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Reduction of Nitrogen Oxides by Means of Highly Turbulent Combustion and Modification of Air Composition

通过高湍流燃烧和空气成分改变来减少氮氧化物

基本信息

批准号：
07455096
负责人：
IKEGAMI Makoto
金额：
$ 4.86万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

This study aims at obtaining suggestions for reducing NOx and clarifying the marginal limit of the reduction in the heterogeneous combustion process in practical burners and power systems. The contents of the present study are summarized as follows :1.Production and destruction of NOx in the dilution process of fuel-rich burnt gases are investigated based on detailed chemical kinetics. It was shown that fast mixing due to strong turbulence enables a great deal reduction in NOx formation, and that NOx concentration can be halved if the temperature decreases with the volume expansion in a high-speed piston-engine motion prior to the heat release due to dilution.2.A high swirl burner was tested to investigate the mechanism of the flame stability and the NOx formation. The obtained results showed that a diffusion flame having the same low-NOx level with that in a premixed flame would be formed under a higher swirl number and a stoichiometric fuel-air ratio. Furthermore, the NOx reduction by means of burnt-gas addition in the diffusion combustion was investigated based on a detailed chemical kinetics. It was shown that the burnt-gas temperature should be reduced during recirculation process to reduce NOx, and that a lower temperature can reduce NOx a great deal.3.Exhaust-water-selective recirculation, which operates as a closed system without a supplementary water charge, was proposed for reducing NOx in diesel engine exhaust. The feasibility of the system was experimentally assessed on a single-cylinder test engine. In addition, the effects of intake-air dilution with N2 and CO2 and EGR on the exhaust emissions were predicted and discussed based on a stochastic model. The predicted results showed that cold EGR does not much affect the average temperature, but diminishes gas pockets having a higher-temperature greater than 2,500K,resulting in a great reduction of NO formation.

本研究的目的是获得减少NOx的建议，并澄清在实际燃烧器和动力系统中的非均相燃烧过程中减少NOx的边际极限。本文的主要研究内容如下：1.基于详细化学动力学理论，研究了富燃烟气稀释过程中NOx的生成和破坏过程。结果表明，强湍流引起的快速混合可以大大减少NOx的生成，在稀释放热之前，通过活塞发动机高速运动中的体积膨胀降低温度，可以使NOx浓度减半。2.对高旋流燃烧器进行了火焰稳定性和NOx生成机理的试验研究。结果表明，在较高的旋流数和化学计量比下，可以形成与预混火焰相同的低NOx扩散火焰。此外，通过燃烧气体添加在扩散燃烧的NOx还原进行了研究的基础上详细的化学动力学。结果表明，在再循环过程中，应降低烟气温度以降低NOx排放，降低烟气温度可显著降低NOx排放。3.提出了一种不需补水的封闭式排气水选择性再循环系统，用于降低柴油机排气中的NOx。在一台单缸试验发动机上对该系统的可行性进行了实验评估。此外，基于随机模型预测和讨论了N2和CO2的进气稀释和EGR对排气排放的影响。预测结果表明，冷EGR对平均温度影响不大，但减少了温度高于2, 500 K的气穴，从而大大降低了NO的生成。