Aerodynamic optimization design of general parameters for cycloidal propeller in hover based on surrogate model

A surrogate-model-based aerodynamic optimization design method for cycloidal propeller in hover was proposed, in order to improve its aerodynamic efficiency, and analyze the basic criteria for its aerodynamic optimization design. The reliability and applicability of overset mesh method were verified. An optimization method based on Kriging surrogate model was proposed to optimize the geometric parameters for cycloidal propeller in hover with the use of genetic algorithm. The optimization results showed that the thrust coefficient was increased by 3.56%, the torque coefficient reduced by 12.05%, and the figure of merit (FM) increased by 19.93%. The optimization results verified the feasibility of this design idea. Although the optimization was only carried out at a single rotation speed, the aerodynamic efficiency was also significantly improved over a wide range of rotation speeds. The optimal configuration characteristics for micro and small-sized cycloidal propeller were: solidity of 0.2-0.22, maximum pitch angle of 25°-35°, pitch axis locating at 35%-45% of the blade chord length.      

三元共掺杂对YSZ热障涂层热物理性能的影响

采用NiO、Er_2O_3、Yb_2O_3、Y-2O_3、ZrO_2粉末为原料,用高温固相合成法制备复合陶瓷材料,研究该复合陶瓷材料的比热、热扩散系数、热导率等热物理性能,并与传统8YSZ热障涂层材料进行对比。利用XRD测定所制备的陶瓷样块的晶体结构和物相组成,分析该陶瓷试样的物相组成及高温相稳定性。结果表明:NiO、Er_2O_3、Yb_2O_3共掺YSZ后,室温至1500℃范围内的热扩散系数为0.36～0.56 mm^2/s,与8YSZ相比,降低了约20%;室温至1500℃的热导率为1.45～1.55 W/(m·K),比8YSZ降低了18%;2EYNYSZ陶瓷材料具有单一的相结构,经1500℃热处理100 h之内不发生相变。     

腐蚀条件下基于Gerber模型的DFR推导及实测

为了研究等寿命曲线模型的选取对细节疲劳额定值计算结果的影响,针对六种典型航空材料对比了Gerber模型和Goodman模型对于高周疲劳数据的拟合精度;推导基于Gerber模型的DFR计算公式、腐蚀折算系数CC的表达式;针对2024-T3铝合金(表面阳极化)进行了预腐蚀0 h、6 h、12 h、24 h、36 h和72 h的疲劳实验并分析预腐蚀72 h的疲劳断口。结果表明:Gerber模型适用于LY12CZ等铝合金,并且在N_95/95>10~5次时,基于Gerber模型的DFR法才能发挥延性材料的潜能;随着预腐蚀时间增长,2024-T3铝合金DFR值下降,基于Gerber模型计算的DFR分别为84.251 MPa、84.721 MPa、79.683 MPa、80.745 MPa、77.026 MPa和74.996 MPa,腐蚀折算系数CC为1.006、0.946、0.958、0.914、0.890,拟合得到DFR随预腐蚀时长的变化曲线是DFR=84.251[lg(t+10)]^-0.15578;断口分析发现预腐蚀产生的蚀坑和材料中的夹杂物会加速疲劳裂纹的形成和扩展,导致结构的疲劳性能降低,但与裸材相比,阳极化过的试件的DFR在腐蚀环境中下降趋势减缓。     

民机飞行结冰参数的模拟与校准

结冰问题的研究对于民用飞机设计十分重要,采用结冰风洞试验是主要的方法之一,欧美国家有很多成熟的结冰风洞用于型号研究。结冰风洞中需要对很多参数进行控制,其中水雾参数精确控制的难度很大,而且一般通过间接方法来进行测试校准,往往误差较大,导致不同结冰风洞试验结果往往有所差异。文章介绍了在意大利宇航中心的IWT 结冰风洞完成的冰风洞校准试验,对结冰风洞水雾参数校准方法进行了阐述,为民机结冰风洞研究提供参考。     

发动机引流推力矢量方案数值研究

针对从燃烧室引流喷射的推力矢量控制方案,采用数值模拟的方法进行流场计算与分析,比较了引流向喷管内喷射、向无弹翼的弹体外侧喷射和向有弹翼的弹体外侧喷射三种方案。数值模拟结果表明:向喷管内引流的侧向力与喷流位置和喷射角度相关,最大侧向力与轴向推力的比值与引流管喉部面积占总喉部面积的比值大致相等;向弹体外引流时,喷口附近的弹翼对流场有很大的影响,若没有弹翼,则侧向力放大因子小于1,不宜采用;弹翼对喷流侧向力起显著的增强作用,放大因子可达1.5或更高。     

