不同钝体宽度下的驻涡燃烧室排放试验

为了研究空气流量分配对驻涡燃烧室对排放特性的影响,了解对驻涡燃烧室内污染物生成的过程及其影响因素,设计了一个能够改变中心钝体宽度、仅凹腔供油的驻涡燃烧室.在常压下对该驻涡燃烧室进行了排放特性试验,进口温度保持200℃.试验中,燃烧室进口马赫数为0.15~0.3.影响排放的因素主要包括雾化质量、凹腔当量比以及与进口马赫数相关的驻留时间等.总体来说雾化质量、凹腔当量比的提高对降低CO和HC的排放是有利的,但是这会使NOx排放增加.在低凹腔当量比时,CO排放曲线变化下降比较平缓,甚至出现上升趋势,而HC排放曲线比较陡峭.这是由于HC的消耗速度比CO消耗速度快,随着凹腔当量比的增加,供油压力提高,燃油雾化粒径变小,燃油蒸发时间缩短,使HC排放快速减少,中间产物CO大量产生而来不及消耗.凹腔当量比进一步上升时,由于燃烧温度的提高,使得CO排放快速减少.在燃烧室内燃烧过程中,NOx的形成和消耗是非常复杂的过程,目前只能作一些定性的分析,而CO和HC的反应过程相对简单.通过对不同钝体槽宽下,具有相似凹腔前壁流量的工况的比较,发现CO和HC的形成主要受凹腔内工作状况影响,而NOx的形成过程更复杂,主流也对其产生着重要的影响. 

Experiment on emissions of a trapped vortex combustor with different bluff body widths

To reveal the effects of air flow-rate distribution on emission characteristics of trapped vortex combustor and understand the generating processes of emissions as well as the factors affecting the processes, a trapped vortex combustor with different centric bluff body width was designed. And the combustor was designed to be fueled only in cavity. Emission experiment was conducted at atmospheric pressure. And inlet temperature of the combustor was kept at 200℃. Inlet Mach number varied from 0.15 to 0.3.Atomization quality, cavity equivalence ratio in combustion zone, and inlet Mach number and residence time influenced emissions in combustors. Generally, improvement of atomization quality and increase of cavity equivalence ratio can enhance combustion process and consequently reduce emissions of CO and HC. However, it will also lead to increase of NOx emission. As cavity equivalence ratio is relatively lower, CO emission curves decline gradually, and even ascend in some cases. HC emission curves descend rapidly here. This is mainly because the consumption of HC is much faster than CO. When cavity equivalence ratio is increasing, the fueling pressure is elevated and thus atomization is enhanced, so vaporizing time of fuel spray is shortened. This will result in rapid decline of HC emission. Although, a large amount of CO will be produced and there is no enough time to consume. CO emission declines rapidly when cavity equivalence ratio is high enough because of the higher temperature in the combustion zones. In gas turbine combustors, the producing and consuming process of NOx is very complicated, and there is no enough data to demonstrate it. Comparison between different bluff body widths has been made as the cavity air flow-rate on front wall are similar. And it reveals that the emissions of CO and HC are mainly determined by the cavity condition. However, NOx emission is also impacted by the mainstream.