In this paper a direct simulation Monte Carlo method is used to investigate the effect of obstacle layout and flow injection on the micro mixing of two flows in a channel with 16 µm long and 1 µm heigh. The concept of mixing length is utilized, which is the distance that two species are completely mixed. Eight cases with different blockage ratios are considered to assess the impact of obstacles. In all cases, two gases including CO and N2 enter the channel and are separated by a plate that extendes one-thrid of the channel length. With the addition of obstacles, the blockage ratio is increased due to the reduction of flow cross-section exposed area. By increasing the blockage ratio, the mixing length decreases up to 10%, and the mass flow rate decreases significantly. Moreover, flow injection into the channel is explored by considering four cases. The cases are: (1) without injection, (2) with cross injection, (3) with inverse injection, and (4) with cross injection through the obstacle. Simulations indictate that the mixing length increases by up to 17% and 5% in the second and third cases, respectively. In the fourth case, the mixing length decreases by 2% due to the obstacle arrangement.
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