【作者】 陈文武；

【导师】 李国卿； 桑凤亭；

【作者基本信息】 大连理工大学 ， 材料科学与工程， 2010， 博士

【摘要】 氧碘化学激光是波长为1.315μm的连续波化学激光器,是目前世界上输出能量最高的激光器之一,主要由单重态氧发生器(包括反应液体储罐、收集罐、气体供应系统)、氧碘混合喷管、光腔、扩压器及辅助系统(如冷冻系统、真空系统等)组成,其中单重态氧发生器为激光器提供输出激光所需的化学能源——单重态氧,是激光器的核心部件,其体积与重量占激光器系统的80%以上。但由于氧碘化学激光体积和重量相对庞大,极大地限制了其应用环境,如车载、机载、太空等各种机动平台,因此氧碘化学激光的轻型化是拓展其应用范围的必然要求,而其关键是氧发生器的轻型化——减小体积和重量。提高氧发生器的轻型化水平的技术途径主要有两个方面：其一是提高氧发生器的体积效率和化学效率,即提高单位体积内的反应物流量(以Cl2计量)和单重态氧产率(单位Cl2流量产生的单重态氧流量)；其二采用低密度材料取代传统的不锈钢材料以减轻重量。单重态氧发生器的研究发展历经数次技术更新,从第一代的鼓泡发生器、第二代的转板发生器到第三代的射流发生器。本文研究的是第四代均匀液滴发生器。较其它类型发生器,均匀液滴发生器更适应移动平台,具有更高的化学效率和体积效率。本文采用压电振荡器强制振动的方法使碱性过氧化氢形成时空分布均匀的均匀液滴阵列,研制出一种新的化学反应技术路线,强化了气液两相流反应的传质、传热过程,提高了发生器体积效率和反应稳定性；通过数值模拟和实验研究优化发生器的结构设计和工艺条件,高效产生单重态氧。在氯气流量为0.5mol/s时,氯气利用率为90.6%,02(1△)绝对产率大于50%,02(1△)浓度达到2.94×1017mol/cm3,高于公开报道的均匀液滴氧发生器指标2.5×1017mol/cm3。均匀液滴发生器的能量通量即O2(1△)流量较射流发生器提高了27.3%,也就是发生器的体积效率提高了近1／3。该发生器在万瓦级激光器上进行了出光考察实验,在无冷阱情况下输出功率9.55kW,喷管功率密度达到121.3W／cm2,验证了均匀液滴氧发生器具有体积小、效率高等优越性。发生器体积较目前应用最成功的射流式发生器可缩小1／3；碱性过氧化氢用量减小,在同等氯气流量条件下,其用量可减少1／3,从而减小了发生器的辅助系统,提高了激光器系统小型化水平。本文提出采用耐低温、化学稳定、低导热系数、耐真空以及力学性能良好的碳纤维复合材料制作单重态氧发生器,碳纤维复合材料的密度仅为不锈钢的五分之一,以其取代不锈钢来减轻发生器的重量。通过有限元分析表明,在抽真空条件下载荷为1个大气压时,储液罐所受最大应力为94.9MPa,远小于碳纤维的屈服强度,在1个大气压下的最大变形发生在顶端与发生器的连接部位,最大位移为0.428mm,所以用碳纤维复合材料代替不锈钢制作单重态氧发生器是可行的；同时给出了发生器封头的最优化方案——采用八条辐射状加强筋来加强封头的强度,并制作了碳纤维复合材料反应罐,使用效果与不锈钢制材质相当。同容积下,其重量为不锈钢制材质发生器重量的1／4-1／3左右。因此,用碳纤维复合材料代替不锈钢制作单重态氧发生器是有效的,可极大地减小系统重量,为氧碘化学激光轻量化指明了可行的技术路线。为验证氧碘化学激光的工业应用可能性,本文采用该激光对纯铝及铜锌合金材料表面进行了辐照试验,激光束斑直径为6mm,功率密度为10000-20000W／cm2,在激光能量作用下瞬间发生熔化。以傅立叶热传导模型为基础,利用ANSYS对该过程进行了数值模拟,并对铜锌合金的热参数求解进行了深入探讨。当功率密度为17783 W／cm2时,纯铝在0.273秒开始融化,至0.91秒辐照结束,形成的熔池为直径9.6mm,深度为4.08mm的球冠；当功率密度为17950W／cm2时,黄铜在0.393秒时开始熔化,至0.95秒辐照结束,形成的熔池为直径6.4mm,深度1.64mm的球冠。两者熔池形貌均与试样熔池形貌相符；当作用时间为1秒时,模拟求解纯铝发生熔化失效的功率密度阈值为4200-4500W／cm2；当作用时间为0.95秒时,模拟求解黄铜发生熔化失效的功率密度阈值为6100-7300W／cm2。氧碘化学激光辐照金属材料发生破坏的程度与激光功率密度、作用时间及材料本身热物性参数相互关联,通过模拟,能够求解熔池深度、温度分布及不同功率密度激光辐照黄铜发生熔化破坏的功率密度阈值等信息。该模拟方法为简化试验和选择激光工艺参数提供了参考依据。更多还原

