The spatial distribution of concentration and velocity of a gas jet impinging with abump is studied in this paper. The conception of mean dispersion rate of concentrationis employed to describe the mixing process of gas jet in the near wall. The result showsthat the radial non-dimensional distribution of concentration and velocity of the second jetare normal, the axial nonudimensional distribution of concentration is exponential and theaxial non-dimensional distribution of velocity is lineal. The mixing rate of the jet gas in thenear wall is enhanced because of the existence of the bump. Base on these results, a new"space-wall-space" mixing conception for small or medium D.I. diesel engine is proposed.