复合材料管道连接件真空辅助成型工艺树脂流动研究

对采用真空辅助树脂传递模塑成型工艺(VARTM)制造复合材料管道连接件的树脂流动过程进行分析,考虑树脂注模工况下的注射口和出射口位置,采用有限元/控制体积方法分别模拟了4种可能树脂注模方式所需工艺时间和树脂流动前锋形状,并确定了合适的注模方式。模拟结果表明:与点注射的树脂注模方式相比,线注射方式可以得到更均匀的树脂流动前锋;进而采用线注射-线出射树脂注模方式能够有效浸润织物。采用模拟所得注模方式开展了VARTM工艺试验,制造了复合材料管道连接件缩比件和整体连接件筒构件,所得试验结果与数值模拟结果一致,验证了模拟结果的可靠性。     

Numerical simulations of turbulent flows in aeroramp injector/gas-pilot flame scramjet

To uncover the internal flow characteristics in an ethylene-fueled aeroramp injector/gaspilot(ARI/G-P)flame scramjet,a Reynolds-averaged Navier-Stokes(RANS)solver is constructed under a hybrid polyhedral cell finite volume frame.The shear stress transport(SST)k-x model is used to predict the turbulence,while the Overmann’s compressibility corrected laminar flamelet model is adopted to simulate the turbulent combustion.Nonreactive computations for Case 1(G-P jet on),Case 2(ARI jets on),and Case 3(both ARI and G-P jets on)were conducted to analyze the mixing mechanism,while reactive Cases 4–7 at equivalent ratios of 0.380,0.278,0.199 and0.167 respectively were calculated to investigate the flame structure and combustion modes.The numerical results are compared well to those of the experiments.It is shown that the G-P jet plays significant role in both the fuel/air mixing and flame holding processes;the combustion for the four reactive cases takes place intensively in the regions downstream of the ARI/G-P unit;Cases 4 and 5are under subsonic combustion mode,whereas Cases 6 and 7 are mode transition critical and supersonic combustion cases,respectively;the mode transition equivalent ratio is approximately 0.20.     

下端壁流向槽抽吸对高负荷扇形扩压叶栅性能影响的数值研究

为探究附面层抽吸对亚声速高负荷扇形扩压叶栅气动性能和流场结构的影响,利用数值方法对叶栅进行了下端壁流向槽附面层抽吸的研究。对比原型和各抽吸方案发现:下端壁附面层的抽吸可以有效抑制下角区低能流体的分离及回流,降低下角区总压损失并提升叶栅近端壁区域的扩压能力,但上角区分离会略有加剧。当抽吸质量流量为原型叶栅质量流量的0.50%时,抽吸槽起始于角区分离点下游附近的抽吸方案(EW2)效果最佳,叶栅整体总压损失降低27.65%,静压比提升8.69%。     

碳纤维预浸带切割剪裁平台系统研究

自动铺带技术是碳纤维复合材料的重要成型技术。根据最新提出的预浸带切割和铺放分离的"两步法"铺带技术,详细探讨预浸带切割平台的设计方案。设计方案包括预浸带双刀切割试验平台设计和搭建,基于自动铺带轨迹规划软件的双刀切割轨迹算法的研究和切割信息的植入,以及试验探究切割平台双刀切割典型边界所存在的问题及试验误差分析,以期为"两步法"铺带的研究提供基础。     

融合机床精度与工艺参数的铣削误差预测模型

为弥补现有五轴联动数控铣床加工飞机结构件的加工精度评估系统的不足,提出利用机床精度检测数据和零件特征及其工艺参数来构建评估指标体系,基于BP神经网络建立了飞机结构件加工误差预测模型。通过完成训练的网络权值分布,计算出各输入指标对最后评估结果的影响,并通过实例分析检验了模型的可靠性。结果表明,经BP神经网络模型训练得到的结果和样本零件的三坐标测量机测量数据基本吻合,选取的评价指标具有有效性。该评估模型能够有效地融合机床精度检测数据和零件特征及其加工工艺参数,对飞机结构件的铣削加工误差进行预测。