【Abstract】 Chemical oxygen-iodine laser (COIL) whose wavelength is 1.315μm is a continuous wave chemical laser. It is one of the highest energy output lasers at present. It consists of singlet oxygen generator (reacted fluids tank, collection tank, gas supplying system), oxygen-iodine mixing nozzle, optical cavity, diffuser and auxiliary system (freezing system, vacuum system etc). Singlet oxygen generator, which provides chemical energy for laser output, is the core component of laser. Its volume and weight account for more than 80% of whole laser. However, the application of the chemical oxygen-iodine laser, just as vehicle, airborne and space etc mobile platform, is limited for its relatively huge volume and weight. Therefore, lightening of chemical oxygen-iodine laser is inevitable for expanding its application. And lightening of singlet oxygen generator is the key. There are two ways to lighten singlet oxygen generator:one is increasing the volumetric efficiency and chemical efficiency, namely, increasing reactor flow per unit volume (calculated by Cl2 flow) and increasing yield of singlet oxygen (singlet oxygen flow generate by per unit Cl2 flow); the other is lightening the generator weight by using low density material instead of traditional stainless steel.Several technical innovations happened on singlet oxygen generator research:From the first generation of bubble-column generator, the second generation of rotating-plate generator, the third generation of jet generator to the forth generation of uniform droplet singlet oxygen generator. In contrast with the other generators, uniform droplet singlet oxygen generator which has higher volumetric efficiency and chemical efficiency is more suitable for mobile platform. Uniform droplet singlet oxygen generator was researched in this paper. Basic hydrogen peroxide formed uniform droplets in spacetime by the forced shock of piezoelectric oscillator. Based on this, a new reaction technology which enhanced mass and heat transmission in gas-liquid reaction was produced to increase the volumetric efficiency and reaction stability of generator. Generator structure and process conditions were optimized for higher yield of singlet oxygen by numerical simulation and experimental research. When the Cl2 flow is 0.5mol/s, Cl2 utilization ratio is 90.6%, and the absolute yield of O2(1△) is more than 50%. The concentration of O2(1△) reaches 2.94 which is higher than 2.5×1017mol/cm3-the reported index of uniform droplet singlet oxygen generator. Light extraction experiment was done on lOkW class laser driven by this generator. Output power reaches 9.55kW, and power density of nozzle reaches 121.3 W/cm2 when cold trap was not offered. It verified the high efficiency of uniform droplet singlet oxygen generator in spite of the small volume. In contrast with the most successful applied jet generator at present, generator’s volume reduced by 1/3～1/2,and the usage amount of basic hydrogen peroxide reduced by 1/3～1/2 in the same Cl2 flow. The auxiliary system of generator was reduced which improved the miniaturization level of generator.In order to reduce the weight, carbon fiber composite was suggested to replace stainless steel to make singlet oxygen generator. Under vacuum conditions the max stress of liquid storage tank is 94.9MPa with latmsphere pressure loaded. which is far lower than the yield strength of carbon fiber composite. The max displacement is no more than 0.428mm which occurs on the top of tank—the connecting point with generator, it is feasible to make singlet oxygen generator by carbon fiber composite instead of stainless steel. Meanwhile,8 radialized fortifiable spokes were suggested to use on the generator vessel head to enhance the vessel head. A reaction tank which has equivalent application effect with stainless steel was made with carbon fiber composite, and its weight is only 1/4～1/3 of stainless steel made at the same volume. It is effective to use carbon fiber composite instead of stainless steel for generator manufaction. System weight was reduced greatly. A feasible technical route was shown clearly for lightening chemical oxygen-iodine laser.To verify the possibility of COIL’s industry application, an experiment on aluminum and copper-zinc alloy surface radiated by laser was done. Samples melt in a twinkling by the laser energy. The diameter of laser is 6mm. power density is 10000-20000 W/cm2. Numerical Simulation of interaction of chemical laser with two component alloy was done based on Fourie thermal conduction mode through ANSYS in this paper. Numerical simulation results show that the aluminum began melt at 0.273s, a spherical cap molten pool whose diameter is 9.6mm, depth is 4.08mm was formed at last when the power density of laser is 17783 W/cm2: The copper-zinc alloy began melt at 0.393s, a spherical cap molten pool whose diameter is 6.4mm, depth is 1.64mm was formed at last when the power density of laser is 17950 W/cm2. The power density threshold value of aluminum melting is 4200-4500W/cm2,the power density threshold value of brass melting is 6100-7300 W/cm2. The simulation results above are consistent with the results of experiment. Damage extent of alloy radiated by COIL is related with power density of laser, radiated time and performances of material itself etc. According to the simulation results, appropriate process parameters of laser can be chosen in the practical application of material radiated by laser.更多还原