Spray flame soot sampling and morphology analysis of butanol–diesel blends

To investigate soot formation, concentration and morphology differences affected by adding butanol to diesel, an experimental study was performed to compare in-flame soot morphology of diesel and butanol–diesel blends in a constant volume combustion chamber. Direct thermophoretic soot sampling was conducted in single-shot spray flame of pure diesel and 30% butanol-70% diesel blends. Soot samples were observed with a Transmission Electron Microscope, and soot morphology was analyzed and compared by subsequent image processing. Spray flame combustion process was recorded by a high-speed digital schlieren optical diagnostic system. Flame status variance of adding butanol was discussed and connected with soot formation and morphology differences. The result indicates that blending butanol could promote fuel atomization, optimize fuel-air mixing, delay ignition, accelerate combustion, and restrain soot formation. In butanol diesel blending spray flame, soot number and mass concentration are significantly smaller, and average size is smaller than that of pure diesel fuel, soot geometry and morphology are also changed.