Efficiency optimized fuel supply strategy of aircraft engine based on air-fuel ratio control

Accurate fuel injection control of aircraft engine can optimize the energy efficiency of UAV power system while meeting the propeller speed requirement. Traditional injection control method such as open-loop calibration causes instability of fuel supply which brings the risk of power loss of UAV. Considering that the closed-loop control of AFR can ensure a stable fuel feeding, this paper proposes an AFR control based fuel supply strategy in order to improve the efficiency of fuel-powered UAV while obtaining the required engine speed. According to the optimum fuel injection results, we implement fuzzy-PID method to control the set AFR in different situations. Through simulation and experiment studies, the results indicate that, to begin with, the calibrated mathematical model of the aircraft engine is effective. Next, this fuel supply strategy based on AFR control can normally realize the engine speed regulation, and the applied control algorithm can eliminate the overshoot of AFR throughout all the working progress. What is more,the fuel supply strategy can averagely shorten the response time of the engine speed by about two seconds. In addition, compared with the open-loop calibration, in this work the power efficiency is improved by 9% to 33%. Last but not the least, the endurance can be improved by 30 min with a normal engine speed. This paper can be a reference for the optimization of UAV aircraft engine.     

用PIV技术研究四角切圆锅炉燃烧器区冷态燃烧流场的湍流积分尺度

四角切圆锅炉内煤粉的燃烧过程对提高锅炉运行效率及NOX减排有着显著的现实意义。通过搭建四角切圆锅炉冷态模型,利用粒子成像测速技（Particle Image Velocimetry）,采用空间相关分析方法,针对燃烧器区四角射流复杂湍流的涡拟序结构,开展基于湍流积分尺度来表征的3个典型水平层面涡尺度分布规律研究。通过对湍流积分尺度和时均速度的相关分析研究,认为冷态燃烧器区湍流涡尺度分布不仅与风口流速相关,同时还与风层位置密切相关,并不与风口流速呈线性变化规律,上一次风层涡尺度分布与其它两个风层的相比存在很大差异,因此湍流积分尺度的研究对煤粉高效洁净燃烧具有一定的理论指导意义。     

Milling surface roughness for 7050 aluminum alloy cavity influenced by nozzle position of nanofluid minimum quantity lubrication

In nanofluid minimum quantity lubrication (NMQL) milling of aviation aluminum alloy, it is the bottleneck problem to adjust the position parameters (target distance, incidence angle, and elevation angle) of the nozzle to improve the surface roughness of milling, which has large and uncontrollable errors. In this paper, the influence law of milling cutter speed, helical angle, and cavity shape on the flow field around the milling cutter was studied, and the optimal nozzle profile parameters were obtained. Using 7050 aluminum alloy as the workpiece material, the milling experiment of the NMQL cavity was conducted by utilizing cottonseed oil-based Al₂O₃ nanofluid. Results show that the high velocity of the surrounding air flow field and the strong gas barrier could be attributed to high rotating velocities of the milling cutter. The incidence angle of the nozzle was consistent with the helical angle of the milling cutter, the target distance was appropriate at 25–30 mm, and the elevation angle was suitable at 60°–65°. The range and variance analyses of the signal-to-noise ratio of milling force and roughness were performed, and the chip morphology was observed and analyzed. The results show that the optimal combination of nozzle position parameters was the target distance of 30 mm, the incidence angle of 35°, and the elevation angle of 60°. Among these parameters, target distance had the largest impact on cutting performance with a contribution rate of more than 55%, followed by incidence angle and elevation contribution rate. Analysis by orthogonal experiment revealed that the nozzle position parameters were appropriate, and R_a (0.087 μm) was reduced by 30.4% from the maximum value (0.125 μm). Moreover, R_sm (0.05 mm) was minimum, which was 36% lower than that of the seventh group (R_sm = 0.078 mm).     

子午工程探空火箭伸杆展开机构技术研究

根据子午工程探空火箭电子和电场探测需求,设计了套筒式伸杆展开机构.通过电子伸杆和电场伸杆的结构方案设计、力学仿真分析,伸杆单项力学试验,伸杆与整箭的匹配力学试验以及伸杆飞行试验验证得出,该伸杆技术方案合理可行,伸杆总体构型、布局设计及结构方案设计满足科学探测各项技术指标的要求.      

Anti-plane problem of four edge cracks emanating from a square hole in piezoelectric solids

By constructing a new numerical conformal mapping and using the Stroh-type for-mulism, an anti-plane problem of four edge cracks emanating from a square hole in piezoelectric solids is investigated. The explicit expressions of the complex potential function, field intensity fac-tors, energy release rates and mechanical strain energy release rate near the crack tip are obtained under the assumptions that the surfaces of the cracks and hole are electrically permeable and elec-trically impermeable. Numerical examples are presented to show the influences of the geometrical parameters of defects and applied mechanical/electrical loads on the energy release rate and mechanical strain energy release rate under two electrical boundary conditions.     

基于移动最小二乘法的机载SAR成像运动误差补偿方法

机载SAR平台在飞行过程中产生的运动误差会导致成像质量下降,利用测量数据提取运动误差是机载SAR运动补偿的重要手段之一。通过对机载SAR运动误差理论的推导,提出一种基于移动最小二乘法的机载SAR成像运动补偿方法,方法借助于惯性导航系统记录的东北天三维速度信息,对其进行处理,进而获得雷达平台的三维空间信息,再与后向投影算法结合,完成SAR成像运动补偿。方法是对最小二乘法进行改进,使其不需要对数据进行分段估计和平滑,还可以保证估计结果的正确性。实验结果验证方法对运动误差估计的准确性和有效性。     

区间贝齐尔曲面的逼近(英文)

根据摄动理论,提出一种使用最小能量法的区间贝齐尔曲面逼近有理曲面的方法。该方法采用了恰当的范数,可以对摄动曲面以较多的限制,并通过实例演示了该方法的应用。实验可以与细分技术相结合,得到有理曲面的分片区间多项式的逼近。     

微量Er对Al-Mg-Mn合金组织与力学性能的影响

采用半连续铸造法制备Al-6.8Mg-0.3Mn和Al-6.8Mg-0.3Mn-0.4Er(质量分数,%)两种合金铸锭。合金铸锭经均匀化处理—多道次热轧成4mm薄板;研究不同退火温度下微量Er对Al-Mg-Mn合金微观组织与力学性能的影响。结果表明:添加微量Er能显著提高Al-Mg-Mn合金强度,改善合金强度和塑性的配合,能明显提高合金的抗再结晶能力和室温力学性能;Al-Mg-Mn-Er合金板材经300℃退火1h后可获得理想的综合力学性能,其σb、σs与ψ分别为421MPa,310MPa和18.3%。     

固体推进剂药浆改进Herschel-Bukely模型及其在仿真分析中的应用

为研究固化反应对一种固体推进剂药浆流变参数的影响并建立相应的仿真模型,对药浆进行了大量流变学实验,对实验数据进行了分析。得到了该固体推进剂药浆各流变参数随时间的变化规律,并将其拟合成时间的函数。将时间变量引入Herschel-Bukely模型,建立新的本构模型。使用新模型,对药浆流平实验进行了数值计算。计算结果与实验结果吻合度较高,证明改进后的本构模型可以较好地表征药浆的流变特性。     

高光谱侦察技术特点及其对地面军事目标威胁分析

介绍了高光谱成像探测的原理和特点。给出了国外高光谱侦察技术的发展现状、主要计划项目和趋势。讨论了高光谱侦察技术在战场情报侦察、伪装隐身目标探测,以及机动目标追踪识别等对地面军事目标的侦察威胁。