镍基耐高温自润滑刷式封严涂层研究

为满足先进航空发动机刷式封严对涂层材料自润滑耐磨性能的要求,采用等离子喷涂技术制备了NiCoCrAlY-Cr_2O_3和NiCoCrAlY-Cr_2O_3-AgMo两种复合涂层;采用扫描电子显微镜、X射线衍射、拉曼光谱和高温摩擦磨损试验等分析测试手段研究了涂层的物相组成、微观结构、力学性能以及摩擦磨损性能。结果表明:研制的两种新型涂层具有较低的孔隙率、较高的显微硬度和结合强度,从20℃到800℃的磨损量都在10~(-5)mm~3·N~(-1)·m~(-1)数量级,显示出优异的耐磨性能;NiCoCrAlY-Cr_2O_3涂层在摩擦系数随着温度的升高而降低,在800℃达到最低值0.3;NiCoCrAlY-Cr_2O_3-AgMo涂层从400~800℃的摩擦系数一直保持在0.23左右。对其摩擦机理的研究表明:400℃时涂层与高温合金GH4145对磨件之间形成连续的含Ag润滑膜,600℃以上时摩擦表面生成的Ag_2MoO_4自润滑相显著降低了涂层的摩擦和磨损。     

火箭涡轮泵机械密封研究综述

机械密封作为一种适合在苛刻工况下使用的轴封形式,在火箭各类涡轮泵中得到了广泛应用。涡轮泵的特殊性给机械密封的应用带来了一系列问题。对火箭涡轮泵机械密封方面的研究概况进行简述。首先从高速旋转轴系中的机械密封动力学方面,介绍了高速工况下轴系与机械密封的耦合关系和机械密封主动控制的尝试;然后对火箭涡轮泵机械密封中的摩擦磨损与润滑问题进行了介绍,涉及高速摩擦磨损下的可靠性、热力耦合与变形问题、材料配副、流体膜形成机理与端面几何特征优化等各方面问题;最后介绍了涡轮泵带压长期贮存的工作特点造成的静态慢渗问题。     

Reliability estimation of mechanical seals based on bivariate dependence analysis and considering model uncertainty

The reliability estimation of mechanical seals is of crucial importance due to their wide applications in pumps in various mechanical systems. Failure of mechanical seals might cause leakage, and might lead to system failure and other relevant consequences. In this study, the reliability estimation for mechanical seals based on bivariate dependence analysis and considering model uncertainty is proposed. The friction torque and leakage rate are two degradation performance indicators of mechanical seals that can be described by the Wiener process, Gamma process, and inverse Gaussian process. The dependence between the two indicators can be described by different copula functions. Then the model uncertainty is considered in the reliability estimation using the Bayesian Model Average (BMA) method, while the unknown parameters in the model are estimated by Bayesian Markov Chain Monte Carlo (MCMC) method. A numerical simulation study and fatigue crack study are conducted to demonstrate the effectiveness of the BMA method to capture model uncertainty. A degradation test of mechanical seals is conducted to verify the proposed model. The optimal stochastic process models for two performance indicators and copula function are determined based on the degradation data. The results show the necessity of using the BMA method in degradation modeling.     

Dynamic performance of a C/C composite finger seal in a tilting mode

The complex operating state of aeroengines has an impact on the performance of finger seals.However,little work has been focused on the issue and the dynamic performance of finger seals is also rarely studied.Therefore,a distributed mass equivalent model considering working conditions is proposed in this paper for solving the existing problems.The effects of the fiber bundle density and the preparation direction of the fiber bundle of a C/C composite on the dynamic performance of a finger seal are investigated in rotor tilt based on the proposed model.The difference between the C/C composite finger seal performances under the rotor precession and nutation tilt cases is also investigated.The results show that the fiber bundle density and the preparation direction of the fiber bundle have an influence on the dynamic performance of the finger seal as rotor tilt is considered,and the dynamic performance of the finger seal is different in the two kinds of tilting modes.In addition,a novel method for design of finger seals is presented based on the contact pressure between finger boots and the rotor.Finger seals with good leakage rates and low wear can be acquired in this method.     

