石墨密封材料高温摩擦磨损行为及预测

利用HT-1000型高温摩擦磨损试验机研究了石墨M210密封材料高温下摩擦磨损性能,采用扫描电子显微镜（SEM）观察分析了磨损表面形貌.基于试验数据,通过灰色理论GM（1,1）建立了摩擦因数和磨损率预测模型.结果表明:石墨M210密封材料摩擦因数呈先增大再减小,而后趋于一稳定值,试验温度为450℃时,摩擦因数最小;磨损率随着试验温度升高而增大.试验温度在低于300℃,磨损表面具有明显的黏着、撕裂和无序的塑流动痕迹,高于400℃时,塑流动痕迹具有明显的方向性,出现了剥落和断裂痕迹.温度较低时,石墨材料表面主要是水汽物理吸附膜起润滑作用,随着试验温度升高,由物理吸附膜润滑逐渐转向反应膜润滑.基于试验数据建立了精度等级均为1级的摩擦因数和磨损率的预测模型.      

直升机发动机舱通风、遮挡和隔热对红外辐射特性的影响

为了降低直升机发动机舱蒙皮的温度,减弱直升机红外辐射能量,采用数值仿真的方法研究其处于悬停状态、考虑了旋翼下洗作用的发动机舱蒙皮温度场和直升机红外辐射特性.针对基准发动机舱结构提出了在舱内加设辐射遮挡套、增开通风百叶窗、排气管尾缘修型和蒙皮内侧敷设隔热层等改进方案,研究了上述改进方案对直升机发动机舱蒙皮温度场和红外辐射特性的影响,得到了如下结论:①在发动机舱内加设辐射遮挡套后,整机侧向探测方位角内3~5μm红外辐射强度出现了约25%的增幅,8~14μm波段红外辐射与原始结构相当.②在发动机舱顶部增开通风百叶窗,直升机3~5μm红外辐射低于原始结构约12%,8~14μm波段红外辐射与原始结构相当.③在发动机舱顶部增开通风百叶窗的基础上,对排气管尾缘采取延伸遮挡以及在发动机舱蒙皮内侧敷设隔热层,整机3~5μm波段红外辐射的最大值下降约70%,8~14μm波段红外辐射的最大值下降约10%.      

Influence of measure-density on combustor characteristics

The apparatus of scan measurement was used to gather the temperature pattern at the combustor outlet,where the average working temperature of gas was about 1700Kand the maximum temperature was about 1 950K.Consequently,the measurement part was cooled by water or air.Usually,for intermittent measurement devices,the interval of circle angel could be changed to get a high-density temperature distribution.A continuous measurement manner was adopted to get point in circle.The angle between two measurepoints was 1.286°.The annular combustor outlet was about 40to 50mm in height,where 5or 6measure points were usually arranged.In this device,10measure points were arranged in a range of 45.5mm.Four thermocouples were arranged in circle to obtain 2 800measure-points of the temperature field in a single experiment.Data were drawn from the whole datasheet at intervals.Each group of data whose number decreased in turn,included temperature points of 2 800,1 400,700,and 350,respectively.Several groups of temperature distributions with different densities were established.Subsequently,data processing was conducted to calculate the main combustor characteristics,including arithmetic or integral average temperature,OTDF(overall temperature distribution factor)and RTDF(radial temperature distribution factor).It is found that the data from different groups with different measuring densities result in significant difference on the combustor characteristics.The veracity of temperature characteristics increases with the growing measure-density.     

取样密度对燃烧室试验测量结果的影响

在航空发动机和燃气轮机燃烧室部件试验中,取样密度会对燃烧室出口温度测量结果产生影响,如果取样密度过小,会造成燃烧室出口温度测量值与"实际值"之间偏离度过大。基于此,对3种燃烧室的试验数据进行了分析。同时将试验采集到的"高取样密度"的原始数据沿圆周方向进行均匀"拆分","拆分后"得到不同密度的"低取样密度"数据,将该数据与原始"高取样密度"试验数据的分析结果进行了对比,得出了取样密度与测量偏离度之间的关系,并给出了满足工程研制需要的取样密度。     

