腈纶/芳纶共混短纤维用量对柔性绝热层材料性能的影响

比较了腈纶短纤维增强EPDM／NBR共混橡胶（EN体系）、芳纶短纤维增强EPDM／NBR共混橡胶（EA体系）、腈纶／芳纶混杂短纤维增强EPDM／NBR共混橡胶（ENA体系）等3种体系中,短纤维用量对材料不同方向上力学性能的影响;EA和ENA两种不同体系中,短纤维用量对材料烧蚀性能和相对密度的影响。在短纤维用量为6份时,ENA体系的拉伸强度和伸长率比EA体系大,烧蚀性能比EA体系好,相对密度也比EA体系低。     

白炭黑与硼酚醛树脂用量对EPDM/NBR柔性绝热层材料性能的影响

通过比较分析白炭黑与硼酚醛树脂用量对EPDM/NBR柔性绝热层材料拉伸强度、断裂伸长率、质量烧蚀速率和线烧蚀速率以及相对密度的影响,得出随着白炭黑或硼酚醛树脂用量的增加,柔性绝热层材料的拉伸强度和相对密度呈递增趋势,烧蚀速率呈递减趋势,断裂伸长率在白炭黑和FB用量各自为20份时有极大值.     

固液混合火箭发动机固体燃料的燃速计算

分析了固液混合火箭发动机的燃烧特点、燃烧中气相过程和固体燃料内部的传热过程,利用由传热理论得出的固体燃料燃速公式和阿累尼乌斯(Arrhenius)燃速公式耦合计算,得到了燃速与氧化剂流率、轴向距离、装药初温和时间的变化规律.计算结果表明固体燃料燃速主要受氧化剂流率和轴向距离的影响,随氧化剂流率的增加而增加,随轴向距离的增加而减小.固体燃料燃速温度敏感性小,在设计发动机时可以不考虑装药初温的影响.利用热力计算得到了绝热燃烧温度与氧化剂流率和药柱长度的变化规律,绝热燃烧温度随氧化剂流率的增加存在一最大值.计算结果与相关文献的报道比较吻合,为进一步研究固液混合火箭发动机的燃烧及流动问题打好了基础.     

航材消耗的时间序列分析

本文采用时间序列分析法对某种航材故障率进行预测,用移动平均法消除时间序列的长期趋势和周期变动,然后按月平均法求出季节指数,并对季节指数进行调整,然后根据拟合的趋势方程对此种航材的故障率进行预测.其结果能为航材的可靠性保障提供理论依据.     

Simulation and experimental investigation of inner-jet electrochemical grinding of GH4169 alloy

GH4169 alloy is one of the most commonly used materials in aero engine turbine blades, but its machinability is poor because of its excellent strength at high temperatures. Electrochemical machining (ECM) has become a common method for machining this alloy and other difficult-to-machine materials. Electrochemical grinding (ECG) is a hybrid process combining ECM and conventional grinding. In this paper, investigations conducted on inner-jet ECG of GH4169 alloy are described. Two types of inner-jet ECG grinding wheels were used to machine a flat bottom surface. The machining process was simulated using COMSOL software, and machining gaps under different machining parameters were obtained. In addition, maximum feed rates and maximum material removal rates under different machining parameters were studied experimentally. The maximum sizes and the uniformity of the distributions of the gaps machined by the two grinding wheels were compared. The effects of different applied voltages on the machining results were also investigated.     

Joint TDOA,FDOA and differential Doppler rate estimation: Method and its performance analysis

Considering the estimation accuracy reduction of Frequency Difference of Arrival(FDOA) caused by relative Doppler companding, a joint Time Difference of Arrival(TDOA),FDOA and differential Doppler rate estimation method is proposed and its Cramer-Rao low bound is derived in this paper.Firstly, second-order ambiguity function is utilized to reduce the dimensionality and estimate initial TDOA and differential Doppler rate.Secondly, the TDOA estimation is updated and FDOA is obtained using cross ambiguity function, in which relative Doppler companding is compensated by the existing differential Doppler rate.Thirdly, differential Doppler rate estimation is updated using cross estimator.Theoretical analysis on estimation variance and Cramer-Rao low bound shows that the final estimation of TDOA, FDOA and differential Doppler rate performs well at both low and high signal–noise ratio, although the initial estimation accuracy of TDOA and differential Doppler rate is relatively poor under low signal–noise ratio conditions.Simulation results finally verify the theoretical analysis and show that the proposed method can overcome relative Doppler companding problem and performs well for all TDOA, FDOA and differential Doppler rate estimation.     

