固定马赫数转级（Ma∞=4.0）和区间马赫数转级（Ma∞=3.0~4.0）模式下的流动与性能特性。结果表明：该进气道在两种转级模式中均正常工作,进气道的捕获流量均能实现由引射火箭通道向冲压通道平稳过渡。固定马赫数转级时,由于分流板的调节,进气道总流量系数由0.92降至0.91,喉道马赫数从2.47降至1.99。引射火箭通道出口总压恢复系数随分流板的逐渐关闭从0.28下降至0.13,冲压通道出口总压恢复系数从0.27升至0.48。区间马赫数转级时,进气道总流量系数从0.89上升至0.91,喉道马赫数从1.63增至1.99。引射火箭通道的出口总压恢复系数随分流板的逐渐关闭从0.60下降至0.13,冲压通道出口的总压恢复系数从0.55下降至0.48。两种转级模式下,冲压通道的抗反压能力均逐渐增强,但结合通道内流动特性与各项性能参数,选择区间马赫数下转级可提高该组合进气道的综合气动性能。     

微阴极电弧推力器工作性能影响因素研究

采用试验方法研究了微阴极电弧推力器中峰值放电电流及外加磁场对其推力、比冲、寿命的影响规律。试验结果表明:峰值放电电流增加,阴极烧蚀量增加,元冲量增大;相比于较低的峰值放电电流(10A),更高的峰值放电电流(40A)可延长推力器的工作寿命;外加磁场增强,推力器喷射等离子体轴向速度增大,比冲增加。     

基于性能退化缓解的双发推力匹配控制

为了解决退化程度不同而导致的双发推力不匹配问题,首先介绍基于发动机性能退化缓解控制的双发推力匹配控制系统(在发动机基准控制系统的基础上添加外围控制回路实现对推力的间接控制,并通过设定双发共同遵循的期望推力减少由于发动机退化程度不同造成的双发推力差异),之后对该系统所涉及的推力设定、参数估计、转速指令修正等关键技术进行研究,最后在MATLAB/Simulink环境下进行仿真验证,结果表明:该系统可以在发动机参数限制范围内合理地设定双发共同遵循的期望推力,减少推力差异,满足自动协调双发推力匹配的设计要求。     

单线圈小功率SPT设计及实验

为了研究小功率SPT（稳态等离子推力器）内部的磁场分布和性能特性,应用参数化方法研制了单线圈小功率SPT。利用简化模型计算了磁场分布,并与实验进行对比,对其整体性能特性进行了实验研究。磁场测量结果和计算结果基本吻合,说明简化计算模型的可行性;实验中SPT能够顺利点火,性能测试结果达到了设计要求,结果表明,SPT可稳定工作在100～450W;当出口最大磁感应强度为300Gs,梯度为300Gs/cm时,SPT效率较高。     

Optimum detection and location estimation of target lines in the range-time space of a search radar

The average likelihood ratio detector is derived as the optimum detector for detecting a target line with unknown normal parameters in the range-time data space of a search radar, which is corrupted by Gaussian noise. The receiver operation characteristics of this optimum detector is derived to evaluate its performance improvement in comparison with the Hough detector, which uses the return signal of several successive scans to achieve a non-coherent integration improvement and get a better performance than the conventional detector. This comparison, which is done through analytic derivations and also through simulation results, shows that the average likelihood ratio detector has a better performance for different SNR values. This result is justified by showing the disadvantages of the Hough method, which are eliminated by the optimum detector. To have an estimate for the location of the detected target line in the optimum detection method as the Hough method, which detects and localizes the target lines simultaneously, we present the maximum a posteriori probability estimator. The estimation performance of the two methods is then compared and it is shown that the maximum a posteriori probability estimator localizes the detected target lines with a better performance in comparison with the Hough method.     

航天器测控系统数据库特点及性能测试策略

航天器测控系统的数据量大,信息关联复杂,一般都用大型的关系数据库作为其数据存储与管理的基础平台。存储系统建成后,数据库性能究竟如何,数据库性能该如何衡量,这一直是系统集成者和应用者关心的课题。本文从测控数据库的特点出发,客观分析了数据库实际运行性能,提出了一种较为全面的航天器测控系统数据库的性能测试策略。     

用线性曲线拟合判断固态功率放大器饱和点

在自动化测量系统中,软件需要根据测量数据自动寻找并判断功率放大器的饱和点。在受噪声影响较大的在轨测试中,这是个难点。本文根据固态功率放大器AM/AM特性曲线的特点,提出一种使用多项式线性曲线拟合测量数据建立增益曲线预测关系式,并通过增益趋势线准确判断饱和点的方法。经过真星在轨测试验证,该方法与实际特性吻合很好。