This paper describes the experimental and numerical investigation on the spray characteristics of diesel and dimethyl ether (DME) fuel according to the combustion chamber shape under ambient pressure injected through the common-rail system. For the experimental study, diesel and DME fuels were injected into combustion chambers with two shapes (narrow and conventional type). The investigation on the spray behavior according to the various injection conditions (injection pressure, duration, nozzle-wall distance, etc.) was conducted by the visualization system utilizing an Nd:YAG laser as the light source. In order to investigate the numerical study, a three-dimension computational grid was created as the shape of combustion chamber and thermodynamic properties of DME fuel were inserted into the KIVA code. Also, the hybrid breakup model combining the primary and secondary breakup was used to analyze the spray characteristics on the evaporation conditions. In the macroscopic characteristics such as the spray developing process and spray tip penetration, the calculated results were compared with the experimental observations and the evaporation distribution and rate were predicted by the numerical method. It was revealed that the calculated results of spray tip penetration agreed with the experimental observations of DME and diesel fuel for the different combustion chambers. The evaporation characteristics such as vapor phase distribution and evaporation rate were investigated in terms of two kinds of fuels and combustion chamber shapes.