基于MIV的碳钢大气腐蚀速率影响因子权重分析

通过平均影响值（MIV）影响因子权重分析算法,以碳钢Q235、Ste355、St12和Q450腐蚀速率的暴露时间、气候因素和环境因素数据为依据,以|MIV|值为评价依据,定量分析15种影响因子（暴露时间、平均温度、平均相对湿度、日照时数、降水量、平均风速、海盐粒子浓度、SO₂、HCl、NO₂、H₂S、硫酸盐化速率、NH₃、降尘量-非水溶性、降尘量-水溶性）对碳钢腐蚀速率影响的权重大小。结果表明: 当MIV调节率从5%逐步递增至25%时,同种影响因子对腐蚀速率的影响权重变化不大,但4种碳钢对各影响因子的敏感度略有不同;气候因素对腐蚀速率影响最大,其次为暴露时间,环境因素中SO₂和降尘量对腐蚀速率影响较大;平均相对湿度、日照时数、平均温度是影响腐蚀速率最主要的3个因子。      

多腔室凹槽对涡轮叶顶流动传热特性影响的数值研究

现代航空发动机为获得更大输出功率和推重比,涡轮进口温度不断提高,因此高温燃气在无围带动叶叶顶间隙的泄漏引起叶顶热负荷急剧增加,甚至导致叶片烧蚀、失效,严重影响涡轮运行安全。为降低叶顶热负荷,抑制泄漏流,本文以GE-E3第一级叶栅为研究对象,通过求解三维Reynolds-Averaged Navier-Stokes (RANS）方程和湍流模型研究了多腔室凹槽对叶顶流动传热性能的影响。研究结果表明:在多腔室凹槽中,叶顶换热系数随着叶顶空腔数量的增加而逐渐减小,凹槽腔室内刮削涡可有效降低泄漏流量。格栅结构在凹槽中起到“气动篦齿”作用,在0至20%的流向区域内泄漏流控制效果显著。Case7的叶顶换热系数最小,比Case1降低了40.44％;Case2和Case3可显著抑制叶顶泄漏量,与Case1相比分别降低了33.82％、28.90％。     

高燃速HTPB／IPDI推进剂低温力学性能研究（Ⅰ）细AP及工艺助剂PA？…

研究细粒度ＡＰ及工艺助剂ＰＡ含量对丁羟高燃速推进剂低温（－４０℃）力学性能的影响，结果显示：大量细粒度ＡＰ加入高燃速配方中，一方面加剧了单向拉伸过程中填料（主要是细ＡＰ）颗粒附近的应力集中；另一方面降低了填料／粘合剂间的粘结强度，是造成低温力学性能偏低的主要原因。由于工艺助剂ＰＡ极性及刚性，使得它易于富集于填料表面，低温下降低了界面层的柔性，物理作用也极大地束缚了填料附近粘合剂网络的分子运动，因此     

应用光透仪测量细高氯酸铵粒度的研究

在固体火箭发动机推进剂中,细高氯酸铵的粒度,通常是用沉降法测量.此法的缺点是,测试周期长,费时费力.应用先透仪测细高氯酸铵粒度可大大缩短测试时间,省时省力,并消除了人工处理数据的误差.本文给出了光透仪测细高氯酸铵粒度的精度;光透法与沉降法测细高氯酸铵粒度的相关关系及其精度;论述了在大型发动机装药中,应用光透仪测细高氯酸铵粒度可控制推进剂的燃速,保证了发动机产品的质量.