Mixing process between the injectant and air in supersonic crossflow depends on the injector configuration and the jet-to-jet spacing heavily. In the current study, the three-dimensional Reynolds-averaged Navier Stokes (RANS) equations coupled with the two equation SST k-omega turbulence model were employed to simulate the mixing process induced by an array of three spanwise-aligned small-scale rectangular portholes, and the influences of the jet-to-jet spacing, the jet-to-crossflow pressure ratio and the aspect ratio of the injector on the flow field properties were evaluated. Two quantitative objectives were considered in this article, namely the fuel penetration depth and the mixing efficiency. The obtained results show that the flow field induced by the array of three spanwise-aligned small-scale rectangular portholes is a multiobjective design optimization problem, and the large aspect ratio is beneficial for the mixing enhancement in supersonic crossflow. However, it is not beneficial for the flame holding. The interaction between the adjacent injectors has a great impact on the fuel penetration depth in the far-field, especially for the larger jet-to-crossflow pressure ratio, and this is due to its wider fuel plume. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.