高金属含量水冲压发动机点火过程多相耦合计算

Multi-Phase Simulation of High-Metal-Based Water Ramjet During Ignition

关键词:  高金属含量水冲压发动机  点火  燃面温度  多相耦合计算  点火药

Key words:  High-metal-based water ramjet  Ignition  Burning surface temperature  Multi-phase simulation  Ignition powder

摘要:

为准确模拟高金属含量水冲压发动机点火过程的流场特征及燃面温度变化，基于N-S方程，将高金属含量燃料和点火药向气相流场的质量、动量和能量输运转化为对应守恒量控制方程在近燃面第一层网格和点火药包覆盖区域网格的源项，将脱离燃面的熔融镁近似为燃烧室入口释放的镁液滴，实现了含镁质量百分数为73%的水冲压发动机燃料燃烧/点火药燃烧/发动机内流场的多相湍流燃烧的耦合计算，并对比分析了黑火药和硼/硝酸钾点火药对燃料燃烧影响。结果表明:40g黑火药点火和0.5kg/s的进水量下，燃料平衡燃面温度约为943K，可实现可靠点火与稳态燃烧。相同质量的硼/硝酸钾点火药与黑火药相比，可实现较高的平衡燃烧温度，但需较长的平衡建立时间。

Abstract:

To exactly simulate the flow filed characterization and burning surface temperature during ignition，based on the Navier-Stokes equations，where mass，momentum and energy transported to the gas flow filed from the fuel or igniter were respectively transformed into the corresponding conserved quantity governing equation source items in specific computation grids，which imply the first column grids adjacent to the fuel surface for fuel and the igniter coverage grids for the latter，and where molten magnesium detached from the burning surface were converted as the magnesium droplets injected from the combustion chamber inlet. A multi-phase turbulent combustion/flow simulation coupling fuel combustion，igniter combustion and motor chamber flow together for water-ramjet with Mg mass percentage of 73% was accomplished. Affection to fuel combustion between different ignition powders named black powder and boron/potassium nitrate were analyzed. Reliable ignition and continuous burning could be approached by igniter with 40g black powder and 0.5kg/s water injection，and the final burning surface temperature keeps steady at 943K. This temperature could be higher achieved by boron/potassium nitrate than black powder of the same mass，but the prior one simultaneously calls for more time to establish steady state.