A Numerical Study on Hypergolic Combustion of Hydrazine Sprays in Nitrogen Tetroxide Streams
A Numerical Study on Hypergolic Combustion of Hydrazine Sprays in Nitrogen Tetroxide Streams
复制标题
DOI：
10.1080/00102202.2017.1402010
复制
发表时间：
2018-03
影响因子：
1.9
通讯作者：
Hiroumi Tani;H. Terashima;Y. Daimon;M. Koshi;R. Kurose
中科院分区：
文献类型：
--
作者：
Hiroumi Tani;H. Terashima;Y. Daimon;M. Koshi;R. Kurose
摘要对四氧化二氮(NTO，NO2-N2O4)气流中的肼(N2H4)喷雾进行了非定常模拟，以研究双组元推进器中的自燃现象。采用详细的化学动力学机理求解Navier-Stokes方程，通过直接数值模拟对分散液滴进行数值模拟。当环境气体的热传递和氢提取反应的放热之和超过液滴的潜热时，发生自燃。虽然液滴的蒸发随着液滴尺寸的减小而增加，但由于N2H4蒸汽和四氧化二氮混合物的温度较低，点火延迟时间增加。火焰达到稳定状态后，出现了由外扩散火焰和内分解火焰组成的双重火焰结构。当液滴尺寸一定时，内分解火焰和N_2H_4蒸汽流呈正弦运动。这一行为是由局部膨胀的分解气体启动的，并通过在相对较高的温度下向分解气体提供N2H4液滴而发展。在液滴尺寸较大和较小的情况下，正弦行为并不明显，这分别是因为N2H4液滴的蒸发较少和N2H4蒸汽的温度较低。分解火焰的正弦行为增强了燃料组分(即N2H4、NH3和H2)的混合和反应。研究表明，液滴大小对火焰动力学有很大影响，说明喷雾细小并不总是有利于自燃推进剂燃烧迅速消耗燃料组分。
ABSTRACT Unsteady simulations of hydrazine (N2H4) sprays in nitrogen tetroxide (NTO, NO2-N2O4) streams were conducted to explore the hypergolic combustion in bipropellant thrusters. The Navier–Stokes equations were solved using a detailed chemical kinetics mechanism and dispersed droplets were modeled through direct numerical simulations. Auto-ignition occurred when the sum of the heat transfer from the ambient gas and the heat release from hydrogen abstraction reactions exceeded the latent heat of the droplets. Although the evaporation of the droplets was enhanced as the droplet size decreased, the ignition delay time increased due to the lower temperatures of the mixtures of the N2H4 vapor and nitrogen tetroxide. After the flames reached a steady state, a double flame structure appeared, comprised of outer diffusion and inner decomposition flames. The inner decomposition flame and N2H4 vapor flow exhibited a sinusoidal behavior at a certain droplet size. This behavior was initiated by the locally expanded decomposition gases and developed by the supply of N2H4 droplets to the decomposition gases at relatively high temperatures. In cases of larger and smaller droplet sizes, the sinusoidal behavior was not significant due to less evaporation of the N2H4 droplets and a lower temperature of the N2H4 vapor, respectively. The sinusoidal behavior of the decomposition flames enhanced the mixing and reactions of the fuel components (i.e., N2H4, NH3, and H2). The present study demonstrated a large impact of droplet size on flame dynamics, suggesting that a fine spray is not always better for hypergolic propellant combustion to consume the fuel components quickly.