抄録
CO emission sources in diesel combustion with multiple injections are analyzed by using in-cylinder CO imaging and 3-D numerical simulation. For the in-cylinder CO imaging, a two-photon excitation LIF was applied. While overlapping of the blue color component of the luminous flame (emitted by the soot particles) over the weak CO fluorescence became as a serious problem, it was solved by optimizing the viewing direction. A comparison of the CO distribution results as obtained by CO-LIF imaging and CFD simulation shows good agreement on the location of the dense CO gas clouds. The major source of CO emissions under low-load conditions is the over-diffusion of the pilot sprays. A large amount of CO, formed from the pilot flame, is emitted without being oxidized by the high temperature main flame. In contrast, under high-load conditions, the major source is the fuel rich region of the flame front because of the low O_2 concentration.
