Control of Heat Loss and Pollutant Emission for Combustion in Variable-Shaped Closed Vessel

本研究的目的是探讨利用可变形状燃烧室控制燃烧和污染物排放特性的可能性。在本研究的第一阶段，利用纹影照相技术对不同形状的封闭容器的火焰传播行为进行了观测。还测量了燃烧室压力随时间的变化。结果表明，封闭容器的形状对火焰传播行为和压力历史有很大影响。结果表明，火焰锋面形状是影响燃烧特性的主要因素之一。为了探讨热损失对燃烧和污染物排放特性的影响，利用火焰传播过程中的人工热损失测量了燃烧室压力和NO浓度随时间的变化。结果表明，燃烧初期的人为热损失使NO浓度降低约40%，而对与热效率密切相关的最大燃烧室压力影响不大。这一结果表明，由于热损失导致燃气温度的降低，导致了NO浓度的降低。为了研究气体运动和湍流对燃烧和污染物排放特性的影响，进行了高温环境下甲烷射流的燃烧实验。重点研究了喷油器布置对燃烧的影响。结果表明，对向喷流的NO浓度比单喷流低。这一结果可能是由于对向喷流和单喷流的混合和燃烧过程不同造成的。

The objective of the present study was to investigate the possibility of the control of combustion and pollutant emission characteristics using the variable-shaped combustion chamber. At the first stage of this study, the flame propagation behavior was observed for closed vessels with various shape using the schlieren photography. The variation of the chamber pressure with time was also measured. The results showed that the flame propagation behavior and pressure history were affected largely by the shape of the closed vessel. It was suggested that the shape of the flame front was one of dominant factors of the combustion characteristics. To explore the effect of the heat loss on the combustion and pollutant emission characteristics, the variation of the chamber pressure with time and NO concentration were measured with the artificial heat loss in the flame propagation. The results showed that the artificial heat loss at the early stage of the combustion leads to about 40% reduction of NO concentration, while it has little effect on the maximum chamber pressure, which is closely related to the thermal efficiency. This result indicates that the decrease in the temperature of the burned gas which due to the heat loss leads to the reduction of NO concentration. To investigate effects of gas motion and turbulence on combustion and pollutant emission characteristics, the combustion experiments of the methane jets in high temperature environments were made. The atttention was paid to the effect of the arrangement of injectors on the combustion. It was found that the NO concentration for opposed jets is lower than that for single jet. This result may be caused by the difference between mixing and combustion processes for opposed jets and single jet.