Diagnostics of in-cylinder flow, mixing and combustion in gasoline engines

In a premixed leanburn engine employing an in-cylinder rotating flow, tumble, the influence of the in-cylinder flow field structure on combustion was investigated with a two-dimensional PTV, a three-dimensional PTV and the analysis of continuous and cycle-to-cycle UV flame images. As a result, optimum combustion control was achieved by controlling the generation of turbulence. In a gasoline direct injection engine adopting a wide spacing layout, the characteristics of mixture preparation were investigated by visualizing a fuel spray with laser shadowgraphy and LIF, and deriving the mixture strength at the spark plug from spectrum analysis of spark discharge emission. Also, the combustion characteristics were investigated by analysing flame emission spectra continuously, and imaging UV luminescence and thermal radiation of flame emission simultaneously. Consequently, it was clarified that combustion control is achieved by controlling air-fuel mixing.