Experimental investigation of a gliding discharge plasma jet igniter

Relight of jet engines at high altitude is difficult due to the relatively low pressure and temperature of inlet air. The penetration of initial flame kernel affects the ignition probability in the turbine engine combustor greatly. In order to achieve successful ignition at high altitude, a deeper penetration of initial flame kernel should be generated. In this study, a Gliding Arc Plasma Jet Igniter(GAPJI) is designed to induce initial flame kernel with deeper penetration to achieve successful ...     

基于边界层燃烧方法的宽速域飞行器内流道减阻研究

为了降低宽速域飞行器的内流阻力，基于边界层燃烧方法，分析了系列进口马赫数条件下二维扩散段总阻力中摩阻和压阻的特性，研究了不同进口马赫数下摩阻和压阻分量对总减阻的贡献、燃烧影响区域和壁面热流密度，探讨了喷射参数对减阻效果的影响，探索了边界层燃烧方法在典型混压式进气道中的减阻应用。结果表明，随着进口马赫数的增加，总阻力中摩阻分量随之增加；边界层燃烧对摩阻和压阻减阻的机理有所不同，壁面附近流场特性变化使得摩擦系数减小，燃烧局部增压对壁面产生的增推效果使得压力系数减小；从总内阻减阻百分比看，在相同燃料/空气当量比下，低马赫数工况下边界层燃烧减阻效果不如高马赫数工况，且在低马赫数工况下，喷嘴附近壁面热流密度会显著增加；在本文所研究的参数范围内，摩阻和压阻对当量油气比更为敏感，而对喷射方向和喷射速度不敏感。     

客机隔热隔声棉点火特性与产烟毒性研究

为研究客机隔热隔声棉点火特性与产烟毒性,使用相关装置进行了试验研究.结果表明:点火持续时间和辐射板温度均对隔热隔声棉点火具有明显促进作用.点火持续时间越长,火焰沿Y轴蔓延距离越大,点火15s时,明火附近区域的隔热隔声棉出现被烧穿现象,但烧穿面积不大.火焰沿Y轴蔓延距离增长速率却随点火持续时间的增大而减小,验证了隔热隔声...     

CFRP薄壁圆筒壳端面磨削工艺研究

阵列碳纤维复合材料管是由碳纤维增强复合材料(CFRP)薄壁圆筒壳阵列排布后粘接制备而成，兼具碳纤维复合材料和蜂窝结构的优异性能，是一种新型的可应用于深空探测反射面板的理想材料结构。由于材料和制备方面的特殊性，在阵列碳纤维复合材料管加工过程中会由于磨削力过大导致多种加工损伤，为其高效低损伤加工带来了挑战。本文开展CFRP薄壁圆筒壳磨削加工正交试验，系统研究磨削深度、切出角度、主轴转速、进给率对磨削力的影响规律和影响程度。研究结果表明:工艺参数对水平面合力的影响程度依次为进给率、磨削深度、切出角度、主轴转速，对轴向力的影响程度依次为切出角度、主轴转速、进给率、磨削深度。研究对阵列碳纤维复合材料管高效低损伤加工工艺的制订具有参考意义。     

Improving performance of macro electrolyte jet machining of TC4 titanium alloy: Experimental and numerical studies

Electrolyte jet machining (EJM) is a promising method for shaping titanium alloys due to its lack of tool wear, thermal and residual stress, and cracks and burrs. Recently, macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes. However, macro-EJM generates large amounts of electrolytic products, thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality. Therefore, for enhanced product transport, a novel tool with a back inclined end face was proposed for macro-EJM of TC4 titanium alloy. For comparison, also proposed were ones with a standard flat end face, a front inclined end face, and both front and back inclined end faces. The flow field distributions of all proposed tools were simulated numerically, and experiments were also conducted to validate the simulation results. The results show that one with a 5° back inclined end face can decrease the low-velocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool, thereby promoting rapid product removal. A relatively smooth bright-white groove surface was obtained. The same tool also resulted in the highest machining depth and material removal rate among the tested ones. In addition, rapid product removal was beneficial to the subsequent processing. Because of its rapid product removal, the machining depth and material removal rate during deep groove machining using the tool with a 5° back inclined end face were respectively 7% and 14% higher than those produced using a standard one. Moreover, the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm, and a plane with a depth of 0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5° back inclined end face.