基于多分类器决策融合的印鉴真伪鉴别方法

印鉴的自动识别对于实验银行印鉴数字化及计算机管理，实现银行对公业务的通存通兑有重大意义，符合票据法的要求，是银行业发展的需要，本文研究了模式识别领域中印鉴识别这一问题，提出了特征抽取和分类的新方法，基于差图像的成分统计特征抽取方法，发展了骨架图像的结构特征抽取方法，提出了特征点距离特征和笔划曲率特征内两种新的有效特征，本文提出了基于支持向量机（support vector machine,SVM)多分类器融合印鉴鉴别的方法，试验结果表明，本文的方法大大提高了印鉴的鉴别能力和可靠性，效果令人满意。     

流体动压密封设计

基于有限元Matlab软件平台对流体动压密封进行了计算机数值仿真分析与计算,研究了流体动压密封动环对数螺旋槽半径和螺旋角与流体动压密封开启力和泄漏量之间的关系,得出了流体动压密封设计准则;通过激光打标工艺试验得出了激光打标刻蚀对数螺旋槽的工艺规范,采用该工艺规范加工出的对数螺旋槽动环满足设计要求。流体动压密封介质运转试验结果表明:流体动压密封有限元Matlab计算机数值仿真分析与计算是合理的,流体动压密封设计和工艺规范是正确和有效的。     

Effects of tooth bending damage on the leakage performance and rotordynamic coefficients of labyrinth seals

Tooth bending damage resulting from an intense impact by the rotor sometimes occurs in the transient operation. To investigate the influence of after-damage clearance and tooth bending length on the leakage performance and rotordynamic coefficients of labyrinth seals, three tooth bending damages were taken into consideration, including the unbent tooth damage (abbreviated as Unbent), the partial tooth bending damage (abbreviated as Pbent) and the complete tooth bending damage (abbreviated as Cbent). The transient CFD solution was utilized to calculate the leakage flow rates and rotordynamic coefficients of labyrinth seals with clearances of 0.3, 0.4, 0.5, 0.6 mm for three tooth bending damages. The obtained result shows that the Unbent tooth damage leaks least while the Pbent tooth bending damage leaks most, and an increase of 6.1% for Cbent tooth bending damage and an increase of 19.4% for Pbent tooth bending damage are discovered at the tooth clearance of 0.6 mm in comparison with the Unbent tooth damage. Compared to the Unbent tooth damage, the effective damping for Pbent tooth bending damage and Cbent tooth bending damage is lower and drops by 9.7%–33.6% and 8.5%–22.6% respectively at the tooth clearance of 0.6 mm, suggesting that Pbent tooth bending damage or Cbent tooth bending damage tends to weaken the seal stability when compared to the Unbent tooth damage.     

周向收敛型动压式指尖密封的结构优化及其动态性能仿真

周向收敛型动压式指尖密封是一种可用于航空发动机的非接触式柔性气封.根据周向收敛型动压式指尖密封的工作性能要求,提出密封性能优化数学模型.采用人工神经网络和遗传算法相结合的优化方法,通过建立反向传播(BP)神经网络确定设计变量与目标函数之间的隐含关系,再利用遗传算法对周向收敛型动压式指尖密封进行结构参数优化,获得了性能较...     

封严涂层的性能评价及研究进展

封严涂层系统可以改善飞机燃气涡轮发动机中旋转部件和固定部件之间的密封性,已成为提高发动机工作效率．延长发动机服役寿命的主要方法之一。本文阐述了目前封严涂层的应用及性能评价的研究进展．描述了未来封严涂层的发展趋势。     

涡轮径向轮缘密封非定常燃气入侵和封严效率的数值研究

为防止燃气入侵涡轮盘腔,提高运行安全性,对盘腔和轮缘密封间隙内非定常流动机理进行了深入研究。采用数值求解三维URANS（Unsteady Reynolds Averaged Navier-Stokes）和SST湍流模型的方法,研究了涡轮径向轮缘密封的非定常燃气入侵和封严效率。数值计算的径向轮缘密封的封严效率和环量比与实验数据吻合一致,验证了数值方法的可靠性。分析了6种冷气流量下径向轮缘密封的非定常压力分布、封严效率和燃气入侵与冷气出流特性。研究表明：冷气流量的增加阻止了径向轮缘密封处的燃气入侵和强化了冷气出流,径向轮缘密封盘腔内的封严效率随着冷气流量的增加而增加;动盘附近的封严效率高于静盘;入侵燃气基本被限制在径向轮缘密封的间隙区域。径向轮缘密封间隙出口处的主流周向时均压力随着冷气流量的增加而增加,周向时均压力最大值与最小值的差值随着冷气流量的增加而减小。当动叶前缘与静叶尾缘距离较近且不断靠近的过程,主流周向压力最大值与最小值的差值增大,动静叶相分离的过程周向压力最大值和最小值的差值减小。在静叶和动叶间非定常干涉作用下,轮缘密封间隙出口区域主流周向压力最大值与最小值差值较大时刻的主流低压区域具有优良的封严效率,同时高压区域的燃气入侵导致封严效率降低。