Generation Mechanism of Environmental Pollutants in the Frame Integrated Supersonic Nozzle Exhaust

当那些自然地依赖先进技术的人对超音速飞行的兴趣日益增加时，当今世界范围内的关注涉及绿色房屋效应和平流层臭氧层损耗现象，这生动地表明了对我们的科学和技术成就缺乏充分的信心。环境效应是今后探索新技术发展的首要问题，本文研究了HST（HyperSonicTransport）系统用氢燃料超音速燃烧冲压发动机的废气排放。重点是在这样的推进系统，不可避免地在平流层大气中运行，并具有与飞行器结构完全集成的几何特征的热流体化学过程中产生的污染物（即，NOx）。理论部分目前处理的计算改进有关的数值刚度由于化学反应涉及H-O-N物种。新开发的方案与流体运动的Navier-Stokes方程相耦合，以揭示高反应性SCR冲压发动机射流外部喷管流动的细节。实验部分包括NO气体注入到一个空间室中，其中的压力和臭氧浓度可以调节，以模拟在高空大气中。采用纹影和LIF光学方法进行流场显示，研究了注入物的激波结构、密度梯度场和NO数密度分布，并由此获得了NO注入引起的O3损耗。

Whilst the interest for the faster than supersonic flight is ever increasing amongst those who feel natural to rely upon advanced technology, the world-wide concerns today involve the green house effect and thestratospheric ozone depletion phenomena, which vividly shows a lack of full confidence in our scientific and technological achievements. The environmental effect should be hereafter the first issue to be treated in exploring the developments of new technology.In the present study, the exhaust gas emission from the hydrogen fueled SCRam (Supersonic Combustion Ram) jet engine for HST (HyperSonic Transport) system has been examined. An emphasis is upon the thermo-fluid chemical process to produce pollutants (namely, NOx) at such propulsion system that inevitably operates in the stratospheric atmosphere and possesses a geometrically particular feature of full integration with the vehicle structure.The theoretical part presently treats computational improvements concerning the numerical stiffness due to the chemical reactions involving H-O-N species. The newly developed scheme is coupled with the Navier-Stokes equations of fluid motion to reveal the details of highly reactive SCRam jet external nozzle flows.The experimental part consists of NO gas injection into a space chamber in which the pressure and the Ozone concentration can be adjusted to simulate in the high altitude atmosphere. Flow visualization using schlieren and LIF optical method is employed to examine the injectant shock wave structure, the associated density gradient field and the NO number density distribution, wherefrom the depletion of Ozone due to NO injection is accessed.