NOx Formation Mechanism in engines of next generation aircraft and Effects of Emission of NOx on Global Atmosphere

对25公里高空平流层飞行排出的烟羽对臭氧的消耗进行了数值分析。用扩展盒法模拟了排气羽流在平流层中的扩散过程。用五阶BDF方法估算了反应的化学物种浓度和臭氧浓度的归一化灵敏度。化学动力学包括NOx、Hex和Ox化学。结果是，羽流中的臭氧浓度在1 ppb以内需要两天多的时间才能达到环境水平。臭氧扰动受烟羽排放时间的影响而发生变化，且白天大于夜间。臭氧浓度对反应的灵敏度分布也随着羽流发射时间的变化而变化。为了研究超燃冲压发动机燃烧室中液体煤油的燃烧模式和着火极限，对废气中NOx对臭氧的消耗大于对Hox的消耗。使用了三个有向后台阶的燃烧室，其中一个有一个空腔，可以在台阶的上游注入气态氢。将煤油正常喷入马赫数为2.0的高焓气流中，用CCD摄像机观察煤油的喷射和燃烧过程。根据燃烧室顶壁的静压分布来判断燃烧模式。因此，雾化行为对液体燃料在超音速气流中的着火起着重要的作用。当喷油器内径为0.3 mm时，在任何总温下都不能观察到点火和稳定燃烧。当喷油器内径为0.5 mm时，点火发生在主流总温2300K以上。

Numerical analysis of ozone depletions by exhaust plume from stratospheric flight at the altitude of 25 km was conducted. Expanding box method was employed to simulate a diffusion of exhaust plume in the stratosphere. Concentrations of chemical species and normalized sensitivities of ozone concentration for reactions were estimated by fifth-order BDF method. Chemical kinetics include NOx, Hex and Ox chemistry. As results, it takes over two days that ozone concentration within a plume becomes ambient level within 1 ppb. Ozone perturbations were changed by an effect of plume-emission time, and they are bigger in daytime than in nighttime. Distributions of sensitivities of ozone concentrations for reactions are also changed for plume-emission time. Ozone depletion is greater by NOx than HOx in an exhaust plume.An experimental research on combustion of liquid kerosene in a scramjet combustor was conducted in order to investigate combustion modes and ignition limits. Three combustors, which had a backward step, were used, and one of these had a cavity and could inject gaseous hydrogen at the upstream of the step. Kerosene was injected normally into a Mach 2.0 high-enthalpy airflow, and the injection and combustion of kerosene were observed by a CCD camera. Combustion modes were judged from a distribution of static pressure on the top wall of the combustor. As a result, atomization behavior is an important role for the ignition of liquid fuel in a supersonic air flow. The ignition and stable combustion is not observed when the inner diameter of fuel injector is 0.3 mm for any total temperatures of the main flow. The ignition occurs for above 2300K of the total temperature of the main flow when the inner diameter of the fuel injector is 0.5 mm.