Abstract Uniform gas mixing is important in various scientific and engineering domains, particularly in a chemical reactor design employing pre-mixed gases for processes. Assessing the performance of different mixer designs through physical prototypes can be resource-intensive and time-consuming. Consequently, this study underscores the significance of numerical simulations to optimize gas mixing and distribution systems in energy conversion applications. The research primarily focuses on varying the base mixer geometry by modifying the configuration of cross-flow inlets alongside the chambers. By employing numerical simulations, critical factors influencing mixing uniformity are identified, and innovative solutions are proposed to enhance system performance. Additionally, this work extends its application to improving the operational conditions of an industrial biomass gasifier, underlining the practicality of numerical modelling in addressing complex engineering challenges.