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

尽管那些自然地依赖先进技术的人对超音速飞行的兴趣与日俱增，但当今世界范围内的关切涉及温室效应和平流层臭氧消耗现象，这生动地表明了人们对我们的科学和技术成就缺乏充分信心。环境影响是今后探索新技术发展首先要考虑的问题。本文对用于高超声速运输系统的氢燃料超音速冲压发动机的废气排放进行了研究。重点是在这样的推进系统中产生污染物(即NOx)的热流体化学过程，该推进系统不可避免地运行在平流层大气中，并具有与飞行器结构完全集成的几何特征。目前的理论部分讨论了由于涉及H-O-N物种的化学反应而导致的数值改进。新开发的方案与流体运动的Navier-Stokes方程相结合，揭示了高反应性溅射射流外喷管流动的细节。实验部分包括不向空间腔内注入气体，空间腔内的压力和臭氧浓度可以调整以模拟高空大气。采用纹影和激光诱导荧光光学方法进行流动显示，研究了注入激波结构、相关密度梯度场和NO数密度分布，从中可以看出不注入对臭氧的消耗。

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.