水下固体火箭发动机燃气射流及推力特性研究

When the hot gas generated from a solid rocket motor used for a high speed underwater vehicle inject into water, the process is essentially unsteady and turbulent; additionally, the high ambient pressure, high velocity and high water-to-gas density ratio can result in complicated flow structures. The different characteristics between the underwater engines and the aero engines must be take into consideration when the motor is used as propulsion devices for high speed underwater vehicles. Both numerical simulation and experimental study are needed..The mathematical model and numerical simulation of supersonic gaseous jets injected into water is needed to investigate the characteristic of the motor. Combined with the simulation results, the relationship with water depth, combustion pressure and expansion ratio should be analyzed. The coupling model between the process of solid propellant combustion and the process of gaseous jets injected into water is also needed to investigate the influence of exhaust plume to the motor's thrust. The caution of thrust climb up process, the negative thrust and thrust vibration appeared when the motor working a the deep water can be analyzed based on the simulation results. The study of design conception of the thrust stand, experimental measurement method and data processing method are also need deployed. This could be helpful for the characteristic research of the underwater solid rocket motor. The combination of numerical investigation and experimental results could provide great help to the design, optimization and performance prediction of the motor.

以用于深水高速航行器助推用固体火箭发动机为背景，针对发动机燃气射流注入水中形成的含有高压、高速、高密度比、非稳态、湍流等复杂因素的气、液两相流过程，通过数值仿真研究复杂流场结构的特点及其对发动机推力和燃烧过程的影响，探索水下推力测试方法。首先，建立水下超音速气体射流数学模型，结合数值模拟得到的射流流场状态及形貌结构特点，分析发动机推力与工作水深、燃烧室压强、喷管扩张比等参数的关系；其次建立推进剂燃烧与水下超音速气体射流的耦合计算模型，研究排气反压对发动机工作过程的影响，分析发动机点火建压过程中推力爬升和负推力等现象出现的原因；最后开展推力测试方法和数据处理方法研究。研究成果可为水下固体火箭发动机的结构设计和性能预估提供理论依据和技术参考。

针对深水高速航行器助推用固体火箭发动机的实际工作过程中存在的典型气液非稳态混合两相流问题，进行了数值仿真和试验探索两方面的研究工作。首先，建立了发动机起动过程中尾部燃气泡的等压滞止球形气泡模型和喷管-燃气泡组合的柱形准一维模型，解释了水下发动机推力在起动瞬间产生峰值的机理和规律，分析了发动机各参数、工作环境参数的改变对推力变化规律、推力峰值和气泡内压强的影响；然后，利用商用计算流体动力学（CFD）软件平台，建立了二维轴对称和三维实体模型，利用二维轴对称模型进行了典型射流结构的计算和分析，以及远场压力脉动和噪声的监测，同时针对有来流的特殊情况进行了仿真分析。利用三维实体模型，建立了水平和竖直两种方向的气-水两相流射流模型，得到了射流流场状态及形貌结构，根据射流的仿真结果分析了重浮力和相变作用下，不同工作水深、燃烧室压强、喷管扩张比对发动机推力的影响；其次，建立了铝颗粒与水反应的推进剂燃烧和水下超音速气体射流耦合计算模型；针对高速旋转下推进剂/点火具燃烧特性的变化以及燃烧室内流场变化进行了仿真计算；最后，开展了水下燃气射流及其相关流场和推力测试方法的研究。以上研究成果对于水下固体火箭发动机的结果设计和性能预估具有重大的意义。