The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at th...The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at the bottom of the gearbox and alarm directly affects the flight safety of the helicopter.Based on the CFD method,the factors affecting the accessibility of metal particles are analyzed by using the volume of fluid-discrete phase model(VOFDPM)coupling model,the RNG k-ɛturbulence model and the dynamic grid technology.Furthermore,the optimization research on the casing structure is conducted.Experimental results show that the accessibility of metal particles is optimal when the gear speed is 6000 rad/min or the immersion depth is 24 mm.The density of metal particles exhibits a nonlinear relationship with their accessibility,and the particle size has a relatively small impact on their accessibility without an order of magnitude change.展开更多
文摘目的建立并优化大体积进样-离子色谱法(ion chromatography,IC)测定食品接触用塑料制品中高氯酸盐(ClO4-)迁移量的检测方法。方法选用水、3%乙酸(m:V)、4%乙酸(V:V)、10%乙醇(V:V)、20%乙醇(V:V)、50%乙醇(V:V)、95%乙醇(V:V)作为食品模拟物,以14.0 mmol/L无水碳酸钠和20%乙腈(体积分数)混合溶液作为流动相进行等度洗脱,进样量800μL,流速1.0 mL/min,采用Metrosep A Supp 4离子色谱柱(250 mm×4.0 mm,9.0μm)和Metrosep A Supp RP Guard保护柱(50 mm×4.0 mm,9.0μm),柱温30℃,以电导检测器进行测定,外标法定量。结果方法验证结果表明,该方法线性关系良好,标准工作曲线的线性相关系数大于0.995,方法检出限为0.15μg/kg,定量限为0.50μg/kg,加标回收率为83.2%~99.1%,精密度为2.7%~9.1%(n=6)。结论该方法可靠、方便、灵敏,分离效果好,适用于食品接触用塑料制品中高氯酸盐迁移量的检测。
基金supported by the Na‑tional Natural Science Foundation of China(No.52075241)the National Key Laboratory of Science and Technology on Helicopter Transmission(Nanjing University of Aeronau‑tics and Astronautics)(Nos.HTL-A-22K04 and HTL-O21G13).
文摘The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at the bottom of the gearbox and alarm directly affects the flight safety of the helicopter.Based on the CFD method,the factors affecting the accessibility of metal particles are analyzed by using the volume of fluid-discrete phase model(VOFDPM)coupling model,the RNG k-ɛturbulence model and the dynamic grid technology.Furthermore,the optimization research on the casing structure is conducted.Experimental results show that the accessibility of metal particles is optimal when the gear speed is 6000 rad/min or the immersion depth is 24 mm.The density of metal particles exhibits a nonlinear relationship with their accessibility,and the particle size has a relatively small impact on their accessibility without an order of magnitude change.