限制域、预混气初始温度对多孔介质表面火焰熄火特性的影响

为了对基于多孔介质表面火焰的微型燃烧室技术进行优化设计,以甲烷/空气预混气为研究对象,针对不同的限制域、预混气初始温度,开展了多孔介质表面火焰熄火特性实验研究.实验结果表明:在石英玻璃限制域下,多孔介质表面火焰可以维持在0.188~0.436m/s的低预混气速度下,速度升高容易发生推举和吹熄;而限制域的长度未产生影响作用;随着预混气初始温度从293K升高至550K,多孔介质表面火焰的熄火速度极限得以提高.当量比为1.0时,预混气熄火速度从293K的1.176m/s增加至550K的2.678m/s,并存在不同斜率的上升过程,而初始温度对熄火本质没有影响.     

光子晶体光纤陀螺仪关键技术研究及进展

光子晶体光纤具有辐照不敏感、热敏感度低等特点,可以显著增强光纤陀螺仪的空间环境适应性,并有利于减小光纤陀螺重量、尺寸和功耗。本文分析了光子带隙型光子晶体光纤和折射率导引型光子晶体光纤的特点,详细阐述了光子晶体光纤陀螺仪的原理、关键技术及国内外进展。     

Numerical investigation of windage heating within shrouded rotor-stator cavity system with central inflow

The rotating disk surface temperature rise due to windage heating effect by numerically modeling the turbulent flow within a rotor-stator cavity which is available with a peripheral shroud and imposed through airflow was dealt with. The windage heating may be defined as viscous friction heating caused by relative velocity differences across the boundary layers between the fluid and the rotating disk surface. The kinetic energy dissipation process could transform the rotating shaft power into thermal heating. Commercial finite volume based solver, ANSYS/CFX was employed to numerically simulate this physical process by using the shear stress transport (SST) turbulence model. CFD results include the rotating disk surface temperature axial distribution and tangential velocity distribution of the fluid domain. The velocity difference between the result obtained by particle image velocimetry (PIV) experiments and CFD simulation are within 5%. The adiabatic disk temperature rise can be calculated by the tangential velocity of disk and fluid in large gap ratio and turbulent parameter. CFD temperature distribution results and those estimated via velocity differences are within 10%.     

离心通风器通风阻力的影响因素

为分析航空发动机离心通风器通风阻力的影响因素,应用计算流体动力学(CFD)和雷诺应力模型(RSM)对离心通风器内流场进行数值计算.比较相同工况下通风阻力的计算与试验值,保证模型的适用性.通过计算得到不同工况和结构的足够拟合数量的离心通风器阻力值,对数据进行二元二次空间趋势面回归分析.结果表明:流量和转速的增加都带来更大的通风阻力;通风孔偏心设计与减小辐板顶圆半径可以减小通风阻力,通风孔偏心设计存在最佳偏心距约为7.5mm.     

Ti6Al4V钛合金大进给铣削切削力与切削温度的试验研究

采用可转位涂层硬质合金刀具对Ti6Al4V钛合金进行了大进给铣削试验,研究分析了大进给铣削Ti6Al4V钛合金时每齿进给量、切削速度、轴向切深以及径向切深等切削参数对切削力和切削温度的影响。研究结果表明,随着每齿进给量和轴向切深的增加,切削力均呈现增大的趋势,而切削速度和径向切深对削力的影响并不明显;随着每齿进给量和切削速度的提高,切削温度亦呈现升高的趋势。     

高性能抗氧化SmCo高温永磁材料

航空航天及现代工业高技术领域对使用温度达到500℃的永磁材料提出了明确需求。SmCo永磁材料因其高的居里温度、强的磁晶各向异性和高的饱和磁化强度成为现有永磁材料中高温永磁材料的首选。然而,商用的2∶17型SmCo合金因其高的矫顽力温度系数使其最大工作温度不超过300℃。本文重点研究了2∶17型SmCo高温永磁材料、1∶7型纳米晶SmCo高温永磁材料以及SmCo高温永磁材料的抗氧化行为;研制出了可以在500℃及550℃应用的2∶17型SmCo高温永磁体;获得了具有各向异性的1∶7型纳米晶SmCo磁体;1∶7型纳米晶SmCo永磁材料在500℃具有良好的结构和磁性能时效稳定性;合金化和表面改性显著提高了SmCo磁体的高温抗氧化能力。